FM tuner problem?

[TheDogHouse]

I got the same problem with two boxes that I'm fixing. The left channel is mute
or very weak when playing through the FM tuner. Only with the FM tuner.

Tape and tape adapters work fine, phonos work fine. Both channels are in balance
and the VU-meters rock. When I switch to radio the left channel dies or weakens a lot and
the VU meter on the left side is absolutely motionless.

No matter if it's the national broadcast, local broadcast or FM transmitter from 10cm away.
It's the same thing.


The boxes are based on ISP and SHARP technology. I had some other left channel issues with the
ISP (Luma), but I've fixed them already.

Before diggin' into it any deeper, could this be a common thing with "easy" solution? Anyone
had the same problem?

 

[jimmyjimmy19702010]

I've had the same problem before. Usually it's the band selector switch. Many of my Hitachi's have this fault when I get them, usually on one channel only for some reason. Deoxit that switch and after a lot of switching and cleaning, it may fix your problem.

Good luck,

James....

 

[baddboybill]

Actually I would clean both band and function switches good. This usually clears up weak or dead channels

 

[TheDogHouse]

Thanks guys. I'll try that.

 

[TheDogHouse]

I really didn't think it would help cause I HAD already cleaned all the switches. Well, first it didn't.
Then I decided to soak the switches with cleaner and then just strum the hell out of them. I did that like three times
and always let them dry in between.

What do you know, at least for Luma it finally worked! I got clear reception on both channels with
FM radio now!

Thank you!

BTW I don't have Deoxit and I don't think they sell it in Finland, but I used CRC electronic cleaner instead.
Somehow I've got the feeling that you guys here at the Boomboxery are big fans of Deoxit. Do
you think it would be worth the effort to try to get my hands on Deoxit? Is it that much better stuff?

 

[Superduper]

Nowadays, good quality gear uses switches and controls with "noble" metal coatings on the contacts. Because noble materials such as gold (and other fancy alloys) do not oxidize and corrode like plain tin, brass or copper, they last a whole lot longer and many many more cycles and don't really require the cleanings that common metals do. Unfortunately, on a lot of older gear, or cheaper quality new gear, the contacts are indeed made of tin or brass and do oxidize. Once they do, the frequency of cleanings seem to accelerate. The way to effect longer lasting repairs is to disassemble the controls and manually clean off all traces of oxidation and then treat the contacts with conditioner/preservative before reassembly but the risk of damaging the controls in the process is not worth it. Deoxit is a name brand made by Caig. They offer many similar products and the quality is top notch. It is not the only brand that works but in my opinion, is best for electronics work. Some of the other cleaners are better suited for electric work and not fragile or sensitive "electronics" work. Some will evaporate without residue. Others do not Some adds film of lubricant. All will work to some extent. If you do a lot of such cleanings and maintenance, I recommend you get yourself a bottle or two although the aerosol products might not be available internationally due to airmail restrictions agains aerosolized chemicals. One can of deoxit lasts a very long time.

 

[TheDogHouse]

Okay. Thanks.

I'm using CRC Oxide Clean for cleaning and CRC Contact Protector for the switches I recon are
gonna benefit from lubrication. I use the same stuff in maintenance for my Jukebox and Pinball
machine, but that's another story...

I'm going to be in the States this summer. Maybe I ought to buy a can or two of that Caig's stuff
and try to bring it home with me... We'll see...

 

[TheDogHouse]

All right. Next item. To all you wizards out there.

Got the Luma/ISP working, but the same tricks don't seem to be applying to my Sharp. It's GF-9191.
I have now cleaned and re-cleaned all the switches, in this case they are mostly push buttons and
sliders. I have a sound present in both channels, but it's not completely in balance. It's little bit
weaker on the left channel. It was a lot weaker prior to cleaning, I have to admit there's some
improvement. The VU-meter is just sitting still on the left side, eventhough there is sound. That's
weird.

Any ideas? Should I just keep on cleaning or could this be something else?

Is there some slider type switch specific issues? Or push button?

 

[baddboybill]

The boxes with controls on top usually are the worst when it comes to dirt and oxidation. Sometimes they are so badly oxidized that like Superduper stated they will need to be taken apart for a much better cleaning/repairing, Sharp, JVC and Crown are well known for this problem and the sliders are the worst because of how open they are on top

 

[TheDogHouse]

Okay, thanks again. I guess I will be disassembling some switches then. Man's gotta do what man's gotta do...

Cheers

 

[TheDogHouse]

All right, here's the push button rod from disassembled FM switch of the Sharp GF-9191.

As you can see I got it all shiny and clean and I also worked the rest of the switch accordingly.

But am I crazy? Shouldn't there be six of those metal connector pieces on it, not five?

 

[baddboybill]

Yes there should be 6. Did you check inside if it fell out?

 

[TheDogHouse]

I'm pretty sure there was only five of them when I pulled it out. Is that even possible? Could it have
been working at all with one missing? I have to remind that it wasn't working 100%, could this be
the reason?

 

[baddboybill]

I'm pretty sure there was only five of them when I pulled it out. Is that even possible? Could it have
been working at all with one missing? I have to remind that it wasn't working 100%, could this be
the reason?

Check the solder joints of switch to see if legs are soldered to board in area where the metal slide goes into switch

 

[TheDogHouse]

Yeah. Judged from the position and count of the legs that are soldered on the board there should be six of these
little pieces.

 

[baddboybill]

Yeah. Judged from the position and count of the legs that are soldered on the board there should be six of these
little pieces.

They look similar to others so maybe finding a parts unit with push button switches and using the metal slide from it

 

[TheDogHouse]

Yep, I took one metal connector from one of the AM channel rods and put it in the FM rod. Works
like charm. I reconed I'm not in so much hurry to get the AM channels working cause I don't even
think they broadcast anything on them up here. I'm gonna fix the AM channel when I get the spare.
I'm not looking so intensively, though, but eventually I'll for sure get around fixing it.

I still have some issues with "Searcher's" tape deck, that's what I'm concentrating now.

And then I have a GF-9494 with multiple issues lined up as next patient. Thanks for all
your help!


Cheers

 

[TheDogHouse]

That's her pic.

She's not terminal by any means, no, just needs a little TLC and complete cleaning to be perfect.

 

[LJV]

Don't be surprised to find missing or poorly assembled part, even if unit has never been opened before. People assemble parts, and people make mistakes.

Once a neighbor brought his Phillips TV, saying that it lost control over volume. I've opened it up, and found that one big IC on the PB was still held with some factory tool they obviously use for positioning before pressing it into slot. I've removed that tool, pressed the IC into slot, and it started working like a charm. It was a 1.5mm thick steel clamp, that prevents bending or breaking of IC pins while it is being positioned over slot, before the final push. It allows the pins to enter holes in the slot only partially, not all the way. The IC in my neighbor's TV was only initially attached, the tool was never removed, so after a while IC got loose, and lost all of poor contact it had.

Live and learn...

 

[TheDogHouse]

Yeah, I'm pretty sure that actually was an assembly fault. Obviously the box was never opened,
I mean you could see that. At least the push button switch was never opened, that's for sure.
Unless someone opened it and poured dirt in it...

And I did not drop it while pulling it out!


This is my story and I'm sticking to it.