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

heybluez74

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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.
 

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heybluez74

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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

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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

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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?
 

dan40

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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

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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?
 

heybluez74

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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
 




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