AB763 Amp Build Problems

[h4ck.b0x7]

I just got finished converting a DRRI to a Hoffman AB763 2-Channel turret board. After getting done and going through the tests I am finding that my preamp tubes aren't lighting up. What should be my first course of action to solve this issue?

The Rectifier and Power tubes are working just fine and I biased the power tubes.

Thank you in advance!!!

[h4ck.b0x7]

Ok, so it looks like I'm getting about 7v AC across the heater wires on the everything up until and including the phase inverter. After the phase inverter none of the other tubes light up. I guess I can check continuity to see which wire has a short.

[sluckey]

Ok, so it looks like I'm getting about 7v AC across the heater wires on the everything up until and including the phase inverter. After the phase inverter none of the other tubes light up. I guess I can check continuity to see which wire has a short.

I would expect an open, not a short. Maybe a broken wire or poor connection. Look at the wires between the phase inverter and the next tube.

[h4ck.b0x7]

That's what I meant Slucky. It's been a long night. I'm just going to sleep now. I'll get up in a couple hours and see if I can't track it down before I head to the Buckethead concert tonight. I quickly tested continuity and didn't notice anything wrong, but then I realized that I did it with the tubes in the sockets and I'm pretty sure that defeats the purpose. I'm too tired to be sticking my hand in a 400+ V environment.

[EL34]

read this post first and do the double check method

http://el34world.com/Forum/index.php?topic=19361.0

[h4ck.b0x7]

Doug, I made sure to triple check everything as I was going along and checked it again when I was done.

After tracking it some more, continuity looks good. Voltages on the top and in the sockets all measure good. I plugged a tube into V1 and found that it gets power just fine. So I started adding one tube at a time and found that all tubes get power until I plug in the V6 phase inverter tube.

[h4ck.b0x7]

[h4ck.b0x7]

The problem was a bad connection between pins 4 & 5 on V6. The sushi I had for dinner was good too!! (I needed some chopsticks for poking around)

This thing has tone so creamy it's like a hunk of butter melting on a big 'ol pile of flapjacks!!

[sluckey]

We would love to see some pics. And since Dave is doing the same conversion I'm sure he would be interested also.

[HotBluePlates]

Nice! Congrats on getting it going!

[h4ck.b0x7]

I would have posted pictures earlier but I had tickets to see Buckethead.

[h4ck.b0x7]