[Hallicrafters] S-38C dial tracking and AGC

[Edward B Richards]

Hi Craig;

If the VTVM does not track with the volume, you may have self oscillation
that the meter sees but you cannot hear.
Many alignment procedures call for a meter across the speaker. You might
try that. Self oscillation could affect the AVC action too. Good luck.

Ed Richards K6UUZ

On Thu, 11 Dec 2003 11:38:43 -0600 Craig Roberts <crgrbrts at verizon.net>
writes:
> My thanks to Don Erlich for his thoughts regarding the insufficient 
> AGC action and inaccurate dial tracking on my S-38C.
> 
> Regarding the dial tracking, he makes a very good point about IF 
> alignment. I performed the IF alignment with an RF generator and 
> VTVM but noted, at the time, that peaks in output voltage and 
> speaker volume were not coincidental. It is possible that I took the 
> "old-time repair" approach and tweaked for loudness. I'll re-do the 
> alignment tonight. just in case.
> 
> With respect to the AGC problem, the IF amp tube could be at fault. 
> My early, perfectly functioning S-38A uses the usual All-American 
> Five 12SK7 in that slot. The later S-38C employs a 12SG7. While I 
> have a pile of 12SK7s, I do not have a spare 12SG7 to substitute in 
> the "troubled" receiver. I've ordered a couple, though, and will 
> make the swap when they arrive.
> 
> Again, many thanks to Don.
> 
> 73,
> 
> Craig
> W3CRR
> 
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