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#1 2013-12-15 05:22:33

sochart
New member
Registered: 2013-12-08
Posts: 7

Service manual for 210827-1 and 210828-2

I'm looking for the service manual for the boards of my 1976 VT-22.
Thanks a lot for your help.

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#2 2013-12-18 04:49:33

hangman
Banned
From: Seattle Washington
Registered: 2006-09-04
Posts: 1848

Re: Service manual for 210827-1 and 210828-2

All schematics are located under the schematics page of this site.   Every version of the v4/vt22 is there

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#3 2013-12-18 17:52:18

sochart
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Registered: 2013-12-08
Posts: 7

Re: Service manual for 210827-1 and 210828-2

I was much talking about the PCB schematic like the service manual PDF available for other versions (AmpegV4_V22.Service Manual).

There are like "test points"

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#4 2013-12-18 22:47:16

hangman
Banned
From: Seattle Washington
Registered: 2006-09-04
Posts: 1848

Re: Service manual for 210827-1 and 210828-2

There should be dc test voltages on the schematics,   I have not seen a service manual for the later v4/vt22.   Is there something particular you are having trouble with?

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#5 2013-12-19 03:52:44

sochart
New member
Registered: 2013-12-08
Posts: 7

Re: Service manual for 210827-1 and 210828-2

Yes, the disto is absolutely ugly and there is a drastic loss of volume when using it. I've read that the distortion is not very effective on this model, some people having replaced the 12DW7 with a 12AX7 and shunted the two diodes D1 and D2.
In my case, shunting the diodes disables the disto.

So, to make a long story short, it was thinking to double check the default voltages with the service manual.

Sorry, my english is very poor.

Thks again for your help.

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#6 2014-02-12 11:15:47

Steelyman
VIP
From: Massachusetts
Registered: 2010-11-17
Posts: 107

Re: Service manual for 210827-1 and 210828-2

sochart,
I think you are referring to the PCB "Layout". Unfortunately, we know of no service manuals available for the other V4 models. The PCB layout you need is unavailable.

I think the foot switch is needed to turn the "distortion" on and off. The circuit uses 2 Opto-Isolators to accomplish this. If you think there is a problem with the distortion circuit, take a look at the optos. One or both may be defective.

Last edited by Steelyman (2014-02-12 11:33:58)

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