Completely Out of My Depth - Modulus 50w 69 Build

[kingfredward]

Fuse back in and it’s good. I got HT voltage

This is without tubes

And clipped on the 1ohm resistor

Again that’s nothing and that’s with the standby OFF so now really scratching my head. The tubes glow up and warm up fine too

Anyone got any ideas?

 

[Marcomel79]

The tubes are not conducting because if they were, your ht would be lower. I cant see from the pics but is there a lead going to ground from pin1 of the power tubes?

 

[kingfredward]

The tubes are not conducting because if they were, your ht would be lower. I cant see from the pics but is there a lead going to ground from pin1 of the power tubes?

Sorry I should have clarified. that was without tubes. Shall I try with tubes? I can garantuee ill have the same result

Yup definately grounded on pin 1

 

[Marcomel79]

Man!! Without tubes you have no reading!!! Before you install the tubes, clip your black lead to ground, and your red lead to pin5. Adjust the trimpot to max negative voltage, so the tubes will be safe. After you do that, turn the amp off, drain the caps, install power tubes and measure voltage from pin 8!

 

[kingfredward]

sure thing thank you!

Okay pin 5 and maximum negative voltage done

Put in tubes



Not clear but they glowed up great

Then I put a clip on the corner of pin 8

And … still nothing

 

[Marcomel79]

Negative 162 volts?? Sounds like a lot!!

 

[Marcomel79]

Turn amp off, drain filter caps and with dmm on continuity test, check between this junction and pin3 of power tubes. Report back readings