Hello
I am stuck with a vintage mono amp, it hums... it has a 5Y3 rectifier. I changed this tube, all power supply capacitors, resoldered the ground connection etc. then I removed the rectifier tube, and inserted an external power supply , voilá, the hum disappears. if I insert the tube while the external power supply is connected, the hum reappears.
It does not matter where I connect the negative of the external power supply, near the orginal electrolitics or far away , no hum at all. I am really desperate as I can not find a logical explanation, or a solution.
any help will be appreciated
AR
I am stuck with a vintage mono amp, it hums... it has a 5Y3 rectifier. I changed this tube, all power supply capacitors, resoldered the ground connection etc. then I removed the rectifier tube, and inserted an external power supply , voilá, the hum disappears. if I insert the tube while the external power supply is connected, the hum reappears.
It does not matter where I connect the negative of the external power supply, near the orginal electrolitics or far away , no hum at all. I am really desperate as I can not find a logical explanation, or a solution.
any help will be appreciated
AR
The exact model is j12T,never found the exact schematic, but this one is very close.
I tried to ground 7591’s inputs or tying them togheter to isolate the rest of the circuit.
I also tried to ground either side of the 6.3 heather supply.
Thanx !!
I tried to ground 7591’s inputs or tying them togheter to isolate the rest of the circuit.
I also tried to ground either side of the 6.3 heather supply.
Thanx !!
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A few initial queries come to mind:then I removed the rectifier tube, and inserted an external power supply , voilá, the hum disappears. if I insert the tube while the external power supply is connected, the hum reappears.
It does not matter where I connect the negative of the external power supply, near the orginal electrolitics or far away , no hum at all.
Are you using the original transformer to provide heater voltage?
What external power supply are you using, and was it connected across C1A?
Did the external supply have a series diode protected output - as you connected it in parallel with the original supply when you put the 5Y3 back in.
Have you tried another 5Y3?
Have you put 1N4007 in series with each anode of the the 5Y3 - just in case the 5Y3 is leaky?
What circuit voltages have you measured and do you know if they are acceptable?
What meter are you using?
YesA few initial queries come to mind:
Are you using the original transformer to provide heater voltage?
It’s a vintage Eico variable power supply, and Yes indeed.What external power supply are you using, and was it connected across C1A?
I don’t know, it’s an old tubed PSDid the external supply have a series diode protected output - as you connected it in parallel with the original supply when you put the 5Y3 back in.
SeveralHave you tried another 5Y3?
Nope, should I try it ?Have you put 1N4007 in series with each anode of the the 5Y3 - just in case the 5Y3 is leaky?
Yes they areWhat circuit voltages have you measured and do you know if they are acceptable?
A fluke scopemeterWhat meter are you using?
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