Rip and rebuild, for sure. You seem to have already spotted the big
fault.
With the input properly connected to the cathode, coils of "the usual
dimensions" made from less rigid wire, and a long, hard look for any
other errors (RF chokes, for example?) then it should work fine.
73 from Ian GM3SEK
>-----Original Message-----
>From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of N1BUG
>Sent: 30 April 2017 22:50
>To: 'Amps'
>Subject: [Amps] 144 MHz GS35B input circuit
>
>Just looking for a reality check here. I am trying to get an amp
>running. It was not built by me and had apparently been sitting for
>quite a while.
>
>Everything seemed to be working but the input SWR wouldn't tune
>below 4:1 with about 25W drive. I understand it will change some at
>full power but I don't think this circuit is working as desired and
>am reluctant to put my SS driver PA into it.
>
>I pulled the bottom cover to look at the input circuit. It's the
>usual T with two coils (not the usual dimensions) and shunt
>capacitor between them. BUT, it is connected to the bottom
>connection of the tube. I think that is the filament connection that
>is NOT common to the cathode. There is NOT a capacitor across the
>two filament/cathode connections. All of the circuits I could find
>online this afternoon show the RF input to the next ring up on the
>tube (filament/cathode common). Some show a capacitor across the
>filament connections, some don't. Comments?
>
>I am inclined to rip this out and rebuild. The 10 AWG hard silver
>plated wire the coils are made from makes it impossible to spread or
>compress turns to experiment with the match.
>
>Thanks,
>Paul
>
>
>
>--
>Paul
>N1BUG 160m-2m DXCC Honor Roll
>WI2XTC 2200m-630m Experimental license
>FN55mf ME Piscataquis County
>http://www.n1bug.com
>http://www.aurorasentry.com
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