VT100 video board repair.

[Bill Pechter]

I believe that you can get by with a fairly wide range of diodes and 
caps if you just readjust the video after throwing the cap and diode in.

If I remember correctly the diode was 50v -- and should be at least 100 
as you say.

I think I used a 47uf once since I had the right voltage on the shelf at 
Radio Shack.
The good news is I think the thing's still working.

Bill


Allison wrote:

>>Subject: RE: Discharging a VT100 CRT
>>  From: "Julian Wolfe" <fireflyst at earthlink.net>
>>  Date: Wed, 09 Nov 2005 12:43:29 -0600
>>    To: "'General Discussion: On-Topic and Off-Topic Posts'"	<cctalk at classiccmp.org>
>>
>>Well, you were right.  Something did blow on the VT100 video board, and in a
>>bad way.  It looks very much like it was that diode you speak of, cause
>>there's a huge burnmark on the board at the contact points of the diode.  If
>>that's not an "I died" indicator, I don't know what is.
>>
>>Can anyone tell me what diode to buy to replace it?  I'm thinking of getting
>>a replacement video board, and then replacing the diode on that, just in
>>case it took something else with it.  The whole "y" trace has a brownmark
>>around it that the diode was connected to, and that has a big cap next to
>>it.
>>    
>>
>
>Check the diode first as often they survive.  If it didn't it may be 
>the 1A 1000V device (1n4007 will work) at CR102.   The cap is correct value
>(22uf) but about half the required working voltage so it shorts after a 
>long time. I forget if it was C102 or c103 and the working voltage should 
>be at least 100V but not more than 160V.   or so memory says.
>
>Allison
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