DIY 5F2A: Distortion, not loud. Where do I look?

[heybluez74]

Hello,

I had these parts from years ago and decided to try to put together a 5F2A. It 'works' but the output is distorted and weak. I am checking wiring, etc and can't find where I didn't connect correctly. I am wondering if it is the PT or OT. FWIW, I am using a 272FX PS and a 125ESE OT. Also including a pic of the wiring.. PS please don't judge too hard -- I am moving things around.. will tidy up when I get this working.

VIDEO -->.

QUESTION.. where should I look next?

Thank you.

 

[printer2]

List the voltages on the pins and the PS voltages.

 

[Powdog]

Scrutinize your solder connections/grounds carefully.

 

[Lowerleftcoast]

It is hard to see from way over here but it looks like the output jack is wired wrong. Ground to tip maybe?

 

[Lowerleftcoast]

Welcome to TDPRI.

 

[heybluez74]

Welcome to TDPRI.

thank you!

 

[heybluez74]

List the voltages on the pins and the PS voltages.

I think I pulled this correctly --

5Y3GT

PIN 2+8
Measured with probes on pins 2+8: 5.7VAC
Measured DC with ground and probe on pin : 438V

PIN 4+6
Measured AC probe on ground and pin 4 or 6: 342V

6V6GT

PIN 1:
PIN 2: 3.59 VAC
PIN 3: 434 VDC
PIN 4: 372 VDC
PIN 5:
PIN 6:
PIN 7: 3.59 VAC
PIN 8: 23.8 VDC


12AX7

PIN 1: 209 VDC
PIN 2:
PIN 3: 1.7 VDC
PIN 4: 3.6 VAC
PIN 5:
PIN 6: 200 VDC
PIN 7:
PIN 8: 1,7 VDC
PIN 9: 3.6 VAC

 

[Powdog]

If you’re running parallel filaments, pin 5 of your 12AX7 needs to be soldered directly to pin 4. Also, on the filament string, pin 2 of the 6V6 should go to pins 4/5 on the 12AX7 and pin 7 of the 6V6 should go to pin 9 of the 12AX7.

 

[heybluez74]

It is hard to see from way over here but it looks like the output jack is wired wrong. Ground to tip maybe?

wilco

 

[heybluez74]

wilco

wow... this definitely improved it!! thx. will now get back together and see about a buzz...

 

[heybluez74]

If you’re running parallel filaments, pin 5 of your 12AX7 needs to be soldered directly to pin 4. Also, on the filament string, pin 2 of the 6V6 should go to pins 4/5 on the 12AX7 and pin 7 of the 6V6 should go to pin 9 of the 12AX7.

I have it with a wire jumper now.. you saying bend the pins together and solder them?

 

[Powdog]

A jumper will work fine. This is how I do it.

 

[dan40]

Your plate voltage seems very high. Are you really reading 434v on pin 3 of your 6v6? If so, you are approaching 150% dissipation on the power tube which should be causing it too redplate. That may also be why you are hearing a hum. What is the value of your cathode resistor for the 6v6?

 

[Lowerleftcoast]

Are you running a vintage 5Y3 rectifier tube or JJ 5Y3? These tend to drop more voltage than other 5Y3 rectifiers.
(It needs less voltage or a change in the cathode resistance on the 6V6 to have the 6V6 run a little cooler.)

You have a 500R resistor on the cathode of the 6V6. Do you have resistors to make roughly 600R for that cathode resistance?

 

[Lowerleftcoast]

If you are not already... use the (120v option) black and white primary wires of the PT.

 

[heybluez74]

Are you running a vintage 5Y3 rectifier tube or JJ 5Y3? These tend to drop more voltage than other 5Y3 rectifiers.
(It needs less voltage or a change in the cathode resistance on the 6V6 to have the 6V6 run a little cooler.)

You have a 500R resistor on the cathode of the 6V6. Do you have resistors to make roughly 600R for that cathode resistance?

Are you running a vintage 5Y3 rectifier tube or JJ 5Y3?

Tube Amp Dr 5y3GT / 6087 TAD

 

[heybluez74]

If you are not already... use the (120v option) black and white primary wires of the PT.

all the PT has is two black

 

[Lowerleftcoast]

Tube Amp Dr 5y3GT

It might drop more voltage with a vintage 5Y3.

 

[tubeToaster]

all the PT has is two black

If it is a Hammond 272fx it should have two primary options.

 

[heybluez74]

If it is a Hammond 272fx it should have two primary options.
View attachment 1056327

I must have gotten the budget version...lol. It only has 2 blk wires.