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 09:00:02
Archive generated by hypermail 2.3.0.
