Hi all,
I have done a search, but was really unable to find the help.
I have a 1995 Jolida 202a, this is the model before they used circuit boards, so all Point to Point wiring. It is also un modified.
This amp always had a hum, no matter if I cheated the ground, changed inputs, changed outlet circuit, changed houses, cords... etc.
My recent assumption was a cold solder joint, so I opened it up and re-flowed all the joints. It did help, but it is still there.
So my question is... could it be the power supply? would cheap diodes cause this? or cheap capacitors? or even the transformer?
Or, is it something completely different?
Before I order parts, I would like to get some opinions.
and BTW... although a novice, I have built a few tube headphone kits, and realize the dangers involved with high voltage. I just am not sure on the trouble shooting.
Thank you so much for all your future help, if this is in the wrong place, my apologies.
-kev
I have done a search, but was really unable to find the help.
I have a 1995 Jolida 202a, this is the model before they used circuit boards, so all Point to Point wiring. It is also un modified.
This amp always had a hum, no matter if I cheated the ground, changed inputs, changed outlet circuit, changed houses, cords... etc.
My recent assumption was a cold solder joint, so I opened it up and re-flowed all the joints. It did help, but it is still there.
So my question is... could it be the power supply? would cheap diodes cause this? or cheap capacitors? or even the transformer?
Or, is it something completely different?
Before I order parts, I would like to get some opinions.
and BTW... although a novice, I have built a few tube headphone kits, and realize the dangers involved with high voltage. I just am not sure on the trouble shooting.
Thank you so much for all your future help, if this is in the wrong place, my apologies.
-kev
Kudos to astouffer!
Yes, the first step is to identify the symptom, 60Hz or 120Hz.
Effective troubleshooting always starts with a complete and accurate listing of the symptoms (see the questions above, and the observation below *** ).
If you post a schematic, it would be helpful.
Is this a preamp, power amp, integrated amp?
I normally don's search the web for schematics, or product information.
For example, a two stage preamp with RC coupling and 2nd stage self bias, ground the 2nd stage grid. If the hum is still there, check the B+ ripple.
Troubleshooting is an art.
Shotgunning is not.
*** The original poster said the amp always had hum. If that meant from new,
then it was not from worn out old capacitors, even though they might be worn out now.
In that case, there might presently be more than one cause of hum.
Join the Navy, and learn to troubleshoot a piece of electronic gear with the knowledge that the captain of the ship is anxiously waiting for an instant cure, so he does not want to have to report the "equipment down" to the fleet.
Yes, the first step is to identify the symptom, 60Hz or 120Hz.
Effective troubleshooting always starts with a complete and accurate listing of the symptoms (see the questions above, and the observation below *** ).
If you post a schematic, it would be helpful.
Is this a preamp, power amp, integrated amp?
I normally don's search the web for schematics, or product information.
For example, a two stage preamp with RC coupling and 2nd stage self bias, ground the 2nd stage grid. If the hum is still there, check the B+ ripple.
Troubleshooting is an art.
Shotgunning is not.
*** The original poster said the amp always had hum. If that meant from new,
then it was not from worn out old capacitors, even though they might be worn out now.
In that case, there might presently be more than one cause of hum.
Join the Navy, and learn to troubleshoot a piece of electronic gear with the knowledge that the captain of the ship is anxiously waiting for an instant cure, so he does not want to have to report the "equipment down" to the fleet.
Hey all,
Thanks for all the info.
@Euro21, Thanks I will look into it.
@duncan2, Yes I am glad it is a simpler amp, I figured I would replace all the caps just to be sure. Would you suggest some fancy Mundorf film caps for the C1? and then Panasonic or Nichicon for the power supply?
@astouffer, It is a 120hz hum
@6A3sUMMER, I am sorry for lack of information, I will try and be better next time. I agree, Trouble shooting is an art, and I am just a wee babe when it comes to this.
This is a Integrated 40watt el34 based amp.
Schematic:
jolida_jd202a.s01_amplifier_schematic | KevinHull | Flickr
More info on the amp:
JoLida 202A Integrated Tube Amplifier: Sound and Sanity by Wayne Donnelly
Thanks everyone, I appreciate everyone's help.
-kev
Thanks for all the info.
@Euro21, Thanks I will look into it.
@duncan2, Yes I am glad it is a simpler amp, I figured I would replace all the caps just to be sure. Would you suggest some fancy Mundorf film caps for the C1? and then Panasonic or Nichicon for the power supply?
@astouffer, It is a 120hz hum
@6A3sUMMER, I am sorry for lack of information, I will try and be better next time. I agree, Trouble shooting is an art, and I am just a wee babe when it comes to this.
This is a Integrated 40watt el34 based amp.
Schematic:
jolida_jd202a.s01_amplifier_schematic | KevinHull | Flickr
More info on the amp:
JoLida 202A Integrated Tube Amplifier: Sound and Sanity by Wayne Donnelly
Thanks everyone, I appreciate everyone's help.
-kev