Speaker pop on shut off Sanyo JCX2900

[curtisw99]

Negative on the triac.
Look carefully at the schematic of the protection circuit. This kinda caught me by surprise. There is a set of NC contacts on the power switch that ground the relay drive when the power switch is moved to off. When turning the unit off, be decisive about it. You may have to take that switch apart and clean those contacts with some Brasso or Flitz. Make sure you get all the residue out.
If this works, it will be the first time I've seen fixing a power switch correct a "pop" condition.

New switch didn’t fix the pop.
The old switch was also a replacement.
Video added to show the “pop” sound

I’ll start looking in the protection board.

 

[lissenup]

New switch didn’t fix the pop.
The old switch was also a replacement.
Video added to show the “pop” sound

I’ll start looking in the protection board.

What switch did you use? Picture of the old switch?

 

[tarior]

Does your new switch have the same arrangement of contacts as the old switch?

 

[curtisw99]

What switch did you use? Picture of the old switch?

This is the new switch, and it was also the switch that I pulled out. I’ll bet whomever had this before was also chasing the “pop”

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[tarior]

Where is the protection circuit connected on the switch? On the slide section?

 

[curtisw99]

Where is the protection circuit connected on the switch? On the slide section?

When you say protection circuit, do you mean the board that runs the speaker relays?

The switch is only directly hooked to the transformers and the power

 

[tarior]

Have you looked at the schematic? The one I have shows two parallel sets of contacts (S14-1, 2) that when the unit is on and operating, are connected to nothing. When the unit is powered off, those contacts ground R420 in the protection circuit. If that resistor isn't being grounded upon power off, I can see the relay taking its sweet time to break.

 

[curtisw99]

Have you looked at the schematic? The one I have shows two parallel sets of contacts (S14-1, 2) that when the unit is on and operating, are connected to nothing. When the unit is powered off, those contacts ground R420 in the protection circuit. If that resistor isn't being grounded upon power off, I can see the relay taking its sweet time to break.

I get continuity from ground to the leg of r421 (edit: R420) with switch off. I get open circuit with switch on.
R421 measures 970k with switch off

Haven’t had a chance to measure the relay board parts except for C431.
C431 was 20% high.

 

[tarior]

R421 isn't our concern. R420 is, which should be 220 ohms and one end grounded when the power is off. R421 is for the headphones and should be 680.

 

[curtisw99]

R421 isn't our concern. R420 is, which should be 220 ohms and one end grounded when the power is off. R421 is for the headphones and should be 680.

My typo
Meant R420; my schematic says 1k

 

[tarior]

That's the wiring diagram, not a schematic. Either way, 970K is pretty much open compared to 1K or 220.

 

[Nashou66]

I wonder if his DMM is showing .970K not 970K .

Nashou

 

[tarior]

 

[curtisw99]

That's the wiring diagram, not a schematic. Either way, 970K is pretty much open compared to 1K or 220.

Oops!!

970ohm. I knew that’s what it was and for some reason I’m writing “k”

Sorry for making this confusing; my brain’s a bit fried. it’s been a really good holiday break. Need to get back to the office so I can rest.

 

[tarior]

My 2900K has a 220 ohm R in that position. It doesn't pop.

 

[curtisw99]

My 2900K has a 220 ohm R in that position. It doesn't pop.

The one at the end of the pencil?

 

[tarior]

That's the one. The board layout says 1K, the schematic says 220. Mine has a 220 (red, red, brown). I'm suspecting a revision. Maybe to address a power down pop issue. I guess we'll see what happens with yours.

 

[mroboto]

Is there a switch contacts saver capacitor across power switch lugs ?

The purpose is to limits arcing on switch contacts at turn On/Off, but sometimes as you switch off the unit, the capacitor discharge may cause a pop (Not always equal).

That always or often happens with tube amps, maybe other type of amps without a speaker outputs relay.

Sometimes, the switch is rare and unobtainable so I prefer to keep the capacitor, even if the pop bothers me.

If this is a cheap switch that can be purchase anytime, I remove that capacitor.

 

[tarior]

Is there a switch contacts saver capacitor across power switch lugs ?

The purpose is to limits arcing on switch contacts at turn On/Off, but sometimes as you switch off the unit, the capacitor discharge may cause a pop (Not always equal).

That always happens with tube amps, or amps that don't have a speaker output relay.

Sometimes, the switch is rare and unobtainable so I prefer to keep the capacitor, even if the pop bothers me.

If this is a cheap switch that can be purchase anytime, I remove that capacitor.

That won't cause a pop condition in a receiver like this.

 

[curtisw99]

That's the one. The board layout says 1K, the schematic says 220. Mine has a 220 (red, red, brown). I'm suspecting a revision. Maybe to address a power down pop issue. I guess we'll see what happens with yours.

View attachment 3666588

No dice
Pop is still present.

the one cap I replaced was 20% high. All the caps are original; maybe it’s time to recap the power supply, amp and relay boards?