I think it reminds me of a microphone effect.
Look for anything that can resonate at this frequency.
A tuning cap, tube.....basically it looks like the power switch introduces a quick jerk annd then something resonates at the frequency you hear.
Thanks Morzh, I'll check those things. Have you ever had this problem? Do you think it could be caused by the switch?
Eric
yes it potentially can be the switch itself if it bounces a lot.
here's the test (somewhat dangerous...that is requiring observing some safety, so be careful. Use an isolation transformer and never hold two wires or a wire and the chassis with both hands at the same time....you know the spiel);
Desolder one wire to the switch, turn the switch on and keep it on, so you can have the volume where it works, and use that desoldered wire to make/break connection. If the sound persists, it is not the switch, if it goes away - it is the switch.
Well Morzh, it looks like it's the switch. My deoxit order should be here on Thurs or Fri. I'll get back to you after I treat it.
Thanks,
Eric
You're alive, that's a relief.
Deoxit is a good stuff but it may not necessarily cure the problem: if the switch has an excessive bounce Deoxit won't do a dang thing about it. It is mechanical. Then again, if this is the extent of your problem, it's nothing really bad.
Yup! Gotta keep one hand in the pocket!
I'll try the Deoxit before I take the switch apart.
Thanks,
Eric
I have one of those, your set is prettier, mine does not make that sound. Actually for a small set they perform quite well. I DX on it sometimes.
Paul
Thanks Paul, it took a lot of cleaning and polishing. I haven't got my Deoxit yet and from the testing I'm sure the problem is in the switch. If I put pressure on it and shut it off there is no noise.
Eric
Yup, just about always that. Causes a transient that briefly saturates output transformer above its limit to suppress such stuff. Best fix it lest you looking for new iron.
Hey Morzh,
That did it. Just a little spray into the control and...no noise.
Thanks,
Eric
Yup! Probably has hsppend to most of us.
Great! Well, dirt also causes bounce. Obviously.