Thank you for pointing that out. It was my mistake. It was "vertical size", not "horizontal size". That would make a little more sense too :) Santo On Tue, Jul 18, 2023 at 2:45 AM David Roberts <daver21145_at_gmail.com> wrote: > I am not sure why replacing the HORIZONTAL size potentiometer would affect > a VERTICAL scan problem though? > > A VERTICAL size potentiometer (if one is fitted) - yes. > > Dave > > > On Mon, 17 Jul 2023, 21:34 Santo Nucifora, <santo.nucifora_at_gmail.com> > wrote: > >> 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 2023-07-18 12:00:03
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