Completely Out of My Depth - Modulus 50w 69 Build

[Marcomel79]

Impossible to get a voltage across the bias point?

Double check the Modulus layout and make sure that all the points that need to be grounded are un fact grounded. Also, how did you bias the amp?

 

[kingfredward]

Pin 3 wires are inverted! And got exactly the same noise and loud hum

It hasn’t been biased yet considering the fact I am unable to read any bias current

 

[LyseFar]

You HAVE to check all your wiring from left to right. Ground scheme. Component values. Triple check the potmeter wiring (I have sometimes switched those around in a build - I have to admit - which can result in low or no sound). Tube wiring. Look for possible shorts.
EDIT: And your jack input wiring also…

Then use Rob Robinettes safety amp upstart procedure to check ground and all.

Amp Startup

Tube Amplifier Startup

robrobinette.com

Important….

 

[kingfredward]

All this was hurting my head too much

Think I need to take a break from it all so put it in the head shell and I guess I can just admire it for now lol

Really appreciate everyone’s help on all this

 

[LyseFar]

Maybe a good idea with a break.
I am sure that you sooner than later will succeed and enjoy the amp.

 

[Marcomel79]

Yeah man, take the night off and start fresh tomorrow. Sometimes is like that. Youll get it working

 

[kingfredward]

Thanks all you guys are massive legends. I think I was rushing it as I am off to Canada for work soon for 1.5 weeks so wanted to get it finished

Also I noticed when discharging caps that the voltage creeps back up even when I haven’t got it plugged in. Is that normal?

Had a tiny shock today so now super paranoid and that was discharging everything and checking all the voltages carefully

I’ll take a look tomorrow. Appreciate all your guys help

 

[PelliX]

Also I noticed when discharging caps that the voltage creeps back up even when I haven’t got it plugged in. Is that normal?

Yes, that's normal. To avoid it you can - after fully draining the cap - clip its positive terminal to ground.

Had a tiny shock today so now super paranoid and that was discharging everything and checking all the voltages carefully

Healthy survival instinct, excellent

 

[BlueX]

Thanks all you guys are massive legends. I think I was rushing it as I am off to Canada for work soon for 1.5 weeks so wanted to get it finished

Also I noticed when discharging caps that the voltage creeps back up even when I haven’t got it plugged in. Is that normal?

Had a tiny shock today so now super paranoid and that was discharging everything and checking all the voltages carefully

I’ll take a look tomorrow. Appreciate all your guys help

Sorry you ran into problems. Good idea to take a break, and come back with fresh mind.

The noise you hear could be caused by something simple like bad solder joint (could be tricky to find though). Follow structured best practice , like Robrobinette's startup procedure and troubleshooting steps, and you will get this amp working, I'm sure.