Hey guys,
I picked up a Pioneer SX-636 in good exterior condition a while back and have been working on repairing the thing for quite a while now. When I got it, it barely worked, so I recapped all of the important parts of it, including the large coupling caps, which had bloated like nothing I have ever seen before. After this, it worked in a sense, however it would send loud crackles to the speakers, which I found to be short bursts of DC, about 5 to 10 volts or so. I tested the main output transistors (2SB531/2SD371) independently and out of circuit, and found them to be good. I then replaced the known-bad 2SA726 and 2SC1451 transistors with KSA992F and KSC3503 transistors. However, after these replacements the speaker terminals show a near-constant 30 volts, only occasionally dropping down to near zero for short bursts. Returning the original 726s and 1451s brings back the original bursts, but noticeably worse, spiking to around 12 volts more frequently and for longer. Any advice on this issue would be greatly appreciated.
Thanks.
I picked up a Pioneer SX-636 in good exterior condition a while back and have been working on repairing the thing for quite a while now. When I got it, it barely worked, so I recapped all of the important parts of it, including the large coupling caps, which had bloated like nothing I have ever seen before. After this, it worked in a sense, however it would send loud crackles to the speakers, which I found to be short bursts of DC, about 5 to 10 volts or so. I tested the main output transistors (2SB531/2SD371) independently and out of circuit, and found them to be good. I then replaced the known-bad 2SA726 and 2SC1451 transistors with KSA992F and KSC3503 transistors. However, after these replacements the speaker terminals show a near-constant 30 volts, only occasionally dropping down to near zero for short bursts. Returning the original 726s and 1451s brings back the original bursts, but noticeably worse, spiking to around 12 volts more frequently and for longer. Any advice on this issue would be greatly appreciated.
Thanks.