[TenTec] Corsair dying on TX- help, hints, please

[geraldj]

On Mon, 2006-03-27 at 12:21 -0500, j_r_abercrombie wrote:
An eBay buy, it worked OK for a day or so, and I made
> a few QSOs on 20m SSB with it. 
> Then it started showing 'funny' behavior on TX. (All
> symptoms below are with radio in the "lock"/tuneup
> position, into a Cantenna-type 1kw dummy load. All the
> cabling, dummy, power supply etc work fine with a
> TenTec Omni here, so I'm quite sure it is the radio-
> not a PS, or cabling problem).
> First, intermittent, pulsing-type draw on the power
> supply 15-20A range when putting out full power in the
> 'lock' position. Drive control advanced till ALC lit.
> This evolved into output power dropping down to a few
> watts after 30 sec or so of TX. 
> 
> Now, whenever the drive control is advanced to give
> more than a few watts of output power (Ic of 3 amps or
> so), the radio shuts down completely. Power off-power
> on and RX is fine again, but TX still shows the same
> symptoms.
> 
> I don't know if this is something in the SWR sensing
> board, or in the RF PA or what. Should I be looking
> for a blown cap? My expertise is generally limited to
> simpler repairs.
> 
> I'd appreciate any ideas/advice on this. The rig is
> probably not worth shipping (from Canada) to TN for
> repairs, but it seems too nice to become a 'parts rig'
> just yet.
> Thanks.
> 73
> John
> VE7JAV
> 
> I haven't yet seen that with my Corsair II, but I suspect board grounding. Go through
checking the board mounting screws and grounding. Tighten them. Screws through a PCB
loose their pressure over time because the plastic relieves the applied pressure and the
shock and vibration of shipping can loosen them more. I've fixed many rigs over the
years by tightening the board mounts. Hasn't mattered who made them.

-- 
73, Jerry, K0CQ,
All content copyright Dr. Gerald N. Johnson, electrical engineer