PCjr monitor

Hardware questions and modifications

PCjr monitor

Postby KenG » Wed Aug 24, 2016 1:18 pm

My PCjr monitor works great when it is first turned on. Over the next half hour or so, the black background slowly turns ligher until it is difficult to read 80 column test. Anyone here have any ideas on what could be wrong? I don't want to spend much money fixing it. If it takes much I will just buy the RGBI digital to alnalog board and a analog CGA to VGA converter. It would be nice to have the original PCjr monitor working though.
Enhanced PCjr with a jr-IDE (1GB DOM) and a parallel port side car with a compact flash reader and backpack 1.44mb floppy attached. Tandy video mod.
KenG
 
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Re: PCjr monitor

Postby Hargle » Thu Aug 25, 2016 6:25 am

You probably need a cap kit. It seems that most monitors this old need to have their capacitors refreshed after ~30 years.
I have a couple jr monitors that need it as well.
I'm ok with soldering, but am wary of opening up monitors and playing around with voltages that can throw you across the room if you do something wrong, otherwise I would have fixed mine a long time ago.
If anyone here wanted to try and work together on this, count me in. I'm thinking about lots of pictures on a wiki page with step by step instructions on how to refurbish a monitor safely. A bill of materials for ordering a replacement set of caps from mouser or jameco would be part of that information too.
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Re: PCjr monitor

Postby KenG » Thu Aug 25, 2016 8:41 am

OK, thanks for the information. I decided to order a digital RGBI (CGA) to analog RGB (CGA) converter and an analog CGA to VGA converter. That should let me use a more modern monitor. It loks like I can get old 4:3 TFT monitors at goodwill really cheap. I have a VGA CRT that works that I will test everything on first. I just thought that if there was a cheap and easy fix for the PCjr monitor it would be great to keep the system as original as possible.

I dug my old Commodore 1902 monitor out of storage and tried it last night. Switch lights up but no picture. I don't here any high voltage come on. I took it apart and there is no apparent damge. Very clean inside since it was stored in the original box. Anyone have any ideas on that one? It is really a nice monitor because it can do composite, digital CGA (both positive and negative), and analog CGA. Would be nice to get it working. I will be testing the rest of my Commodiore equipment over the next few weeks. If it doesn't work there is no reason to keep it. LOL.
Enhanced PCjr with a jr-IDE (1GB DOM) and a parallel port side car with a compact flash reader and backpack 1.44mb floppy attached. Tandy video mod.
KenG
 
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Re: PCjr monitor

Postby Hargle » Thu Aug 25, 2016 11:00 am

Please post what converters you ended up picking up and how things look when you get them running. I went the microbee route:
http://www.microbeetechnology.com.au/st ... -full.html
and after finally putting it together a couple weeks ago, I have (likely) performed some error in assembly, since I have garbage on the top 1" of my screen and the contents is continuously jumpy. I also noticed a very long (20mS or more) lag between me pressing a key and it showing up on the screen. In its current state, it is complete unusable and a major disappointment.
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Re: PCjr monitor

Postby KenG » Thu Aug 25, 2016 8:21 pm

What I ordered looks similar, except the RGBI to RGB analog board is already assembled. No case, I will have to figure that out. Were the ICs installed into sockets or did you have to solder them to the board? If you solder to the board, it is very important to use a heat sink to avoid overheating the ICs. That, bad solder joints, or a wiring problem between the digital to analog converter and the scalar are the most likely issues. You could also have a bad 8200. I did read something about this causing a delay. I hope it isn't too bad when I get mine done. If this doesn't work I will have to bite the bullet and get my CGA monitors fixed. I will post here once I get mine together. For games you might try the composite output to a monitor or TV. That won't be as clear but shouldn't have any lag. I plan to try that and see how bad it is this weekend. With the larger screens we have, it might not be too bad.
Enhanced PCjr with a jr-IDE (1GB DOM) and a parallel port side car with a compact flash reader and backpack 1.44mb floppy attached. Tandy video mod.
KenG
 
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Re: PCjr monitor

Postby MikeModified » Thu Aug 25, 2016 11:06 pm

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Re: PCjr monitor

Postby KenG » Fri Aug 26, 2016 6:03 am

Yes, that is one of the threads I read that got me to try it. I hope mine works out as well. I ordered the 8200 instead of the 8220. As far as I could tell the only difference was that the 8220 has 2 VGA outputs at a higher cost. I didn't think I would need that.
Enhanced PCjr with a jr-IDE (1GB DOM) and a parallel port side car with a compact flash reader and backpack 1.44mb floppy attached. Tandy video mod.
KenG
 
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Re: PCjr monitor

Postby KenG » Sun Sep 04, 2016 1:46 pm

I received the digital to analog converted yesterday and assembled it this morning. I spent a bit of time adjusting setting on the monitor and Gonbes 8200 (V.4). Got everything working great except the colors were very dark. I finally figured out to turn the pots for R/G/B, all three of them, all the way counter-clockwise. White now looks white and I was able to turn the monitor's brightness down a bit. One of the greys looks slightly purple, but other than that it is working great. I can now use 80 column mode! My next step will be to buy a cheap 4:3 LCD monitor from Goodwill and try it with that. I haven't noticed any delay between pressing a key and seeing the text. It should only be 1/60th of a second or so. The upscaler has to digitize a whole screen, upscale and convert it, and then display it. So there has to be a one screen delay. I really feel better since my attempt to convert my parallel port sidecar to bi-directional failed yesterday. I was close to deciding that vintage computing just wasn't for me. The Digital to analog converter I used came from http://bit-c-128.com.
Enhanced PCjr with a jr-IDE (1GB DOM) and a parallel port side car with a compact flash reader and backpack 1.44mb floppy attached. Tandy video mod.
KenG
 
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Re: PCjr monitor

Postby KenG » Mon Sep 05, 2016 6:45 pm

I had an idea and readjusted things a bit. Less saturation and some tweaking of the RGB pots on the 8200. True greys now. :)
Enhanced PCjr with a jr-IDE (1GB DOM) and a parallel port side car with a compact flash reader and backpack 1.44mb floppy attached. Tandy video mod.
KenG
 
Posts: 149
Joined: Sat Jul 16, 2016 5:36 pm

Re: PCjr monitor

Postby KenG » Mon Sep 05, 2016 6:45 pm

I had an idea and readjusted things a bit. Less saturation and some tweaking of the RGB pots on the 8200. True greys now. :)
Enhanced PCjr with a jr-IDE (1GB DOM) and a parallel port side car with a compact flash reader and backpack 1.44mb floppy attached. Tandy video mod.
KenG
 
Posts: 149
Joined: Sat Jul 16, 2016 5:36 pm

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