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Old 11th January 2008, 07:39 PM   #1
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Default Adcom gfa 555 help

I have an Adcom GFA 555 with a damaged input section. I have a 555 service manual but the front end circuit board (A020 A) and related parts list don't match. I understand two different boards were used for the 555 (not counting the 555II). If anyone has information one the other configuration (my board says S394V-0) I would greatly appreciate it.
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Old 10th February 2008, 01:34 PM   #2
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Default 555 bias adjustment

I don't have an answer to your question, but I do have a 555 that I could take a look at for you. I am looking for the test points and bias voltages called out for the 555, but do not have the service manual. Does your manual cover this? I will go check the p/n of my board and report back
Bill
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Old 10th February 2008, 01:59 PM   #3
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Default Front end Board Part Number

The Part number on my 555 for the front end board is 72-2174-0-1
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Old 11th February 2008, 09:59 PM   #4
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Do either of you know what the vac is coming out of the trans former. Also could you tell me the vdc on the caps.
I have the 555 manual via PDF if you need it.
Ben
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Old 11th February 2008, 10:38 PM   #5
pchw is offline pchw  United States
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Quote:
Originally posted by ben62670
Do either of you know what the vac is coming out of the trans former. Also could you tell me the vdc on the caps.
I have the 555 manual via PDF if you need it.
Ben
According to http://www.diyaudio.com/forums/showt...44#post1423844
VAC is 52-0-52, and VDC unloaded is 75.
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Old 11th February 2008, 10:53 PM   #6
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Tranformer Primary Voltage = 122.9
Secondary Voltage = 121.8
DC Votage Across Capacitor 81.2

No input signal idle
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Old 12th February 2008, 06:26 PM   #7
K-amps is offline K-amps  United States
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Quote:
Originally posted by bigcrabass
Tranformer Primary Voltage = 122.9
Secondary Voltage = 121.8
DC Votage Across Capacitor 81.2

No input signal idle

Sounds about right.... for the Mk. II it was about 83vdc.
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Old 29th March 2009, 03:43 PM   #8
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Default adcom gfa 555 service manual request

Quote:
Originally posted by ben62670
Do either of you know what the vac is coming out of the trans former. Also could you tell me the vdc on the caps.
I have the 555 manual via PDF if you need it.
Ben

Help me, I need of ADCOM GFA-555 , full service manual in PDF they can send me?
Thank you. Roberto
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Old 29th March 2009, 05:00 PM   #9
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Default Manual for GFP 555

Post your email address and I will email you the manual. I can't get your email from your registration.
Bill
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Old 29th March 2009, 05:00 PM   #10
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Default manual request

Yes , you can send service manual for adcom gfa 555, at may email:

blobbulobis@inwind.it

Kindly Roberto
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