Adcom GFA-585 HELP NEEDED! - diyAudio
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Old 17th October 2003, 02:06 AM   #1
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Default Adcom GFA-585 HELP NEEDED!

I`ve been trying to get this amp running properly now for long time and it now seems that a previous repair was not done correctly, the zener diodes near the input that are Adcom specials, (look like transistor), may been replaced with the wrong value, the zener diodes left channel are d111,d112,d113 and d114, the right channel are d161,d162,163 and 164.
Does anyone know or can measure the correct voltage of these zener diodes for me so i can finally get this amp up and running properly.
Cheers, manly thanks from downunder in Australia, George.
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Old 17th October 2003, 03:08 AM   #2
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Default Re: Adcom GFA-585 HELP NEEDED!

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Originally posted by georgehifi
I`ve been trying to get this amp running properly now for long time and it now seems that a previous repair was not done correctly, the zener diodes near the input that are Adcom specials, (look like transistor), may been replaced with the wrong value, the zener diodes left channel are d111,d112,d113 and d114, the right channel are d161,d162,163 and 164.

Are you shure that they are zeners and not transistors???....is not usual so much zeners at the input of a amplifier...

As they are 4 for each channel it seems that they are a double diferencial (double LTP)...
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Old 17th October 2003, 05:03 AM   #3
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Oh, yeah their zeners alright, not right at the input but close, i`ve got the circuit, if only i knew how to post the circuit diagram i`d put it on one of these posts so you guys could see it, is it easy as i`m hopless on a computer. (Yeah they look like transistors three legs but two are linked together on the board.)
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Old 17th October 2003, 05:06 AM   #4
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you say that they look like transistors...Why?...they have 3 pins?
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Old 17th October 2003, 05:10 AM   #5
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They might be zeners...with those transistor packaging...commonly known as voltage references...but I'm not sure if they are used in amps...
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Old 17th October 2003, 06:15 AM   #6
ben goh is offline ben goh  Singapore
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Default adcom

try this link



Adcom 555II - Nelson Pass ?
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Old 17th October 2003, 06:56 AM   #7
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Nuh, Ben, good try but the gfa-555 is a different circuit to the 585, can anyone tell me in simple english how to post the circuit i have for the 585 it might help to get to the value of the zener diodes.
Cheers
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Old 17th October 2003, 07:39 AM   #8
ben goh is offline ben goh  Singapore
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Hi George,

U can try scan the schematic with a scanner with a PC attached

or use a digital camera to take several portion.

Thanks
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Old 17th October 2003, 08:09 AM   #9
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This look familiar?

http://www.diyvideo.com/forums/attac...p?postid=66400
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Old 17th October 2003, 08:25 AM   #10
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Yep, very close, what model is that? it`s almost the same, the zener diodes are the ones in the bottom left corner.
Can anyone now let my know what voltage zeners they are?
Cheers George. Thanks DJK!
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