what would happen if

[Joeboo]

Hi, i quite new at amp building.
I am interested in building a 5e3, i have all the parts except a PT
I do have a PT that is 400 0 400.
Just curious because I saw a schematic for a 5e3 from trinity amps and the voltages on the schematic say 384ac, but other schematics say 330ac on the secondaries.
If i used the PT i have what would happen?
Thanks, Joe

[stokes]

You wont hurt anything,if thats your concern.Voltages will be higher than stock,I would suggest checking the bias and adjusting the cathode resistor on your power tubes accordingly.You could bring the voltage down by putting an appropriate value zener diode on the HV CT ground.

[loudthud]

Even with a 5Y3 the B+ will be over 500V. This will kill most filter caps and leave you with a smoldering mess. Death or injury could result !!! Spend the bucks and get the correct transformer.

[stokes]

My mistake,I assumed he would be using caps rated for his B+.I have the exact transformer in an amp I built for my son,ended up with 487v on the cathode biased power tube plates.Thats with a 5R4 rect tube.I should have taken note of his first line.

[trevorus]

Do you have multiple taps on the input side of the PT?

[Chuck H]

I would rather know the rest of the PT specs before saying this, but... Just drop the voltage with a zener (or string of zeners) on the HV CT. You need to drop 60V!!! So a string of six 5W 10V zeners will do it. Using one big zenner for such seems to have the effect of the diode unsoldering itself. You can get 10V/5W zeners in a DO type pakage through Mouser. Just float them. WRT the primary taps... You don't really want to go there. The filament voltages could suffer. Please spec the PT you have on hand.

[stokes]

Mouser has the larger zeners that bolt to the chassis.You can also drill a hole thru a couple penny's to use as a heat sink between the zener and chassis.

[Joeboo]

Thanks, for replying guys:
I have ordered the right PT but its on back order, my local store doesn't charge shipping, but I've been waiting 3 weeks and counting!
I have that big PT sitting in front of me, calling out to me. I got it from my father-in-law and i knew i would probably never use it, but i was just wondering...the specs of it are ~ it only has 9 leads, i measured 120 in, 400 0 400, 5v 0 and 6.7(across 2 wires).
Funny thing was, i was out hiking with my wife in the boonies and i came across 2 old beehive's laying in the bush. I did a quick measurement and took one home (no bees and it didn't have the gratings for honeycombs, just a shell)so i took it to recycle into a cabinet for this 5e3 build!.
So thanks, i dont want to make too many mods to get the big PT to work and chance melting everything.
EDIT:
Oh i was wondering why one schematic from (trinity amps) says 384ac on the secondaries and why
another schematic from somewhere elsesays 330ac...would that be because one layout was maybe thinking a NOS 5y3 recifier tube?

[J M Fahey]

330VAC is perfect for SS diodes.

[Bruce / Mission Amps]

Thanks, for replying guys:
I have ordered the right PT but its on back order, my local store doesn't charge shipping, but I've been waiting 3 weeks and counting!
I have that big PT sitting in front of me, calling out to me. I got it from my father-in-law and i knew i would probably never use it, but i was just wondering...the specs of it are ~ it only has 9 leads, i measured 120 in, 400 0 400, 5v 0 and 6.7(across 2 wires).
Funny thing was, i was out hiking with my wife in the boonies and i came across 2 old beehive's laying in the bush. I did a quick measurement and took one home (no bees and it didn't have the gratings for honeycombs, just a shell)so i took it to recycle into a cabinet for this 5e3 build!.
So thanks, i dont want to make too many mods to get the big PT to work and chance melting everything.
EDIT:
Oh i was wondering why one schematic from (trinity amps) says 384ac on the secondaries and why
another schematic from somewhere elsesays 330ac...would that be because one layout was maybe thinking a NOS 5y3 recifier tube?

It's more money invested, but you could still use the old 400vac PT with a choke input filter ... find yourself a decent 3-5Hy 150ma Hammond choke.
Put the DC output voltage from your 5V rectifier (use a NOS 5Y3GT...GE. RCA Sylvania, etc., not a Russian one) right into the choke with no cap to ground.... then after the choke, use a 16uF-22uF 475-500v E-cap.
You'll end up with a slightly higher voltage then optimal, but totally useable.

[Joeboo]

thanks, for answering me Bruce, you guys have taught me alot.
This will be my second build. I built a Lightning clone (not from a kit) and that went well, but i like the "thumpiness" that the 5e3 has.
I now have the PT that was on back order from Hammond, it is the one that is 330 0 330.
I haven't started yet, but am looking forward to starting soon. I have a JJ 5y3 rectifier ( at the time I bought it I didnt even know what a NOS was)
In my lightning i was getting a B+ of 364vdc with a 5ar4 in it so i plugged in the 5y3 to test, and it dropped 10 more volts? Mind you i have 2 el84s in that. so this JJ5y3 is ok for the 5e3 build? i imagine the math will bring me close to the right B+ for the 5e3
thanks, again