6g15 power transformer

[Bluemolded85]

Hello everyone,
My first real post here. I'm currently building a 6g15 tube reverb. I'll be using a full wave bridge rectifier in the circuit and had a question about power transformers and the full wave bridge rectifier.

I live in Anaheim California which is right down the street from Pacific audio magnetics. They make very accurate recreations of classic iron. I picked up one of their 6g15 power transformers. It's gorgeous. Very accurately made.

The question I had was regarding the high voltage leads. On this particular transformer, there are two high voltage leads. There is one solid red and one red/yellow. When measured across the two leads , the voltage is 290v unloaded. I assumed the red/yellow lead indicated a center tap but the manufacturer stated that the HT is not center tapped. Any idea if I can used this tranny with a full wave bridge ?? I would be using a modified schematic. The schematic and layout indicates two red leads going to the bridge. Would I be able to just ignore the fact that one lead is red/yellow and just treat it like my second solid red high voltage lead?
Just for reference, I'm using a fender 6g15.2 schematic/layout I found. I'm also referencing Doug Hoffmanns layout and "Uncle Doug's" layout. It's a bit of a hodgepodge, incorporating elements from the 3 layouts that I like from each.Please let me know what you guilts think. Thanks !
-Frankie

[Latole]

"  Any idea if I can used this tranny with a full wave bridge ? " : Yes , you can

You forgot the heater center wire green/ yellow; it must go to ground.

 Google ;

[tubeswell]

voltage is 290v unloaded. Any idea if I can used this tranny with a full wave bridge ??

FWB will make about 410VDC. You can make a single-ended 6V6 amp with that if you keep Pmax within limits, but I wouldn’t run a 6K6 at that voltage. In fact I’d probably go for a JJ6V6S biased to 14W. But yes, you can make that work.

[pdf64]

I suggest to follow the RI schematic.
It'll save you a load of grief in regard of mains hum loops and might save you from a shock.

 https://el34world.com/charts/Schematics/files/Fender/Fender_63_reverb_manual.pdf

[Latole]

I suggest to follow the RI schematic.
It'll save you a load of grief in regard of mains hum loops and might save you from a shock.

 https://el34world.com/charts/Schematics/files/Fender/Fender_63_reverb_manual.pdf

His PT is too powerful !
RI use 294 V dc

[Bluemolded85]

Thanks everyone for the replies.

From what I'm reading so far, the Pacific 6g15 transformer with a full wave bridge will be a bit over spec. Is this because the full wave bridge is much more efficient and sorta boosts the DC much more than a half wave rectifier ?
I actually built another 6g15 last year for a friend. I used a mercury magnetics transformer which is nearly identical in specifications to this pacific transformer. My B+ on that build was only about 300vdc if I recall. I used the original 6g15 schematic with the half wave rectifier. I was lucky enough that I got zero ground loop hum. Kinda wild to me that if I use a full wave bridge my B+ would be that much higher than with the half wave rectifier! I'm glad to be learning from you all !

I'm sorta at acrossroads here. Do I continue with this tranny and have a pretty hot B+ and plan on cooling the bias like any other single ended cathode bias amp ?
Or do I save this tranny and use on other 6g15 build in the future and simply purchase the relatively cheap Hammond 290wx which runs at about 250vdc and continue with the full wave bridge.
I already finished fabricating my board and populated it. Also fabricated my little sub board with the full wave bridge so I got holes drilled in my chassis. No turning back, I'm commited to the full wave bridge.

[dogburn]

If you want to run the 6K6, you need to aim for the 295V B+ of the original - and lots of people who play through 6G15 units say the 6K6 makes a notable difference in the sound and better captures the sound of the original. Since you are committed to FWB rectification, the Hammond at 250v is still too higher. You want ca. 295V, so divide that by 1.414 to get 208.6v - then there is some dropping with the diodes and choke, so factor that in.

[SEL49]

No turning back, I'm commited to the full wave bridge.

It's very easy to connect a FWB to operate as a single diode half wave rectifier.

[Willabe]

I built a stand alone Fender verb, I used a Mercury Mag. PT. I ran the B+ with a FWB. 

I can't find the tread for it, it should have the B+ dcv I ended up with.

[Latole]

I built a stand alone Fender verb, I used a Mercury Mag. PT. I ran the B+ with a FWB. 

I can't find the tread for it, it should have the B+ dcv I ended up with.

This one ?
https://el34world.com/Forum/index.php?topic=12338.msg117502#msg117502

All your treads here; https://el34world.com/Forum/index.php?action=search2

[bullkelp]

Ive built a few of these units now.
Can I recommend a couple of things?

Use isolated jacks both for input/output and RCA reverb return and send.
Grounding is key. I used merlins ground lift/hum isolation network on my builds with good effect.
My first tank I built in 2015 (approx) is still going strong and has been put through numerous indoor and outdor gigs and kicked at each time we play Cecelia Anne   

Thanks for posting uncle dougs schematic I havent seen that one.
My builds have followed the weber ad-verb 5g15 and TAD schematics and as stated grounding per merlins rules/network.

Grain of salt: I'm a low teir hobbyist builder so DYOR and im happy to be stood corrected by the grown ups 

P.s i think the 6g15 is one of fenders greatest circuits. I play surf music principally. Not only is this the best drippy springy reverb, it seems to behave as a preamp too for your guitar which works great with single coils.

p.p.s choose a decent pan! there are some awful pans out there. A proper belton or USA made acutronics.
I was surprised the variation between manufacturers in terms of sound.

Good luck!

[Willabe]

This one ?
https://el34world.com/Forum/index.php?topic=12338.msg117502#msg117502

Yes, that's it, thank you.   

I didn't have a problem with too high of a B+ dcv using a FWB rectifier.

Looking back, I didn't need to use that many B+ filter caps.     Part of it was I was reading Kevin O'Conors TUT books and he would use no larger than 22uF filter caps. If more uF was needed he recommended to use multiple 22uF's.   

From TUT 3, 2-12;

"An ideal capacitor has a resistance that decreases as frequency increases. This should make the supply impedance very low at high frequencies, helping to suppress broadband noise and augmenting amplifier stability. However, lead inductance, internal resistance and leakage capacitance conspire to erode this ideal. There commodities are smaller in lower value caps than in high capacitance units, so several low-C caps will out perform one high-C cap of the same net value." 

I would go with 1 extra stage of filtering before the 6V6 tube, because it's a SE amp.

So, 2 x 22uF > choke, then feed the 6V6 OT/plate with 2 x 22uF, then a single 22uF screen, then I would use a single ecap for each 12AX7, not 1 ecap for each triode.   

[Bluemolded85]

Well I'm still debating what to do with the power transformer but here's a sneak peak of the project so far. Go easy on me, I'm a rookie.

[Willabe]

I know Fender put the PT inside the chassis. But put the PT on the outside, it will run cooler.

Just hook up the PT's B+ put 1 B+ filter cap on the FWB output and see what the B+ dcv measures.

[Willabe]

It's good that you ran the heater wires down into the corner of the chassis.

But here's a better way to solder up the wires at/to the tube sockets. Scroll down to the very bottom.

https://www.valvewizard.co.uk/heater.html

[passaloutre]

What are the names of those white caps and red resistors? Vishay and Dale? What series?

[mresistor]

 I would assume all the components on the board are Vishay brands


The film caps are MKP1839

[Bluemolded85]

What are the names of those white caps and red resistors? Vishay and Dale? What series?

The Caps are Vishay MKP1839. I like these a lot.

The resistors are PRP (Precision Resistive Products) PR series resistors.I love them they are dead quiet and the leads are super long for point to point builds.