Thanks for the many responses to my TL922 question.
I should add that this amp has seen a great deal of travel and
contesting. In fact, it is in Barbados right now. The frequent travel
has created a number of mechanical issues that we might not normally
see. I suspect it was part of the problem with the blocking cap
failing. Since it is about the most heavy duty part in the box, I
suspect it was a mechanically induced failure.
>From the responses, I see two possibilities.
1. Replacing the blocking cap may have necessitated increasing the
padder caps on 80 and 160. It seems like all the load positions are a
bit less than the manual would indicate. The other bands are still in
range.
2. The 80 meter padder cap, which is also used on 160, is actually 2
ganged sections of the 5 section Load variable cap. It is possible that
this cap has become disconnected somewhere in the path from the
bandswitch to ground. The 160 padders are discrete components
When I get to work on the amp again I will,
1. Check the mechanical integrity of the 80 meter padder cap connections
2. Up the blocking cap to 2000pf since this seems to be a better value
for this purpose.
3. IF these do not work, add some more padder capacitance to the 80
meter Padder.
Does this sound right?
73, Tom
-----Original Message-----
From: Georgens, Tom
Sent: Monday, August 28, 2006 8:39 PM
To: amps@contesting.com
Subject: [Amps] TL-922 question
Hello -
I have a question about my TL922.
When I tune on 80 and 160, the LOAD control bottoms out before I can
peak the power. The output power is about what I would expect so the
peak must be close but I am uncomfortable that the tubes are not seeing
as good of a match as they could.
The amp has always been real close to the 0 position but I don't
remember it being quite like this. To be complete, I have made the
following mods to the amp.
1. Inserted a HV fuse resistor
2. Directly grounded the 3-500Z grids
3. Replaced a blown blocking cap (1000pf). The service manual says to
use 2000pf but the operating manual says 1000pf 4. Replaced the tubes
(unmatched)
The seems to work otherwise and has seen extended operating on the high
bands.
I would like to get the tuning back in range. Could any mods have had
this effect? Is it worth trying to add to the padder caps?
Thanks and 73
Tom W2SC
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