Amp breaking up later after rebuilding?

[martin manning]

The rectifier is a JJ GZ34 that came with the reissue amp. The customer has some kind of NOS or ANOS 5Y3 coming in the mail to drop the voltages.

Get the thing back and figure out what went wrong.

[Yoda]

Yeah I’ll be getting the amp back soon as the owner wants to do another mod (tone stack lift/raw switch) so I’ll have a chance to go through it again and check where all the power supply node wires are going.

[martin manning]

B+1 is supposed to be 445 with 5AR4. 5Y3 might not have enough current capability. I wouldn't go there.

[Yoda]

Yeah I offered a GE 5U4GB I have on hand here but the owner has gone off the deep end reading comments on Reddit and YT for ideas and that’s how he decided on the 5Y3 himself.

[martin manning]

Either way that's just treating the symptom.

[Yoda]

I agree, I wanted to be closer to the schematic voltages with the same rectifier called for on the tube chart and schematic, the 5AR4/GZ34. Trying to keep this amp ‘stock’.

[maxkracht]

Maybe suggest a sag resistor to emulate a 5y3 if he still wants it after the power supply issue is sorted?

[Yoda]

I’ll run that by him when I get the amp back. I’ll report what I find once I have it in my hands again. Thanks for the help.

[johnnyreece]

Maybe try a 5R4? Can handle double the current of a 5Y3 and more than double the AC voltage with a similar voltage drop to a 5Y3. Just a thought!

[Phil_S]

Yeah I offered a GE 5U4GB I have on hand here but the owner has gone off the deep end reading comments on Reddit and YT for ideas and that’s how he decided on the 5Y3 himself.

It can be a real challenge when someone insists on something that is not appropriate or likely to fail. If I was in your shoes, I'd tell the customer I won't do it because the 5Y3 rating is inadequate for the circuit. Tell him you can perform the necessary repairs using the 5U4GB. If he still wants to use the 5Y3, he's free to make the swap on his own after you are done. There is no way to know for sure, but this sounds like a situation that may very well have no happy outcome, so you might as well do it on your terms. You may ultimately need to part ways with the customer. You can't control what others think, say or do. At least you keep a clean conscience about it.

[Stephen1966]

Higher voltages tend towards greater headroom/less distortion...

How good a match did you find with your power transformer? The old Fender transformers I believe had high secondary resistance and poorer regulation. If the transformer you use is offering a greater current the first (reservoir) node will recharge better and provide higher voltages.

[Yoda]

Yeah I’m really eager to get the amp back to check out the power supply nodes inside but once I confirm everything is correct there I shouldn’t have to deal with him anymore.

I didn’t object to the 5Y3 when he told me because off the top of my head I thought well the tweed Deluxe has a 5Y3 so it should be OK. Not correct of course, but incorrect in a safe direction at least. He was showing me quotes from another webpage where a guy had his PR biased to 30 mA and a 5Y3 installed by Alessandro and he wanted the same and after ordering the 5Y3 he was asking me about how much mA his amp is set to and I told him we can’t compare without also knowing the plate voltages too but it didn’t matter, he read what he read somewhere and now the ideas are in his head. Same with him seeing some YT videos and telling me now he wants the brass plate under the pots and jacks because that’s how Fender did it. Insert face palm here. Fortunately I can ignore most of this and simply focus on delivering as great of an amp as possible, it’s not far off from being perfect.

I assumed (I know I know, but it was an educated assumption!) that the stock PR reissue iron was good to go so we reused it without a second thought. They are Schumacher transformers which are perfectly authentic but I don’t know if the specs match vintage ones. This amp is from 2021.

[Stephen1966]

You might measure the internal resistance of the secondary's HT lines to the CT and increase resistance or add zeners to drop the voltage if it is too high. Too much headroom is not usually a problem. The speaker efficiency may also be higher than the comparitive model. It isn't totally clear from here what the problem is meant to be but you certainly have a demanding customer. Maybe advise him that all these modifications he is asking for are all going to cost him and there are no guarantees that they will work or make any difference leading to further costs and time later down the line when you have to correct things. Charge him appropriately. It's his amp, and you don't have to agree to his ideas. If he's going to be happy with something half-baked that's going to fry his tubes in a heartbeat, it's his dime.

[Yoda]

Oh trust me he’s definitely paying for my time. But this is his first tube amp ever so I’ve managed to dissuade him from the majority of the mods that he’s read about because I told him that the Princeton Reverb is a very famous and popular amplifier for a reason and I said play it and get to know it in stock format first before asking for any big changes.