Hello!

I'm quite new to fixing electronics, so I hope you can bare with me. I can solder and test things, but I just don't have the knowledge to fix this. This boombox has two separate problems:

- the left channel is almost silent, mostly putting out hiss/noise.

- cassette play is muddled

Here's a video I recorded

http://www.youtube.com/watch?v=U1RKfFBP6Dg

First you hear the muddled sound of cassette play. It sound like it is coming from underground, yet it is playing at correct speed (at least correct enough). Here you also  hear the left channel being silent as I change the balance.

From 0:28 on the playback comes from radio. The sound is good and clear, but near silent on left channel.

Any help on how I could restore the left channel and cassette play is much appreciated!

Hi! Where would I apply it? I don't think the balance potentiometer is the reason, as it doesn't crackle at all.

Also I just tried with headphones and the same applies there, the left channels is silent. So it is not the speaker at least.

Try cleaning the record bar of the tape deck, then all switches and pots.

There could be an electronic problem but you will need the service manual to do some checking.

I tried cleaning the balance pot and tape/radio/phono switch to no help.

Here's an mp3 recording of the headphone output to better demonstrate. First radio on right channel then left, then tape on right & left channel after that.

edited out

I found schematics for gf-8585 which I believe is quite similar.

edited out

If cleaning doesnt help... Best to start measuring voltages around IC203. If this schematic works for the 8686...

I opened up the radio and tried cleaning the pots and switches but no help. If I jump wire the amp section I do get sound on both channels, so the amp is working also I think?

How would I go in identifying what is the culprit, and what else might it be than faulty potentiometer? None of the condensators bad to me (bulging, leaking) but I'm no the best judge for that.

Other symptoms I can list are:
-the left channel has inherent noise, that is different from the amp noise. This is easily noticed when selecting the phono input and playing with balance and volume.
-> right channel noise is the amp hiss while left channel has a louder, more like white noise character.

-When pressing the record bar the left channel degrades a lot more than the right channel (can be hear even though the left channel signal is always so silent).

Here's a couple of pictures of the pcb if it helps.
http://i42.tinypic.com/52i33s.jpg
http://i44.tinypic.com/30trw54.jpg
http://i42.tinypic.com/1m26s.jpg

Give me a little time to study the schematic and try and point you in the right direction.

Also, we could do with the full service manual to be sure because the 8686 is likely different.

Does the 8686 have any Dolby ?

Hi!

Thanks for all the help! Yes they seem different, 8585 and 8686.

There's no dolby.

I couldn't find the the service manual, so I had to buy it. I hope to get it soon, I will then share it.

How does it sound when you use the line-out on the back? This will override the volume and balance pots and power-amp section...

Besides the switches, you need to dismantle and clean the headphones socket.

Looks like it has GF-8585's tape door, original GF-8686 door is different.

There's no line out, at least not an RCA one.

There's a DIN 5 connector but I imagine it is also only input?

Strange, my gf-8686 has a RCA line-out on the back. it's a gf-8686Z. Think there will be an output in the DiN connector, but I don't know wich pins you have to use.

your z model mate is a u.s market version,most likely its an 8686e in question here,and rather stupidly,sharp only fitted a 5 pin din socket on a lot of 'e' spec gf's,as a cost cutting measure for certain markets.the only e model of gf from that period with rca plugs was the 9494 i had-i had a 9696 with rca plugs too but that was a z model.

Hi docs & others,

here's the service manual for gf-8686.

https://www.dropbox.com/s/lmx9...86HHB_SM_SHARP.pdf?m#

DIN output is silent too on the left channel.

Also, I recorded a sound file with different information on channels to test with, and noticed that the little sound there is on the left channel is bleed from right channel.

Loudest is the white noise, then the silent bleeding signal from right channel and far behind them is the actual signal input of the channel.

To take a shortcut, your problem sits somewhere between switch 10 (phono, radio, cassette selector) and the power-amp. You could check the voltages on ic 201, ic 301 and the line-amp transistors to see if there are a difference between both channels or the ones they give in the manual.

I would also suggest to check te resistance on switch 102, 105, 10. To check if they are working.

But lets see what docs says. I'm far from being a pro haha 

I reflowed solder on switches and preamp section and it fixed it, great! Thanks for the help. Cassette got satisfactory just adjusting the azimuth by ear.

result happy days   .

great stuff, glad you got it sorted.

Here's a little video of the GF-8686 working in full stereo, hope you don't mind the music choice...

http://www.youtube.com/watch?v=h7N_Obla810

It's a nice little & good looking box. The sound is good at lower volumes, higher volumes  & deep bass of course are not handled as good as with bigger radios. 

I'll take some of the files I uploaded down soon, as they are on my personal webspace, but I'll leave the service manual up here for anyone in need.

Yeah, it's a nice radio. Glad you got it fixed! I like mine too. Only thing missing is a separate bass and treble control. Mine is lacking a little treble, but it sounds quit good for its size. Thanks for the manual, hope I never have to use it lol...

Hi htk, I have a sharp gf 9191 with similar problem in left speaker, in radio mode both channels works fine (woofer and tweeter) but in tape mode, the left channel sounds a bit lower than right channel and the sound is not "crystal" as it is in the right one, could you please share me the video you posted in youtube (cause it says private). And can you tell me pointing in pictures where you resolder to fix it? thank you!!

and clean the heads guys

Problem solved, it was bad solder points on tape head, resoldering better and ready to go!!