I just acquired an Amp Supply LK-500ZB which looks to be in pretty
good condition. I took some pictures and put them on a web page at:
I have several questions regarding modifications and potential improvements.
1. The fan works at both speeds but is pretty loud in the Hi speed mode.
Other than trying to isolate it from the chassis with some rubber
grommets (or is there a better way to shock mount the fan), is there a
more modern replacement fan that runs quieter and has the same or
greater air flow? Are there any other cooling modifications that would
be desirable to perform?
2. Even though it might not be necessary, I want to beef up the power
supply board. I plan on replacing the caps with 470uf / 450v
replacements and replacing the diodes with 6A versions. Are the
currently installed 1 meg ohm resister that are in parallel with the
diodes necessary? Can or should they be removed. I'm also replacing the
cap bleeder resistors with Metal Oxide Film type resistors.
3. It appears the 10 meter mod is only half way installed. The input
circuit appears to be there but there is no coil tap on the output tank
coil. According to the manual on the BAMA web site, the tap should be on
loop #6 as counted from the inductor end of the coil. That would put it
2 turns from the existing 15 meter tap and 3 loops from the end of the
coil. Is this the correct location? If you look at the input trimmer
caps on the input board for the 10 meter position in my pictures, it
looks kind of funky, Is this a normal install or does this need to be
4. Are the stock RF suppressors ok or would installing the "Richard
Measures, AG6K - Low VHF-Q parasitic suppressor retrofit-kit" be a worth
while investment for this amp?
I have access to some parts from a LK-550 amp and have already installed
the step-start circuit. Also considering installing the QSK board from
that amp as well.
Any other things that I should address or modify?
Thanks for any suggestions!
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