Gutted - 777 woes

Mark1892

Mark1892

Member (SA)
Aug 21, 2018
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Hi all, haven't used my GF-777 for a few weeks then come to use it the other day and absolutely no sound at all out of the speakers and nothing registering on the VU Meters. Powers up fine with power to run the cassette decks and APLD lights but nothing else.

I've so far done a visual check of every wire and plug and looked over all the boards but nothing obvious standing out. Worked great and without issue when I last used it so was wondering if anybody can assist with a few things to try.
 
Fatdog

Fatdog

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May 3, 2009
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I would first check the power leaf/micro switch. I had the same issue with mine when it first arrived. Flipping the power switch pushes two pieces of flat, "springy" metal together. If those two pieces don't get good enough contact, you will have problems. You can try

1) polishing the two contact areas
2) slightly bending one or both to achieve better contact
3) attaching a small, thin, plastic booster (about 1/16" thick) onto the plastic power switch arm that will apply more pressure to the contact pieces
4) maybe all of the above

Number 3 is what I did and I have not had any problems since.
 
Mark1892

Mark1892

Member (SA)
Aug 21, 2018
111
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Durham, UK
Thanks for the reply Fatdog, I just assumed that if I had contact and the power light came on, that would be enough to indicate I had power, maybe not the case? Not enough voltage getting to the box?

I'll try all 3 of your suggestions and report back 👍

Fatdog said:
1) polishing the two contact areas
2) slightly bending one or both to achieve better contact
3) attaching a small, thin, plastic booster (about 1/16" thick) onto the plastic power switch arm that will apply more pressure to the contact pieces
Click to expand...
Tried cleaning the contact areas a little, used a small sliver of plastic as a bolster which pushed the contacts on to a firmer contact but unfortunately no change. I'll try to polish them a bit better tomorrow if I can find something suitable to get in there.
 
JVC Floyd

JVC Floyd

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May 6, 2009
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You should compare the voltage coming out of the power supply against the factory rated voltage and see if maybe you have some bad caps on the power board.
 
Mark1892

Mark1892

Member (SA)
Aug 21, 2018
111
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Durham, UK
JVC Floyd said:
You should compare the voltage coming out of the power supply against the factory rated voltage and see if maybe you have some bad caps on the power board.
Click to expand...
My meter is at work but have swapped the rear panel complete with working power supply from another box and still the same symptoms.

Jimmy
Do you know the point at where the power splits and maybe the first point to check the supply to the amp?

Thanks everyone so far 👌
 
Radio raheem

Radio raheem

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May 13, 2009
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i have seen these blow a resistor more than once at which point there is no sound, wish i could be more helpful than this
 
Mark1892

Mark1892

Member (SA)
Aug 21, 2018
111
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Durham, UK
baddboybill said:
I would recommend to start by cleaning all your switches first as this is simplest way to start narrowing down issues.
Click to expand...
Done when I first got it and was working fine, then done them all twice since the sound went off 🙁
 
Fatdog

Fatdog

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I just had another thought... do you have any sound out of the headphone jack?
 
Mark1892

Mark1892

Member (SA)
Aug 21, 2018
111
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Durham, UK
Fatdog said:
I just had another thought... do you have any sound out of the headphone jack?
Click to expand...
Nothing at all 🙁

Speakers have a slight bit of static coming out of them and can also hear a bit of a click through the speakers and headphones when flicking the loudness switch.
 
Mark1892

Mark1892

Member (SA)
Aug 21, 2018
111
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Durham, UK
Boomboxholic said:
Have you tried to use some contact cleaner and spray out the volume controls and the recorder switch?
Click to expand...
Yes mate done everything,right in there a couple of times.

baddboybill said:
Have you checked all functions? Radio, tape and line in? Also have you checked with batteries?
Click to expand...
Yep checked all, no sound and nothing on VU meters in any function, tried with batteries (all good ones).
 
B

Boomboxholic

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Jan 12, 2019
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Is there any fuses on the machine? If so check if there is any blown out ones. Also check out for worn out power regulators.
 
Mark1892

Mark1892

Member (SA)
Aug 21, 2018
111
3
18
Durham, UK
Boomboxholic said:
Is there any fuses on the machine? If so check if there is any blown out ones. Also check out for worn out power regulators.
Click to expand...
Fuses all good and what be the easiest way to check the power regulator? Bear in mind I have basic electronic skills 😉

This is looking like I'll have to pass it on to somebody with more knowledge than myself.
 
docs

docs

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It's obviously something common to all functions and not a separate channel issue.
I think it will be something in the power section myself, while powered off try flicking the voltage selector switch.
Failing that i would move on to doing some voltage checks and probably start at IC115.
 
Mark1892

Mark1892

Member (SA)
Aug 21, 2018
111
3
18
Durham, UK
docs said:
It's obviously something common to all functions and not a separate channel issue.
I think it will be something in the power section myself, while powered off try flicking the voltage selector switch.
Failing that i would move on to doing some voltage checks and probably start at IC115.
Click to expand...
Thanks Docs, I'll try that tonight 👍
 
Mark1892

Mark1892

Member (SA)
Aug 21, 2018
111
3
18
Durham, UK
Today is a good day. It's fixed. I don't know what was wrong with it or what actually sorted out the issues but I done a full strip down, removed every wire, connector and fuse, cleaned connections, cleaned pots and switches for about the 5th time which has had a positive effect.

Thanks for all your help 👍
 
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