[Boatanchors] Gonset G76 modulation and other issues

[Gary Schafer]

Check audio low stage tubes for grid filament short.

73
Gary  K4FMX

> -----Original Message-----
> From: boatanchors-bounces at mailman.qth.net [mailto:boatanchors-
> bounces at mailman.qth.net] On Behalf Of howard holden
> Sent: Tuesday, February 06, 2018 4:42 PM
> To: boatanchors
> Subject: [Boatanchors] Gonset G76 modulation and other issues
> 
> Have a G76 which was working well a few years ago, now all I get on
> modulation in the AM mode is a loud hum on the carrier. Can't pick up
> the audio anywhere. Mic is OK, all audio circuitry seems to be OK - caps
> and resistors all tested, interstage and mod trannies all show proper
> continuity including ground on the interstage center tap, and relay
> switching seems to be doing all it should.  I do show about 120V of 60Hz
> across the interstage output to the mod tubes when I key up. It isn't
> there on the high power CW mode and the signal is clean. Anyone got a
> good idea?
> 
> 
> Also I  know Gonset's documentation isn't the swiftest. But on the 12AQ5
> clamp tube the schematic shows two 47K 2W resistors from the HV plate
> supply to the clamp plate. My unit has only one, and no signs of the
> other ever having been there. (mine reads 76K ohms so it's gotta go, but
> it has little effect on output). Question is, which is correct? I recall
> reading something a long time ago about the resistors in the clamp
> circuit but don't see anything on it these days.
> 
> 
> Thanks,
> 
> Howie WB2AWQ
> 
> 
> 
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