Komet 60 help

[EstimatedAntelope]

I finished a Komet 60 build for a friend. All of my start up procedures worked great and I popped in the power tubes (KT77) along with my dummy load to hopefully bias the amp and get it ripping. I am getting low voltages on pins 1 and 3 of V1 and some others much higher than expected. I attached the voltage chart I took with the amp off of the light bulb limiter.

Pin 8 of the rectifier is at 550V as well.

I can't get any good bias readings. When plugged in the amp sounds short and fizzy but full. Is this a heater issue on the power tubes? I haven't tried another set of tubes in the amp yet.

IMG_6877.jpg

[sluckey]

The bias voltage on pin 5 of the KTs is way too high. I've never used KT77s but if they are similar to EL34s they will make a lot more sound if pin 5 is about -40v.

[martin manning]

The bias voltage on the output tube pin 5's is much too low. It should be -45V or so. If you can't adjust it to that level there is something wrong with the bias circuit.

[EstimatedAntelope]

So I dug back into my wiring and remembered my mistake...

The "Asteroid" build from here uses a different bias pot than what I put in the amp. I intentionally left it unhooked to remind myself to not look at the layout and wire like a normal pot...well I didn't remember and hooked it up while staring at the layout in my fugue state of finishing the build. Basically legs 2 and 3 were swapped....I felt like an idiot but glad I remembered my mistake while lying awake last night.

[EstimatedAntelope]

Now that my bias issue is fixed, the amp is alive. Sounds like what I think a Komet 60 should sound like. Tight but sort of hairy on the gain. With my LP it was fun letting the notes bloom out while still have a lot of control via pick and guitar volume control...however...

My V1 plate and cathode voltages (1,3) are driving nuts....why are they so low? Is it worth my time to go back and troubleshoot this or if it works it works?

Thanks for the help

[martin manning]

Have you tried changing the tube?