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QCX has started emmiting a high pitch tone #qcx40
Kent K5KNT
I've been away from the hobby for a while and I just recently got my QCX-40 out of storage. I had it set to practice mode, attached it to a dummy load and began practice CW using a cwmorse camelback straight key. After about 30 seconds, I began hearing a high pitch tone in my earbuds. I've powered off and back on and I still get the same tone. My power source is a 9v battery.
Any suggestions on what the problem might be?
Thanks,
Kent, K5KNT
Any suggestions on what the problem might be?
Thanks,
Kent, K5KNT
Kent, check your battery voltage. Could be dropping.
Ron
On Mon, Mar 20, 2023 at 21:06 Kent K5KNT <kent@...> wrote:
I've been away from the hobby for a while and I just recently got my QCX-40 out of storage. I had it set to practice mode, attached it to a dummy load and began practice CW using a cwmorse camelback straight key. After about 30 seconds, I began hearing a high pitch tone in my earbuds. I've powered off and back on and I still get the same tone. My power source is a 9v battery.
Any suggestions on what the problem might be?
Thanks,
Kent, K5KNT
Hi Kent. As long as that's the voltage of the battery with the key pressed, you should be OK. If that's the open circuit voltage of the battery, then you might want to also check with the key pressed.
If voltage is OK (> 7 volts) you should next do the Op Amp bias voltage checks. Use your DVM and check voltages on pins 1 & 7 of all 6 Op Amp ICs. You should see about 2.5v on pins 1&7 of ICs 5,6,7 &8. You should also see 2.5v on pin 7 of IC9, 4.9v on pin 1 of IC9 and slightly less than half the input voltage on pins 1 and 7 of IC10. These are approximate readings. Please do those checks and report back ... Thanks .. Ron
On Tue, Mar 21, 2023 at 7:11 AM Kent K5KNT <kent@...> wrote:
Hi Ron,
The battery measures 8.4 volts.
If you have one go ahead band use the 12v supply and see if that fixes it.
On Tue, Mar 21, 2023 at 08:56 Kent K5KNT <kent@...> wrote:
The 8.4 v was an open circuit voltage. I'll check with the key pressed and the Op Amps as suggested. It might be a couple of days. Should I do a check using a 12 v power supply?
Kent