>
>Hello everyone,
>
>The other day I (we) were trying to get my home brew 8877 HF amp fixed in
>time for the CQWW CW contest, but ran into a dead end. I thought maybe
>someone here could point me in the right direction and give me an idea
>where to look.
>
>Several months ago the amp when 'bang' while running on 40 meters.
>(Actually, it went 'FWOOOOP!!' since I did have a 20 ohm surge resistor in
>the B+; controlled 'bang'.) The culprit was traced to be a Millen HV
>connector which arced thru at 4kv. (I know the tendancy for these
>connectors to absorb moisture has been discussed here.) The surge resistor
>was blown apart as expected. Replace both pieces With the amp off using
>external low voltage pwr supply, the grid trip circuit was adjusted for 75
>mils and the grid current meter was calibrated.
>
>When fired up and keyed, the amp draws no plate current, and at the
>slightest hint of RF the grid current climbs and quickly trips out. Our
>first thought was the HV had gone away, but it is still there. I didn't
>see it, but was told there is a slight twitch or rise in the plate current
>as the grid shoots up.
>
>Knowing the grid trip was working, I stuck my spare tube in and got the
>same results.
>
>Any ideas would be appreciated.
>,
Measure the cathode to grid potential. Measure the cathode to neg. HV
potential.
- Rich..., 805.386.3734, www.vcnet.com/measures.
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