I just finished sorting out a reverb hum on my Princeton reissue. It still has a little bit of noise, but not nearly as bad as it was. I replaced the reverb cable, turned around the tank and then made the mod you discussed in a previous video with the blue wire and green wire across the tube socket. Thanks for these informative videos.
Thank you Lyle, been trying to fix a noisy 65 DRRI reverb and have had so little success. Only set backs. New Reverb driver tubes, return tubes, new cables, rotating tank 180, even trying that rewiring V3 tube I believe you went over with a 68 DRRI. No luck. Appreciate all the tips. Might be time to try a new tank, came stock with a Ruby Tubes Tank. Have bought lots of Mojotone things, perhaps I will give their tank a go. I like a drippy one.
Did you fix it? There are many other more involved things internally that a tech can do to address that hum like changing the neg. feedback resistor, remove heater filament, ground the power section capacitor point CP13, remove jumper lead from V7 and more. Not exactly DIY but a good Fender amp specialist should know what to do to get it whisper quite. If all else fails- sell it and buy a Dr. Z MAZ MKii (not 1) head or combo. Very quiet and overall higher quality (and price.)
Those loose transducers inside the tank can be secured tighter by using a wide enough pair of pliers to simply move the plates tighter, and close the gap. Its just a riveted connection within plastic. No need for glue, but it can sometimes help too.
If reverb tank hum comes and goes gradually while you move the tank around, the actual reason for it is the leakage magnetic flux from the power transformer being picked up by the receiving reverb transducer. Consequently, the quieter orientation is the one with the receiving transducer located farther away from the transformer. Sometimes just rotating the tank is not enough to cancel all the hum, then you can put a steel sheet cover plate over the bottom opening of the tank at the receiving transducer end to serve as a magnetic shield, and this should fix it (provided the tank enclosure itself is steel and not aluminum.) The plate doesn’t have to cover the entire length of the tank, covering just about 1/3 of the length should do it. I used to use a piece of an old floppy drive chassis cut to size with great results.
Good assessment and repair advice. The Princeton may have been just a bit too short a cabinet, who knows. I've seen the odd small reverb tank that looked to be made out of a copper alloy of some type, probably because less magnetic. Sounds like the shield would need to be slightly magnetic though, correct? I'm not up on that theory.
@@cloudconnect Thanks. I've seen a small blue plastic tank in some very cheap amp and it was downright awful. You're correct that magnetic shield should be of a magnetic material (a ferro-magnetic).
I’m pretty sure the larger, dual channel Fender amps also feed the reverb transformer primary (as well as the trem oscillator triodes) using the screen grid PS node.
Instead of changing the reverb transformer feed from B to C, what about adding a choke in between A and B like on the Deluxe Reverb? Don’t have to change the internodal resistors and retain the plate voltage? Would the choke provide enough filtering? Or up the capacitor from 20 to 40uf.? Or both? C node is a unused tap for high voltage, why? To add filtering to D node which feeds the preamp tube. I know I ask too many questions! Love from springtime in the Rockies. Thanxz
Reverb is tricky with noise. When I got my '67 Deluxe Reverb, the reverb was horribly noisy... like unusable. Before I took it back to the shop for a look over, I turned it around and checked the tubes, and sure enough, someone had swapped the tubes in v2 and v3 putting a 12AX7 in the reverb driver. I swapped the tubes and all the noise disappeared.
Do you know if they make an awesome tank like this one for the Princeton red knob chorus? Mines from like 1991. My reverb is really springy sounding not ideal. Thanks anything would be great that you could share.
is it possible to replace tubes with jfet transistors in the reverb circuit making it kind of solid state tube thing? would it still need an output transformer ?
Anything is possible. Look at the solid state reverb units from the late 60’s to see how it was done. You likely will have to install a secondary low voltage power transformer though.
i was more thinking of being an antychrist and making the whole thing from tube analog transistors did you ever worked on such an amp where schematic looked tube -ish and all components were some simple 3 leged black boxes?
None of the circuits that were made without the reverb driving transformer into a spring tank sounded as good as the transformer circuits. Tube or solid state. There is just something about driving that circuit with a lot of current, I think. That's maybe what is so special about the stand-alone unit in comparison to the amp version. The hot rod deluxe amps use a fairly good solid state circuit with no transformer, and its really quite good, just not AS good.
If the hum is caused by ripple at reverb driver transformer's supply voltage, and not by magnetic fields, then a tank with a driver coil of poorer low end will probably be passing less 120Hz hum and is "better" even if it isn't Hi-Fi wise. 🤔 On the other hand if there is room for an extra smoothing resistor and electrolytic cap in the amp, it would be possible to add some extra ripple filtering to the reverb driver circuit. If the amp's transformer layout is not optimal, the reverb transformer as well can of course take hum from other transformer's magnetic fields. I just recently added a reverb tank into a very beaten up early 70's Laney L100 tube head's ceiling and was sure that it's not gonna work because that 550V B+ Partridge PT is a monster hum source, but against all odds it works just fine even if the driver coil is pretty close to the PT because the coils seem to be in good position to each other. I a**r*ped that old and ugly British wreck to 50 watter by removing two EL34s and installed a 12AU7 reverb driver (kicking a small Hammond OT) and 12AX7 recovery tube. It works very well indeed. The tank is made by TAD, 4AB3C.... The tank is quite OK but much darker sounding than a reference tank I compared it to, which was a middle 80's Accutronics, Made in USA.
Look at the Princeton schematic. See that unused extra filter node there. They kind of handicapped the Princeton so it wouldn't overlap with the Deluxe. Change the dropping resistor values/ratio and move the PI and reverb xformer to that node and you have a louder less compressed amp with quieter reverb.
@@PsionicAudio True. BTW Fender has sometimes used same standard driver tube 12AT7 cathode resistor values in different amps even if the supply voltages can be quite different, which is not very smart, and bias and operation point then is not necessarily optimal, causing often either very distorted reverb driver sound or overheated driver tube, or both. And some people try to use 12AU7 instead of 12AT7 without understanding that those two tubes need totally different load and different bias voltage to give best possible result.
Can an old reverb tank be fixed? I have old reverb tank from a mid 60's blackface deluxe reverb that has one spring that came off. The little thing that it connects to on one end is missing. The real tiny little thing.
Hey Lyle, long time listener first time caller. What would be your thoughts on placing a reverb tank inside a cabinet in a head+cab configuration and running the RCA cables from the head to the cabinet? You'd lose the ability to change the cab you're using, but I reckon the noise reduction would be worth it.
Hello Lyle, I just swapped out my stock reverb tank for a mojotone, definitely better sound. Question the old reverb tank is enclosed in bag and had two pieces of foam inside the tank between the springs as well as piece of cardboard, I took the foam out but did leave the cardboard, your thoughts? Also I tried swapping a celestion gold speaker for the stock Jensen the hum was so loud I sent the speaker back and replaced it with an eminence Arjun Cajun, question why might the celestion have so much hum? Thanks in advance for the terrific videos
That foam should never have been left in there. Factory error. You wouldn’t have had much reverb with it. Cardboard is to keep the bag from contacting the springs. Speakers cannot cause hum. Something else was wrong.
I have a 65 reissue twin. There is a hum off the reverb. Its not loud but its a good bit louder than my friends twin. When i connect the footswitch and engage the reverb there is a loud hum. This isn't the case on my friends one either. i tried his tank and cables in my amp but it made no difference either. Ive also checked all the tubes. Anybody have any ideas?
Welp! The big weird sound your reverb tank makes when you place it in the cab im facing the same sound even when i tap the top of the amp even when the volume is down. Can someone advise a fix for this.
Had the same issue with a mojo princeton kit, had to wrap the tank in magnetic shielding tape. Not sure if the vintage ones had similar issues or the tanks were better shielded? Also not sure how changes to the power node could possibly help a proximity issue?
So accutronics and Belton are to be avoided, and mojo is the way to go. I've been debating building a spring tank pedal to go with my tweed champ build vs buying a princeton rev kit vs buying a princeton rev hand wired reissue. Any thoughts? I don't like noise, so you've made me a bit worried about the PR route. Any other suggestions for low watt fender tones with spring reverb and ideally trem? Thanks!
Either the PR HW or any PR kit can be wired with the reverb driver driven from the quieter node. Weber's PR kit, for instance, shows reverb driven from the "B" screen node, and with the power supply "C" node marked "unused". Doesn't mean you can't use it -- see the SF princeton reverb with boost-pedal schematic for suitable power supply dropping resistor values if you do. (You needn't implement the boost circuit -- it doesn't affect the power supply and you won't miss it.) el34world.com/charts/Schematics/files/Fender/Fender_princeton_rev_boostpedal.pdf
Uh I watch Tomo Fukita's channel. He was doing a gigging gear reveiw of his vintage Fender Pro amps. He's a pro with great ears o.k.? He was saying his amp was fluxuating output in the reverb. I don't think I've seen that problem. Bad tube? Values drifting?
Why does Fender keep using these inferior reverb tanks? Isn’t it worth a few extra $$ to have satisfied happy customers? Must be people don’t care and still buy their amps!
I have 2 Blues Juniors. Version 3 has a long reverb and version 4 has a short one. So I swapped the reverb tanks and what happened? Version 3 reverb stays long and version 4 stays short! Who has any idea? Is there more than a reverb tank alone that I should look at?
Hi @joeyjojo8200, did you find out a way to uprgrade your reverb from Short to long? I have a Marshall Valvestate 8080 and I love its reverb but I would like it to be a little longer... any ideas on how to do it??
@@PsionicAudio This amp has a negative feedback defeat pot, I suspect therein lies the culprit. Alas I am an amateur. I'll take it to Bob Dixon here in LA. Thanks, Lyle.
I had an issue with a noisy reverb. The owner had changed the speaker to one with a larger magnet. I had to rotate the tank to where the jacks were facing to the rear of the cabinet. It quieted right down.
Wow a night and day difference..what a difference a day makes..hit that like and subscribe for the real deal experience here ..its keeping him honest....learn something important....
I just finished sorting out a reverb hum on my Princeton reissue. It still has a little bit of noise, but not nearly as bad as it was. I replaced the reverb cable, turned around the tank and then made the mod you discussed in a previous video with the blue wire and green wire across the tube socket. Thanks for these informative videos.
he has a patreon account ;)
This is an amazing channel. Thanks for sharing this wealth of information
Thank you Lyle, been trying to fix a noisy 65 DRRI reverb and have had so little success. Only set backs. New Reverb driver tubes, return tubes, new cables, rotating tank 180, even trying that rewiring V3 tube I believe you went over with a 68 DRRI. No luck. Appreciate all the tips. Might be time to try a new tank, came stock with a Ruby Tubes Tank. Have bought lots of Mojotone things, perhaps I will give their tank a go. I like a drippy one.
Did you fix it?
There are many other more involved things internally that a tech can do to address that hum like changing the neg. feedback resistor, remove heater filament, ground the power section capacitor point CP13, remove jumper lead from V7 and more. Not exactly DIY but a good Fender amp specialist should know what to do to get it whisper quite.
If all else fails- sell it and buy a Dr. Z MAZ MKii (not 1) head or combo. Very quiet and overall higher quality (and price.)
Unbelievable.... I just happen to be tracing out a Reverb Circuit. And here you are with a video!
Those loose transducers inside the tank can be secured tighter by using a wide enough pair of pliers to simply move the plates tighter, and close the gap. Its just a riveted connection within plastic. No need for glue, but it can sometimes help too.
Oh my goodness I believe you just saved me a ton of money. We’ll see. Thank you Lyle
I learn something new every time! Thanks!
Oh man you may have just solved one of the things I was having trouble with, thank you Lyle
If reverb tank hum comes and goes gradually while you move the tank around, the actual reason for it is the leakage magnetic flux from the power transformer being picked up by the receiving reverb transducer. Consequently, the quieter orientation is the one with the receiving transducer located farther away from the transformer. Sometimes just rotating the tank is not enough to cancel all the hum, then you can put a steel sheet cover plate over the bottom opening of the tank at the receiving transducer end to serve as a magnetic shield, and this should fix it (provided the tank enclosure itself is steel and not aluminum.) The plate doesn’t have to cover the entire length of the tank, covering just about 1/3 of the length should do it. I used to use a piece of an old floppy drive chassis cut to size with great results.
Good assessment and repair advice. The Princeton may have been just a bit too short a cabinet, who knows. I've seen the odd small reverb tank that looked to be made out of a copper alloy of some type, probably because less magnetic. Sounds like the shield would need to be slightly magnetic though, correct? I'm not up on that theory.
@@cloudconnect Thanks. I've seen a small blue plastic tank in some very cheap amp and it was downright awful. You're correct that magnetic shield should be of a magnetic material (a ferro-magnetic).
4:01 "it amazes me what people live with thinking that it's normal"
very good and interesting information, Thanks Lyle
ótimo
I never used reverb till i had a prs sonzera i really like the amp and like its reverb more but it was a lemon.
I’m pretty sure the larger, dual channel Fender amps also feed the reverb transformer primary (as well as the trem oscillator triodes) using the screen grid PS node.
Said screen node being fed, not incidentally, from the filter choke the PR conspicuously lacks.
Exactly. Makes a huge difference.
Instead of changing the reverb transformer feed from B to C, what about adding a choke in between A and B like on the Deluxe Reverb? Don’t have to change the internodal resistors and retain the plate voltage? Would the choke provide enough filtering? Or up the capacitor from 20 to 40uf.? Or both? C node is a unused tap for high voltage, why? To add filtering to D node which feeds the preamp tube. I know I ask too many questions! Love from springtime in the Rockies. Thanxz
That’s the way. Done it many times
Great video! How would I go about using a reverb tank as an outboard effect? Would I need to amplify the signal? Does it require power?
Dig your work philosophy 😎👍
Reverb is tricky with noise. When I got my '67 Deluxe Reverb, the reverb was horribly noisy... like unusable. Before I took it back to the shop for a look over, I turned it around and checked the tubes, and sure enough, someone had swapped the tubes in v2 and v3 putting a 12AX7 in the reverb driver. I swapped the tubes and all the noise disappeared.
What is the model number of the mojotone tank? Thanks in advance. Great videos brother.
Mojotone SKU 4037206
Thank you sir
Where is a good place to get a Mojotone tank (4037206) For my 65 Princeton reissue? Thanks for these great vids!
More i watch this channel more i found that i can't find a good amp.
Do you know if they make an awesome tank like this one for the Princeton red knob chorus? Mines from like 1991. My reverb is really springy sounding not ideal. Thanks anything would be great that you could share.
is it possible to replace tubes with jfet transistors in the reverb circuit making it kind of solid state tube thing?
would it still need an output transformer ?
Anything is possible. Look at the solid state reverb units from the late 60’s to see how it was done.
You likely will have to install a secondary low voltage power transformer though.
i was more thinking of being an antychrist and making the whole thing from tube analog transistors
did you ever worked on such an amp where schematic looked tube -ish and all components were some simple 3 leged black boxes?
None of the circuits that were made without the reverb driving transformer into a spring tank sounded as good as the transformer circuits. Tube or solid state. There is just something about driving that circuit with a lot of current, I think. That's maybe what is so special about the stand-alone unit in comparison to the amp version. The hot rod deluxe amps use a fairly good solid state circuit with no transformer, and its really quite good, just not AS good.
If the hum is caused by ripple at reverb driver transformer's supply voltage, and not by magnetic fields, then a tank with a driver coil of poorer low end will probably be passing less 120Hz hum and is "better" even if it isn't Hi-Fi wise. 🤔
On the other hand if there is room for an extra smoothing resistor and electrolytic cap in the amp, it would be possible to add some extra ripple filtering to the reverb driver circuit.
If the amp's transformer layout is not optimal, the reverb transformer as well can of course take hum from other transformer's magnetic fields.
I just recently added a reverb tank into a very beaten up early 70's Laney L100 tube head's ceiling and was sure that it's not gonna work because that 550V B+ Partridge PT is a monster hum source, but against all odds it works just fine even if the driver coil is pretty close to the PT because the coils seem to be in good position to each other. I a**r*ped that old and ugly British wreck to 50 watter by removing two EL34s and installed a 12AU7 reverb driver (kicking a small Hammond OT) and 12AX7 recovery tube. It works very well indeed.
The tank is made by TAD, 4AB3C.... The tank is quite OK but much darker sounding than a reference tank I compared it to, which was a middle 80's Accutronics, Made in USA.
Look at the Princeton schematic. See that unused extra filter node there. They kind of handicapped the Princeton so it wouldn't overlap with the Deluxe. Change the dropping resistor values/ratio and move the PI and reverb xformer to that node and you have a louder less compressed amp with quieter reverb.
@@PsionicAudio True.
BTW Fender has sometimes used same standard driver tube 12AT7 cathode resistor values in different amps even if the supply voltages can be quite different, which is not very smart, and bias and operation point then is not necessarily optimal, causing often either very distorted reverb driver sound or overheated driver tube, or both. And some people try to use 12AU7 instead of 12AT7 without understanding that those two tubes need totally different load and different bias voltage to give best possible result.
@@PsionicAudio For values, check the SF Fender_princeton_rev_boostpedal schematic, which does feed the reverb from the previously unused node.
Very interesting !
I’m building a mojo kit at the moment. If the reverb happens to be noisy I will test this mod 👍
Any thoughts on vertically mounted tanks Meester Lyle
...like old Ampegs and such?
Thanx in advance
Can an old reverb tank be fixed? I have old reverb tank from a mid 60's blackface deluxe reverb that has one spring that came off. The little thing that it connects to on one end is missing. The real tiny little thing.
Hey Lyle, long time listener first time caller. What would be your thoughts on placing a reverb tank inside a cabinet in a head+cab configuration and running the RCA cables from the head to the cabinet? You'd lose the ability to change the cab you're using, but I reckon the noise reduction would be worth it.
Could be a fine thing. Certainly would take away proximity noise.
Hello Lyle, I just swapped out my stock reverb tank for a mojotone, definitely better sound. Question the old reverb tank is enclosed in bag and had two pieces of foam inside the tank between the springs as well as piece of cardboard, I took the foam out but did leave the cardboard, your thoughts? Also I tried swapping a celestion gold speaker for the stock Jensen the hum was so loud I sent the speaker back and replaced it with an eminence Arjun Cajun, question why might the celestion have so much hum? Thanks in advance for the terrific videos
That foam should never have been left in there. Factory error. You wouldn’t have had much reverb with it. Cardboard is to keep the bag from contacting the springs.
Speakers cannot cause hum. Something else was wrong.
I have a 65 reissue twin. There is a hum off the reverb. Its not loud but its a good bit louder than my friends twin. When i connect the footswitch and engage the reverb there is a loud hum. This isn't the case on my friends one either. i tried his tank and cables in my amp but it made no difference either. Ive also checked all the tubes. Anybody have any ideas?
under warranty? if so shouldn't fender replace it?
Welp! The big weird sound your reverb tank makes when you place it in the cab im facing the same sound even when i tap the top of the amp even when the volume is down. Can someone advise a fix for this.
Had the same issue with a mojo princeton kit, had to wrap the tank in magnetic shielding tape. Not sure if the vintage ones had similar issues or the tanks were better shielded? Also not sure how changes to the power node could possibly help a proximity issue?
The proximity issue is separate from the hum injected into the Send by the unfiltered transformer.
So accutronics and Belton are to be avoided, and mojo is the way to go. I've been debating building a spring tank pedal to go with my tweed champ build vs buying a princeton rev kit vs buying a princeton rev hand wired reissue. Any thoughts? I don't like noise, so you've made me a bit worried about the PR route. Any other suggestions for low watt fender tones with spring reverb and ideally trem? Thanks!
Either the PR HW or any PR kit can be wired with the reverb driver driven from the quieter node. Weber's PR kit, for instance, shows reverb driven from the "B" screen node, and with the power supply "C" node marked "unused". Doesn't mean you can't use it -- see the SF princeton reverb with boost-pedal schematic for suitable power supply dropping resistor values if you do. (You needn't implement the boost circuit -- it doesn't affect the power supply and you won't miss it.)
el34world.com/charts/Schematics/files/Fender/Fender_princeton_rev_boostpedal.pdf
Uh I watch Tomo Fukita's channel. He was doing a gigging gear reveiw of his vintage Fender Pro amps. He's a pro with great ears o.k.? He was saying his amp was fluxuating output in the reverb. I don't think I've seen that problem. Bad tube? Values drifting?
Could be a number of common things. I can't speculate but it wouldn't be anything too difficult to sort out.
That’s Tomo Fujita, with a J.
Why does Fender keep using these inferior reverb tanks? Isn’t it worth a few extra $$ to have satisfied happy customers? Must be people don’t care and still buy their amps!
I have 2 Blues Juniors. Version 3 has a long reverb and version 4 has a short one. So I swapped the reverb tanks and what happened? Version 3 reverb stays long and version 4 stays short!
Who has any idea? Is there more than a reverb tank alone that I should look at?
Hi @joeyjojo8200, did you find out a way to uprgrade your reverb from Short to long? I have a Marshall Valvestate 8080 and I love its reverb but I would like it to be a little longer... any ideas on how to do it??
Speaking of what we should live with: is it normal to have a very low volume, sub bass thump in the tube biased trem of a PR?
Common, yes, but not normal.
Easily fixed by a good tech.
@@PsionicAudio This amp has a negative feedback defeat pot, I suspect therein lies the culprit. Alas I am an amateur. I'll take it to Bob Dixon here in LA. Thanks, Lyle.
I had an issue with a noisy reverb. The owner had changed the speaker to one with a larger magnet. I had to rotate the tank to where the jacks were facing to the rear of the cabinet. It quieted right down.
What’s the correct model for the Mojotone reverb tank for the Princeton ?
SKU 4037206
@@PsionicAudio thank you. I love your videos
Wow a night and day difference..what a difference a day makes..hit that like and subscribe for the real deal experience here ..its keeping him honest....learn something important....
All well and good, but I have to tell you I prefer the rib tips at Corky's. 🤣
Silly New York transplant.
Cozy Corner is where it's at.
@@PsionicAudio No argument from this nosher
It's the lack of correct atmospheric conditions and some less-than-beautiful women assembling those newer tanks that's your problem.
Haha. Oddly enough, I think the Folded Line tanks were aluminum, which isn't magnetic. So you're probably right.
What happened to your hand, that looks painful and not good for a guitarist.