2 problems with SHARP GF 777

I have Sharp GF 777 with 2 problems:

1- Left VU meter not working properly - reported a very low level.
When I push VU button to Batt Check - Left VU metter go to right - this is normally.
Is it possible to have mechanical problem whith this VU meter.

2 - Fader between tape 1 and tape 2 works only to the right channel.
In the Left Channel I hear mix between tape 1 and 2.

I can not understand why is it.
If someone have any idea???

Spray all knobs and switches whit contact cleaner, move them a few times and report after . Check here are a lot of treads about that. And .

Thanks for the reply.
What I needs to do, to reach the buttons:
To remove all knobs and push through a spray ->

or need to disassemble the entire boombox?

You can just remove the knob and switch covers. It helps if your contact cleaner spray has the small red straw / tube.

The VUs on the GF-777 only measure input volume. They are not tied to the output volume. If you are using a line-in source like an iPod, try increasing the volume on the iPod and see if the VU meters measure more.

I remove the knobs and push through a spray in a holes:

but without result - left VU indicator has a very low level.
I have no problems with the sound: sound is good and balanced.

When I turn the knob on the mic fader into the mix position - I have the same problem (just like tape fader)
fader works only to the right channel, sound is still mixed in the left channel.
I guess, there is some more serious problem...
Or is necessary to open and disassemble the boombox and cleaned thoroughly.

Spray the switches on the back as well . And move em many times.

I opened the back cover of the boombox - (this is not my picture):

What is that thing with the spring (arrow A)??
I found the place of buttons (arrow B).
If i wanna clean them with a spray, I will have to disassemble everything!
Now, is no time to do this ...
I found a board that is connected to the VU indicators (arrow C).

Here's a picture of the service manual:

I decided to do some measurements:
I measured the voltage supplied to the VU indicators:
Submitted to the same voltage to both VU indicators.
D-F = 0.3 volts (right channel) D-E = 0.3 volts (left channel);
I measured the resistance of the VU indicators:
Left indicator has much more resistance from the right!!!
ME201 = 1.3 K ohms (right channel); ME202 = more than 800 K ohms (right channel);
There is some problem with the left VU indicator- this is bad news!
I do not know whether it can be repaired or replaced with another??
If anyone has ideas let write here...

Did you remove the meters from the circuit or did you test them in-circuit?

Also, it's my personal opinion that one should ALWAYS clean controls and switches by disassembling as far as necessary to obtain good access. Spraying them from the front through the cabinet is not nearly as effective and causes other issues as the solvent gets all over the place. Most switches in quality boomboxes will deliberately shroud the switch contacts at the opening to prevent dust from entering. The shroud can be a hard plastic or metal "deflector" or it could be a felt pad.

Try reading this thread
viewforum.php?f=53

Superduper said:

Did you remove the meters from the circuit or did you test them in-circuit?

Click to expand...

Of course, that cast off the connecting wires and then made ​​measurements.
ME201 = 1.3 K ohms (right channel); ME202 = more than 800 K ohms (right channel);

Voltage supplied to the Left VU indicator in the VU meter mode = 0.3 v.
Voltage supplied to the Left VU indicator in the battery check mode = 1.6 v.
(Boombox work with 220 v, and I push the metter/light button, and check the voltage).
In battery check mode the Left VU indicator work and arrow goes to the right position.
This 1.6 v in the battery check mode, is bigger than 0.3 v in the VU meter mode,
and is enough to drive the VU indicator.

Then I did another test: exchanged points of the wires to thе VU meters ( L to R and R to L),
and again only worked right indicator....
This convinces me, that the problem is in the left indicator.
Then connected the wires correctly.
Now, I dont know what to do?

goodman said:

Superduper said:

Did you remove the meters from the circuit or did you test them in-circuit?

Click to expand...

Of course, that cast off the connecting wires and then made ​​measurements.
ME201 = 1.3 K ohms (right channel); ME202 = more than 800 K ohms (right channel);

Voltage supplied to the Left VU indicator in the VU meter mode = 0.3 v.
Voltage supplied to the Left VU indicator in the battery check mode = 1.6 v.
(Boombox work with 220 v, and I push the metter/light button, and check the voltage).
In battery check mode the Left VU indicator work and arrow goes to the right position.
This 1.6 v in the battery check mode, is bigger than 0.3 v in the VU meter mode,
and is enough to drive the VU indicator.

Then I did another test: exchanged points of the wires to thе VU meters ( L to R and R to L),
and again only worked right indicator....
This convinces me, that the problem is in the left indicator.
Then connected the wires correctly.
Now, I dont know what to do?

Click to expand...

If the right meter then worked that would be the lead going to meter is the problem and not the meter itself

If you are convinced that the meter is bad, you can replace it. Good luck finding parts though. Someone might have a parts unit they are wiling to part out for you.

As for measuring voltage in VU and BATT mode -- that tells you nothing. That's because both functions are different and so you would expect the readings to be different. In BATT mode, the signal is supposed to be a static representation of full battery voltage. In VU mode, you will get a dynamic representation of the audio signal so unless you are playing back a steady sine wave, the variations in the signal will result in a low average reading anyhow and if the signal transitions is too fast for your multimeter, then your readings don't mean much.

I suggest you adjust VR105 and see if you can bring up the meter level to your satisfaction.

Superduper said:

I suggest you adjust VR105 and see if you can bring up the meter level to your satisfaction.

Click to expand...

Yesterday I thought about this option. VR105 is currently in the middle position.
I will need to open the back cover for the third time.
The bad thing is, that many openings and closings, breaks socket screws ...

These days I found another problem - with the recording.
When recording from microphone sound is good.
When recording from radio, cassette or line-in sound is not very good. Sound is hoarseness.
On this link you can hear the test recording:
http://kiwi6.com/file/i68aed6xb0
Click on play button "Listen to mp3"
Is anyone had a similar problem?

i have this problem to, with the VU meter
I think, a amplifier in the Potiboard is broken and some poties don't work without a voltage...(or minus pole)
Bass and treble don't works to on one channel.
And some potentiometers are very stiff.

Then i have other screws in my 777. Original is 70 milimeters long and 4 mm thick.
My screws are 4,2 mm thick...i works very good

ok, my reply is a bit late
(sorry for my englisch, i try to give my best )