Rowan (and group)
?
A report on progress here.? A bit of catch up history..?
?
My QMX+ was reported with a 1000 hz tone with some kind of faint digital signal modulation on 12 and 6 Meters.? It was also seen on 10M but not nearly as loud.? Reported initially, the signal was isolated to be within the RX.? Several other members reported the very same or similar symptoms.? The TX works great.
?
In the process of poking around the RX areas trying to change LP filter plots, I killed the entire RX.? This turned out to be IC402 and when replaced, the RX came back to life.?
?
I noticed that there was NO 1000 Hz tones in the audio output when IC402 was dead.? There were no signals either, but the filter 'sounds' of narrow CW seemed to work fine.? It sounded just like the RX should, but no signals.? Once IC402 was replaced, the tones on 12 and 6 meters are back. as well as the expected signals.??
?
I replaced the PMS1804 chip. MANY THANKS to Jeff Moore and others who have plowed this ground before me.? It was a relatively painless experience.? Briefly if you have the 10$ ChipQuik kit, some solder wick, and the iron you built the kit with, you too can change this very intimidating chip.? This did not cure the 1000 Hz tone.? I believe Jeff has seen this happen too.??
?
So I have gone around the block, learned new skills but I have not solved the original problem.
?
I am on the verge of ordering a front end chip ( the first RF stage in the RX ) because the tone disappeared when I cut that chip off from the rest of the radio by killing the IC402.
?
I am open to ideas.??
?
73
Dick
W4PID
?
PS Rowan, I did notice some tabs on the bottom of the board to be perilously close to the case.? I trimmed these and no more threat exists there.? Thanks for the heads up.? It may or may not have been the issue, as I was only scooting turns around on the 160M RX filter toroid when the failure occurred.? But it did cause me to pull the board and trim, maybe averting some issue down the road.
?
?
?
Richard Hattaway