[CQ-Contest] Alpha 9500 - getting at input match filters

Stu Phillips stu at k6tu.net
Wed Oct 12 11:32:55 EDT 2016


A friend of mine (truly! - not me!) has an Alpha 9500 that is exhibiting a gain fault on 80m – no output power, gain fault and the gain LED bar is hard over on the left red end.  This was accompanied by a “burning smell”.  All other bands are fine.

Looking at the schematic, I’m surmising that one or both of the capacitors on the cathode input match for 80m has been fried (or worse, perhaps the relay has croaked but I think that’s less likely)…

I have replacements for the caps in shipment and so will attempt open heart surgery on the patient this coming Saturday.

The input filters are on the Cathode board which is under the RF deck.  I’ve removed the main control board before (the one with all the SO239 connectors) and but not the RF deck.

Has anyone experience of removing the RF deck (with pictures would be awesome if possible) that they could share disassembly hints with me?

I’m familiar with working on high power amps – especially in letting the caps bleed down (!) - but any disassembly ideas would be most helpful!

Hopefully replacing a pair of $5 caps (no kidding) will be a less expensive proposition than two way freight and factory repair.

I believe in the Ham version of the Medical Hippocratic Oath…  and first, don’t create more problems than you started with!

Please reply off reflector is you can help.
Thank you!
Stu K6TU

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