Deluxe Reverb power transformer change?

[pdf64]

Derek at Watford Valves advises that the Philips ECG WGB run fine in pretty much any guitar amp, even the crazy high voltage late 70s Fenders.
And a mere £50 each!
He better puts his prices up before they migrate back across the pond
https://watfordvalves.com/product_detail.asp?id=1313

[pjd3]

Yeah look at that.

His prices are quite good on that tube compared to some other places over here. I was told by the seller for my pair to not push them much past 470vdc and I was right at that threshhold. So, being that I will never need anywhere near the full clean headroom (at any plate voltage) then, I may as well give them a little break and maybe see an extra year two or three from them.

I have the pair at about 445vdc plate and biased around 65%. Sounds nice n big n bold. And still loud.

Best,

Phil D

[Yerffej]

I have a 66 deluxe reverb which is much happier when run around 110vac input from a variac. For me that brought the heaters down to 6.3 from close to 7v, and my plate voltage at the tube to 410v when biased at 60%


I would clip your dmm on the heater supply and dial down the variac until you get 6.3. those are the operating conditions the amps of that era were designed for and your tube life should be significantly better

[Roe]

Derek at Watford Valves advises that the Philips ECG WGB run fine in pretty much any guitar amp, even the crazy high voltage late 70s Fenders.
And a mere £50 each!
He better puts his prices up before they migrate back across the pond
https://watfordvalves.com/product_detail.asp?id=1313

they sold me two quads of jan 7581As for roughly the same price (or even cheaper) some years ago

[Helmholtz]

Neither a WBG nor a 5881 can replace a real 6L6GC in a circuit, where it's pushed to/above its voltage or power limits - no matter what tube dealers tell you.
All 3 are different tubes.
E.g. the screen voltage limit of a 6L6WGB is 300V (absolute max.) while its 400V (design center) for a 5881 and 450V (design max.) for a 6L6GC.
Around 20 years ago I bought ten 6L6WGBs. Certainly not going to use them in an amp where screen voltage is above 400V.
Speaking of original tubes.

[pjd3]

Hi Hemholz,

Thanks for chiming in on that, although a bit alarming. In that case I will have to see what the screen voltage is on the 6L6WGB in the blackface amp I built. And will definitely see about addressing the screen voltage should that be the certain max screen voltage.

With my plate voltage at around 435vdc I would suspect that the screen voltage isn't sitting much lower than that if I put in a classic design choke (which I suspect I did).

thank you,

Best,

Phil D

[B Ingram]

My second tube noob question. I'm putting it in the Fender amp section as it seems (to me) to be more historical than it is technical.

Does anyone know if the PT turns ratio changed when Fender Deluxe Reverb changed from AB763 to AB868 circuit? I am aware of the heater winding center tap removal and the rectifier tube change but the published schematic voltages did not change.

I have a vintage '65 Deluxe Reverb that has a K025130/606334 ('73 Xfrmr). The AC output to the rectifier seems high. ...

Posting for others still watching this thread...

Fender used at least 4 different power transformers in the Deluxe Reverb and their high voltage output kept changing, even though the changes were generally not indicated on a schematic. 125P23B, 125P23C and 125P23D were all used up to about 1966, and they each had successively higher B+ output. The 1964 DR I used to own had the 125P23B transformer, and delivered 394v DC to the 6V6s.

By late 1967 Fender switch to 6-digit part numbers (usually starting with "022___"), and the Deluxe reverb PT began to be marked 025130. When silverface amps come along, there is a letter-prefix (I've seen K, J, L and M) though I haven't measured enough of those to understand whether there is a voltage-change with a new letter-prefix.

[Stevem]

EL34s can’t just be dropped into a Fender amp even once you change the screen resistors to 1K from 470 ohm!

Pin 1 needs to be hooked to pin 8.
The end of the 1.5k resistor on pin 1 then needs to be removed, stood up and the bias voltage feed wire connected to it.

The bias adjust circuit will need to be modified to drop about 10 volts out of it.

And last but by far not least the power transformer will need to have about another addition 1 amp of heater current available ( which it does not) to not burn up at some point.

[nuke]

FWIW, my 1979 Deluxe Reverb and the black-panel Deluxe Reverbs all seem to be designed to center on 117VAC mains. (I've had since about 1982 or so when I was a teenager)

A quick test to see what your power transformer is meant for is to measure the filament power output, with load on it and adjust the AC input with a variac until you see exactly the filament voltage expected (usually 6.3 volts AC, RMS for Fenders).

The silverface era went to the 5U4GB rectifier and results in lower B+ voltage as noted. I've found that good quality USA-made 6V6's will hold up just fine with the 420-430v plate supply. Sylvania 6V6GT tubes seem last the longest, and Fender was using GE with the wafer base when mine was made.

I think Fender went with the 5U4GB rectifier to save a few bucks and to reduce their warranty claims in the silver panel era. As the silver-face amps evolved over time, you'll see more defensive measures employed, like the rectifier change, slight changes in the power supply, additional suppressor caps on the output tubes and so on.


For my 1960 Bassman (5F6A), it really needs a reduced AC mains voltage, they were definitely building for 110 vac or less. I built a simple voltage-bucker into an old Tripplite surge suppressor housing. (nice all metal one with heavy-duty outlets) that knocks to the all too common 122-124 VAC mains of today down to something more sane. I always run it on the bucker. It still has very high plate voltage. The real JAN 5881/6L6WGB Tung Sol tubes seem to handle it fine. 6L6GC would be wiser probably.