On Wed, 30 Sep 1998 06:23:23 -0700 Jonathan Kaplan <jonk@moonlink.net>
writes:
>
>Hi all,
> Here's an elementary question:
> The power output of the amp on the various
>bands has recently declined. On some bands,
>I can't get more than 200 watts out with 100 watts
>in. I'm wondering if the tubes are bad. Is there
>another explanation? If not, is there something else
>I can do to check the tubes before spending major $$$
>or is the loss of power the best symptom?
>
>Thanks for any help.
Replacement 572B's is not considered major $$$ by any standard. QRO is
not for the cheap.
With that said and done there are a few things in that amp to look at
first.
Has the input VSWR increased?
If so check the input circuitry from the connector, thru the relay and to
the terminal strip by the sockets, look for any blown caps.
Is the power about the same on 80 as it is on 15/10 ?
Weak tubes usually fall off rapidly on the highest frequencies.
Have you been spending a lot of time on 15/10 ?
That amp is known for overheating the wires from the coil taps to the
switch, causing the solder to crystalize. Replace with #14 (silver plated
preferred) and all new solder. While at it do the same with the leads to
and from the plate blocking cap.
Any WARC use?
A fried plate choke is often the result. Use the Ameritron AL572 choke
for a replacement.
Finally, unwind all 4 parasitic suppressors and check resistance, should
be within 10% of original. Blown resistors will cause all sorts of tuning
problems.
RF Parts and others have good prices on Cetron and Chinese 572B's. Do not
use Svetlana.
GL Carl KM1H
>
>73
>Jonathan ko6xs
>
>
>--
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>
>
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