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IBM 4863 /PCjr monitor/ power supply/schematic


Experienced Member
Apr 25, 2020
Hi all,
I'm currently awaiting one of these clunkers and I was wondering if anyone got a complete copy of the schematics, i.e. including its audio amplifier and power supply stage. There's some info on the Web which states that these monitors are internally similar to an IBM 5153, which has a PSU that works on both 120 and 230 volts AC with an automatic switchover. On the back-side of a 4863 though, there's only 120 volts AC input, which can make sense as I'm not sure if these machines ever made it over the pond.
In the PCjr technical reference, there's only a schematic of the guts driving the screen, which looks more-or-less identical to the schematic of a 5153.
I guess even if that thing lacks the dual voltage switchover, it could run with some series capacitive reactance straight from 230 volts... I won't tell anyone. :) And since it's a direct-drive, I guess it doesn't matter if the mains AC is 50 or 60Hz since there will be some kind of a rectifier. If anyone could have a look that'd be greatly appreciated.

Here's some info and a poor scan of the schematic.


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  • IBM PCjr Monitor 4863 schematic.jpg
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There is an error in the MONITOR.DOC attachment above.
C402 should be 0.1 µF @ 35v.
...NOT 1.0 µF as it says in the document.

I am certain of this because I removed and measured C402 in my now working 4863. I fixed my monitor by simply reflowing the solder on the flyback transformer and the CRT socket on the neck board. No components were bad.

Interesting enough, there is a handwritten note in the upper left corner of the attached schematic that says C402 is 0.1 µF.
Sure wish I could find a better schematic somewhere!
Attached is a more readable schematic. The original is way too large for my scanner so I took a few photos with my phone.


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