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Post subject: Super Sonic 22 bad cap in power supply?
Posted: Fri Oct 10, 2014 5:38 pm
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Hi,
I recently traded for a SS22 combo that initially sounded great, but then developed a bad hum & hiss sound. I noticed one of the JJ 6v6S power tubes glowed brighter than the other (tested 415 V, and 22/24 mV each tube), so I replaced both power tubes with a matched set of EH 6v6GT and re-biased the amp (430 V, 22 mV both).

The hum went away, but there was still annoying hiss that did get worse with volume, gain, and/or reverb turned up. Replacement of the 12ax7 preamp tubes (stock GT) with low noise EH 12ax7 tubes didn't help. I also replaced the stock 12at7 tubes with JJ 12at7's and replaced the reverb cable with a better insulated one. Still some hiss.

At this point I noticed a loud hum & clicking sound from the chassis (near the power transformer) that seemed to translate to the hiss in the speaker. I looked closely and saw yellowish dried powder on capacitor C90 and a little bit on C91, which are on the power supply PCB board. So, these caps look bad. The schematic says these run to the power tubes, which could have been the cause of the bad power tube in the first place, and perhaps the hiss.

Picture of bad SS22 caps:
Image

I feel like I've found the root cause of the problem, and feel reasonably confident I can change these caps (with appropriate pre-cautions to drains caps). I have basic solder skills and have done a few mods on pedals and such. But would like to know if there anything else I need to look for? E.g. would more caps possibly be bad? Could these leaking caps cause some of the resistors to short? Should I just take to a technician with more knowledge? Would Fender warranty work on this amp?

I really like this amp, and would like to keep it for awhile. It's only one year old (Fender said 11/13 mfg. date based on the serial number), but don't know if I can warranty the work since I got it through a trade deal (no receipt).

Thanks,
JD


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Post subject: Re: Super Sonic 22 bad cap in power supply?
Posted: Sat Oct 11, 2014 1:42 am
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Joined: Fri Feb 05, 2010 4:31 am
Posts: 14049
Location: Province de Québec, Canada
jdbreshears wrote:
Hi,
I recently traded for a SS22 combo that initially sounded great, but then developed a bad hum & hiss sound. I noticed one of the JJ 6v6S power tubes glowed brighter this do not mean is bad
than the other (tested 415 V, and 22/24 mV each tube), so I replaced both power tubes with a matched set of EH 6v6GT and re-biased the amp (430 V, 22 mV both).

The hum went away, Tubes was unmatched or when removing tubes you clean contact and hum go away . Try old tubes but there was still annoying hiss that did get worse with volume, gain, and/or reverb turned up. Replacement of the 12ax7 preamp tubes (stock GT) with low noise EH 12ax7 tubes didn't help. I also replaced the stock 12at7 tubes with JJ 12at7's and replaced the reverb cable with a better insulated one. Still some hiss.
Try cleaning tubes socket 's contacts
At this point I noticed a loud hum & clicking sound from the chassis???? (near the power transformer) that seemed to translate to the hiss in the speaker. I looked closely and saw yellowish dried powder on capacitor C90 and a little bit on C91, which are on the power supply PCB board. So, these caps look bad.Not sure of that The schematic says these run to the power tubes, which could have been the cause of the bad power tube in the first place, Sure no and perhaps the hiss.

Picture of bad SS22 caps:I did not see yellow powder
Image

I feel like I've found the root cause of the problem, and feel reasonably confident I can change these caps (with appropriate pre-cautions to drains caps). I have basic solder skills and have done a few mods on pedals and such. But would like to know if there anything else I need to look for? E.g. would more caps possibly be bad? Could these leaking caps cause some of the resistors to short? Should I just take to a technician with more knowledge? Would Fender warranty work on this amp?

I really like this amp, and would like to keep it for awhile. It's only one year old (Fender said 11/13 mfg. date based on the serial number), but don't know if I can warranty the work since I got it through a trade deal (no receipt).

Thanks,
JD



C90 and C91 are use for the solid state component , op amp power supply . Minus 15 V and plus 15 volts. Nothting to do with Output Power tubes


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Post subject: Re: Super Sonic 22 bad cap in power supply?
Posted: Sat Oct 11, 2014 8:41 am
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Joined: Sun Jun 22, 2014 7:49 pm
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Thanks for the clarification! I see now where those caps run in the schematic - looks like it powers the switches? So, would those caps failng eventually lead to switching problems?

Perhaps this amp just has a lot of hiss (as many have reported) and I have to learn to live with it! It's not noticeable when playing at volume, but annoying when recording or keeping it quiet for the family!


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