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

2 of the 4 terminals on the replacement are duplicates of the other 2. With a DMM you will find that there will be 2 pairs that always have continuity, and that when pressed all pins will have continuity with each other.
Essentially it is a SPST with extra terminals....

If the mech can deal with the switch not being centered you could clip the duplicate pins and only solder 2 (if that works some superglue between the new switch and the board may be a good idea) ....Other wise you could possibly solder the duplicates together, and add new centered leads to go through the board.

Mount them rotated 45 degrees and clip off two opposing corners. so instead of [] with pins at all 4 corners, its <> with pins top and bottom.

Thanks for the info. That gives me some ideas to try.

Phil Nelson

Woo-hoo! The new switches worked.

The replacements will fit the PC board holes diagonally if you turn them 45 degrees and snip off opposing leads. I also had to bend the leads slightly inward to fit the holes. They have a slightly shallower body and a longer shaft than the originals, which makes them a little taller, overall.

http://antiqueradio.org/art/SonyKV-4...esCompared.jpg

I was afraid the new switches would be too tight vertically, so I skimmed a bit off the shaft ends with a Dremel tool.

http://antiqueradio.org/art/SonyKV-4...chTrimming.jpg

I won't pretend it was easy to install these teeny switches and get everything back together, but with patience it all got done. The red arrows point to the new switches; note the diagonal placement.

http://antiqueradio.org/art/SonyKV-4...sInstalled.jpg

Now, all four switches are operational. I can select low/high/UHF, turn the channel indicator on/off, and choose channel up/down in auto tuning mode. Pretty fun! I had never been able to use auto tuning before, so it was gratifying to see that kick in.

I'll eventually write an article for my website showing the process with some additional photos.

Thanks again to WISCOJIM, Electronic M, and NoPegs for their great advice, and especially for the free parts!

Jim mailed me 8 extra switches, and I doubt I'll ever need the extras. (I don't like repeating projects, and cramped PC boards are not my favorite thing to work on.) If anyone else would like some switches, send me a PM and I'll be happy to pass 'em along.

Regards,

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

Phil, thanks for showing us it can be done. Hopefully one day I'll get around to fixing up my sets.

.

As threatened, here's a little article with some additional photos of the switch replacement:

http://antiqueradio.org/SonyKV-4000ColorTelevision.htm

Regards,

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

Phil, in the name of "full root-cause investigation," would you consider parting with some or all of your original switches that went bad?


I'd like to do two things with them: :scratch2:


First, carefully autopsy them to see exactly what is the cause of failure, since this issue affects many if not most of the surviving examples of this model.


Second, I want to attempt to "graft" a modern construction replacement tactile button switch onto the "roots" of the original switches. If successful we could then begin a very interesting game of lets-pass-the-parts. :naughty:


If I'm successful in refitting all of your removed dead switches, then the reincarnated switches can be sent to the next person that desires a return to the pushbutton auto tuning age of wonders. Since the parts that would be sent to them are direct drop in replacements, the task of swapping them out becomes a straightforward process: just desolder the old and busted switches, put in my hybridized refurbished units, button the chassis back together, and then send their duds my way for rework in preparation for another go-around.


I'm confident that I have all the tools and skills needed to make reworked switches using strategic pieces of the old ones (Specifically the baseplate with the perfectly sized and oriented leads.) that won't require any trimming, rotating, or bending; and will have actuator shafts that stick out precisely as far from the surface of the board as the originals did. The end result should be that the feel of the front panel button push is just like the originals felt the day it came out of the box. :thmbsp:


If anyone else is interested, you can pull out your broken buttons and send them my way, your set will just be on the bench for a few days without switches, possibly up to two weeks if I somehow happen to not have any properly sized buttons in my stash. I'd then have to select and order suitable replacements. I'd put the chances of that happening around 30% or less... I already have quite an exciting assortment of tactile switches on hand. :yes:

Sure, you can have the old ones. PM sent.

I was thinking of cutting one open, just to see what's inside, but you'll probably do a neater job.

Phil Nelson

...

PM replied to!

Not only do I hope to do a neater job, but the YL loves macro photography, so look forward to seeing some very up close and personal autopsy shots soon. :yes:

Gentlemen...

I have met with success! :banana:

Photos forthcoming tomorrow when the YL actually remembers to grab her camera bag complete with macro stuff.



*BZZZT!* No rubber in these.

What actually seems to cause the failure is the (tiny!) chunk of conductive plastic popping through the cone that holds it, which explains why the "stalks" don't have any downward movement... Photo details hopefully tomorrow evening.

Phil,

Nice job! Just one little nit-pick in your website description of the KV 4000 CRT. "--- with very fine dot pitch." The KV 4000 uses a Trinitron CRT with vertical stripes, not dots. I'm sure you knew that though.

Thanks for your note. I have corrected the article.

Phil Nelson

Photos are here!


Successful graft attempt. Ugly but meets the design specifications. I'm exploring options to improve it aesthetically.

http://www.funkengine.net/vk-img/201...8/IMG_6586.JPG

Precisely 3/8" from board to tip, and 1/64" shorter when depressed.

http://www.funkengine.net/vk-img/201...8/IMG_6587.JPG

So where does the magic happen inside? Here's a peek...

http://www.funkengine.net/vk-img/201...8/IMG_6595.JPG


This is the second one I opened, the carbon slug is still almost where it should be, but it has slipped just a bit too far into the plastic cone that holds it.

http://www.funkengine.net/vk-img/201...8/IMG_6598.JPG

http://www.funkengine.net/vk-img/201...8/IMG_6600.JPG

This is how the first one looked when I opened it up.

http://www.funkengine.net/vk-img/201...8/IMG_6601.JPG

http://www.funkengine.net/vk-img/201...8/IMG_6602.JPG

Here's more or less how the "graft" works out.

http://www.funkengine.net/vk-img/201...8/IMG_6603.JPG

In addition to aesthetic improvements I need to select a suitable adhesive to fill the gap here that is non-corrosive, non-conductive, and able to withstand soldering temps at least briefly. Without something holding it together things can get out of kilter when actually installing the units.

http://www.funkengine.net/vk-img/201...8/IMG_6604.JPG


Another option I found in my tac-switch drawer would be these guys. They have exactly the necessary lead spacing to be drop-in replacements, but to get everything to line up right they'll need a bit of a shim between them and the board to bring everything up to the required height.

http://www.funkengine.net/vk-img/201...8/IMG_6592.JPG


Look for "revision 2.0" coming shortly. :thmbsp:

Thanks again to Phil for getting the ball rolling on the whole thing. :banana:

Well, I have to admire your micro-surgery skills (and patience!), both better than mine.

Phil Nelson

Another KV-4000 owner noticed my article and asked whether I still have any spare switches. Sorry! I have donated the extras that I got from Jim.

But I might as well ask . . .

Has anyone else with a KV-4000 found a source for these switches? They all seem to go bad, so a reliable source would be helpful to know about in future.

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

Dont remember who but someone had a ton of
TAC switches in there catalog years ago. Try a
search for TAC switch & see whats out there. May
not find the exact ones but maybe something that can be moused.

73 Zeno:smoke:

I like the switches that NoPegs found. Looks like they could just be soldered in a bit above the board, and then need no shims. NoPegs - do you have an ID on those?

.

Deja Vu on this thread. Thanks to Phil Nelson and his excellent write up of this switch issue. I bought this set brand new on 1-28-83 for whopping $456 wholesale. Mine was manufactured in June of 1982. I know Sony brought this out in 1980 and at the time was the worlds smallest CRT color television. Here is my record of the repair.

Taking the six underside screws out reveals this board. But switch board is still a bit underneath. Having problems posting more than one photo at a time.

Repair went nicely. I must have had same type of switches Phil did as I had to cut two of the ends off and mount it diagonal. Taking out four screws lets this piece remove so you have some additional room to work.

Now that that is repaired I wanted to test my B&K 1246 color generator I purchased on eBay more than a year ago. These Sony KV-4000 sets have solder pads that you either remove solder at one place or add it at another place on the B board to do vertical and horizontal Centering. My horizontal is slightly to the left of horizontal center. I'll try the adjustment called out in the manual.

Here is a close up of the B board with a toothpick end showing where the solder pad that you short to move the horizontal centering more to the right. The one directly underneath it you can see is already shorted. This would be the pad pairs that center it more to the left of horizontal center.

Set has slight overscan, which I believe was somewhat common. I wish the adjustment had moved it a little more to the right side. But overall I think I'm done. My avatar is this set on color bars after the centering. Here is crosshatch pattern after all my adjustments. Unfortunately there are no pin cushion or barrel adjustments on this set. This is already quite compact and Sony probably made some circuit cuts where they had to for space.

Did this all on the dining room table. Glad I bought the manual when I worked at the shop. I bought a lot of Sony gear and always made a point to also purchase a manual. Here's a shot of my limited workspace last night.