Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: PsychicFuzz on October 26, 2020, 01:38:29 pm
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Hello!
New to the forum. Came across the site looking for answers for my Blues Jr. figured I'd join the fun :icon_biggrin::BangHead:
My Fender Blues Jr USA Green Board just started buzzing with a slight crackle.
I traced it to the reverb. With reverb pot all the way down it's fine - no noise. But as I gradually bring pot back up the buzzing/crackling reappears. The crackling is quieter than the buzz...Once reverb pot hits around 6-7 the buzz level remains consistent
I know the Reverb circuit on green board suffers from poor design, and I've always just dealt with it. But it has gotten significantly louder than usual.
Any insight would be greatly appreciated. I don't just want to hand it off to my tech and shell out $$$ if I don't have to
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buzzing/crackling reappears.
those are pretty classic, broke connection, bad solder joint, broke foil run, sloppy tube socket
lots of eye's on usually spots it
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buzzing/crackling reappears.
those are pretty classic, broke connection, bad solder joint, broke foil run, sloppy tube socket
lots of eye's on usually spots it
I'll open it up tonight and give it a closer look. This is my first time working on an amp...so I'll try not to die
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buzzing/crackling reappears.
those are pretty classic, broke connection, bad solder joint, broke foil run, sloppy tube socket
lots of eye's on usually spots it
I'll open it up tonight and give it a closer look. This is my first time working on an amp...so I'll try not to die
Blues Jrs are somewhat easy to work on. Take the back cover off and you have access to almost everything. With the back cover off, discharge the capacitors with a multimeter or in another standard way. Do this everytime!
The reverb is solid state, so the tubes wont affect the reverb circuit on its own. I would definitely look at reflowing solder joints on all the tubes if they look cloudy. light touch, just get it flowing and let it be. Depending on how old it is it may benefit from a recap job.. its not expensive on that particular amp.
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Blues Jrs are somewhat easy to work on. Take the back cover off and you have access to almost everything. With the back cover off, discharge the capacitors with a multimeter or in another standard way. Do this everytime!
The reverb is solid state, so the tubes wont affect the reverb circuit on its own. I would definitely look at reflowing solder joints on all the tubes if they look cloudy. light touch, just get it flowing and let it be. Depending on how old it is it may benefit from a recap job.. its not expensive on that particular amp.
Ok thank you...I've never done before but will make sure I discharge before
I actually just had serviced in May. Here's the receipt from tech
sorry about link couldn't figure out attachment
https://imgur.com/a/x5Ucdn9
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I actually just had serviced in May. Here's the receipt from tech
sorry about link couldn't figure out attachment
https://imgur.com/a/x5Ucdn9
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Blues Jrs are somewhat easy to work on. Take the back cover off and you have access to almost everything. With the back cover off, discharge the capacitors with a multimeter or in another standard way. Do this everytime!
IMO it is not easy for a beginner first time work on a amp; there are no access to solders.
PhsychicFuzz, take good picture before you remove all knobs and output tubes circuit; All 5 grey ribbon wires must be replace / bend in the same way.
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> All 5 grey ribbon wires must be replace / bend in the same way.
Looks to me like the big potential c0ck-up is the power connectors on the left (in your picture) and how they go to the 1/4" lugs. I can't read them from here but I bet some are 120/240, some are 6V, and some 300V. So a mix-up could be very exciting (once).
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a mix-up could be very exciting (once).
2 came my way AFTER, the 1st was pure, "um, i probably....." I didn't take it on. the 2nd, those contacts didn't get the memo on good solder practices. bridged 2" sections of foil. I also RE-soldered 90% of the ribbons, most of the VDC and ground, I got compensated, the amp got sold
the only "repair" for that amp is Doug's mod
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Blues Jrs are somewhat easy to work on. Take the back cover off and you have access to almost everything. With the back cover off, discharge the capacitors with a multimeter or in another standard way. Do this everytime!
IMO it is not easy for a beginner first time work on a amp; there are no access to solders.
PhsychicFuzz, take good picture before you remove all knobs and output tubes circuit; All 5 grey ribbon wires must be replace / bend in the same way.
The only ones that are "tough" are on the tube boards.. but pretty subjective! Maybe for a first timer. Once you get the knobs and pot nuts off, disconnect the ground screw, and the screws holding down the PCB and the whole things opens towards you. Push down just a little bit to get the pots to clear and don't use too much pressure as to mess up the pot to board connection. Leave the whole thing connected.
but honestly.. send us pictures of the solder joints in and around the reverb circuit if you can find it. Also on the board the tubes connect to. If it was serviced that recently I dont suspect those would be the problem. But then again, IDK if id charge someone $40 for a pair of JJ El84s either.
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> All 5 grey ribbon wires must be replace / bend in the same way.
Looks to me like the big potential c0ck-up is the power connectors on the left (in your picture) and how they go to the 1/4" lugs. I can't read them from here but I bet some are 120/240, some are 6V, and some 300V. So a mix-up could be very exciting (once).
You did not understand what I mean. :BangHead:
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For whatever reason the amp has cured itself....maybe it was a UFO flying by? :dontknow:
Either way I'll be back if anything else comes up. This seems like a great forum as I do want to get into amp repair. I have an old Univox amp I'll be inquiring about soon. Thanks guys :smiley: