Melted Power Supply Choke

Hardware questions and modifications

Melted Power Supply Choke

Postby James » Tue Apr 07, 2015 5:36 am

I had a floppy drive develop read problems. It is the A drive in a PCjr with a Racore Drive II. I swapped it out with a known good drive. I decided It would be easier to just pull the power supply card (10") out to swap the fan power cable. It wouldn't come out. I tugged a little harder and got it out. When I looked at the card it appears that the blue Siemens choke had leaked a blue gel like substance that dripped down onto the motherboard. It didn't look fresh. It could have happened last month, it could have happened in the early 90s. I swapped out the power board.

Even though I have the 10" Power supply and Racore power supply, I wonder if I am still drawing too much power. i was running three sidecars, jrIDE with DOM, IBM Parallel Port and PCE Megaboard, which I use as Expanded Memory. I am temporarily removing the Megaboard which I would assume has a healthy power appetite.

Ideas? Overdraw or typical time related failure?
-PCjr (1989)-DOS 3.3, Racore Drive II, jrIDE-128 MB DOM, jrExcellerator, Tandy Mod, Serial Card, Combo v2, Config Plus, IBM Parallel Port, Megaboard, Xircom PE3-10BT
-PCjr (2001)-DOS 3.3, jrIDE-128 MB DOM, NEC v20, Parallel Port, Comswap, Xircom PE3-10BT
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Re: Melted Power Supply Choke

Postby jmetal88 » Tue Apr 07, 2015 6:40 am

I'm not sure what the cause was, but my PCjr had the same problem when I got it. After I cleaned it up, it's been working fine ever since, though (and I'm powering both a laptop hard drive and an external floppy off the internal power supply). Yeah, some of you might know I replaced my PCjr after I accidentally shorted a power supply pin to some point on the main board, but I'm actually using my original power supply because it's the longer card and I needed the extra power compared to the smaller card that came with my replacement.
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Re: Melted Power Supply Choke

Postby James » Thu Apr 09, 2015 5:54 am

I put the Megaboard back on. I recently switched from a crippled Rapport Drive II System (nothing but the floppy worked) to a working Racore Drive II unit. The Racore unit has a more robust power supply and supplies both +12V and +5v to the sidecar. I am thinking of adding a small exhausting fan to the power supply side of the Racore unit.
-PCjr (1989)-DOS 3.3, Racore Drive II, jrIDE-128 MB DOM, jrExcellerator, Tandy Mod, Serial Card, Combo v2, Config Plus, IBM Parallel Port, Megaboard, Xircom PE3-10BT
-PCjr (2001)-DOS 3.3, jrIDE-128 MB DOM, NEC v20, Parallel Port, Comswap, Xircom PE3-10BT
James
 
Posts: 112
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Re: Melted Power Supply Choke

Postby Chuckphd53 » Tue Jun 19, 2018 12:46 pm

Is there a schematic for the Racore/Rapport powersupply
seems I have one that needs attention..

UPDATE: Repaired the PS, just a few bad components...replaced all small caps , works well
also put heatsink compound under the switching transistors to allow better heat transfer.
seems to run very cool...
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