Thanks all for your answers regarding the tubes. Now that I have
decided to replace the 572B's in the AMP, do any of you have comments,
preferences, warnings, etc, regarding which brand, price point, and where
I should buy those tubes??
Thanks again
73
Jonathan ko6xs
At 10:37 AM 9/30/98 -0400, km1h@juno.com wrote:
>
>
>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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Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
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