[Milsurplus] Re: [Hammarlund] BC-779 Latest Update

[Al Klase]

OK Joe, Try this:

Observe the voltage on the bottom of the secondary winding of T6.  (This 
is the transformer that drives the AVC rectifier.  I'm working from an 
R-270 manual, so component designations may be different.)  Anyway, the 
27K (R53)  resistor here is the DIODE LOAD for the AVC rectifier.  The 
voltage here should go distinctly negative when you tune through a 
strong signal in either AVC or MANUAL mode.

If you have negative going voltage on the diode load, look at the other 
end of the 1-meg resistor (R52) that's connected to this node.  The 
voltage her should go distinctly negative, but will be somewhat 
smaller.  If you have AVC voltage on the diode load and not here, find 
out why.

Regards,
Al


Carole White-Connor wrote:
> Not much progress on the AVC problem. I'm giving the voltages. Perhaps 
> this will give someone an idea of the problem.
>
> _AVC Rectifier (6H6)_
>
> In Manual and in AVC, the cathode voltages are -3.2.  That's what the 
> manual specifies.
>
> In Manual, the plate voltages are -3.5. The manual says they should be 
> -3.2.
> In AVC, the plate voltages are -12.0. (The manual specifies only 
> voltages in Manual mode)
>
> _AVC Amp (6SK7)_
>
> In Manual and in AVC, the plate voltage is +270 and the screen is 
> +140. (The manual says they should be 240 and 110).
>
> In the Manual, the input grid is -3.2. The manual specifies -1.5V.  In 
> AVC, it is -12.(The manual specifies only voltages in Manual mode).
>
> In Manual, it actually is starting to sound like a Super Pro. 
> Replacement of the out-of-spec resistors and the caps has made a 
> difference. I just pulled C-34 out of the T-1 can. It's a Micramold 
> and was leaking like most of them do. It was a pain to get to but 
> worth the effort.
>
> As always, thanks for your help. Any insights would be gratefully 
> appreciated.
>  
>
> Joe Connor
>
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-- 
Al Klase - N3FRQ
Flemington, NJ
http://www.skywaves.ar88.net/