[Amps] AL-811H problems

[John E.]

AL-811H up date:
I  removed the top cover and found one tube was not lit.
Removed all tubes and tested on a TV-7D/U.
Found one tube was open.
One has a micromhos of 850 that is low.
Two tubes have a micromhos of 1,300 -ok-

Any one have two Svetlana 811A's pulls around this micromhos value?

I have only had single tube amp's in the past, Will one bad tube on a
muti-tube amp
cause a SWR problem?

Any thing else I am missing?
Thanks de John KØCQW

"John E." wrote:

> I was on 80m CW the other night with my new to me (used) AL-811H, when
> the
> amp stopped working and the high SWR light came on the display on the
> FT920.
>
> When I shut off the AL-811H the SWR went down to normal using 90w.
>
> Today started to by pass tuner, external SWR meter etc. I ended up with
> the
> dummy load connected into the output of the amp and started testing
> again.
>
> Found the amp would stop transmitting and the SWR would go high, Changed
> out
> the jumper between the radio and amp.  no difference.
>
> Found after 45 sec of key down in to the dummy load and multiple keying
> on and
> off sending CW the amp would stop working.---Must be in the amp--
> The amp has not blown any fuses and the HV runs at 1700v.
>
> I have no idea the condition of the tubes(811's),  the amp when working
> will  put out 400w CW.
>
> Any thoughts?
>
> Thanks de John KØCQW
>
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