PCJR Internal PS Items

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chuckphd53
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PCJR Internal PS Items

Post by chuckphd53 »

Here are a couple picture of the PCJR power supply that was part of the original JR back in the day..

The smaller card was a 33 Watt unit while the later version, a larger board with more power touted a 45 Watt supply.

There are a few issues with these today, mostly the electrolytic caps tend to dry out over the years and go bad.
these are easily replaced. You can find the 33Watt cap kit here :
https://console5.com/store/ibm-pcjr-com ... -watt.html

Replacing these caps is pretty simple, simply heat up the back side connection of each pin on the cap and 'gently' pull on the cap, side to side
until it comes out. I usually try to span both cap solder joints at once with a wide tip solder iron, you can use a touch of flux on the joint
to help the solder flow better (recommended) then again 'gently' pull the cap off...
NOTE : CAUTION, if you man-handle the cap, pulling it out, you can damage the board via and then it gets a bit sticky to fix.( I'll cover this later)

Once the cap is out, use solder wick or solder sucker to remove the excess solder in the via holes.
Now they are ready to put the new caps in place.

I the picture below I show the new caps installed, but NOTE: they are standing off the board a small amount...
This is preferred as it give you the opportunity to make sure your solder has flowed completely when you reinstall the caps.
( This is personal preference )
Note also that you should keep the caps from touching the metal heat sink or any other metal. The caps have a plastic heat shrink over them
but if heated up can melt and if touching an active part of the power supply can short out as the outer part of the caps are attached electrically
to the ( - ) pin on the cap...
So Rule of thumb 'ISOLATION'.

Finally after your RE-CAP adventure is done, use a sacrificial JR to test out the Power supply. I use a stripped down version of the PCJR with
nothing other than the extra video memory board install, no drives or other boards.
You can power it up and see if it counts memory and even do the CTRL ALT INS to try some of the Video screens.
If this all works, you did a GREAT JOB ! :D

More below on the 45 Watt supply !

33WATT POWER SUPPLY
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33WATT POWER SUPPLY
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The 45 watt supply, while is it a nicer design with more power has felt its age over the years also with the cap..
These should be replaced to ensure you have finely tuned power supply.
You can get most of these from any local distributer, Mouser, Digikey etc..

One item of interest that I found was, in the second picture there is a choke coil on the input power, this is the large BLUE device shown
in the picture.

Note the YELLOW arrow. One unit that I found in an EBAY unit I purchased had this power supply card in it and when I removed it to
inspect the caps, it was 'stuck' and I had to pull on it a bit. I noticed that coming out of the choke coil was a bunch of GREEN waxy substance.
This is the original filler used when making these coils, uses to isolate and keep the coil in place.
This is NOT a failure of the coil, rather is it just a storage problem that the heat, over time, allowed the filler wax to pour out and onto the JR
mother board.
How to Fix... You can simply clean up the excess wax everywhere, I recommend using a plastic tool so as not to damage any traces on the mother board or power supply card. You can use some alcohol and Q-tip to clean if desired.
But be asurred that the COIL is not damaged, it will work just fine as is ever after leaking the wax. This is just a simple input choke coil and will not have any issues after leaking.
This is the only item on the 45 Watt that I have encountered was an issue with these. If you have other experiences please post your results here!


45WATT POWER SUPPLY
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45WATT POWER SUPPLY
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“I never commit to memory anything that can easily be looked up in a book.” (AE)
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