Transformer/Rectifier Wiring

[Howlin' Mad Mac]

I just finished wiring up a homebrew 5f1 ptp champ build and followed the schematic to the letter but the transformer I'm using has only a center tap for the B+ secondary (red/yellow) but no center tap for the 5 or 6.3 volt secondaries. The 6.3v is no problem as I've created the equivelent using (2) 100 ohm resistors grounded but my question is with no center tap on the 5v secondary should I ground pin 2 coming off the 5Y3 rectifier or is this not necessary?

[JoeM]

No, dont ground pin 2! The 5V wiring (probably yellow) go to pins 2 and 8 on the rectifier socket. No ground necessary.

[Enzo]

If you ground one side of the 5v winding, you will be shorting your entire B+ supply to ground, Believe me nothing good would come of that.

Your 5v winding floats at the B+ voltage... Think of those high voltage power lines that run across the countryside. Now look at the birds sitting on those wires. The wires have 200,000 volts on them. So then do the birds. What do you think would happen if we grounded one of the birds? (Hint: gravy and mashed potatoes would go with it.)

[Chuck H]

But if you've ever put gravy on your amp, you know it's hardly worth it.

If you've followed the schematics "to the letter" you should see that there is no CT for the 5V tap. You seem to be aware of the false CTR for the 6.3V tap but again, if you've followed the 5F1 schematic to the letter you won't need this as the filaments are not wired this way on that amp. What are you trying to do? We can't help if we think your following the schem but you are actually wiring the amp differently. You and we won't be on the same page.

Chuck

[Howlin' Mad Mac]

What's happeneing is I built a 5F1 from all new parts with the following exceptions: creating the false center tap for the 6.3 winding using a pair of 100 ohm resistors & omitted the .047 death cap & rather than use a tag board I decided to just wire the thing up point to point using a few little terminal boards. Got it all soldered together, checked & double checked to make sure everything is connected properly, plugged in the tubes & everything lights up but no output & can't figure out where I went wrong.

[loudthud]

Mac, I looked over some of your old posts and in one you made a reference to going to a technical school so I hope I can assume you know how to safely measure voltages in an amp. If not, read up on this before proceeding. With a voltmeter of some kind and the tubes installed measure and post the voltages to ground on each pin of each tube. If you have a camera, a picture of the inside of the amp would also be helpful.

If the tubes light up and get hot we can assume the heater supply is connected properly and skip those voltages.

On the 5Y3 expect a big AC voltage on pins 4 and 6 (we need to verify this) and just measure the DC voltage on pin 8 or 2.

6V6 skip pins 1, 2, 6, 7. Should be close to zero volts on pin 5 (you may hear a click or hum through the speaker).

On 12AX7 skip pins 4, 5, 9. Should be very close to zero volts on pins 2 and 7 (you may hear a click or hum through the speaker).