Silverface Pro Reverb Ultra linear with a power transformer mystery that is winding me up

[vintagekiki]

Full wave voltage doubler rectifier found practical application in guitar amplifiers.

https://www.jt30.com/schematics_archive/FENDER/CHAMP/champ_12_schem.pdf

https://music-electronics-forum.com/filedata/fetch?id=857435

https://www.manualslib.com/manual/872011/Hohner-Orgaphon-30-Mh.html?page=13#manual

https://alelino.files.wordpress.com/2007/11/davolielettrico.jpg

[vintagekiki]

To retain this info into the future, those pdfs need downloading for independent hosting, as Classictone look to be ceasing trading very soon.

A bequest for the future.

http://www.classictone.net/ClassicTone-Part-Number-Guide.html

[pdf64]

Exactly.
See post #18.....

My perception was that my post was supplementary to nickb's?
It's a bit of a sore point for those who frequented TGP around this time last year, as an awful troll began their campaign of misinformation by arguing that this type of full wave bridge with CT rectification, due to the voltage doubling effect, made an amp's OT more liable to damage from back emf spikes https://www.thegearpage.net/board/in...ttage.2099670/
Apologies to Jon, in mentioning the above I'm absolutely not making any connection / comparison to him and his excellent contributions here

[g1]

It's a bit of a sore point for those who frequented TGP around this time last year, as an awful troll began their campaign of misinformation by arguing that this type of full wave bridge with CT rectification, due to the voltage doubling effect, made an amp's OT more liable to damage from back emf spikes https://www.thegearpage.net/board/in...ttage.2099670/

Oh my word. Fun starts at post #12. The authoritative stance, incessant posting, and 'expertise' in Marshall & Mesa makes me wonder if it could be a particular 'guru' that used to post here. Haven't got too far into it yet though.

[pdf64]

Oh my word. Fun starts at post #12. The authoritative stance, incessant posting, and 'expertise' in Marshall & Mesa makes me wonder if it could be a particular 'guru' that used to post here. Haven't got too far into it yet though.

Oh yes, sure enough it's him!
Sorry to send you down that rabbit hole - for the sake of your blood pressure, escape now

[Helmholtz]

My perception was that my post was supplementary to nickb's?

Not quite sure what you mean. Also my post #18 was meant to be supplementary the nickb's earlier post.

I don't frequent other forums.

But I think we agree on the interpretation of this sc "voltage doubler" circuit?

[christarak]

Full wave voltage doubler rectifier found practical application in guitar amplifiers.

https://www.jt30.com/schematics_archive/FENDER/CHAMP/champ_12_schem.pdf

https://music-electronics-forum.com/filedata/fetch?id=857435

https://www.manualslib.com/manual/872011/Hohner-Orgaphon-30-Mh.html?page=13#manual

https://alelino.files.wordpress.com/2007/11/davolielettrico.jpg

Thank you Vintage. Another good learning from this group.

[christarak]

THE FINAL OUTCOME: Once again, I am humbled by the individual and collective knowledge of the group. Thank you for your help.
I spoke to the customer, and he agreed that the best way forward is to keep the UltraLinear SF Pro Reverb as close to the original design as usual. I ordered the Hammond 290YEX as suggested by Juan (I double checked the specs, but I knew he'd be right). One of the 220uF caps was leaking, and considering the stress the power supply was put under, and as suggested by PDF64, I replaced all the main filter caps (incl bias) and rectifier diodes with 1N5408 (a big overkill...but if changing them anyway...)
All of the voltages came up to spec perfectly. As the heater supply was centre tapped in the 290YEX, I clipped the leads going to the Hum Balance pot. The amp is now quiet as a mouse and is putting out 63w before any detectable clipping on the scope. Bias set to 34mA (@510V) after winding out any crossover distortion and using the balance pot. Annoyingly, both my Weber Bias tool and Asharp BiasPro have gone to bias tool heaven and I used Voltage across OPT primary DC resistances method.