Sharp GF508 no sound at all.

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BoomboxLover48

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This is the Japanese version of 9696.

I had some free time to work on this box and found the following issues.
The last time I tried it was working okay except it needed belts.

Power turns on but no sound. :blush:
Tape functions work, need to replace belts to see if I get audio.
When the volume slider is moved there is no sound at all from speakers
VU meters show no signal activity.
I cleaned the tape fader switch and headphone jack.
In radio mode when I turn the tuning knob I can see the stereo FM LED turns on to show stations, but no LEDs of VU meter glows.

I was wondering what can cause this.
There is not even a faint sound from the speakers. :bang: :bang: :bang:
 

Reli

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Bad amps, caps?

Or just a dirty function switch?

Also, I think there are multiple switches for FM and Wireless FM on that Japanese version.
 

BoomboxLover48

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Reli said:
Bad amps, caps?

Or just a dirty function switch?

Also, I think there are multiple switches for FM and Wireless FM on that Japanese version.
I cleaned all the push switches on the top but left the sliders alone. Looks like the amp is completely out. No warmth on the heat sinks. Top rear push an engage ones are those for power, Tape, FM. AM and all
 

Reli

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What about when you use Aux? I had one of those boxes, and it had Aux but I forgot which switch it was. It was one of the push buttons next to the power switch.
 

BoomboxLover48

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I will try that soon. It is that next to power switch/fader control switch. It is a rectangular mixing microphone slot with two plug holes and we use the larger hole. I cannot find connector for that now. :blush:

I am doubtful the power switch is working okay. When I press it is not turning on anything. When I release it doesn't make any difference.

The rotary fader control is on the top and a switch at the bottom in that metal box enclosure.

I was wondering if anyone opened and work on it.

Just found this link....

https://boomboxery.com/forum/index.php/topic/23588-sharp-gf-9696-junker-rides-again-updated-20615/?hl=%2Bpower+%2Bswitch+%2B9696


James worked on it and may be can throw some light here...
 

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Reli

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My 508 had jacks on the back that worked as Line In, and there was a button for Line In between the power button and the tuner band buttons.
 

BoomboxLover48

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Reli said:
My 508 had jacks on the back that worked as Line In, and there was a button for Line In between the power button and the tuner band buttons.
That is correct! I was thinking about 9696.
I saw a youtube video where they were using a IPod and playing it through the far left connectors when you look from the rear..
 

jimmyjimmy19702010

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Being a Japanese model, is there any chance of an AC over voltage situation? The reason I ask is that in many cases, the main amp circuit is not protected by voltage regulators and are often fried first. Voltage sensitive components like tuners are usually well protected by regulators and often still work OK after an over voltage event.
 

BoomboxLover48

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jimmyjimmy19702010 said:
Being a Japanese model, is there any chance of an AC over voltage situation? The reason I ask is that in many cases, the main amp circuit is not protected by voltage regulators and are often fried first. Voltage sensitive components like tuners are usually well protected by regulators and often still work OK after an over voltage event.
I always used a 120V to 100V step down transformer.

The previous owner might have used regular 120V line. :sad:
 

jimmyjimmy19702010

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Pressing play on the deck will usually provide power to the amps bypassing the power switch. If you get no sound from the speakers with the play button pushed down whilst in tuner or phono mode then the power switch way not be at fault.

Come to think of it, if the tuner and deck are getting power on AC, then the transformer should be ok which elimates an over voltage situation as the transformer would be fried first.

Might be time to get out the DVM and see if that amp board is getting any juice.
 

BoomboxLover48

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jimmyjimmy19702010 said:
Pressing play on the deck will usually provide power to the amps bypassing the power switch. If you get no sound from the speakers with the play button pushed down whilst in tuner or phono mode then the power switch way not be at fault.

Come to think of it, if the tuner and deck are getting power on AC, then the transformer should be ok which elimates an over voltage situation as the transformer would be fried first.

Might be time to get out the DVM and see if that amp board is getting any juice.
Thanks James!

That is where I want to start!
 

Reli

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Where did this 508 come from? If it came from Europe, maybe the owner replaced the transformer with a 220V one.
 

baddboybill

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Where did this 508 come from? If it came from Europe, maybe the owner replaced the transformer with a 220V one.


That's true and best way is test transformer with meter on dc out


Bad Boy Bill
 

baddboybill

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Royce one thing I will say are the Sharps and other units with top mount switches and pots are always prone to issues with dirt and even worse oxidation. Both mixed and sometimes cleaning the insides takes time and even needs to be opened up to do good job. I've had a few that took a while to get them clean. This is most likely the culprit 😉. Good luck!!!


Bad Boy Bill
 

BoomboxLover48

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baddboybill said:
Royce one thing I will say are the Sharps and other units with top mount switches and pots are always prone to issues with dirt and even worse oxidation. Both mixed and sometimes cleaning the insides takes time and even needs to be opened up to do good job. I've had a few that took a while to get them clean. This is most likely the culprit 😉. Good luck!!!


Bad Boy Bill
As always! Thank you Bill for your help! :bow:

This box is like it came from a NEW BOX....that is what I worry about it.


Like James said the previous owner might have connected it to our 120 to 129 V supply and killed the amp. :-O :sad: :'-(


What can I say! It was working when I got it say a few years ago...might have been on the last stages of life.......... :blink: :sad:
 
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