Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: leevc5 on July 29, 2026, 08:27:46 pm
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AC into WU4GB copper cap rectifier = 280 using red/white wires out of W025130 xfmr
DC out of rectifier = 320 vs 420
B = 310 vs 400
C = 276 vs 320
6V6 pin 3 = 315 vs 410
V4 pin 1 = 185 vs 260
V4 pin 3 = 1.8 vs 2.4
Bias set 30MA
any suggestions?
BTW, the amp sounds great and has beautiful reverb just like it should.
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Connect the PT red wires to the rectifier to kick the B+ up to about 400V. Readjust the bias. Does the trem work now?
Post the Weber schematic so we don't have to chase it down.
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We have tremelo!!!
Thank you professor sluckey.
The only thing going on now is an occasional pop sound. Thinking that's maybe the filter can caps breaking in.
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... the filter can caps breaking in.
That is not "a Thing."
The only thing going on now is an occasional pop sound.
The most-likely culprit is an intermittent connection. Especially since this is a new-build, we might think of a missing or imperfect solder-joint, or a loose ground connection (hopefully bolted, rather than soldered).
- If you used soldered-grounds and the brass strip at the control panel, then the brass-strip connections should be soldered before the brass is bolted to the chassis using the pots. The reason is the chassis is a big heat-sink; soldering before installation means you can use a ~40-60w iron but soldering after installation means a ~150w iron is necessary.
- It is easy to get in a rush wiring pot lugs and socket lugs. Make sure these areas have good soldering, and no loose-wires from partial-soldering of the lugs.
- Input/Speaker jacks generally should be soldered before being bolted in, at least for the Ground connections. Again, the chassis acts as a heat-sink for those connections, and can prevent a good solder-joint.
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Thank you. The speaker jack seems to have caused the popping. Didn’t get a good solder connection on the ground of that fender clam shell style plug.
Still have some intermittent noise so will continue to go through and verify the remaining connections.
Overall very pleased with the results. Nice upgrade (or perhaps just a nice change) from the 5F1 and 5E3 have been using for years.
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Here again with a new problem on this build. Either: no volume on start up; has volume on start up but goes to zero or volume drops ~75%. Keep playing and rotating the volume pot from low to max and boom, breakthrough volume returns to normal.
Have tested tubes on a 5e3. Have gone through and reflowed solder on all tube pins and pots.
Any suggestions for next steps in trying to isolate and correct this?
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Keep playing and rotating the volume pot
what happens when you just set the volume n leave it?
what are the VDC readings of the power rail at powerup?
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Check/re-solder the connections to the output jacks, and try a different cable to the speaker. I had a problem with my Princeton Reverb build that was like this, and the problem was in the jack/cable connection. You may also try replacing the volume pot, since messing with that changes things. I also had a bad volume pot in a different amp I built, so such things can happen.
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Yep, what dogburn says. And also check all ground solder connections on pots and elsewhere - a cold solder joint might be a culprit. Try chop-sticking the amp, where you go around and tap connections with a WOODEN chopstick while the amp's powered up on the bench - being very careful of high voltage of course. If you hit a bad solder joint, you'll know it.
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princeton reverb low volume: tracked signal through preamp section, working good; both 6v6 tested good; output to speaker is lower than preamp section output.
Any ideas would be appreciated.
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Is the speaker maybe plugged into the external speaker jack rather than the speaker jack?
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Is the speaker maybe plugged into the external speaker jack rather than the speaker jack?
No, speaker is connected to proper jack.
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I've had issues with new pots. Since you've traced the signal to the pot, you could bypass it as a test by removing it and jumping the signal from the treble wiper to the grid of the recovery triode with a resistor to ground as a grid leak. Then just adjust your signal volume to test...
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output to speaker is lower than preamp section output.
does the output sig "track" the pre signal...when you increase pre, does the PA increase also?
any chance you switched the probe to 10X on the PA measurements?
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I've had issues with new pots. Since you've traced the signal to the pot, you could bypass it as a test by removing it and jumping the signal from the treble wiper to the grid of the recovery triode with a resistor to ground as a grid leak. Then just adjust your signal volume to test...
Thanks, but the pot is working fine. When I trace the signal through the preamp section adjusting the pot changes the volume level as expected.
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output to speaker is lower than preamp section output.
does the output sig "track" the pre signal...when you increase pre, does the PA increase also?
any chance you switched the probe to 10X on the PA measurements?
Yes, the output from the speaker increases proportionally to the preamp increase when I increase the volume. If I am understanding you correctly.
The probe is not switched to 10x.
It just seems like the 6v6s, that work perfectly in my 5e3 and were initially working in this amp and have all the correct voltages are not working.
Is it possible that the output xfmr could have been damaged somehow?
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output to speaker is lower than preamp section output.
What does that mean? Are you comparing voltages on a scope? Give us some numbers.
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output to speaker is lower than preamp section output.
What does that mean? Are you comparing voltages on a scope? Give us some numbers.
Not that scientific. Playing Alan Jackson thru amp input. Have .1uF 630 V cap as probe connected to pignose amp and listen to the volume changes through the preamp section to the 6v6 input and then the tip of the speaker output. Maybe there is a flaw in my signal tracing
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Playing Alan Jackson thru amp input.
:thumbsup:
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Maybe there is a flaw in my signal tracing
while your musical choice is fine, your "analysis" might need a bit of technical input
how does the VDC at the anode match up with the build directions from weber?
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Maybe there is a flaw in my signal tracing
while your musical choice is fine, your "analysis" might need a bit of technical input
how does the VDC at the anode match up with the build directions from weber?
Plate voltage on 6v6 tubes is 351 VDC. Weber does not include anything but layout and schematic, no voltages. Although typical AA1164 are 420 or so but Weber is notoriously lower because they use the lower voltage wire from PS to rectifiier, 270 vs 340 I think.
someone on TDPRI forum did a comparison chart:
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Have come across a curiousity. With tremelo off and both pots at zero the AC Volts into pin 5 V6 is oscillating between 28 - 0 Volts AC.
This can't be correct can it?
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I crammed my AB1164 into a vibrochamp chassis. Using a Hammond 290AX and a Sovtek 5AR4 I get B+ of 368 with the red/white taps and 442 with the red/red taps. It gets hot with either set up so I currently have a Sovtek SSR (silicon diodes-not a tube rectifier) with the R/W PT supply and have B+ of 374 and a cooler PT and chassis.
Still plays pretty loud with bias set to 22 ma (54%).
The red taps should give more authentic PR results.
But I suspect the real problem is elsewhere because a Princeton Reverb is LOUD at home even with a B+ less than 400 volts.
Did you install the optional master volume? If so, remove it to see if the un-modded amp works.
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Have come across a curiousity. With tremelo off and both pots at zero the AC Volts into pin 5 V6 is oscillating between 28 - 0 Volts AC.
This can't be correct can it?
That's really bad! Should be about -35vdc.
You're experiencing some really weird symptoms with this little amp. It's past time for you to post some hi-rez pics so we can see what you are dealing with. And tell us which brand/model meter you are using.
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Have come across a curiousity. With tremelo off and both pots at zero the AC Volts into pin 5 V6 is oscillating between 28 - 0 Volts AC.
This can't be correct can it?
That's really bad! Should be about -35vdc.
You're experiencing some really weird symptoms with this little amp. It's past time for you to post some hi-rez pics so we can see what you are dealing with. And tell us which brand/model meter you are using.
V6 pin 5 DC voltage reading is -36.
It is the AC voltage measurement that is oscillating.
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What ac voltage? You have the tremolo switched off and you are not injecting a signal into the amp, are you?
What is the frequency of this ac voltage? What test equipment is seeing this ac voltage?
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What ac voltage? You have the tremolo switched off and you are not injecting a signal into the amp, are you?
What is the frequency of this ac voltage? What test equipment is seeing this ac voltage?
no signal injected. Thinking maybe one of the tremelo caps is leaking AC. Have ordered a set of caps from Hoffman.
Southwire 10020N DMM is seeing the AC voltage.
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Pull the tremolo tube (V4). Does that ac voltage go away?
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Pull the tremolo tube (V4). Does that ac voltage go away?
No, not at V6 pin 5 or at V4 pin 1 or throughout that area of the circuit.
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Everywhere I checked it sounds like this oscillation is normal.
So, plugged guitar into reverb return and BOOM, loud again....
Now just have to find out what is wrong at and around V1.
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Looking at your photo, I can't see all the connections for the preamp section, so I have a couple of questions. Is the V1a bypass resistor securely soldered at both ends? Are pins 4 & 5 connected together for all the preamp tubes?
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Pull the tremolo tube (V4). Does that ac voltage go away?
No, not at V6 pin 5 or at V4 pin 1 or throughout that area of the circuit.
Well it's not coming from the tremolo circuit then. I don't know what your meter is seeing. I suspect it is lying to you. :icon_biggrin:
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Fixed and sounds glorious!
2 parts coming together in one (apparently) solder filled gromet was not solder filled.
Thank you to everyone for the help! This forum got me through my first 5F1 and 5E3 builds several years ago and once again has come to the rescue.
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That would certainly explain the pops and low volume drops. But what about that crazy ac voltage on pin 5 of the 6V6s? Was that just a red herring?
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That would certainly explain the pops and low volume drops. But what about that crazy ac voltage on pin 5 of the 6V6s? Was that just a red herring?
That AC voltage swings are just a part of how the princeton reverb works. Watched a painful youtube video by a guy in a white coat and a blackboard explaining the unusual temelo and bias set up of these amps. Didn't understand it but it seems to work. :dontknow:
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I know how the PR tremolo works. Read your reply #28. Did you not understand my question, or did I misunderstand your answer?
I understood that you still had that ac voltage even when you pulled V4.
You also said "With tremelo off and both pots at zero the AC Volts into pin 5 V6 is oscillating between 28 - 0 Volts AC."
We certainly have a miscommunication going on. :BangHead:
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I don't even know what a red herring is, so, yes we certainly have a miscommunication going on. :BangHead:
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I don't even know what a red herring is, so, yes we certainly have a miscommunication going on. :BangHead:
A red herring (https://www.google.com/search?q=red+herring&oq=red+herring&gs_lcrp=EgRlZGdlKgYIABBFGDkyBggAEEUYOTIKCAEQABixAxiABDIKCAIQABixAxiABDIHCAMQABiABDIHCAQQABiABDIHCAUQABiABDIHCAYQABiABDIHCAcQABiABDIHCAgQABiABNIBCDIzOTJqMGo0qAIBsAIB&sourceid=chrome&source=chrome.ob&ie=UTF-8) is the fish you catch while on a "wild goose chase (https://www.google.com/search?q=wild+goose+chase&sca_esv=98f9e8ca0b9df2a8&sxsrf=APpeQnuXisNMbCFLZgiKeCP5sQsNSJL1eg%3A1786075032127&ei=mFd1asybB6OYptQPj5_zsAE&biw=1529&bih=674&ved=0ahUKEwjMx9P-z42WAxUjjIkEHY_PHBYQ4dUDCBA&uact=5&oq=wild+goose+chase&gs_lp=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&sclient=gws-wiz-serp)". :icon_biggrin:
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I don't even know what a red herring is, so, yes we certainly have a miscommunication going on. :BangHead:
A red herring (https://www.google.com/search?q=red+herring&oq=red+herring&gs_lcrp=EgRlZGdlKgYIABBFGDkyBggAEEUYOTIKCAEQABixAxiABDIKCAIQABixAxiABDIHCAMQABiABDIHCAQQABiABDIHCAUQABiABDIHCAYQABiABDIHCAcQABiABDIHCAgQABiABNIBCDIzOTJqMGo0qAIBsAIB&sourceid=chrome&source=chrome.ob&ie=UTF-8) is the fish you catch while on a "wild goose chase (https://www.google.com/search?q=wild+goose+chase&sca_esv=98f9e8ca0b9df2a8&sxsrf=APpeQnuXisNMbCFLZgiKeCP5sQsNSJL1eg%3A1786075032127&ei=mFd1asybB6OYptQPj5_zsAE&biw=1529&bih=674&ved=0ahUKEwjMx9P-z42WAxUjjIkEHY_PHBYQ4dUDCBA&uact=5&oq=wild+goose+chase&gs_lp=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&sclient=gws-wiz-serp)". :icon_biggrin:
I certainly was on a wild goose chase. My assumption that the preamp section was A OK based on my faulty signal tracing methodology sent me probing the power section. There I got lost in a Roman wilderness of oscillation misunderstandings.
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Would a 5E3 Tweed Deluxe power transformer work for an AA1164 Princeton Reverb build?
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yes