Hello, I came across a sweet looking Adcom GFA-545 II with a few minor issues.
I was hoping someone out there might e-mail a Schematic and a bias adjust spec for this little jewel.
Many Thanks in advance
email me at: ebayer0u812@sbcglobal.net
I was hoping someone out there might e-mail a Schematic and a bias adjust spec for this little jewel.
Many Thanks in advance
email me at: ebayer0u812@sbcglobal.net
Hello, I have a burnt resistor tied to the emitter of Q605 and no burnt outputs, but blown fuses so I want to completely go thru the thing before restoring power to it.
It appears that it might have frontend damage as I have tested all the outputs and driver and they all appear to just fine.
Hence my request for a schematic. Overall it appears to be a very straight forward design, but I have read it has a offset servo up front and I would rather not second guess that section of the amp.
It also has Adcom marked Ic's up front and if they have been damaged I would like to see the circuitry to allow replacements to be picked tested and installed from my selection of AD and BB chips.
I already have a partial schematic of the output s and drivers section only ( i found that here on the forum) but no front end section is to be found ( I have scotch tape if and when i find it )
Plus I dont like to second guess and invent bias adjustments so hence my request for a bias spec. for the output stage. I normally repair amps all day long. So I can follow any instructions you might have to offer.
I just want to do this old girl justice and see the job completed properly and to spec. It will go nicely on my tech bench with my Adcom tuner preamp I use for a source everyday
Many thanks in advance for any support you might be able to render.
It appears that it might have frontend damage as I have tested all the outputs and driver and they all appear to just fine.
Hence my request for a schematic. Overall it appears to be a very straight forward design, but I have read it has a offset servo up front and I would rather not second guess that section of the amp.
It also has Adcom marked Ic's up front and if they have been damaged I would like to see the circuitry to allow replacements to be picked tested and installed from my selection of AD and BB chips.
I already have a partial schematic of the output s and drivers section only ( i found that here on the forum) but no front end section is to be found ( I have scotch tape if and when i find it
)Plus I dont like to second guess and invent bias adjustments so hence my request for a bias spec. for the output stage. I normally repair amps all day long. So I can follow any instructions you might have to offer.
I just want to do this old girl justice and see the job completed properly and to spec. It will go nicely on my tech bench with my Adcom tuner preamp I use for a source everyday
Many thanks in advance for any support you might be able to render.
Hi justonemoreamp,
The 100 ohm resistor for the current source is burned???
If that's true, the diff pair is toast, and probably Q605,Q615, D605, D607 and more.
Choose a low DC offset op amp for the Adcom 3A if you need to. It's filtered so there is no "sound" from it per se. Pin 7 should be running around +12 VDC supply. Check for capacitor electrolyte on the PC board just in case.
-Chris
The 100 ohm resistor for the current source is burned???
If that's true, the diff pair is toast, and probably Q605,Q615, D605, D607 and more. Choose a low DC offset op amp for the Adcom 3A if you need to. It's filtered so there is no "sound" from it per se. Pin 7 should be running around +12 VDC supply. Check for capacitor electrolyte on the PC board just in case.
-Chris
here's your schematic link--6 years later
Adcom manuals, schematics and brochures - Hifi Manuals
johnny on the spot
Adcom manuals, schematics and brochures - Hifi Manuals
johnny on the spot
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