Re: {Collins} KWM-380 Sudden Loss of Both Tx and Rex

[Jim Warner <jim@xxxxxxxxxxxxxxxx>]

The LPF board(s) are common to both RX and TX. Can you hear the LPF 
reeds switching as you roll the VFO through the band segment transitions?

The t/r relay is two separate reeds and would be odd for both paths to 
be broken. I would refrain from keying the transmitter to prevent 
further damage until you get it untangled.

Jim WA9Z




On 8/6/2019 2:26 PM, Jerry O. Stern via Collins wrote:
> I never cut the internal jumper but your comment triggered my memory that the rear RCA Rcv In jack bypasses the TR relay.  Sure enough I connected an antenna to the rear Rcv In and get perfect reception.  So that narrows it all down to the TR relay - now to dig into the schematic for that component and see if power supply, etc may be at fault.
>
> Thanks for bringing me one step closer
>
> Jerry NY2KW
>
> -----Original Message-----
> From: Marvin Born [mailto:mborn@xxxxxxxxxxxxxxxx]
> Sent: Tuesday, August 6, 2019 12:37 PM
> To: Jerry Stern <jsternmd@xxxxxxx>
> Subject: Re: {Collins} KWM-380 Sudden Loss of Both Tx and Rex
>
> Is the antenna relay jumper still in place in the back?
>
>
> Sent from my iPad
>
> > On Aug 6, 2019, at 10:42 AM, Jerry Stern via Collins <collins@xxxxxxxxxxxxx> wrote:
> >
> > My KM-380 was working perfectly after major alignment earlier in the year.  I turned it on yesterday and no receive or transmit power.   The synthesizer seems to be working fine and also the R-E board because in  CW key down and I can see I a nice clean low power ( mW) signal on my Flex radio at the correct frequencies.  SSB and VOX works fine and I get a nice low power (mW) spectrum on my Flex radio showing the modulated signal.   But it is not just a Tx problem —- the KWM-380 has lots of audio white noise but does not receive any signals.   I am reading 14v on the meter with MOX, also the passband on different filters sounds like it is working fine.  Also I can hear the expected Birdie at 0.910 MHz loud and clear.  Looking at the Block diagram I figure this must be a problem with the  Rx/Tx relay but how could it cause both Rx and Tx issue at the same time?  Can anyone suggest some common points of failure that I can start my diagnostics?
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> > Thanks in advance
> >
> > Jerry NY2KW
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