Search found 11 matches
- Tue Feb 13, 2024 10:08 am
- Forum: Hardware
- Topic: 250407 Board with an AC power issue
- Replies: 2
- Views: 73
Re: 250407 Board with an AC power issue
Fixed. The 74LS193 at U30 was defective.
- Mon Feb 12, 2024 11:58 pm
- Forum: Hardware
- Topic: 250407 Board with an AC power issue
- Replies: 2
- Views: 73
250407 Board with an AC power issue
I've been working on this board for some years now. Worked fine for a long time then stopped. However, I think I've narrowed in on the issue, I just don't know what's causing it. Using a Ray Carlson PSU, the 9v line puts out about 9.5 to 9.6v consistently. This is verified when plugged into the boar...
- Wed May 04, 2022 9:29 am
- Forum: Hardware
- Topic: 250425 Board repair/One Flash on dead test
- Replies: 7
- Views: 1565
Re: 250425 Board repair/One Flash on dead test
Success!!! I missed a floating pin (pin13) on U13. Hey, I just realized! Unlucky 13!!! But it's working now!
- Tue May 03, 2022 8:53 pm
- Forum: Hardware
- Topic: 250425 Board repair/One Flash on dead test
- Replies: 7
- Views: 1565
Re: 250425 Board repair/One Flash on dead test
I just moved that exposed wire back in contact with the adjacent pin and am getting the single flash again. I MISSED A TRACE!!! The patch is on the 74LS257 at U13 (a RAM multiplexer I think). I'm going to have to follow all the traces again to figure out where that goes.
- Tue May 03, 2022 8:40 pm
- Forum: Hardware
- Topic: 250425 Board repair/One Flash on dead test
- Replies: 7
- Views: 1565
Re: 250425 Board repair/One Flash on dead test
It is. But the dead test can present certain RAM failures as a fault in data bit 7 when the real fault is in either bits 0 or 1.levoman wrote: ↑Tue May 03, 2022 10:11 am According to this site D1 is U9 not U12??
https://myoldcomputer.nl/technical-info ... 5-01-c64b/
- Tue May 03, 2022 8:31 pm
- Forum: Hardware
- Topic: 250425 Board repair/One Flash on dead test
- Replies: 7
- Views: 1565
Re: 250425 Board repair/One Flash on dead test
I am assuming that you have swapped the ram chips around to see if the error follows either u12 or u23 and have checked for data bus shorts to ground with a multimeter? The results you are getting would indicate to me either a ground short on D4 ( u23 data ) or more likely a short between D1 and D4...
- Tue May 03, 2022 12:00 am
- Forum: Hardware
- Topic: 250425 Board repair/One Flash on dead test
- Replies: 7
- Views: 1565
250425 Board repair/One Flash on dead test
As the title says, I'm trying to repair a 250425 board that's giving me a single flash on the dead test. I've conducted extensive repairs to the board, removing and eventually socketing almost every single IC on the board (and at this point, all the ICs that went in them). The only exceptions are th...
- Wed Apr 20, 2022 7:35 am
- Forum: Hardware
- Topic: Need a clean image of a C64 250425 PCB
- Replies: 3
- Views: 976
Re: Need a clean image of a C64 250425 PCB
I've actually made some progress today! Going over the board, I've managed to locate and patch 8 broken traces on the board, and have begun repopulating it with machine sockets. In hindsight, maybe I should have slipped in a few zifs for future testing, but I wasn't sure that the board would be salv...
- Thu Apr 14, 2022 10:24 pm
- Forum: Hardware
- Topic: Need a clean image of a C64 250425 PCB
- Replies: 3
- Views: 976
Need a clean image of a C64 250425 PCB
So getting down to it. I've been trying to repair a 250425 C64 board for a few years now. It worked when I first got it, then stopped. And over the years, tracing various faults, and replacing literally every single IC, all I get is a black screen (even on dead test). Suffice it to say, the thing ha...
- Thu Dec 03, 2020 7:57 am
- Forum: Help!
- Topic: C64 3rd party mouse issue
- Replies: 4
- Views: 4097
Re: C64 3rd party mouse issue
OK! So progress... First: It's a Contriver Technology inc. mouse, model M1, not "Computer Technology". God, that text was small! Second, after another round of Googleing, I was able to learn that the odd angles of the LEDs and sensors were not normal, so I bent them back. Sadly. this has n...