Just to close this off, I didn't find the schematic but I did find the issue. Seems to be common as it's affected all three of my Educator 64s in some way. One had complete vertical field collapse, another displayed about 1 inch of width in the middle of the screen and the last one that I thought was good was very glitchy. Adjusting the horizontal pot at R341 would be so touchy that it would collapse with the slightest move. On all three units, I replaced the horizontal size pot at R341 with a 1M ohm potentiometer (Digikey part PT15LV18-105A2020-S) and they are all fine now. One of my units was completely original except for that pot so it must be a common problem. Anyway, I thought I would post for anyone who might find this in the future. Thanks for the assistance all the same Gerrit. Santo On Wed, Jul 12, 2023 at 1:41 PM Turk[z] <alienzone_at_gmail.com> wrote: > Hi, I'll not help you, but I'm searching for help. I've an Educator 64 > too, without his monitor, but i've a pet 8032 monitor. Is possible make it > works? > > Il Mer 12 Lug 2023, 18:04 Santo Nucifora <santo.nucifora_at_gmail.com> ha > scritto: > >> HI Gerrit, >> >> The TDA1170 has been replaced just to make sure it was not that. I am >> fairly sure that during troubleshooting a couple years back, the NE556 was >> swapped and the original put back in but I should recheck that. You do >> make a good point about the socket however. Maybe a quick replacement is >> in order just in case. >> >> I've also replaced most of the caps. A couple of the NP caps I could not >> get direct replacements and I did not replace the largest cap but that >> didn't help. I've also taken out all transistors and diodes and checked >> them out of circuit. >> >> The next thing I was going to do was test the potentiometers. I've used >> contact cleaner in them and they seem clean but they should be tested. >> >> Santo >> >> On Wed, Jul 12, 2023 at 11:16 AM Gerrit Heitsch < >> gerrit_at_laosinh.s.bawue.de> wrote: >> >>> On 7/12/23 16:36, Santo Nucifora wrote: >>> > I am trying to fix a Commodore PET Educator 64 model that has video >>> > issues. There is no schematic that I could find for the board marked >>> > with a part number of "02-96409 REV 3". Would anyone have a schematic >>> > for it? >>> > >>> > Here is a picture, if it helps: >>> > >>> https://vintagecomputer.ca/wp-content/uploads/2023/07/Educator64-02-96409Rev3-videoboard-scaled.jpg >>> < >>> https://vintagecomputer.ca/wp-content/uploads/2023/07/Educator64-02-96409Rev3-videoboard-scaled.jpg >>> > >>> > >>> > From my understanding, the monitor in the Educator 64 allows for >>> shades >>> > of grey (or green in this case) and is not a standard PET monitor so >>> it >>> > may be specific to the Educator 64 only. This monitor will run with >>> > signals from an unmodified C64 motherboard. The PET 64, however, has >>> > extra circuitry on a small daughterboard that changes the video signal >>> > to black and white so that a normal PET monitor will work. >>> > >>> > I currently have vertical collapse on this particular monitor. The >>> video >>> > output of the C64 via an external monitor is good so the signal should >>> > be good as well. Having a schematic would help with diagnosing the >>> > vertical circuit. >>> >>> Can't help you with the schematic, but the TDA1170 is the IC that >>> controls the vertical deflection and a datasheet is easily available. >>> The TDA1180 is for the horizontal part. >>> >>> You might also want to check the socketed NE556 on the left side. >>> Sockets can develop contact problems over time and this doesn't look >>> like a quality socket. Same goes for all the potentiometers and that >>> little switch. >>> >>> Gerrit >>> >>> >>> >>>Received on 2023-07-17 23:00:04
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