Funky switches in Sony KV-4000 TV
 

My Sony KV-4000 color TV has four funky little switches on the front of the bottom part:

http://antiqueradio.org/art/temp/SonyKV-4000.jpg

None of these switches works, although the TV operates fine, otherwise. When I removed the bottom cover to take a look, I saw this:

http://antiqueradio.org/art/temp/Son...00Switches.jpg

These switches are tiny (at least, compared to components on the old tube TVs that I usually work on). They seem to be gravity operated, or else every one of them has a teeny spring inside that is busted. In any case, the white inner portion of the switch goes in and out when you press the tab-shaped part on the outside of the case.

If this were a larger switch on an old tube TV, I'd try to spritz a little DeOxit inside the switch in hopes of making it work.

Is that a good idea? If not, is there any chance of finding replacements?

Thanks for any advice.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

Hi Phil, my 4000 has the same problem, it's common I guess.

I think they had rubber inside that deteriorates so spray probably won't fix them.
They are fairly ordinary I think except they have taller buttons than most, I would bet there's something in the Mouser catalog that would work with a little adapting.

I recently found this circuit board from a GE Refrigerator that has five small switches, I was going to see if I could make them work, they have fairly tall buttons on them but I don't know if the lead spacing is right or not.

They are called TAC switches. We had a junk yard & saved
a lot of boards with different sizes & styles. They are in
everything. Its a matter of finding a fit.

73 Zeno:smoke:

...

Thanks for the info. I'm not eager to dig into this board until I think I have found some potential replacements, since the TV works fine on the low VHF channels with manual tuning. (The pushbuttons are to switch to high VHF channels/UHF, toggle the tuning indicator bar, and scan up/down in auto-tuning mode.)

Time to scout the thrift stores for a while in search of a donor . . . .

Phil Nelson

I'd recommend looking for a Betamax VCR that had individual selection buttons for the VHS channels as they may be very close to the ones in the KV 4000 set. Have the same set and exact same problem, but since you can't use the scan feature I just use it for a monitor now. Good luck in finding something that will work.

Another one here with the same problem.... stuck in low VHF band... will manually tune ch 3 & 4 with the knob and of course the A/V input works. I don't need much else these days. Do they always end up stuck in low VHF when the switches fail?

jr

I have found that the button will activate if pressed real hard. The one giving me the most trouble is the band switch for 2-6, 7-13, and 14-83. But now that analog is gone I just use the video in on the back and have the output from a digital converter feed video in.

Tons of promising looking tactile switches on the 'Bay, but how do you find the correct one? :scratch2:
http://www.ebay.com/sch/i.html?_odkw...witch&_sacat=0

Update: Tons more at the 'Zon place:
http://www.amazon.com/s/ref=nb_sb_ss...le%2Caps%2C609

not affiliated,
jr

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.

http://antiqueradio.org/art/temp/Ani...4000Switch.gif

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

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.

.

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.

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

So, I got the board loose.

http://antiqueradio.org/art/temp/Son...rdLoosened.jpg

And the switches arrived (thanks, Jim!).

http://antiqueradio.org/art/temp/Son...ntSwitches.jpg

The physical size looks close enough.

http://antiqueradio.org/art/temp/SonyKV-4000Switch1.jpg

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

http://antiqueradio.org/art/temp/SonyKV-4000Switch2.jpg

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

Phil Nelson