Harmon Kardon PM665 dirty switch problems.

[HiFiCanada]

I am having a lot of problems with the switches on the Harmon Kardon PM665, I cleaned them six months ago and now its starting to act up again. I was thinking of wiring out the Function and Tape Monitor and Tape Out switches maybe a few more, or replace them, but I doubt that they are still available today.
I think that the switches are worn, they should not need cleaning that often.

Any advise would be appreciated

Thanks in advance


Bob

 

[grateful]

That is the weak area of that generation of HK. If you can jumper out the switches you never use that are in the signal path you may be better off.

 

[cfinchrist]

I had a 655 VXI which did that. It just got worse and worse so I cleaned it more and more. I was told it's the silver contacts which continue to oxidize which causes the problem. I liked the sound of that unit and cleaned as needed for 15 years or so until it ultimately died of something else.

 

[HiFiCanada]

Jumper

That is the weak area of that generation of HK. If you can jumper out the switches you never use that are in the signal path you may be better off.

It will be hard to do as it is all curcuit board on the other side that I need to work on. Once I have all the source switches wired, what happens if someone turns the switch? :scratch2:Since it is all phono and inputs, I don't think if it shorted that could damage anything, would it?

 

[Raccoon1400]

What are you cleaning them with? Deoxit? In my experience deoxit brand is the only way to go.

 

[terra1]

I don't know what you mean by acting up, but those tiny buttons (e.g., muting) can be tough to clean and may still pop occasionally even after cleaning. Sometimes after an initial loud pop, the pop becomes quieter or goes away after pushing it a couple times, but the cycle popping can start over when you power up again next time.

Since I don't really change settings often, I just live with it.

But I see you have removed the face plate. That's what I did to access and clean the upper row of switches. I held the amp face up to squirt from the front hoping some Deoxit would drip down the length of the switches.

 

[terra1]

Also, from your arrows they look like the selector knobs. I have no problem with those after cleaning. And I saturate through all the openings on those.

 

[HiFiCanada]

Also, from your arrows they look like the selector knobs. I have no problem with those after cleaning. And I saturate through all the openings on those.

I also cleaned it that way , saturate the switchs through the openings and worked the switchs back and forth,it's always worked well that way until now.
I am afraid this amp my have other issus which is really sad:tears:,I bought it new way back in the mid 1980's and it really served me well.
I may have to put it on the service bench and rebuild it,which will be a big job, but it will be worth it.
I just hope that it will be succesfull, thats a complicated amp to work on.

 

[KrisM]

My PM660 has been acting up lately. First it was one of the mute buttons. I don't get why there are two of them, to be honest. If it is easy to bypass them I would, they are useless to me.
Now the problem is the source direct button. It actually has some side to side, and up and down play to it. Every so often the right channel drops out, or gets really quiet. A little sideways push to the button fixes things. It's an odd amp. Using the tone controls and the volume control it feels like a well made piece of gear. Using those tiny buttons it feels like a Yorx.

 

[HiFiCanada]

I took a small 5x7 speaker and touched the speaker terminals and the diaphram pushed out about as far as it would go, so I got plenty of D.C voltage. When I first turn the amp on, it plays well and then starts to get softer , I am very lucky not to have blown out my JBL 2245 driver.