700II On/Off Switch ?

[J!m]

Old Kenwood could be the antique voltage regulators too.

That needs proper diagnosis.

 

[wattsabundant]

Replace the switch (you have no choice on that), install a “quencharc” to absorb the switch arcing…
View attachment 81763

I’m very familiar with quench arcs. We use them by the hundreds at my day job. Pack Tron has an excellent data sheet with scope photos of before and after voltage spikes across contacts. Will post it here later

 

[62vauxhall]

Old Kenwood could be the antique voltage regulators too.

That needs proper diagnosis.

I am going with the flow on this one. Over the past two days, I google searched a number of terms and power switch failure was commonly cited as the source of problems with multiple Kenwood, Pioneer and Marantz models. This Kenwood I have is model KR6030 and the power switch is located at the end of the speaker switch shaft.

After re-reading, that AK post mentioned earlier, it was less intimidating than I thought. The OP quoted a maker and part mumber for the device he used. A hand drawn diagram was also included which looks fairly easy to follow.

Even though that thread was started in 2013, the part in question (or a variant of it) looks to be still available and on hand at Digikey. I ordered two.

Q4025L6TP

DigiKey Part Number
F7168-ND
Manufacturer
Littelfuse Inc.
Manufacturer Product Number
Q4025L6TP
Description
TRIAC ALTERNISTOR 400V 25A
Manufacturer Standard Lead Time
12 Weeks
Customer Reference

Detailed Description
TRIAC Alternistor - Snubberless 400 V 25 A Through Hole
Datasheet
Datasheet

 

[J!m]

The power switches are a known issue but it still needs everything checked.

SM will have target voltages at test points and those should be in spec.