On 12/15/2010 5:20 PM, pfizenmayer wrote:
> If you mean 200 ma not 0.2 ma - very likely a blown transistor in the 81537
> FILAMENT_AC board which has the bias regulator transistors and zener on it .
>
> Used to be a 2N3055 and a MPSU101 - and 8.2 v zener.
>
> Later they used a ON Semi MJ15001 instead of the 2N3055 and a MPSW42 for the
> MPSU101.
>
> I suspect you will find the 3055 shorted.
>
> I would replace both after I am in there - only hard part is unsoldering the
> big transformer wire in the eyelet on the board . Rest is easy .
>
> You might want to check cal if there was a big enuff surge - I have had the
> meters get slightly demagnetized and they read low -
>
> Been there - done that - twice - but now have 3.3volt zeners acropss both
> meters so will never happen again .
Most meter coils drop less than 0.1 volt so 3.3 volt zener's aren't much
protection. Better to use 1N4001 single junction silicon diodes, two in
parallel opposite polarity. They won't leak any current until the drop
gets up to about .55 volt.
73, Jerry, K0CQ
>
> 73 de hank K7HP
>
>
>
>
>
>
> ----- Original Message -----
> From:<w7ju@cox.net>
> To:<tentec@contesting.com>
> Sent: Wednesday, December 15, 2010 3:45 PM
> Subject: [TenTec] Centurion 422
>
>
>> I had a 3 500Z Gas and blow a line fuse. Replaced the one tube. On turn
>> on in standby plate voltage is 3100 but show .2 ma plate current.
>> Suggestions?
>> Thanks
>> Ralph W7JU
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