Funky switches in Sony KV-4000 TV

[Phil Nelson]

Which one to choose, indeed? I don't have a manual, so without a schematic or part number to go by, I guess I'd have to pull the board and remove one to see exactly what's needed. Here's an animated GIF that I made to show the switch in action.



Are all of these switches momentary contact? The mechanics of this one aren't clear to me. There must be a little spring or rubber somewhere to push it back out, but all of mine are completely loose. (To make that two-frame animation, I pulled it out and then pushed it in, where it remained.)

Phil Nelson

[jr_tech]

Originally Posted by Phil Nelson

Are all of these switches momentary contact? The mechanics of this one aren't clear to me. There must be a little spring or rubber somewhere to push it back out, but all of mine are completely loose. (To make that two-frame animation, I pulled it out and then pushed it in, where it remained.)

Phil Nelson

I remember taking apart a similar-looking (non functioning) switch years ago... there was just a little conductive rubber donut that when compressed the center portion (where the hole should be) made momentary resistive contact to a pair of electrodes at the bottom of the switch. The push-button was rather loose and flobby with very little travel required to make "contact".
Just played with my set a bit more, and indeed some of the buttons *do* respond heavy pressure. Scan up/down can be forced to work sometimes, by pushing down hard on the tops of the buttons. I can't get the indicator button to do anything. If I push down hard on the band select button for a second or so and release it with a snap by sliding my finger off the front edge, I can nearly always get the band to change... YMMV!

jr

[WISCOJIM]

Originally Posted by Phil Nelson

Are all of these switches momentary contact? The mechanics of this one aren't clear to me. There must be a little spring or rubber somewhere to push it back out, but all of mine are completely loose. (To make that two-frame animation, I pulled it out and then pushed it in, where it remained.)

Phil, maybe this will help.

I was sent these from someone a long time ago for my KV-4000 series sets, but I never got around to installing them. I was told that these fit correctly, but have not personally verified that. They appear to have a piece of spring metal in them to pop them back out. Travel distance on the switch action is very minimal.

.

[rpm1200]

Has anyone tried poking around the stock at Digikey (or another supplier that provides spec sheets)? I found an SMT pushbutton to repair a Sennheiser wireless microphone there by matching up the dimensions I measured to the product spec sheets. Worked perfectly.

[Phil Nelson]

Originally Posted by WISCOJIM

I was sent these from someone a long time ago for my KV-4000 series sets, but I never got around to installing them. I was told that these fit correctly, but have not personally verified that. They appear to have a piece of spring metal in them to pop them back out. Travel distance on the switch action is very minimal.

Yes, those look like the right size (7 mm). I am tempted to try them out. Send me a PM if you're willing to part with them.

This all comes about because I use a Blonder-Tongue agile modulator to transmit TV indoors and I recently switched from using channel 3 or 4 to a higher VHF channel (12). Our house has some nasty RF interference sources and the higher VHF channels are less susceptible to such RFI.

Phil Nelson

[Phil Nelson]

So, I got the board loose.



And the switches arrived (thanks, Jim!).



The physical size looks close enough.



But it looks like the old switches have two terminals, while the replacements have four.



Not sure how to make these work. Am I missing something?

Phil Nelson