Ninetendo Power Supply Smokes R1

supertechnoboy

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Donor 3 years: 2011, 2024-2025
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My DK died. I checked +5, and there was none. I opened up up the power supply (PP-7B), and the magic smoke had been let out of R1 (2W 20 ohm wirewound). I replaced R1 and immediately smoked the replacement. Obviously, I should have investigated further before replacing the resistor.

With the resistor blown, I'm measuring 95VDC across it. Looks like a shorted C6 or C7 would do it, but those appear OK. Maybe a shorted TR1 or TR3?
 
Thanks, Edward. On SCR1, I get high resistance from anode to cathode, or from cathode to anode. I get low resistance from gate to cathode. I think that's all OK. I didn't have a chance to check anything else today.
 
Thanks, Edward. On SCR1, I get high resistance from anode to cathode, or from cathode to anode. I get low resistance from gate to cathode. I think that's all OK. I didn't have a chance to check anything else today.

I had one once where the SCR tested good with my meter.....I couldn't find anything wrong (except R1 smoked at power up!). Out of desperation (and gut feeling), I replaced SRC1.....R1 didn't smoke, power supply worked.

Edward
 
Well, I got finally got SCR1 replaced, and that turned out not to be the problem. Dokert, which caps were you thinking about? C6 and C7?
 
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