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C128 Power supply troubleshooting

I had some more time Saturday to test some of my Commodore equipment. Both of my flat C128s are in working condition, but one of my power supplies is non-functional. I used my multimeter to check voltages at the square connector, but it's not outputting anything except 11 VAC on Pin 5. Does anyone have a link to any troubleshooting guides and/or detailed schematics for these? If I know which components were most likely to be the clulprits and what the voltages are supposed to be at various points inside the unit I might be able to do some futher troubleshooting. Here are photos of the non-working unit:

Bottom Case (P/N, S/N, etc.)Top view

Bottom View

I pulled out the fuses and visually inspected them. They both looked fine, but to take this any further I will need some more information so I can test it properly. I also found this YouTube video from 2014, and was curious about the status of this project:

Jim Brain: New Commodore Power Supply

Edited by: Dragget on 2016-02-08 22:42
Re: C128 Power supply troubleshooting

Dragget wrote:

> Does anyone have a link to any troubleshooting guides and/or detailed schematics for these?

I see you have the lower-powered version of the C128 factory power supply; most C128 p.s.'s I've seen are the 4.3 amp@5 volt version. However, Ray Carlsen's pictures and text may help you out. See

http://personalpages.tds.net/~rcarlsen/cbm/c128/PS%20REPAIR/

If you still have questions, send an e-mail to Ray at rcarlsen(at)tds.net

> I also found this YouTube video from 2014, and was curious about the status of this project:

I didn't know there was a YouTube video about it. As for the status, that is unknown. However, Ray sells his own, new C128 power supplies. See

http://personalpages.tds.net/~rcarlsen/custom%20ps.html

Truly,
Robert Bernardo
Fresno Commodore User Group
http://www.dickestel.com/fcug.htm

I just found three different
I just found three different C-128 power supplies. One 4.3 amp, and two 2.5 amp units. One that's appended with -08 (2.5A) I have never seen before. I usually put a C-64 cable on the 2.5A units and use them on 64s, saving the 4.3 for the C-128s.
C-128 w/2Mb REU, & Video RAM upgrade C-64 w/modern PLA Amiga 2000, '030, 24Mb RAM
Further testing
I haven't had much success finding any sort of comprehensive troubleshooting guide for this PSU online, but I did manage to borrow another (working) C128 PSU and do some comparative testing. That let me see what the voltage outputs SHOULD be at the plug, and the diagram on the back (this was one of the 4 amp units, while mine is 2 amp) showed me which pins are for what, so I am now able to put my tester on the correct pins and get valid readings. Further testing shows that the 9VAC side of my PSU is working fine still (output is just over 10VAC), but I'm getting absolutely nothing from the +5VDC side. Any info on what's the most common issue, and what I should be looking at first would be helpful at this point.
@RobertB: Thanks for the link. I checked it out, but the information was not very sepcific or detailed, so I guess I will have to email Ray Carlsen and see if he can give me any pointers. Right now I'm waiting for a part to repair my C128D, and my other flat C128 is up for sale, so I'm without a working Commodore computer. :(
@Motrucker: are you saying you have a PSU available that you would be willing to sell?
--==--
Moderation in all things... including moderation.
Re: Further testing

Dragget wrote:

> ...I guess I will have to email Ray Carlsen and see if he can give me any pointers.

Actually, Ray appreciates phone calls more than e-mails. If you wish his phone number, I can give it to you in private.

Truly,
Robert Bernardo
Fresno Commodore User Group
http://www.dickestel.com/fcug.htm

I have one listed on ebay
I have one listed on ebay right now. It may not sell however, due to a high-ish BIN price. I had added a best offer too, but no one seems interested yet. this unit is one of the 2.5A models however. "http://www.ebay.com/itm/131737607763?ssPageName=STRK:MESELX:IT&_trksid=p3984.m1555.l2649" I may get another 4.3A model soon, so I would say hang on for a bit. Edit - I dropped the price of the PSU on ebay. The other power supply I got was also a 2.5A model.
C-128 w/2Mb REU, & Video RAM upgrade C-64 w/modern PLA Amiga 2000, '030, 24Mb RAM
Thanks for the heads up. I
Thanks for the heads up. I did manage to locate another 4.3A model in the mean time, all in with shipping it cost me about $35 (plus I had to replace the fuse on the 9VAC side) so I think I got a good price. It would still be nice to get my original one working, but not as urgent at this point.
--==--
Moderation in all things... including moderation.
Glad you found one of the 4
Glad you found one of the 4.3A PSUs. Maybe I have just been lucky, but with all of the 128 PSUs I have had, I only had one that needed work. It needed to have the Caps replaced, which cleared up the video and sound of that C-128.
C-128 w/2Mb REU, & Video RAM upgrade C-64 w/modern PLA Amiga 2000, '030, 24Mb RAM
Re: Glad you found one of the 4

motrucker wrote:

> Maybe I have just been lucky, but with all of the 128 PSUs I have had, I only had one that needed work.

Back in the day, I bought two CBM C128 4.3 amp power supplies from the Grapevine Group. Both didn't power up or failed soon after I received them.

Back from the Dave Needle memorial,
Robert Bernardo
Fresno Commodore User Group
http://www.dickestel.com/fcug.htm

The Grapevine Group was down
The Grapevine Group was down right dangerous to buy from. I bought several chips from them (Amiga and 8 bit) that were no good. I drove up there to confront them about the order, and after seeing their operation, I never bought from them again.
C-128 w/2Mb REU, & Video RAM upgrade C-64 w/modern PLA Amiga 2000, '030, 24Mb RAM
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