Posted By
EEBuckeye
on 2015-11-25
15:16:22
|  Plus4 video problems
My Plus4 was working great but I tried it last night and the video is black with wavy lines. I removed, cleaned and reinstalled all the socketed chips with no luck. Once in a great while I see a normal screen but then the graphics flicker and disappear. 95% of the time I just get the black screen when I turn it on.
Any suggestions? Thanks!
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Posted By
JamesC
on 2015-11-25
16:01:26
| Re: Plus4 video problems
Power supply.
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Posted By
EEBuckeye
on 2015-11-25
17:09:41
| Re: Plus4 video problems
How can I check the voltages? what should I read?
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Posted By
MMS
on 2015-11-25
19:43:44
 | Re: Plus4 video problems
With C16 it would be easier, at it needs only one unregulated voltage, can any multi DC adapter could provide, that has the necessary power output.
If you have circle shaped (an not square shaped) connector, then you have some luck. Without measuring any voltage, you can easily confirm the PSU, if any C64 power supply is around, as the pin layout and voltages are 100% compatible (too bad there is no such adapter exists, as it is much easier to grab a C64 PSU with round connector than a Plus/4 one)
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Posted By
EEBuckeye
on 2015-11-25
22:51:48
| Re: Plus4 video problems
I definitely have C64 power supplies around but no idea how to connect to the Plus 4.
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Posted By
JamesC
on 2015-11-25
23:49:04
| Re: Plus4 video problems
To test the power supply, you need a voltmeter. The top two pins of the plug should each read around 9V AC (anything between 9V and 10.6V is acceptable). The bottom right should read 5V DC. The bottom left is ground or earth -- ensure that your power supply is plugged into a grounded (earthed) outlet.
If these test good, check for 13.8V at the positive (left) side of C7. This is the big cylindrical thing on the Plus/4 motherboard, near the user port.
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Posted By
EEBuckeye
on 2015-11-26
00:46:24
| Re: Plus4 video problems
Thank you very much for the info!
The bottom right pin read 5V but the both the top two read about 0V DC!?!? I guess that is my problem!
Anyone have a spare power supply by chance??
Thanks!
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Posted By
JamesC
on 2015-11-26
10:27:44
| Re: Plus4 video problems
The top two read 0V DC or AC? Your voltmeter needs to be set to AC for the top two pins.
When a power supply fails, there is a chance that something on the motherboard has also failed due to overvoltage. Therefore, a replacement power supply MAY OR MAY NOT bring your Plus/4 back to working order; you need a known good power supply to diagnose further.
For a replacement power supply, we need to know where in the world you are. Most of our forum members are in Europe, but a handful of us are in US and Canada. You'd want the right plug for the outlet on the wall. 
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Posted By
MMS
on 2015-11-26
14:11:57
| Re: Plus4 video problems
Because you seems to have THIS connector: []
I have 3 Plus/4 and 2 have THIS type: [] and one have ROUND O connector
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Posted By
EEBuckeye
on 2015-11-27
00:50:28
| Re: Plus4 video problems
On the power supply I read approximately 10.5V AC on the top pins which seems correct.
I then measured C7 at the left side (+ side) 12.7V DC. Is that too low? Should I check any other points?
Thanks so much for the info!
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Posted By
SVS
on 2015-11-27
08:48:15
 | Re: Plus4 video problems
Are these measures taken when the power supply is cold (just turned on)?
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Posted By
EEBuckeye
on 2015-11-27
13:01:34
| Re: Plus4 video problems
I left the Plus4 on for awhile and it seemed to stay around 12.7V to 12.6V on C7.
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Posted By
EEBuckeye
on 2015-11-28
13:49:13
| Re: Plus4 video problems
Thank you for the info!
I checked voltages and I believe they are within normal tolerances (i.e. 4.7V for 5V) but it seems like maybe the biggest issue is 12.7V and C7+ instead of 13.8V?
Unfortunately I do not have any other tools other than my voltmeter.
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Posted By
JamesC
on 2015-11-28
15:12:23
| Re: Plus4 video problems
The 9V side drives the datasette motor, and is provided to the userport in case some accessory needs it. For your symptoms I don't think we need to worry about it.
The 5V side, however, drives pretty much everything else. Since waveform monitors are pretty expensive, it would be more cost effective to take your Plus/4 (and a printout of the Sam's guide) to a local electronics repair shop and ask if they will diagnose it for you.
But at $60/hour shop labor (for me in suburban Kansas City, yours may be higher or lower) it would be just as cheap to buy another Plus/4 off Ebay. Save the first one for parts in case you have a problem in the future.
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Posted By
EEBuckeye
on 2015-11-28
16:36:15
| Re: Plus4 video problems
I was thinking the same thing.  Thanks so much for the info!
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Posted By
MMS
on 2015-12-07
15:08:37
| Re: Plus4 video problems
So, in the Computer SAVER topic you will find the cable you need between the C64 brick and the Plus/4, if you have rectangular socket for PSU connector on the Plus/4.
I suggest -if you have working C64 bricks- not waste your time repairing a PSU brick even the experts usually gave up (due to extensive use of epoxy), but to use a C64 brick + this cable.
I think I will also need one...
BTW, why the hell they did not offer ONE standard PSU for the C64, Plus/4, 1541/II and 1571, etc?
(background of my frustration: I have 2 Plus/4 with rectangular socket and 1 probably NOK rectangular PSU (dead Plus/4? or dead PSU?), and 1 working Plus/4 with round socket and 2 C64 PSU with round connector. And one 1541/II and one 1571/1581 PSU).
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Posted By
RobertB
on 2015-12-08
01:27:28
| Re: Plus4 video problems
MMS wrote:
> ...why the hell they did not offer ONE standard PSU for the C64, Plus/4...
If you are speaking about the DIN connector of the C64 compared to the square connector of the Plus/4, CBM engineer Bil Herd's answer to that would be that when the Japanese engineers got their hands on the Plus/4, they made many changes, including that of the square connector.
> ...1541/II and 1571, etc?
Well, the IEC female connector is pretty standard. As for the 1541-II and 1581, their round DIN connections with 5 and 12 volts are standard across other p.s.'s, like those for CMD hard drives, CMD RAMLinks v1, Amiga external hard drives (like A590's and GVP's).
> ...1 probably NOK rectangular PSU (dead Plus/4? or dead PSU?)...
Fortunately, I had a C64 repairable p.s. upgraded with modern components and with the square Plus/4 male connector. Unfortunately, I only have one of those... which isn't enough for the other Plus/4's.
...and 1 working Plus/4 with round socket...
Currently, I'm having one of my Plus/4's converted to the round DIN socket.
Truly,
Robert Bernardo
Fresno Commodore User Group
http://www.dickestel.com/fcug.htm
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Posted By
MMS
on 2015-12-12
14:01:22
| Re: Plus4 video problems
Hi Robert,
Thanks for the feedback, and sorry for the previous bad post due to internet access troubles.
The other topic offers such a round--> square converter, and it will solve my issue, as I have two C64s with working PSU.
(I did not mention yet the C16 with the unregulated single Volt input connector, that could be easy to solve nowadays.)
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