jhawkn
New Member
Hi all,
I recently acquired a Sanyo DCX 2500K for $5. Replaced a couple fuses and gave it a good cleaning, and had it working fairly well. I probably should have left it alone, but those old electrolytics in the power supply were calling my name. Maybe I should’ve ignored the voices?
Well, I recapped a few days ago, carefully replacing one cap at a time and noting polarity. Some of the old caps had corroded leads, too, helping me to feel justified in my choice to recap. I plugged in the receiver, powered on, and was greeted by a sort of “pop”, followed by hum. I can get music to play, but one channel is somewhat weak now, and there is 120hz hum.
Somewhat flummoxed, I unplugged the receiver, discharged the caps, and removed the power supply board, taking detailed notes of where all lead wires connected to the board. I gave the underside of the board a gentle clean. Then I checked for continuity and separation on all traces, but everything seemed to be in order.
Then I got to looking at all the filter caps, and noticed an anomaly. All but one of the caps had the negative leg connected to ground. I thought, “Aha!! Here’s the problem—I somehow got one cap backwards!” I then referenced a picture I took of the supply board before the recap, but the old cap did indeed have it’s positive leg soldered to ground.
So......is this capacitor backwards??
Did the old cap somehow work, even though it was backwards? Or am I barking up the wrong tree and there is a different problem entirely? Perhaps I need to reflow some solder?
Here’s a pic of the board before the recap. The cap in question is outlined in red. Note the black line denoting the negative lead, circled in yellow.
Here’s a top view of the recapped board.
Here’s the bottom. The globs of solder are courtesy of the Sanyo factory.
And finally, here’s a pic of the top of the board, with an overlay of the traces and notes to where all the lead wires went. The cap in question is on the bottom in the middle.
I recently acquired a Sanyo DCX 2500K for $5. Replaced a couple fuses and gave it a good cleaning, and had it working fairly well. I probably should have left it alone, but those old electrolytics in the power supply were calling my name. Maybe I should’ve ignored the voices?
Well, I recapped a few days ago, carefully replacing one cap at a time and noting polarity. Some of the old caps had corroded leads, too, helping me to feel justified in my choice to recap. I plugged in the receiver, powered on, and was greeted by a sort of “pop”, followed by hum. I can get music to play, but one channel is somewhat weak now, and there is 120hz hum.
Somewhat flummoxed, I unplugged the receiver, discharged the caps, and removed the power supply board, taking detailed notes of where all lead wires connected to the board. I gave the underside of the board a gentle clean. Then I checked for continuity and separation on all traces, but everything seemed to be in order.
Then I got to looking at all the filter caps, and noticed an anomaly. All but one of the caps had the negative leg connected to ground. I thought, “Aha!! Here’s the problem—I somehow got one cap backwards!” I then referenced a picture I took of the supply board before the recap, but the old cap did indeed have it’s positive leg soldered to ground.
So......is this capacitor backwards??
Did the old cap somehow work, even though it was backwards? Or am I barking up the wrong tree and there is a different problem entirely? Perhaps I need to reflow some solder?
Here’s a pic of the board before the recap. The cap in question is outlined in red. Note the black line denoting the negative lead, circled in yellow.
Here’s a top view of the recapped board.
Here’s the bottom. The globs of solder are courtesy of the Sanyo factory.
And finally, here’s a pic of the top of the board, with an overlay of the traces and notes to where all the lead wires went. The cap in question is on the bottom in the middle.
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