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



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?



Thanks in advance

Jerry NY2KW













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