EDCOR OT with UL and PP leads which is which??

oldtexasdog

oldtexasdog

Well-Known Member
EDCOR OT UL and PP leads, what to do? Mag 175 6V6

I bought an EDCOR OT GXPP15-6-10K to do a 6V6 amp. I asked them which leads were PP and which were UL to plate and screen and this was the answer I got?? I am confused?
"
"The Blue and the Brown is the Plate to Plate. The White/Blue and White/Brown is the UL leads"exact from their e-mail response.

the OT has 5 leads the red is B+ then the schematic shows a blue to plate and white to screen then it shows a brown to plate and a white/brown to screen.
Which is UL which is PP?

I guess I am just DUMB:tears:
 
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PP topology uses two output tubes. PP OPTs, when used with pentodes, can be run in native(pentode) or UL modes.

In pentode mode, use blue and brown wires to the plates, ( blue to tube 1, brown to tube 2), red to B+. The other two wires are not used in this mode. If you want, cut off blue/white and brown/white, just don't forget to seal off the tips with either shrink tubing or tape. If not, coil and tape them nicely.

In UL mode, the blue/white and brown/white go to the screens G2 of the pentodes. Make sure that if you connect blue wire to tube 1 plate, blue/white goes to the screen of the same tube, so blue wire goes to plate of tube 1, blue/white to the screen of tube 1, brown wire goes to the plate of tube 2, and brown/white goes to the screen of tube2. Red goes to B+.

Hope that's what you were looking for...

Cheers, Paul
 
What he said. If the amp squeals when you power it up, reverse the blue and brown leads. If you are running it UL, you'll also have to move the brown/white and blue/white leads.
 
You may not want to cut or shorten any leads as you never know when you may want to sell them or the amp and someone else may want the UL. Heat shrink will work great and be good for decades.
 
prelius said:
PP topology uses two output tubes. PP OPTs, when used with pentodes, can be run in native(pentode) or UL modes.

In pentode mode, use blue and brown wires to the plates, ( blue to tube 1, brown to tube 2), red to B+. The other two wires are not used in this mode. If you want, cut off blue/white and brown/white, just don't forget to seal off the tips with either shrink tubing or tape. If not, coil and tape them nicely.

In UL mode, the blue/white and brown/white go to the screens G2 of the pentodes. Make sure that if you connect blue wire to tube 1 plate, blue/white goes to the screen of the same tube, so blue wire goes to plate of tube 1, blue/white to the screen of tube 1, brown wire goes to the plate of tube 2, and brown/white goes to the screen of tube2. Red goes to B+.

Hope that's what you were looking for...

Cheers, Paul
Click to expand...

Thanks-Guess I am getting dumb with old age but I never had a OT transformer I could wire either way. From what you said this is why it is so dang hard to set a switch to go from PP to UL !!!! Which is what I wanted to do for a 6V6-12AX7-5U4 build. So I guess I will wire it both ways and let my ears be the guide:music:
Thanks again. Big time!!!:thmbsp:
 
Also you may want to validate the secondary wiring before you install them. I had some PP edcors a while back that had one of the plate and UL leads reversed. If you have a digital ohm meter, it's easy to validate with a DC resistance test.

Pick as reference one side of the transformer secondary, let's say blue. Measure DC resistance from the blue secondary lead to each of the other leads in succession: a) blue to blue/white, b) blue to red, c) blue to brown/white, d) blue to brown. The resistances should be increasing at each successive lead measured. If the resistances are not increasing as described, the wires are somehow reversed.
 
Will do thanks again. I just had no idea that you would employ all four leads (not inc. B+) at the same time . I had it in my head you would just switch the pairs. Like I said-Dumber every day:tears: Guess thans to ya'll I will be finding out if UL sounds better or not.
 
prelius said:
PP topology uses two output tubes. PP OPTs, when used with pentodes, can be run in native(pentode) or UL modes.

In pentode mode, use blue and brown wires to the plates, ( blue to tube 1, brown to tube 2), red to B+. The other two wires are not used in this mode. If you want, cut off blue/white and brown/white, just don't forget to seal off the tips with either shrink tubing or tape. If not, coil and tape them nicely.

In UL mode, the blue/white and brown/white go to the screens G2 of the pentodes. Make sure that if you connect blue wire to tube 1 plate, blue/white goes to the screen of the same tube, so blue wire goes to plate of tube 1, blue/white to the screen of tube 1, brown wire goes to the plate of tube 2, and brown/white goes to the screen of tube2. Red goes to B+.

Hope that's what you were looking for...

Cheers, Paul
Click to expand...


Well I turtled up the Maggie 175 and started planning my instal of the UL EDCOR OT's
Question?
The Plate is pin3 on the 6V6G's and the Screen G2 is pin 4 if I am not mistaken (I don't have a schematic) Now B+ (this is where I think I am going nuts) is also Pin4 G2
correct??:scratch2:

Thanks- I hate to sound like an idiot.:drool:

IMG_0621.jpg
 
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EDCOR OT UL and PP leads, what to do? Mag 175 6V6

Maggie 175 6V6G-?? I just have not messed with them much much less for UL? EL84's yep a plenty.
 
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The UL taps go to pin the 4s,,, the B+ is now connected to the lower Right side tap of the fllter cap in your pic... remove the red wires paralleling the the pin 4s on the tubes...
If you think about it, teh screen tap is about 40% of the winding, so it would now have to be separate from B+...
Thats how it looks to me, anyhow!!!
 
That makes sense to me. I just don't have that many experiences with 6V6 tube amps and absolute none with doing UL. I have been reading everything I can on the subject and spending hours and days on thinking about how it works and what it does:scratch2: It is alien to my old brain, but seems like a simple mod to try? Just can't seem to get my head around it. Maybe should have stuck to a EL84 those I understand:thmbsp:
 
Yep,,, I like 6V6s,, built a Maggy 175 amp from scratch... UL tap has to be separate from B+, its a different voltage!
There should be a schematic on the bottom of teh Edcor OPTs to confirm...
I just got a pair of SE tx from them, another coming this week...
Good luck with your project...
 
Well the dang thing started squelling as I brought it up. Going to check and validate the secondary wiring as kward said??
 
Make sure the secondaries are the right polarity, FB is positive secondary,,, and teh screen and plate leads are on the same tube... IIRC Edcor color codes are a little different...
 
Well I brought it up on a varic and it started squealing so I will now validate the OT windings as kward suggested unless someone can see a mistake I made?
Thanks all:thmbsp:

IMG_0630.jpg

IMG_0631.jpg
 
Looks wired right from what I can see in the pic, looked at Edcor schem also... Try connecting teh speakers directly to the OPT secondaries without going thru teh FB circuit, secondary commons may have to be clipped to amp ground... Also, I always bond tx to teh chassis with clip leads, when they aren't bolted to the chassis
 
Could I have the left side(by Pic) wrong and the first tube is the far left? IE the far left tube is number 1 for that channel and then the far right is number 1 for the the other?
 
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