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Adcom GFP345

M

Marantz22xx

Member
Hi everyone a friend of mine has a problem with his ADCOM GFP-345.
He got those high pitched signal tone about 5700 hz from time to time from his GFP345 in both speakers. It disappears and come back again and again.
When the music plays loud then he does not hear these signals but sometimes the beep is really above all else so you can distinguish it easily.
It comes and goes how it wants with no special order.

You think it can be capacitors ?

Do you have any service manual/schematic for GFP345 ?

Cheers :beerchug:
 
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First, establish by process of elimination that this is the actual source of the problem, rather than something connected to it or in the vicinity.
 
Make sure it's not near wifi transmitter or a computer modem, those things cause all kinda noise in audio equipment. Had the same problem here in my office system, finally realized what it was and cured the problem by moving the wifi transmitter away from the stereo.
 
audiojones said:
Make sure it's not near wifi transmitter or a computer modem, those things cause all kinda noise in audio equipment. Had the same problem here in my office system, finally realized what it was and cured the problem by moving the wifi transmitter away from the stereo.
Click to expand...
The problem is the same with or without wifi.
 
Pio1980 said:
Try the preamp in a different setup as a parity check, it is a very simple dual IC based control center.
Click to expand...

This is what i read

C901 4700uF 50V
C902 4700uF 50V
C910 10uF 50V
C911 10uF 50V
C201 220uF 25V
C202 220uF 25V
C207 470uF 25V
C208 470uF 25VF

D202 J555 T912
D201 J555 T912


IC201 ADCOM 6AA9202
IC202 ADCOM 6AA9202


IC203 ADCOM 7AA9150

IC902 DE WAAF ADCOM J3 9024

IC901 KENABVC ADCOM J1 9018

Q901 C945 P213C
Q901 C945 P213C
Q901 C945 P213C

Mini Relay
RY Takamisawa RY24W-K Japan 920481
 
Pio1980 said:
Try the preamp in a different setup as a parity check, it is a very simple dual IC based control center.
Click to expand...

This is what i see ..IMG_20190224_212755.jpg IMG_20190224_212839.jpg IMG_20190224_212905.jpg IMG_20190224_212911.jpg IMG_20190224_212919.jpg IMG_20190224_212944.jpg
What to mod/test first ? :)
Have no service manual.
 

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Are you certain beyond doubt the unwanted interference is from the preamp? There isn't a lot to go wrong in it, and in both channels point to a common mode problem like from outside of the preamp, or a power supply instability from low ESR bypass/reservoir elyticaps in the preamp.
 
Pio1980 said:
Are you certain beyond doubt the unwanted interference is from the preamp? There isn't a lot to go wrong in it, and in both channels point to a common mode problem like from outside of the preamp, or a power supply instability from low ESR bypass/reservoir elyticaps in the preamp.
Click to expand...
Hi i was at my friends house and =
When I connected the DAC directly to the 535II then there was no beeping sound with irregular intervals, even speakers are completely deadsilent but it can be other components. and i plugged back the GFP345 then I get more noise it hears when you are close to speakers but it is other components..but then you have that high "sound" Even when I connected the vinyl player I got the same sound from both speakers it is not all the time but it is annoying. Bass response feels much better now when I changed the cables.

Which one is (power supply instability from low ESR bypass/reservoir elyticaps in the preamp.)?

Cheers

is there any ide to mod it ? If yes what is the best / cheapest mod ?
 
Re mods, it looks like a pretty recently unit as-is, with good parts.
You see two "busy" sections, one near the front panel with two ICs which is the gain portion, and the other near the rear where the power comes in. That's the power supply portion. I would use an in-circuit esr checker on the eltyicaps in that section if it was here, otherwise, it could be one or more weak ones that *might* make a regulator marginally unstable.
 
Pio1980 said:
Re mods, it looks like a pretty recently unit as-is, with good parts.
You see two "busy" sections, one near the front panel with two ICs which is the gain portion, and the other near the rear where the power comes in. That's the power supply portion. I would use an in-circuit esr checker on the eltyicaps in that section if it was here, otherwise, it could be one or more weak ones that *might* make a regulator marginally unstable.
Click to expand...

I can begin with a capacitors they are not so expensive. I do not have esr checker but it is good idea to change capacitors after all those years.

Cheers
 
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