RCA DRC8335 DVD/VCR COMBO Power supply running hot

rumburaski

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Jun 13, 2013
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I have replaced a couple of blown electrolytics including the 2200uf one. Now the combo runs but with issues. For example, the power supply runs scorching hot. The hottest spot being the rectifier diode mbr on the heat sink, just behind the 2200uf electrolytic that bursted (not shown, already replaced). Also the unit continues to display "finalizing" on the screen after dvd burning, even if the finalized disc is ok. To get rid of the "finalize" i have to turn the unit off and let it cool for five minutes. It is challenging for me because i don't have a schematic. Here are some pics.





 

dandragonrage

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I'd imagine the caps you replaced blew because of another problem that caused them to overheat, and you haven't fixed that other problem.

Sorry if that's not helpful.

How much is keeping this unit worth to you?
 

FnordMan

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I'd imagine the caps you replaced blew because of another problem that caused them to overheat, and you haven't fixed that other problem.

Sorry if that's not helpful.

How much is keeping this unit worth to you?
seconded. caps generally don't cause hot PSUs to my knowledge.
 

drescherjm

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Did you replace the rectifier diodes? To me that could have caused your capacitors to fail since AC was getting to the caps. Although I would not have expected it to work at all if the diodes were shorted.
 

rumburaski

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Replaced mbr1045 diode rectifier on heat sink. No luck. Power supply still runs hot. I mean hot as in I can only touch the heatsink with my finger for about 2seconds. There are so many parts (transformers, chokes, zener diodes, transistors, ic). I wish could identify to +12, +5 and -5 voltages and take it from there. Perhaps get some specs on that big transformer and compare it against the datasheet. It puzzles me because the unit runs. Never shuts off. VCR and dvd burner works, expect the performance issues mentioned earlier. So far I replaced capacitors, diode and mosfets. Some progress but not returnable to service.
 

rumburaski

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I thought about adding a fan but this supply is way to hot:). Here are some more findings and pics




 

rumburaski

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After two weeks of pondering I think is a good idea to make an opening and install a case fan. Should I go with 120mm? blue leds? will it run all the time?
 

dandragonrage

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After two weeks of pondering I think is a good idea to make an opening and install a case fan. Should I go with 120mm? blue leds? will it run all the time?
Go with a blower (side exhaust fan) so you can exhaust it out the back and the size / CFM you'll need depends on just how hot it gets. Might need to experiment between heat and noise. Either run it while the machine is on or get a mechanical thermostat called a "snap disc thermostat" and epoxy glue it to the hottest heatsink so it will snap on above say 50C or whatever. Either that or use a fan with a temperature sensor-based variable CFM and hook the sensor up to the hottest heatsink.
 

rumburaski

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Thank you. Where would I find a fan shroud/enclosure for a 60 x 60 x 25 mm fan?
 
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