[Johnson] Fw: Valiant Low Output

[Rodger]

Brian,

If you have normal grid drive I would strongly suspect the meter reading is
wrong.  The Valiants were built with hand cut meter shunts and they are
often far from correct.  I would place a known good meter in series with the
"cold" end of the RF choke and check the actual current flow.  Most of my
Johnson rigs now are using precision low resistance resistors from Mouser
for the meter shunts.

Another common problem area is in the "turnstile" loading capacitor and if
the actual input power is correct then look into these components.

Finally, some Valiants (earlier) were built with too small a coupling/HV
blocking capacitor and will show somewhat lower than expected output on 160
and 80 but this should not show up on the higher bands.

73, Rodger WQ9E

> -----Original Message-----
> From: johnson-bounces at mailman.qth.net [mailto:johnson-
> bounces at mailman.qth.net] On Behalf Of BRIAN ROBERTS
> Sent: Wednesday, February 21, 2007 6:17 PM
> To: johnson at mailman.qth.net
> Subject: [Johnson] Fw: Valiant Low Output
> 
> 
> 
> Gents:  I have a Valiant that appears to have very low output relative to
> the input power.   With 120 watts input (200 ma. with around 600 volts HV)
> to the PA, I'm only seeing 42 watts output.  I'd normally expect to see
> about 60 watts.  Bias and screen voltages are all within limits, and the
> three 6146s have been swapped with known good tubes.    I thought I was
> pretty good at keeping these Vikings cooking, but apparently not.   Has
> anyone else seen this situation or can you offer any suggestions?
> Thanks.  Brian K9VKY   (k9vky at verizon.net)
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