| Posted By
Retroshire
on 2021-07-12
03:58:41
|  Commodore 16: Black and white screen on Composite, color on the RF
Problem with the composite/s-video output on the videoconnector. Connected with RF there is color.
Continuity on pin 13 of the TED with modulator pin 5
Voltages on modulator pins:
1 0,00 NC
2 1,84 Audio
3 5,00 VDC
4 3,32 Luma in
5 3,18 Chroma in
6 1,74 Chroma out
7 1,52 Composite out
8 0,83 Luma out (with s-video connection on monitor, without 1,74V)
Already tried to adjust the trimmer next to the crystal, no effect.
Also different video cables give the same result.
As well with composite connection as with Luma Chroma (s-video) connection: no color
Is there a solution without desoldering/swapping the modulator?
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Posted By
unclouded
on 2021-07-12
06:10:41
| Re: Commodore 16: Black and white screen on Composite, color on the RF
Could it be a problem with EM4? It seems odd that Luma out indicates a lower voltage when loaded but Chroma out does not.
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Posted By
Retroshire
on 2021-07-12
08:27:39
| Re: Commodore 16: Black and white screen on Composite, color on the RF
Swapped EM4, still no color.
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Posted By
siz
on 2021-07-12
08:37:26
| Re: Commodore 16: Black and white screen on Composite, color on the RF
Just a noob question are your computer and display the same norm? I mean PAL/PAL or NTSC/NTSC? A typical symptom of NTSC computer on a PAL display is no color.
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Posted By
Retroshire
on 2021-07-12
08:47:32
| Re: Commodore 16: Black and white screen on Composite, color on the RF
All PAL, two different TV/monitorsets, same result. Color with RF though.
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Posted By
MMS
on 2021-07-12
14:19:37
 | Re: Commodore 16: Black and white screen on Composite, color on the RF
Hi Retroshine,
just few questions:
1) I saw the signal levels on the modulator, they look a little too high for the standars, but there are some further conversions till they reach video connector.
could you confirm, that all the output signals on the video connector at 1.0V P-P?
(actually the Chroma 1V is too high for the standard, some TV tolerates it, some others not)
2) the PAL(German) and PAL B/G (UK) standard difference influences the sound carrier, so it could not explain the situation
3) In case of NTSC and PAL difference there is no picture at all, just running garbage, because of the synch difference (25Hz and 29,97Hz). So it cannot be an explanation.
4) Thinking further the colorless output could be due to color carrier modification by intention. From outside could look like a PAL system, but hacked to SECAM.
CVBS can bring SECAM signal too, and the SVideo is just the separated chroma, luma and sync signals
PAL and SECAM is compatible with each other except color carrier information.
https://support.corel.com/hc/en-us/articles/219517967-What-is-the-difference-between-PAL-NTSC-and-SECAM
(though it does not explain OK RF signal)
If you have this Plus/4 from France or Eastern Europe, there is a chance it is modded to SECAM (just to fit to some old TVs). It was a big business back that time to make next to 64K RAM upgrade the SECAM conversion.
https://en.wikipedia.org/wiki/PAL#PAL-B/G/D/K/I
So worth to check some signs of home made soldering (but could be done by a professional too) or comparing good quality pictures to your PCB
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Posted By
MIK
on 2021-07-13
07:28:36
 | Re: Commodore 16: Black and white screen on Composite, color on the RF
If you have a modern day LCD with composite video it might be worth checking. In the last 15years or so composite video has been updated to support a lot more than the old days. If there is any colour there may be a chance it will work on a modern screen.
I don't know what has been changed but what I know Composite Video Interlaced screen modes have started to show up such as the Super Retrocade. Older TV's tend to show it in black and white, so it could be a 60hz NTSC thing. I have an old screen sat around that won't show the ZX Spectrum Vega in colour yet all others do. But yeah if there is a chance your machine is not 50hz PAL then a modern screen has a better chance of showing it in colour - that's if colour is being sent down the cable.
One last thought. If you have a composite video scart adapter also try the scart ports - as a just in case.
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Posted By
Retroshire
on 2021-07-13
11:19:52
| Re: Commodore 16: Black and white screen on Composite, color on the RF
@MMS How can I identify a SECAM modification on this Commodore 16? A strange thing on this machine are a few extra diods, but not in the video circuit. They are on C30, C10, FB 3, FB4, FB16
Modulatortype: 251847.01, 643T
@MIK black en white screen is on a CRT monitor (S-Video connection), wich displays all my other Commodore machine well.
Color on RF is on a TFT Television, wich has also a composite connection (both connected: color on RF, B/W on composite)
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Posted By
TLC
on 2021-07-13
13:07:29
| Re: Commodore 16: Black and white screen on Composite, color on the RF
RF is basically COMP + SND, modulated to a high-frequency carrier. COMP is basically LUMA + CHROMA added together (with some band limiting). For RF to have color, there already needs to be a perfect COMP. Now, in this case - there is color with RF, but not COMP. Pretty odd.
I could find the schematics of the NTSC modulator. 251844 and (alternatively) 251311. I'd risk that the PAL one produces at least the COLOR, LUM, and COMP outputs very similarly. As you can see, the composite signal which is produced for modulation to the RF carrier, is very similar to COMP (which eventually leaves the computer on the Video socket). Both of them are produced from the same source signals / just using different voltage dividers and series capacitors (R9, R10, C5 for COMP, and R7, R8, C4 for the internal comp). From the fact that there is color on RF, we can rule out any problems before the voltage divider part. Which basically leaves us with three options.
1.) There's a problem somewhere in the signal path from (the PAL equivalent of) R9, R10, C5 and on.
2.) There's a problem with the connection.
3.) There's a problem in the display.
Myself, I'd probably leaning to test options 2.) and 3.) first (because they're easier to rule out, and because they look more likely). For 2.), test if/whether COMP is really taken from PIN 4 of the DIN socket (...and additionally, whether some other Commodore machine produces colours using this cable). For 3.), checking whether a known to well working C16/C116/Plus/4 produces colours on this displays using the composite cable, should do it. For 1.) by itself (without any other knowledge i.e. no verified env at hand), one could really only make sure whether COMP has colour, using an oscilloscope.
Ps. the diodes you mention have been regularly added as overvoltage (ESD) protectors to the serial + tape port inputs.
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Posted By
Retroshire
on 2021-07-13
15:10:42
| Re: Commodore 16: Black and white screen on Composite, color on the RF
@TLC: tried another C16 on the same CRT monitor with same videocable on S-video and composite: both perfect colors
Also measured on the other C16 the voltages on the modulator pins: basically the same values
At last measured the output voltage on videoconnector pin 6 chroma: same output voltage of 1,67V
@MMS: Than we can exclude the SECAM mod.
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Posted By
TLC
on 2021-07-14
04:37:36
| Re: Commodore 16: Black and white screen on Composite, color on the RF
@Retroshire: O.K., I see. All that I can say now that this looks even more odd, given that the machine also didn't produce colour over s-video  . (This rules out anything around the luma + chroma addition part in the modulator. Also, since the RF part takes chroma off the same bandpass + buffer amp where COLOR OUT originates, chroma i.e its presence and analog properties must be correct as-is. On a related note - displays are usually very forgiving about chroma amplitude problems, they're known to catch even very subtle remnants of chroma).
Possible, further options.
- Some problem around the common GND of the Video out socket. (Whatever the problem is, it affects both composite and separate luma-chroma mode, i.e. it can't be because of some continuity problem on one of COMP or COLOR). Can be verified using a continuity tester between pin 2 of the AV socket and the machine's GND traces, even the modulator box).
- The presence of chroma (and correct amplitude) could be verified by a simple test. Switch on the machine, set border and background colours to some saturated one, say, red*. Measure the voltage on pin 6 of the AV socket vs. GND in AC setting using a multimeter. Repeat the test using a known-to-work machine. Compare the results. (--> A very crude method, given the "AC" characteristics of regular multimeters  , yet it should be good for a comparison and indication test).
- The main osc may be a bit off spec. (This is only possible if the display has different colour subcarrier tolerances for RF and baseband video modes). Was the main osc circuit of this machine modified recently (or, anytime before)?
*Ps. I was stupid. Every colours of the TED palette, by-design, have the same saturation level. You can use any colours (except black and white).
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Posted By
MIK
on 2021-07-14
04:24:40
| Re: Commodore 16: Black and white screen on Composite, color on the RF
Just as an idea... If you have an old video tap recorder you could use the RF (in) and then the video recorders composite video (out) to get a picture.
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Posted By
Retroshire
on 2021-07-14
06:05:24
| Re: Commodore 16: Black and white screen on Composite, color on the RF
@MIK creative idea, but with what purpose? To see if I get color from the videorecorder's composite? Isn't that obvious, while the RF has color?
@TLC I tried pin 2 of video and GND, there is continuity. On the main osc circuit, perhaps the trimmer is broken. Turning its wheel does not effect anything. Is there a way to test the functionality of the trimmer?
The chroma AC/GND test : AV pin 6 with color 4,3,1 and color 0,3,1 > 2,9V on C16 without color on composite/s-video, 2,7V on correct working C16
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Posted By
TLC
on 2021-07-14
05:24:19
| Re: Commodore 16: Black and white screen on Composite, color on the RF
@Retroshire: according to the schematics, this is a 40pF trimmer. I think this can only be tested by desoldering and measuring by a multimeter (with one that is capable of measuring capacitance in the pF range). Alternatively, one could desolder the trimmer and replace it (temporarily) with one of a similar range (and test whether adjustment results in some effect now).
BTW, when you made the tests over the RF connection, did adjusting the trimmer have (similarly) no effect? (I.e. did the colours remain, whatever the trimmer's setting?) That really either suggests some problem in the oscillator circuit, or, the fact that the display indeed tolerates colour subcarrier variances very generously in RF mode (maybe both). If you check the oscillator circuit (by simply inspecting the components, the solder joints, maybe checking the connectivities by a multimeter, against the schematics), can you see anything "suspicious" there?
(A small note - the fact that the trimmer can be turned around without limits, by itself, is normal.)
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Posted By
Retroshire
on 2021-07-14
07:53:59
| Re: Commodore 16: Black and white screen on Composite, color on the RF
@TLC on RF no effect when adjusting the trimmer, color on screen remains
One observation, don't know if it is relevant: with the modulator channel switch to the left I get white noise (in audio) on the television. When I set the switch to the right, the white noise disappears.
The chroma AC/GND test : AV pin 6 with color 4,3,1 and color 0,3,1 > 2,9V on C16 without color on composite/s-video, 2,7V on correct working C16
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Posted By
TLC
on 2021-07-14
08:34:19
| Re: Commodore 16: Black and white screen on Composite, color on the RF
@Retroshire: so far I thought, that only NTSC models were equipped with an RF modulator that had a channel switch (...plus the Argentinean PAL-N machines i.e. the Drean Commodore 16, that were built using stock NTSC motherboards with modifications). Honestly, I haven't seen a PAL 264 series machine with a channel switch equipped modulator yet. The machines I've seen look like this or this, and an NTSC modulator equipped one looks like this (minus hack, see switch beside the RF out socket). Doesn't your machine happen to have some kind of "special" origin, record, relevant info, ...whatever?...
To answer your question - on NTSC models, the channel switch selects the RF channel to be used (System M channel #3 or #4, VHF). The TV should be re-tuned once the switch is turned to the other position. I don't know what this kind of switch should be doing on a PAL model. All ones I could see so far, used channel #36 (System G, UHF) exclusively, and there was no switch. (There is in fact a small switch inside the PAL modulator accessible from the top, which only affects the sound modulator's carrier frequency).
The difference found between the average AC voltages of a working / this machine in question, is interesting. That's the first indication (provided that all other circumstances are identical), that this machine does something measurably "differently" to a reference model.
Ps. may be a trivial one, but, could you possibly verify, that the machine's main oscillator has a 17.73447MHz crystal?
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Posted By
Retroshire
on 2021-07-14
11:17:00
| Re: Commodore 16: Black and white screen on Composite, color on the RF
Indeed a PAL crystal
We are talking about the same switch I am afraid, thought it was a channelswitch, but I ment the small switch inside the modulator
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Posted By
TLC
on 2021-07-14
11:50:58
| Re: Commodore 16: Black and white screen on Composite, color on the RF
Yep, this looks like a regular PAL machine indeed.
The small switch toggles between producing a modulated RF signal for System G and I. ("G" has been standard for mainland Western Europe. "I" has been used in the UK, Ireland, and a couple of other countries. "G" uses a 5.5MHz sound carrier gap; for "I" this is 6MHz. Also, "I" had slightly different frequency shaping. With a strictly "G" specific tuner in the TV, one loses the sound from an "I" RF signal... I mean it's not possible to tune both to video and sound at the same time. Honestly, I have no idea why toggling the switch produced white noise in your test.)
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Posted By
Retroshire
on 2021-07-15
04:07:44
| Re: Commodore 16: Black and white screen on Composite, color on the RF
Frustrating: still no color and no clue. What can be wrong? The modulator works fine according the color RF signal and voltages on the AV pins. There is output on the Videoconnector. No GND problems. No broken traces on the PCB. It looks like there is no reason for not giving color on composite/s-video. But there has to be one, while there is no color...
I even swapped the osc trimmer with one of another C16 board. No change.
@TLC is the only thing left swapping of the modulator?
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Posted By
TLC
on 2021-07-15
07:02:38
| Re: Commodore 16: Black and white screen on Composite, color on the RF
@Retroshire yes, this is frustrating indeed. However, I'd say fixing something is always a matter of available options vs. the problem to be solved. High frequency electronics are generally difficult to diag (except for trivial or maybe moderately complicated cases) without proper equipment i.e. an oscilloscope and schematics. If one followed a systematic approach, (s)he'd check signal shapes over the signal path (from the endpoint backwards, at several points), maybe compare the results to a known to working reference if there's one, and draw conclusions from that. Also, the RF modulator is somewhat particularly difficult to diag (compared to the rest of the mainboard), because of its structure (as, there are few chances to even measure things without desoldering the box... there are SMD parts mounted on the bottom side) and because it's an analog high frequency circuit. So, my answer is, if you can get hold of an oscilloscope (can be an expensive call), then you can likely obtain more clues, and eventually find the root cause (which may or may not be easy to fix, a different matter). It's also possible to systematically replace parts with known to working ones - can be a desperate strategy as we all know , and may eventually also lead to results. Sorry, I have no more ideas  .
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Posted By
BSZ
on 2021-07-15
07:36:42
| Re: Commodore 16: Black and white screen on Composite, color on the RF
I understand correctly: the image is in colour on RF, but black&white on the Video connector's Composite out? Maybe the modulator is defective.
The modulator does not directly use the composite output signal to generate RF. There is a some component whose failure can cause this.
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Posted By
TLC
on 2021-07-15
09:06:10
| Re: Commodore 16: Black and white screen on Composite, color on the RF
@BSZ What makes this kind of inexplicable for me is, that he has no colour on separate luma-chroma either. Luma and chroma are mixed-in from the same signal sources for either cases. The difference is that both COMP out / and the internal (for-modulation) composite signal are derived using dedicated voltage dividers and coupling capacitors. I could well explain the lack of colour on COMP from some problem of the chroma coupling capacitor in the RF modulator, but not the fact that there's no valid colour on separate luma-chroma.
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Posted By
Hifi
on 2021-07-15
09:26:33
| Re: Commodore 16: Black and white screen on Composite, color on the RF
Helló,helló Újra ITT vagyok...... Alig vártam, hogy BSZ is beszóljon.... Helló BSZ! SZERINTEM a kapcsolásirajz alapján ha valaki kicseréli a PAL kristályt NTSC kristályra és a TED IC-t NTSC-re állítja, a KIMENETI COLOR-nak NTSC-re KELL hogy beálljon. DE várom a véleményeket! Még én is tanulhatok ennyi ÉV után, (65éves nyugger....) mivel ÉN még nem használtam NTSC módban az RF kimenetet! Szerintem is az RF modult kellene kicserélni (nálam szerviz gyakorlatból 3 darab van még.....természetesen csakis ígyen!)!!! SZERINTEM (2) (már írtam erről előző fórumban....az RF modul alkalmas a PAL/NTSC COLOR feldolgozására) a MITSUMI RF modul OKOS MODUL. DE ha rosszul tudnám, KÉREM a VÉLEMÉNYEKET! A JÓ PAP IS HOLTIG TANUL, pláne a jó szakember! Üdv.: HiFi of TLT
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Posted By
BSZ
on 2021-07-15
09:27:26
| Re: Commodore 16: Black and white screen on Composite, color on the RF
Yes, some information is definitely missing. The first step would indeed be to check whether there is a colour carrier on the composite and colour out is working.
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Posted By
TLC
on 2021-07-15
12:08:00
| Re: Commodore 16: Black and white screen on Composite, color on the RF
@HiFiofTLT: a Kolléga nem akar NTSC-re konvertálni, hanem a gyári, PAL C16-ján nincs szín video-kimenetről, miközben az antenna-kimenetről van. "Látatlanban", jó eséllyel tényleg a modulátorban lehet valami furcsaság, de nem tudom bizonyítani (...és nem erősködtem a modulátor cseréjén, mert h. azt ki kelljen forrasztani, azt én is kétszer meggondolom, vákuumos kiforrasztóval is).
Függetlenül a konkrét géptől, csak az NTSC-konverzióra visszatérve... A kvarc- és a Kernal cseréjével valóban egyszerűen át lehet állni egyik normáról a másikra. Alapsávon, lehet így PAL-ból NTSC-s gépet csinálni- és viszont. RF-en ellenben a dolog nem működik "szabályosan", mert az európában- és amerikában használt tévésugárzási szabványok is sok ponton különböznek (más csatornaszélesség, más hangvivő, más szűrési jelleggörbe). Konkrétan ezért az európai- és amerikai gépeket más modulátorral szerelik. Szóval RF-en a dolog így nem "szabályos", bár a modulátornak megfelelő tuneres tévével talán még így is működik.
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@HiFiofTLT: our friend in fact didn't want to convert his machine to the NTSC standard. The problem he's facing is that his stock PAL standard machine has no colours from AV, whilst it does from RF. Yes, I also suspect something irregular in the RF modulator, but I can't prove that. (I didn't insist on replacing the RF modulator, because, neither I desolder that unit without a good reason, even with having a vacuum desoldering station at hand).
Speaking of the NTSC conversion, yes, one can get away with just replacing the crystal and Kernal ROM, and this works perfectly... at least for baseband video. For RF, this won't work, since, European and American RF modulation standards do differ significatly. European and American machines were equipped with different RF modulators to solve this. RF may still work for local TV sets for a modifief machine (say, NTSC video over European RF), yet, this won't imply standard RF for the respective video.
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Posted By
Retroshire
on 2021-07-15
10:30:22
| Re: Commodore 16: Black and white screen on Composite, color on the RF
Thank you all for thinking with me. I am afraid the most reasonable thing to do for me is swapping the modulator, wich is not an easy task, though I have a trashboard in stock with a hopefully working modulator.
I learned from all your comments. Thanx a lot.
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Posted By
MIK
on 2021-07-15
12:43:39
| Re: Commodore 16: Black and white screen on Composite, color on the RF
Fingers crossed!
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Posted By
Retroshire
on 2021-07-19
12:24:10
| Re: Commodore 16: Black and white screen on Composite, color on the RF >> terror machine!!!
OMG what a terror machine!!!
Swapped the modulator >>>>> still no color, only black and white screen on the composite/s-video.
Already tried to adjust the osc trimmer, no effect.
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Posted By
BSZ
on 2021-07-19
15:41:02
| Re: Commodore 16: Black and white screen on Composite, color on the RF
Trivial questions:
The video connector is OK? All of used connections is fine? The video connector GND is OK? The colour output not short-connect to any signal?
Adjusting the trimmer has no effect of RF signal either?
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Posted By
Hifi
on 2021-07-19
15:59:25
| Re: Commodore 16: Black and white screen on Composite, color on the RF
Helló,helló ÚJRA ITT vagyok..... Háááát mit is mondhatnék..... Mivel az RF kimeneten van color, ezek szerint a TED jónak mondható..... azt a fránya 8 pólusú DIN VCR csatlakozót és környezetét KELL alaposan szemügyre venni! Például a GND ill. a kompozit PIN nem érintkezik...... forrasztási hiba, szakadás és persze zárlat is lehet.... mivel illesztő funkciói (75 ohm) vannak az RF MODULnak ( a le- és szétosztások miatt!) még lehet COLOR az RF MODUL kimenetén!!!!! Találkoztam szerviz gyakorlatban rossz GND kontakttal és a hang KERREGETT ill. BRUMMOS volt! ENNYI! Üdv.: HiFi of TLT
| Re: Commodore 16: Black and white screen on Composite, color on the RF
Hello, hello, here I am AGAIN... Well, what can I say... Since the RF output does have color, we can the TED is fine... that damn 8-pin DIN VCR connector and its environment MUST be given a thorough look! For example, GND resp. the composite PIN is not in contact... there may be a soldering fault, an open circuit and of course a short circuit... since the RF MODULE has interface functions (75 ohms) at the output!!! I met a bad GND contact in service practice and the sound was NOISY! THAT'S IT! Bye: HiFi of TLT
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Posted By
Hifi
on 2021-07-19
16:23:15
| Re: Commodore 16: Black and white screen on Composite, color on the RF
Helló BSZ! Először is az RF MODULban hiába tekergeti a trimmer kondit , a COLOR nem fog változni-----ha pedig a PAL oszcillátornál tekerné a trimmer kondit, az sem fog változást okozni a többszörös frekvencia osztások miatt! Ha rosszul tudnám csak nyugodtam SZÓLJÁL BE, még tudok tanulni!!!! Ha pedig az RF MODULban a potmétert tekergeti, az pedig csak a hang moduláció hangerején változtatná az RF kimeneten! Üdv.: HiFi of TLT
| Re: Commodore 16: Black and white screen on Composite, color on the RF
Hello BSZ! First of all, even if you wind the trimmer conduit in the RF MODULE, COLOR will not change ----- and if you wind the trimmer conduit at the PAL oscillator, it will not cause a change due to multiple frequency divisions either! If I'm wrong feel free to let me know, I can still learn !!!! And if you turn the knob in the RF MODULE, it would only change the volume of the sound modulation on the RF output! Bye: HiFi of TLT
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Posted By
TLC
on 2021-07-19
16:35:39
| Re: Commodore 16: Black and white screen on Composite, color on the RF
@RetroShire not happy to hear that... :-/ At least, the RF modulator can be ruled out completely. What I'd do in this case, is something what BSZ has already suggested. Take the motherboard plus a continuity tester, and do a static verification of the AV (DIN8) socket's area against the schematics. I'd check whether the connections were really there, and also, whether there were any unintentional shorts. (Thinking it over, supposed that this machine is a recent "find", there's a chance that it never in its life was used together with a monitor, but TV sets only. That is, the AV color problem might have gone unnoticed in its whole life ie. it can potentially be there from production). Also, finally I'd take a DIN-8 plug, strip it, connect the "plug" part to the AV socket, and check whether all pins had good contacts to the socket pins (--> continuity between pins and the socket's solder pads, and also any potential shorts). Other than that, I'm clueless.
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Posted By
BSZ
on 2021-07-19
17:02:37
| Re: Commodore 16: Black and white screen on Composite, color on the RF
@Hifi: Természetesen nem az RF modulátorban levő trimmerekről van szó, azokat ne tekergesse senki sehova! Amiről szó van, az az órajelgenerátor Quartz finomhangolására szolgáló trimmer-kondenzátor.
| Re: Commodore 16: Black and white screen on Composite, color on the RF
@Hifi: Of course, we are not talking about the trimmers in the RF modulator, don't wind them anywhere! What we're talking about is the trimmer capacitor for fine-tuning the clock generator Quartz.
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Posted By
Hifi
on 2021-07-19
17:03:22
| Re: Commodore 16: Black and white screen on Composite, color on the RF
Hi BSZ! Mivel a PAL kristály "soros" módban van megrezgetve, az a kis trimmer csak egy "játékszer" a Kristály saját frekvenciájára, PERSZE JÓ ha kristály a névleges (PAL) frekvencián rezeg! Üdv.: HiFi of TLT
| Re: Commodore 16: Black and white screen on Composite, color on the RF
Hi BSZ! Since the PAL crystal is vibrated in "serial" mode, that little trimmer is just a "toy" for the Crystal's own frequency, OF COURSE it's GOOD if the crystal vibrates at the nominal (PAL) frequency! Bye: HiFi of TLT
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Posted By
BSZ
on 2021-07-19
17:39:41
| Re: Commodore 16: Black and white screen on Composite, color on the RF
@Hifi: Persze, de az a trimmer arra pont jó, hogy annyira elhangold a frekvenciát, hogy egy régi, hagyományos TV színdekódere már kikapcsoljon tőle. (Azaz pont hogy FF kép lesz a végeredmény.) A kérdés arra vonatkozott volna, hogy az RF kimeneten levő színes kép se romlik el, ha azt hangolja? (Meg persze kérdés az is, hogy a mai "modern" TV-k mennyire háklisak erre.)
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Posted By
TLC
on 2021-07-20
09:08:39
| Re: Commodore 16: Black and white screen on Composite, color on the RF
@BSZ
Posted By TLC on 2021-07-14 05:24:19 : "...BTW, when you made the tests over the RF connection, did adjusting the trimmer have (similarly) no effect? (I.e. did the colours remain, whatever the trimmer's setting?) That really either suggests some problem in the oscillator circuit, or, the fact that the display indeed tolerates colour subcarrier variances very generously in RF mode (maybe both). ..."
Posted By Retroshire on 2021-07-14 07:53:59 : "...@TLC on RF no effect when adjusting the trimmer, color on screen remains"
Posted By Retroshire on 2021-07-15 04:07:44 : "...I even swapped the osc trimmer with one of another C16 board. No change."
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Posted By
Retroshire
on 2021-07-20
04:11:37
| Re: Commodore 16: Black and white screen on Composite, color on the RF
Today I swapped the Video connector. Not resulting in color. No visual problems beneath it.
When the modulator is ok, the videoconnector is ok, the videocable is ok, the color signal from the TED is ok then it must be one of the components in the video circuit. So one of the ceramic or elco condensators is main suspect?
Already swept: CT1 trimmer, Q3 transistor, EM4 ceramic, C11 ceramic, C12 ceramic
Next swap actions: EM3, EM5, C31
Any suggestions for other swappings?
To bad I don't have a oscilloscoop....
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Posted By
MIK
on 2021-07-20
07:01:10
| Re: Commodore 16: Black and white screen on Composite, color on the RF
If a fix can not be found...
Normally RF comes from the composite video signal on say a ZX Spectrum for example, people do a small hack on spectrum to turn the RF out in to composite video. Not sure how Commomdore went about RF but maybe it can be changed to composite. If it could be done that leaves the video port for sound out.
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Posted By
TLC
on 2021-07-20
09:07:25
| Re: Commodore 16: Black and white screen on Composite, color on the RF
@Retroshire I think the circuit around Q3 (which is a sound buffer amp + mixer + low pass filter) should make no difference w/respect to video, even if it was faulty. C11 / L1 make a low-pass filter for supply voltage (to verify, measure voltage at the "modulator-end" side of L1; 5V +- some tenths is perfect). That IMHO leaves the EMs (3,4,5) between the modulator and the AV socket, FB13 on GND, and possible wire/solder/via shorts and breaks as options.
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Posted By
Hifi
on 2021-07-20
09:10:36
| Re: Commodore 16: Black and white screen on Composite, color on the RF
Helló,helló ÚJRA ITT vagyok..... Hmmm-hmmmm........ Kedves Kollegák..... csodák nincsenek, csak ha MI csináljuk! Ezek után CSAK az fránya KÁBEL lehet a gyanús számomra! Miért? A régebbi időkben közelemben a floppy 1541/2-hőz a 6 PIN-es VHS videóhoz használt kábelt próbálták használni (1 az 1-hez adat átvitel..... aki érti az érti...), mivel nem kaptak kábelt a floppy-hoz. Nem sok sikerrel..... olvasás-írás hibát jelzett! Akkor készítettem nekik olyan kábelt, amiben a ki- és bemeneti kábelek mind SPECIÁLIS 75ohm lezárású és mind ezáltal KÖLÖN árnyékolt kábelek voltak! Nahát.... ÉS LŐN csoda a floppy TÖKÉLETESEN működött!!!! Az EREDETI kábel is ilyen! Nálam saját gyártású több mint 6méteres SPECIÁLIS 75ohm kábel viszi a COPOZIT jelet a monitorhoz (Videoton Super Color PAL/SECAM televízióhoz), persze az AUDIO megfelelő kábellel szintén csatlakoztatva van a monitorhoz. Tehát a kimeneti szintek BŐSÉGESEN elégségesek HOSSZÚ kábelek esetén is! A kábelek minősége és szakszerű használata azért szükséges, mert az úgy nevezett "visszatükröződés" (a kábelen belül.....nagy frekvencia....) sok PROBLÉMÁT okozhat! Az a KÁBEL nagyon GYANUS!!!! Remélhetőleg a MONITOR vagy TV megfelelően feltudja dolgozni ezen jeleket! Ezek a "félvezető-digitális SZŐRNYEK" mindenre képesek ,csak hogy MINKET bosszantsanak! HÁT ennyit innen a távolból. Üdv.: HiFi of TLT
| Re: Commodore 16: Black and white screen on Composite, color on the RF
Hello, hello HERE I am HERE AGAIN... Well-well... Dear Colleagues ..... there are no miracles, unless WE do them! At this point, ONLY the damn CABLE looks suspicious to me! Why? In the old days, I tried to use the cable used for the 6 pin VHS video near the floppy 1541/2 (1 to 1 data transfer ..... who understands that ...) because they didn't get a cable for the floppy -to. Not much success ..... indicated a read-write error! Then I made them a cable in which the output and input cables were both SPECIAL 75ohm terminated and thus SPECIALly shielded cables! Well .... AND WONDER wonder the floppy worked PERFECTLY !!!! The ORIGINAL cable is like that! In my case, a special 75ohm cable of more than 6 meters produced by me carries the COPOZIT signal to the monitor (Videoton Super Color PAL / SECAM television), of course the AUDIO is also connected to the monitor with the appropriate cable. So the output levels are ENOUGH enough for LONG cables! The quality and professional use of the cables is necessary because the so-called "reflection" (inside the cable ..... high frequency ....) can cause many PROBLEMS! THAT CABLE IS VERY SUSTAINABLE !!!! Hopefully your MONITOR or TV can handle these signals properly! These "semiconductor-digital WINGS" can do anything just to annoy US! That's all from me from far away. Bye: HiFi of TLT
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Posted By
BSZ
on 2021-07-20
16:33:33
| Re: Commodore 16: Black and white screen on Composite, color on the RF
@TLC: I lost the thread a long time ago.
@Retroshire: Sorry, but I'm just guessing. It's not a common problem. I would also check the power supply of the modulator, as TLC wrote. However... The oscillator's trimmer does not change the picture... Maybe the problem is the quartz itself? 35+ years old electro-mechanical component... Maybe it is no longer accurate enough and cannot be tuned enough? For some reason the TV tolerates the deviation better on RF than on CVBS / S-Video. Maybe replacing the quartz might be worth a try, just in case. Assuming you haven't already done so.
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Posted By
Retroshire
on 2021-07-21
07:21:52
| Re: Commodore 16: Black and white screen on Composite, color on the RF
@TLC checked the voltages on L1 and C11 on modulator end: gives a proper 5,1 VDC.
@BSZ I will focus on the quartz: don't have a PAL quartz, while already harvested from my salvage C16 board and put it in a NTCS Plus/4 machine, wich is PAL now (also replaced the kernal in it, but it is a working PAL machine now). But: I got that NTSC crystal from it. Let's do something crazy: I make the Black and White C16 NTSC with it, put a NTSC kernal in it, let see what it does . My CRT monitor can do both PAL as NTSC, so that ishould not be a problem.
RESULT: A NICE BLACK AND WHITE NTSC SCREEN, ADJUSTING TRIMMER NO EFFECT >> NO COLOR :(
So: also the crystal is not the problem....
@HiFiofTLT the videocable is proper shielded and works correct with all my other machines. Though I recognise your experience with 1541's and interference with monitorfrequency's.
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Posted By
Hifi
on 2021-07-21
08:51:46
| Re: Commodore 16: Black and white screen on Composite, color on the RF
HEYYyyy BOY Küldök NEKED TED IC-t (azaz 1db TED IC.....) CSAK azért, hogy talán a TED ROSSSSSZ......Ahhhhh.......!!!!!),és talán megoldja a PLOBLÉMÁKAT!!!!! Küldj CÍMET és teljesen ÍGYEN küldöm; MERT MI plus/4-esek (C16....C116....) támogatjuk EGYMÁST!!!!!! Aki a FÓRUMok előző részeit olvasta, (Persze..... AKI Nyomon KŐVETI......) már találkozhatott olyan BESZÓLÁSAIM-ban ,hogy a TED FEKETE-FEHÉR módban működött ill. a SZÍVÁRMÁNY színeiben POPPÁZIK.....(121 COLOR......azért a 121szin nem semmi......ahhhh..... YEEEEAAAHHHH....)!!!!!! Hááátttt ENNYÍT ÜDV.: HiFi Of TLT
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Posted By
Retroshire
on 2021-07-21
11:03:00
| Re: Commodore 16: Black and white screen on Composite, color on the RF
@HiFiofTLT That is very generous of you, but I have tried other TED's with......no result.
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Posted By
MMS
on 2021-07-22
04:45:12
| Re: Commodore 16: Black and white screen on Composite, color on the RF
I tried to find similar cases from the past on other forums, but I could not.
Most of the cases incompatible signals, or bad video cables used, but not in this case.
I agree with one of Hifi's previous comments.
As the TED, the xtals, the video cable closed out, and the RF tuner picture has color. The later proves, that on the board the color signal exists from TED, but fail to reach the video cable via the A/V socket, and that one receives the color signal from tuner via the CN7.
As the modulator generate the composite signal and passing the color signal to A/V too, the failure should be in the modulator or the coils between the modulator and the CN6 connector. I do not say the crystal, as then the RF output also should not have a proper color.
The only logical answer is that there is a defective component / broken track / cold soldering between the video socket and the tuner. As the Composite and the separated Chroma signal also have the failure, I may close out the EM3-EM5 coils too. I highly suspect some bad component or cold soldering within the modulator.
(a small crack could be at the bottom of the connector too. It you press it with the multimeter measuring pins, it may cure it temporarily).
Please try to touch or even move every little component in the tuner to close out bad connection betwen the component and the board.
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Posted By
Hifi
on 2021-07-22
08:36:12
| Re: Commodore 16: Black and white screen on Composite, color on the RF
Helló,helló ÚJRA ITT vagyok...... Helló MMS! Végre van egy PLUSSYS EMBER, aki szépen összefoglalta-OKOSAN- amiről én IS eddig (több alkalommal.....), szó szerint POFÁZOK!!!! Vagy értek valamihez, vagy nem; AKKOR ÉN IS szakemberhez viszem a hibás (általam nem ismert......) berendezést! NAGYON SZÉPEN KÖSZÖNÖM hozzászólásodat! Üdv.: HiFi of TLT
| Re: Commodore 16: Black and white screen on Composite, color on the RF
Hello, hello, HERE I am AGAIN... Hello MMS! Finally there's a PLUSSY MAN who has summed it up nicely - SMARTLY - which I HAVE been trying to TALK about (several times .....)!!! Either I understand something or I don’t; THEN I'll take the faulty equipment (which I'm not familiar with) to a specialist! THANK YOU VERY MUCH for your comment! Bye: HiFi of TLT
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Posted By
BSZ
on 2021-07-22
09:21:15
| Re: Commodore 16: Black and white screen on Composite, color on the RF
@Retroshire: Quartz is again a tip that didn't work.  What have you replaced so far? Everything except the PCB and the filters. I also thought about these filters; but I remembered that they are also plain ferrites, like in plus/4. (What could be wrong with them? If they are just not the right value...) But in C16 these are LC filters (EM3/4/5), not just ferrites, as you can see in the picture from MMS. After all that sucking I would replace them with a short circuit as a test. (Of course, I would short the in+out, the GND is not connected.)
@Hifi: Sajnos 2021-ben ezekhez nem nagyon találsz szakembert a közeledben. Így sokszor marad a "csináld magad" mozgalom!
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Posted By
Hifi
on 2021-07-22
12:22:25
| Re: Commodore 16: Black and white screen on Composite, color on the RF
Helló,helló....... IGEN..... a rajz alapján a EM4 szűrőjének kapacitása ha zárlatos, akkor nem jut a kimenetre a COLOR jel. Persze ha ilyen szűrő van a gépben; több verziós nyákkal találkoztam már! DE ekkor is az RF kimeneten lehet COLOR jel (az RF modulban lévő többszörös szét-és leválasztások miatt....)! Többször, többen már írták a szakadás és zárlat lehetőségét!!! Ezt egy MŰSZERREL már ki kellet volna mérni! Üdv.: HiFi of TLT
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Posted By
MMS
on 2021-07-22
15:31:51
| Re: Commodore 16: Black and white screen on Composite, color on the RF
@HiFiofTLT: Köszi! Viszont ha csak az EM4 pusztult meg, a Composite kimenetnek jónak kellene lennie.
Vagy mindkettő EM rossz, vagy ahol a modulátorban a két jel még közös, ott lesz a gond
Eng: Thanks! On the other hand if only the EM4 is defective, the composite signal should be still OK. So both EM should be NOK, or somewhere in the modulator (where the two are still originated from one color signal) should be tha issue.
Unfortunately none of the EM3-5 visible on the previous photos.
This area could be an area of interest (it is from a saved big resolution MOBO picture from my collection)
BTW (not directly linked to the topic) maybe I saw on the previous photo a not 100% soldering (maybe I am just not well evaluated, but you can compare it to the above picture):
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Posted By
Hifi
on 2021-07-22
15:38:57
| Re: Commodore 16: Black and white screen on Composite, color on the RF
Hey Hóóó........ IGEN,igen...... Az előző hozzászólásomhoz egy kis JAVÍTÁS! Persze ha zárlat lenne feszültséget sem mérhetne az RF MODUL kimeneteken! Persze igaz az, hogy ezekben a kimeneti zavarszűrőkben lévő kerámia kondik (átvezetés.....) okozhatnak meglepetéseket!!!! Hát mit is mondhatnék még..... Üdv.: HiFi of TLT
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Posted By
Hifi
on 2021-07-22
15:50:15
| Re: Commodore 16: Black and white screen on Composite, color on the RF
Hey Hóóó...... Mivel már cserélt RF MODULT, valószínűleg JÓNAK mondható! Üdv.: HiFi of TLT
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Posted By
Retroshire
on 2021-07-22
16:26:46
| Re: Commodore 16: Black and white screen on Composite, color on the RF
OK gentlemen, don't fall of your chair, I found some color, ugly though. But.....strange!!!!!
I tried another television, wiith more specific screensetting. On my Sony Bravia, composite output from videoconnector I got this screens:
@MMS I remember you talked about SECAM and look on what screen I have color! The SECAM. How strange!!!
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Posted By
MMS
on 2021-07-22
16:45:44
| Re: Commodore 16: Black and white screen on Composite, color on the RF
Wow, surprise
for the the most interesting thing that playing it as NTSC still provides a readible picture (I did not expect that)
Well, still that one is still not a legit purple color as the Diag264 color scheme, but close enough... RF color is really different? Or it is just the TV's color rendition?
Would be great to see a really colorful demo, like Sabrina demo from Fire team
(Oh my gosh! it is already 11 years old, I remember to the release of it as if it would happen few years ago).
Those strong color burst patterns are really strange.
Just guessing: may it look like a semifinished SECAM conversion? as SECAM need some buffers to be accurate, if I remember well. If you do not have it, it may have a pattern (pls don't shoot me if I am wrong).
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Posted By
Retroshire
on 2021-07-23
03:23:12
| Re: Commodore 16: Black and white screen on Composite, color on the RF
@MMS I forgot to mention that before these pics I put back the PAL crystal / PAL kernal
RF color is the same.
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Posted By
MMS
on 2021-07-23
06:03:02
| Re: Commodore 16: Black and white screen on Composite, color on the RF
OFF
A good read about the systems and the most comprehensive comparison of them, including RF and composite signal generation:
(BTW based on this the SECAM should have the best, cross-talk free color picture)
https://www.yumpu.com/en/document/read/12034920/chapter-8-ntsc-pal-and-secam-overview-deetc
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Posted By
Hifi
on 2021-07-23
11:49:25
| Re: Commodore 16: Black and white screen on Composite, color on the RF
Helló,helló.......Ahhhhhhhh....... és még egyszer Ahhhhhhhh....... HA valaki a kezében kerülő berendezést, az lehet mechanikus, elektromos és főleg DIGITÁLIS számítástechnikai berendezést (PC, TV, VHS-video.....CD-lejátszó...CommodorePlus/4.....C16....C116.....) szeretné használni, ILLŐ előtte elolvasni a FELHASZNÁLÓ utasítást!!!! AKINEK NEM INGE, NE VEGYE FEL!!!!! Aki érti AZ ÉRTI! NEM AKAROK SENKIT MEGBÁNTANI....... Aki a számítástechnikához fanyalodik, van EGY bizonyos SZINT....... magyar idegen szavakkal, szoftver és hardver ismeretekkel kell hogy rendelkezzen! ITT most nem a JAVÍTÁSOKRÓL ill SZERVÍSZ gyakorlatokról beszéltem! Ennél az esetnél egy másik VCR MONITOR ill. MEGFELELŐ TV készülék megfelelő BEÁLLÍTÁSÁNÁL (NTSC-1-2-XX (jajjjjjj....), PAL, SECAM (ahhhhhhh......) már kiderülhetne a probléma!!!!! IGAZ ehhez is KELL egy kis gyakorlat! Ennyit INNEN a TÁVOLBÓL........ Üdv.: HIfI of TLT
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Posted By
BSZ
on 2021-07-25
16:38:31
| Re: Commodore 16: Black and white screen on Composite, color on the RF
@MMS: "Just guessing: may it look like a semifinished SECAM conversion?"
I think, not. The easiest way to convert PAL to SECAM, required to use one transcoder IC. This would be visible.
@Retroshire: I can take a picture like that:
This is what it looks like when a SECAM decoder receives a PAL source. But you can see is that the output image is in colour, this is good news! I'm getting suspicious of those filters, could it be the wrong type in the machine?
@Hifi: Ne stresszelj ennyit!  Nem a világ utolsó gépét próbáljuk itt megmenteni fogalmatlanul!
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Posted By
Retroshire
on 2021-07-27
05:03:23
| Re: Commodore 16: Black and white screen on Composite, color on the RF
@BSZ You mean the EM3, EM4, EM5 ceramics? In the parts list of the service manual there are no specifics.
Your screenresult looks like mine indeed.
The PCB flies to Italy to be examined by a pro
To conclude this long thread and assistence of you all, I hope he can speak a final word about cause and effect.
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Posted By
Hifi
on 2021-07-26
17:44:03
| Re: Commodore 16: Black and white screen on Composite, color on the RF
Helló,helló ÚJRA ITT vagyok..... Helló BSZ of NST! KÖSZÖNÖM a hozzászólásodat! NOW and FOREVER PLUS/4 SCREEN 2021! Good-Bytes: HiFi of TLT
| Re: Commodore 16: Black and white screen on Composite, color on the RF
Hello, hello, HERE I am AGAIN... Hi BSZ of NST! THANK YOU for your comment! NOW and FOREVER PLUS/4 SCREEN 2021! Good-Bytes: HiFi of TLT
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Posted By
MCes
on 2021-07-27
12:43:57
 | Re: Commodore 16: Black and white screen on Composite, color on the RF
Ok, I'm the italian one....
I'm very curious to test the board with an oscilloscope!
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Posted By
Retroshire
on 2021-07-29
03:19:26
| Re: Commodore 16: Black and white screen on Composite, color on the RF
@Mces hope you can speak the final word in this case
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Posted By
BSZ
on 2021-07-29
16:59:36
| Re: Commodore 16: Black and white screen on Composite, color on the RF
@Retroshire: You mean the EM3, EM4, EM5 ceramics? In the parts list of the service manual there are no specifics.
Yes, I'm thinking of these. Unfortunately, the values for the other filters are not there either. (Have these ever been replaced?) If these are the reasons, the parts are probably good, just not good value. I also wonder about the reasons. Hope to find out soon!
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Posted By
Retroshire
on 2021-07-31
07:28:01
| Re: Commodore 16: Black and white screen on Composite, color on the RF
@Mces solved the problem. In short: a broken capacitor trimmer + a broken crystal.
He wrote to me in an email:
Hi Iwan,
I tested your board (CVBS cable) with a little monitor and.... it's colour is working!
With a second monitor (CVBS cable) it has no colour....
Hypothesis: something is constantly on the border between "work" and "doesn't work",
First suspect: clock frequency (color coding is derived from the same clock), must be 17.734472 Mhz (+/- 200 ppm: ppm = parts per million).
Measured 17,727060 MHz (-418 ppm) TOO MUCH FAR!
Variable capacitor does not tune it, desoldered and tested: it is not good (too less capacitance).
Replaced the capacitor trimmer with proper 40pF, but it doesn't tune properly....
Replaced quartz, now clock can be tuned!
Switched on for 15 minutes (thermal stability reach) and tuned to 17,7344558 MHz (-1 ppm: better than frequency counter precision).
Board test: colour is present on both monitors!
Why on RF your monitor work?
Inside the color decoder there is a quartz which must be locked with the C16 color frequency,
at board powering on C16 frequency has to be inside the "capture range" of the colour decoder, and after to be locked the C16 frequency can remain inside the "lock range".
https://www.rfwireless-world.com/Terminology/PLL-lock-range-vs-capture-range.html
The "capture range" is narrow than "lock range", so my theoretical hypothesis is:
The analogical process of RF modulation (into C16) and RF tuning (into TV) generate a little bit of noise inside the signals,
so it's possible that the noise result in a little jitter
https://en.wikipedia.org/wiki/Jitter
that can permit to lock the decoder, so the decoder remain locked ("lock range" is bigger than ""capture range")
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Posted By
MMS
on 2021-07-31
17:07:43
| Re: Commodore 16: Black and white screen on Composite, color on the RF
Great news, color is ON again!
@MCes: thank you for solving the mistery and curing one more 264 series machine!
(BTW just an idea: maybe the older RF standard just have higher tolerance (%) than the Composite standard, and it may accept worse quality signal, as still treat it as OK, within tolerance signal).
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Posted By
BSZ
on 2021-08-04
10:45:39
| Re: Commodore 16: Black and white screen on Composite, color on the RF
@Retroshire: I'm glad that there were some good ones among the tips. (But to find out, you need the right instrument.) In addition, there were problems with two components.
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