SONY KV-8100 Portable
 

I have a SONY KV-8100 Trinitron 1982 bought new as a backup TV. It has very little use & has never been repaired. It has electronic tuning & 14 presets. It is currently set to all channels in this area & remembers it's settings. Everything works as new except when I checked the tuning function. The tuning lights come on however it's like the the 2 switches (up & down) are not making contact & also Channel clear acts like no contact. These switches have both a removeable cover & an external flip down cover.

The owner manual is currently MIA as I may not have looked at it since 82- it's here somewhere. I have the Sony schematic included w/ the TV.
The Sony schematic shows these 3 switches NO to connect points on
IC 002 CX 760C & a red (on schematic) wire to ground.

Primarily I work on cars including modifications & the electrical. I can pretty much fix anything except electronics at the component level & have never fixed a TV. I have a VOM & soldering iron.

Normally I would shoot some contact cleaner into the 3 switches.
So do you think it just needs the 3 switches cleaned?

Evidently you guys are very good & fixing many TVs w/o the Service manuals. While a Service manual would have limited if any help for me, would it be worthwhile to buy a Service manual for it though probably not needed for this issue?

...

Andy
The switches in question are as you described- evidently bad. So what's your recommended replacement procedure?
Thanks
Bill

...

I had to replace simliar switches on a Sears (Sanyo) beta vcr. (about the same age as this tv) I found some that were similiar in stock at Radio Shack (!) The only difference is the tab stuck up too high on the new ones; I was able to cut them down and they worked fine. Not too hard to solder them in.

Since I only need to tune in 1 preset to Channel 3 or 4, is there some way a probe be used to make the contact?

Pic. of switches. The two ovals at left bottom tune down & up. Over to right past a pin is the round Channel Clear.

I heard that the switches are long gone out of production, but you could probably make something by cutting up the rubber keypad from a late model remote hand unit. They have the exact same concept, and I bet it can be done!

Charles

Andy asked on the 15th for a pic. of the switches & mentioned one thing to watch out for to avoid electrical shock. Does a smaller TV like this Sony 8" AC/DC have less shock hazard voltage/amps than a larger tv like a typical 19"?

I jumped the switches to verify tuning would work fine if the switches were replaced. Later removed the center part of the switch which is snapped in & can be pulled to jump the switch w/ a probe.

The antenna connection is a 1/8" plug. The included adapter, 2 screws to 1/8" plug, was disassembled revealing a direct connection (no electronics).
A UHF 300 ohm bowtie antenna was connected which improves UHF to excellent while VHF remains excellent. Later the schematic was pulled from the Sony box which shows a 75 ohm antenna connection. Any explanation on the 300 ohm vs. 75 ohm antenna connection?