Ok, I'm baffled as as to where to look next. Suggestions welcome. Here are the preconditions:
QMX Built for 12v. Testing at 12.0v.
1_009a firmware
Boots correctly? ?-? 90ma with backlight on/ 80ma off
Tx Power testing? into 51.5 (measured) dummy load
? ? ? Measured peak to peak voltages with scope Siglent 1202X
? ? ? All bands initially had? consistent Tx power? -but low on 30M and 20M
? ? ? 80M 3.5W
? ? ? 60M 3.25W
? ? ? 40M 3.25W
? ? ? 30M 1.9W
? ? ? 20m? 1.25W??? ? ?
All bands (at least initially) have Rx - I think the initial RF sweeps looked fine (but I did not record them)
?
Actions taken:
? ? ?- squeeze / expand 20m?
? ? ?- reflow solder 20 LFP?
? ? ?- reflow solder on all LPF toroids - verified connections
? ? ?- verified C525 and C522
? ? ?No change
? ? ?- reflowed some additional soldered through hole connections
??
Ran Hardware / RF Sweeps
? ? ? Attenuation on 80, 60 and 40 - all peak high outside band - significant in band attenuation
80M
60M
40M
30M? ??
20M
Action taken:
? ? ? ?- Rebuilt? L401 as per Manual rev i
? ? ? -? Reflow solder on T402 and caps surrounding mux chip
? ? ? - measured 2.5v on C406
? ? ? No change to RF sweeps
?
? ? ? - reflowed solder on most through hole connections
Resumed Tx testing
? ? ? - Erratic peak to peak? voltage measurement cycling through band selections,?
? ? ? ? ? ? other than the behavior on 20M, power does not change except after selecting another band
? ? ? ? ? ? ?and returning to the band indicated.?
? ? ? ? ? ? ? ?80M? ?50v? ? or? ? ?37.5v? ? ??6.25W / 3.51W
? ? ? ? ? ? ? ?60M? ?60v? ? or? ? ?35.6v? ? ? 9.0W? /? 9.0W? ?yikes!!!
? ? ? ? ? ? ? ?40M? ?60v? ? or? ? ?59v? ? ? ? ?9.0W /? ?8.7W? ?yikes!!!
? ? ? ? ? ? ? ?30M? ?35v? ? ?steady? ? ? ? ? ? 3.0W? ??
? ? ? ? ? ? ? ?20M? ?62v instantaneously - hits current limiting on supply,? drops to 36v? ?
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?9.61W? / 3.24W? ?yikes!!!? ? ??
Assumptions
? ? ? - Need to resolve erratic Tx voltage first
Action taken:
? ? ? - Verified Dummy load - 51.5 Ohms, Ran 30M QCX-mini Tx into dummy load - steady at 3.75W at 12v
So, I've successfully taken the QMX from very functional albeit weak 30/20M?Tx performance - to erratic Tx behavior and made it deaf on 3 bands.?
I'd congratulate myself, but this is not the desired outcome!
Help?
Reasonable suggestions welcomed!
? ? ? -?
