As always, great suggestions and advice flowed in from the AMMRL community. Thanks go to Jerry, Rich, Margaret, Eric, Dan, Ed, and anyone else I may have forgotten. I'm still working on it, but definitely have been pointed in the right direction(s). Here's a summary of the suggestions I received in the hope they'll help someone else as well.
As a general rule, old amplifiers eventually start to die and need service. The most common symptom/problem seems to be poor voltage regulation caused by one or more components. The big electrolytic capacitors are one likely point of failure, as are the power supply itself, the voltage regulating transistors, the power supply board, and the amplifier "brick" itself. The board and brick are easy to swap between two amplifiers if you have more than one – the hardest part is probably removing the screws.
It also looks easy to convert a dual band amplifier to a single band amplifier; the single one I have has all the wiring for a dual unit with the second set capped in various ways and should basically mean completely disconnecting the unused side and making sure the wires are safely positioned. So far, I've tried this as the "easiest" fix, but the output looked odd on a scope; then again, it only had 20 minutes to warm up and I don't know for sure that the second amplifier is 100% good – they're all about the same age.
Several people mentioned that Lowell Beezley is THE go-to guy for AMT repairs. He does good work and prices/turnaround are reasonable. Here's his company/contact information:
Broadband Power Technology
609 S. Railroad Avenue
Willcox, AZ 85643.
PHONE: (520) 766-5420
FAX: (520) 766-5421
info_at_bptec.com<mailto:info_at_bptec.com>
Cheers,
Andrew
--
C. Andrew Fowler, Ph.D. | University of Iowa
Associate Director | B291 CBRB, 500 Newton Rd.
CCOM NMR Facility | Iowa City, IA 52242
319-384-2937 (office) | 319-335-7273 (fax)
andrew-fowler_at_uiowa.edu
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Received on Tue Sep 25 2012 - 04:15:22 MST