This particular Pioneer receiver has a protection circuit that actuates a relay to prevent things like DC voltage going to your speakers. The problem is that the relay randomly clicks on and off. I've checked for DC voltage at the output transistors and found, what I would consider, a normal 15mV.
Here's what I've tried:
I've tried spraying and cleaning the relay contacts with deoxit, but there's very little clearance so it's hard to see if it made any difference.
I've checked all the voltages listed on the protection board part of the schematic and nothing was more than half a volt off
I removed and tested capacitance on the 3 largest capacitors on the protection board, but they were in tolerance
I also removed and tested the transistor that I believe controls the relay (Q7), and it looked ok
I tried heating portions of the protection board up with a heat gun and cooling it back off with acetone and a small computer fan, but wasn't ever able to get any repeatable results
Here's why I'm posting:
At one point, while looking for a good place to clip my multimeter ground lead, I realized the bolts that hold the power transformer down were loose. I had the receiver flipped over at the time because the circuit protection board is on the bottom. Since tightening them down, the relay seems to work normally. However, everything had been powered on frequently enough or long enough that I would say the unit was at normal operating temperature at this point.
I don't know if the timing was just coincidence. Is it possible that the transformer just wasn't grounding well enough to the chassis, and causing the relay or protection circuit to not ground properly either? I'm skeptical because the transformer has three wires that are either wire-wrapped or soldered directly to pins attached to the chassis. On the other hand, I know enough to know that I don't know everything.
*Unfortunately the schematic file is too big to upload here, but is available freely from HiFiEngine
Here's what I've tried:
I've tried spraying and cleaning the relay contacts with deoxit, but there's very little clearance so it's hard to see if it made any difference.
I've checked all the voltages listed on the protection board part of the schematic and nothing was more than half a volt off
I removed and tested capacitance on the 3 largest capacitors on the protection board, but they were in tolerance
I also removed and tested the transistor that I believe controls the relay (Q7), and it looked ok
I tried heating portions of the protection board up with a heat gun and cooling it back off with acetone and a small computer fan, but wasn't ever able to get any repeatable results
Here's why I'm posting:
At one point, while looking for a good place to clip my multimeter ground lead, I realized the bolts that hold the power transformer down were loose. I had the receiver flipped over at the time because the circuit protection board is on the bottom. Since tightening them down, the relay seems to work normally. However, everything had been powered on frequently enough or long enough that I would say the unit was at normal operating temperature at this point.
I don't know if the timing was just coincidence. Is it possible that the transformer just wasn't grounding well enough to the chassis, and causing the relay or protection circuit to not ground properly either? I'm skeptical because the transformer has three wires that are either wire-wrapped or soldered directly to pins attached to the chassis. On the other hand, I know enough to know that I don't know everything.
*Unfortunately the schematic file is too big to upload here, but is available freely from HiFiEngine
but if you can post and link it elsewhere, I can probably turn that 6.8MB file into something much smaller. Then again I don't necessarily need to if we have a simple quick way to look at it, like 2 clicks at most.
