Pioneer SX-780 Output Relay Quirkiness

e30m3mon

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#1
I was over at a friend's house the other day and while we were talking, his Pioneer SX-780 suddenly started playing. Startled me, as the power was turned on and no sound..I figured the volume was turned down. He said - oh yeah ... it does that. Sometimes when he turns it on, there is a few second delay until the output relay clicks and sometimes there are several minutes' delay. Sometimes he has to turn the power off and see what happens when turns it back on.

Other than a quirky output relay, everything else seems ok for this old timer receiver. Anybody ever experienced this before? I might offer to have a look at it for him, but don't want to open a (dusty) can of worms.
 

MarkWComer

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#2
I have a 780, there’s a frying sound and the left panel lights don’t light for about a minute. If the speakers are engaged, there’s a pop on powerup. Replacing the relay didn’t fix anything. Runs fine after the first few minutes warmup.
 

e30m3mon

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#3
Frying sound is never good in audio equipment!

No such sounds out of this receiver and the lights come on when the switch is flipped.
 

Gepetto

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#4
I have a 780, there’s a frying sound and the left panel lights don’t light for about a minute. If the speakers are engaged, there’s a pop on powerup. Replacing the relay didn’t fix anything. Runs fine after the first few minutes warmup.
the frying sound means it is time to flip it :)
 

Gepetto

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#5
Frying sound is never good in audio equipment!

No such sounds out of this receiver and the lights come on when the switch is flipped.
My old Yamaha AV receiver has output relay failures, the contacts went intermittent and needed replacing. Sound would come in and out erratically.
 

e30m3mon

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#6
My old Yamaha AV receiver has output relay failures, the contacts went intermittent and needed replacing. Sound would come in and out erratically.
I had a Carver Receiver with the same odd behavior, but that was due to dirty/worn contacts inside the relay. This one seems to be ok from that perspective once the relay is "picked" or energized. So I'd believe this problem is in something related to the circuitry attached to the coil.
 

MarkWComer

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#7
I had a Carver Receiver with the same odd behavior, but that was due to dirty/worn contacts inside the relay. This one seems to be ok from that perspective once the relay is "picked" or energized. So I'd believe this problem is in something related to the circuitry attached to the coil.
That’s what I think. The relay is new, so it’s something else.
 

e30m3mon

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#9
That’s what I think. The relay is new, so it’s something else.
A "frying" sound and delayed lights-on make me wonder if your power switches contacts are badly arced/burnt inside - or possibly a component ready to fail is giving you some warning. I lucked out once and bumped into a tall electrolytic that was soldered into a board on a bad RCA XL-100 tv set. The thing fell over as the internal leads had decomposed. Easy and lucky fix ... that TV went on to serve many more years.
 

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#10
A "frying" sound and delayed lights-on make me wonder if your power switches contacts are badly arced/burnt inside - or possibly a component ready to fail is giving you some warning. I lucked out once and bumped into a tall electrolytic that was soldered into a board on a bad RCA XL-100 tv set. The thing fell over as the internal leads had decomposed. Easy and lucky fix ... that TV went on to serve many more years.
Or the sound of bacon... :)
 
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