[Hammarlund] Bias supply zorching the audio driver transformer

[Carl]

The SP-100, 200 and 400 had the identical circuit and I wouldnt be surprised 
if the SP-10 did also with its PP 42's.

Carl
KM1H


----- Original Message ----- 
From: "Al Santangelo" <ve3ajm at gmail.com>
To: "hammarlund" <hammarlund at mailman.qth.net>
Sent: Tuesday, July 24, 2012 8:37 PM
Subject: [Hammarlund] Bias supply zorching the audio driver transformer


> Hi Todd,
>
> Great to meet up with you here OM. Hope to hear/work you soon on 75 or
> 40m for sure. The group is still going strong.
>
> I know it was mentioned to be careful about the bias supply and
> damaging the audio driver transformer in the Super Pros.
>
> I was just looking at the schematic for the SP-400X and I see that the
> schematic shows the use of cathode bias on the PP 6F6s. ie. the centre
> tap of the secondary of the driver transformer is grounded.
> I don"t the SP-210 schematic here, so I'm thinking that this is one
> other difference between the 400 and the earlier SPs?
>
> Al Santangelo
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