Posted By
bailsofdoom
on 2003-04-08
|  Assistance required after recent purchase of a C16
Greetings all!
I found out about this website and forum through a kind fellow on Lemon64, Adam Huemer. He thought someone might be able to help with a problem I've come accross testing a second hand Commodore 16 I found at a second hand store. My essential problem lies in testing the C16.
I'm not certain whether there is an internal chip problem or something, but I simply cannot seem to get any external output at all.
At first I used a friend's video port connection (the single port which leads into the video socket on the c16, to the three blue/white/yellow) then using the same frequency as the c64, tried using my tv with the usual RF connection.
On both tests, I seem to only get a blank/black screen. The power is on, with no visible/aural nasties....but I just can't work out what could be wrong.
My gut instinct says the problem is probably not fixable, but I won't give up seeing as how its the first machine of its kind I've ever owned!
Any ideas? 
Cheers in advance,
Rob Bailey
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Posted By
Obermotz
on 2003-04-08
| Assistance required after recent purchase of a C16
Hi,
most likely the TED chip in your C16 is fried. It is a common problem with this kind of computer 
Peter
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Posted By
MIK
on 2003-04-08
 | ..
I would agree with Obermotz. Using the video port was a good idea, but sadly something is at fault with your C16
If you didn't pay a lot for it then it might be worth keeping it as a spare. Power Adaptor, 1531, outer case and keyboard might be useful if you get another.
If not, take it back and try eBay.
regards,
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Posted By
bailsofdoom
on 2003-04-09
| Assistance required after recent purchase of a C16
Thanks for the feedback guys!
Three people have now put forward this same view that the TED chip is fried, which is odd considering that it is just the sound chip is it not? I've had SIDS go on me before, but still have been able to get some kind of output on c64s.
There's obviously different mechanics at work of course!
It is a shame, but I haven't any software by which to test it at this stage anyway.
I think I will keep it just in case I find another in my travels...it is an artifact of Commodore history after all!
The C16 came with a Commodore Monitor which sadly is also faulty, despite being compatible with my c64. It can be on for about 10-15 minutes before the colour drains out from the screen, starting from the top, then finally disappearing completely in the centre. I very much doubt there'd be ways of fixing this, or am I being too pessimistic here?
I only paid $15 australian for the box everything came in which is nothing really. It was a case of being in the right place at the right time. I'm disappointed, but I'm sure other artifacts will pop up!
Just a final query:
The C16 never actually came with any peripherals other than the monitor itself. I've been using a regular 240v C64 black cased power supply - would this make any difference?
I'm doubting it, but thought I'd best be sure! 
Cheers,
Rob
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Posted By
Csabo
on 2003-04-09
| Re: TED Chip
Actually the TED (short for Text Editing Device, or some sources say Text EDitor) is the heart of the Plus/4. It takes care of all the graphics, sound, cursor, timers, etc. The C64 had the separate VIC and SID, but it's not the case with the C16 and Plus/4.
I'm not sure whether the C64 power supply would cause a problem, maybe someone else knows more on that.
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Posted By
JamesC
on 2003-04-09
| C16 Power Supply
is a 9V 1A on the computer end, the C64 and +4 power supply are 9V on one pin and 5V on another. You may not have enough voltage to the system.
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Posted By
JamesC
on 2003-04-09
| Power Supply Followup
This is the proper power supply for the C16: Ebay US Link
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Posted By
Ulysses777
on 2003-04-09
| Power supplies
There's a variety of power supplies for the C16/Plus4 (and other Commodore computers). As well as the one mentioned above (which is an American power supply), there's this, this, and this style. It's unlikely that it's a C64 power supply he's using, as they have a completely different connector. (C16/Plus4 is square, C64 is circular)
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Posted By
Ulysses777
on 2003-04-09
| Oops...
Correction: the C16 is a single pin DC connector, and the C64 uses a DIN connector
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Posted By
bailsofdoom
on 2003-04-13
| ooops again! ;)
Thanks for picking up on that Ulysses...
Not sure what got me confused about the power connection there lol, perhaps it was because I was testing a C64C as well!
The power connection I've been using to test the C16 has been a Sega master system Dc/240 v. Now that I've cleared that up, I don't suppose this would make a difference?
Thanks for the links as well so that I now know what an original c16 powerpack looks like!
I once had one of the C16 datasettes, although I didn't realise it at the time! (the dark grey model) I thought it was quite cool that the top half was adaptable also for the c64!
Anyhow, shall be picking up another 1541 II tomorrow - which drives were compatible with the C16?
Cheers,
Rob
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Posted By
Csabo
on 2003-04-13
| Re: Drives
Any floppy drive which you can use for the C64 also works for the C16 and Plus/4. (Although it's not true backwards: the 1551 was specifically made for the Plus/4, and it doesn't work with a stock C64.)
Thank god they made the drives compatible. It's bad enough that the tape devices and the joysticks were different.
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Posted By
Hacox
on 2003-04-14
| Re: Assistance required after recent purchase of a C16
I also have a plus4 which shows nothning on the tv, if i switch it on. I was told that it could be the sid. But now i think that is not the case because of a little thing i discovered.
I have switched on and off the powerswitch very very fast. And some times I get a picture on the screen. For example a running Cursor which ends in the message break in ??? or the plus 4 prints basic but not the normal complete startup picture.
So I think it could be the cpu which is dead. I will try to exchange it with a c64 cpu, which is easier to get and don't need the serial port. I will use a CPU adapter, of course.
Hope this helps you, try this fast switchig and look if you can get a picture
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Posted By
JamesC
on 2003-04-14
| Hacox ->
If you get a ?BREAK IN message the CPU is functioning. Either the system is not initializing correctly (function HI and LO roms) or the TED (chip in the metal cage) isn't maintaining the video and RAM refresh signals.
Always be sure that socketed chips are firmly in their sockets -- loose connections are a pain to track down, and can give different results depending on their temperature and the temperature of the surrounding area.
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Posted By
Bacon
on 2003-04-15
| 6510 and 7501 are not compatible
I don't think you can replace the Plus/4 7501 CPU with a C64 6510 CPU, even with an adapter. For one, the 7501 works at a higher speed than the 6510. I'm sure there are other differences that other people know more about.
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Posted By
Ulysses777
on 2003-04-15
| 6502 to 7501/8501 adaptor
There's an adaptor to use a 6502 CPU on the C16/Plus4. There's some info here (in Italian).
As for the CPU speed, I think that's managed by the TED, but I'm not sure...
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Posted By
StormLord
on 2003-04-16
| signal generator
actually I have never compare physicaly an 6510 and 7xxx or 8xxx cpus
But as far as I know its fully compatible so if the socket fits its easy to replace .
Also the ticking signal from +4 is coming from a crystal at 1.828xxxx mhz so for sure there is a frequency divider and the clock of +/4 is at 0.914xxx mhz speed that any 6502 or 6510 can manage.
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Posted By
JamesC
on 2003-04-16
| 6510 vs 7501/8501
The 6510 uses bytes 0 and 1 as on-processor data driection registers. This is why programs on the C64 will have a POKE 1,53 (or something similar) when the program needs to bank out the BASIC or KERNAL ROMs.
On the 264 series, we bank out BASIC or the KERNAL by writing to the data direction registers on TED ($FF3E and $FF3F). The on-processor data direction registers on the 7501/8501 aren't documented well enough for us to muck with them directly.
If the 7501 were 100% backward compatiable with the 6510 then it would share the same numbering sequence (6515 maybe) before jumping up to the 75xx series.
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Posted By
JamesC
on 2003-04-16
| One more thing
the 7501/8501 run at .88MHz when displaying the screen, but 1.76MHz when the screen doesn't have to be updated. Note that your C16 blanks the screen when you load or save on the Datasette, and also blanks when you press F1 on your Plus/4. This is so that the processor doesn't have to be interrupted by TED, and TED can kick the processor up into 'Turbo' mode.
Putting a 6510 in a 7501's socket (presuming it can be adapted, the pinouts are different as well) would leave the system running at 1MHz instead of .88MHz, or similar to running a 50Hz record player on 60Hz electricity..... if it works it'll garble the output.
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Posted By
StormLord
on 2003-04-18
| reply to James
Maybe you are right .
But I think the processor its not clocked by itshelf.
You need an clock signal to time the cpu.
this signal as I can see from my plus4 mobo is coming from an external crystal so I belive there is a divider.
changing the CPU its not the way of changing the timing on the mobo.
Like all cpu's I know (except pic's from microchip) are all external oscilated so even if you change in a circuit only the processor with a cpu capable of faster speed will be no effect.
as for the combatibility I belive you are right.
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