Tube Amp Archive

Look for bad or missing grounds, or ground loops, and any problems with the power supply. So now something weird is happening. I got the signal cleaned up. Just sits with barely any noise on the scope when it's on. But...when I turned my signal generator on (1kHz @ 250mV), the amp runs fine until I...

So I got a call from the friend I built the Komet 60 for...when it left my hands it sounded loud and clean. He started noticing hum and buzz, etc....oh no. I get the amp in and it's making no audible guitar noises and just loud hum and buzz. I first tried a bunch of tubes. I got a combo that sounded...

Can you just measure the hole and cutout centers yourself and make a drawing or are you graphically challenged? I'm more than graphically challenged... In reality, I'm tight on time and my buddy has time at his shop on their laser cutter / engraver so he's pressuring me to just send him a file...he...

Can you just measure the hole and cutout centers yourself and make a drawing or are you graphically challenged? I'm more than graphically challenged... In reality, I'm tight on time and my buddy has time at his shop on their laser cutter / engraver so he's pressuring me to just send him a file...he...

Does anyone have a drawing file for the Mojotone SR chassis? I have one on the bench and need faceplates made, but I'm only using some of the holes. Their tech support is being illusive to giving me the full drawing file. I realize that all of these companies tweak these a bit so I want the actual d...

It's only a bit high as you say. Is your line voltage normal or on the high side? Something ended up getting screwy with the cathode resistor and I was getting some strange readings. I ended up just replacing that end of the circuit instead of trying to figure out why my resistances were varying an...

Does anyone have drawing files for chassis dimensions for the standard Fender lot of amps? I'm working on using a Super Reverb chassis to have a friend make some custom faceplates. It's much easier to start with drawing files or convert to them then measuring and sending out as we're both engineers ...

The top of the 2.7k cathode resistor should not be 0V, more like 2.5. Check the resistance from the cathode to ground. Is it ~2k7? I got it resolved. Something ended up getting screwy with the cathode resistor and I was getting some strange readings. I ended up just replacing that end of the circui...

What are the voltages at the top and bottom of the plate resistor, cathode, and the cathode resistor value? Screenshot 2022-04-29 082144.jpg Sorry if this is a little hard to read, but I added the voltages to a snippet from the Asteroid layout. The tone controls work well so I don't think my issue ...

martin manning wrote: ↑Fri Apr 29, 2022 11:45 am Is the cathode resistor correct?

Yes. All resistors are verified as correct and testing within spec.

Have you tried changing the tube? Tried last night with the same results. I'm getting a huge voltage drop across the 100k plate resistor. Before the resistor, 427V. Immediately after the body of the resistor on the leg, 170V. I even changed out the resistor, which measured 98.6kohm, but wanted to b...

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 v...

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 starin...

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...

ok... they are toys with a narrative. Let me guess for us. lol You are going to be making a 60w single Hi input tweed Bassman head, and the choice you get to make is in selecting a PI. I would pick Marshall LTP with .1u caps. Higher plate on input stage.. 150-180k maybe. This amp needs little or no...