[nullstring]

you should try switching the tubes, and see if it switches then.

 

[kuroguy]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif Actually, it's possible that one of the tubes developed a short. If the plate connections short with the heater connections somewhere inside the tube, then the heaters may see 48V. Just a guess ... but it might explain what you're seeing.

He did say that the problem does not follow the tube. That would usually rule out a bad tube.

 

[tomb]

Quote:

Originally Posted by kuroguy /img/forum/go_quote.gif He did say that the problem does not follow the tube. That would usually rule out a bad tube.

Quote:

The problem does not follow the tube.

Oops! You're right - he did say that..

So, it has to be some of his P2P that's shorting, I guess.

 

[mlau]

Sorry for the dumb question.

What is the part number for the volume knob on the Beezar kit?

I really like the minimalist look of the knob, so I'd like to know how much it costs/where to get it.

 

[tomb]

Quote:

Originally Posted by mlau /img/forum/go_quote.gif Sorry for the dumb question. What is the part number for the volume knob on the Beezar kit? I really like the minimalist look of the knob, so I'd like to know how much it costs/where to get it.

Mouser #450-6007

 

[Nonchalance]

I got some measurements.

48V on MOSFET pin 2 both sides. 48V between R1 and R2, 48V between R7 and R8.

21.55V on tube pin 3 left, 48V on tube pin 3 right.

So I guess the right side is messed up, but the tube on left isn't lighting up and I'm not sure how to fix the voltage problem.

Did I kill the tubes?

 

[the_equalizer]

Quote:

Originally Posted by Nonchalance /img/forum/go_quote.gif I got some measurements. 48V on MOSFET pin 2 both sides. 48V between R1 and R2, 48V between R7 and R8. 21.55V on tube pin 3 left, 48V on tube pin 3 right. So I guess the right side is messed up, but the tube on left isn't lighting up and I'm not sure how to fix the voltage problem. Did I kill the tubes?

Hmmm... 21.55V on pin 3 and the tube is not lighting up? Maybe an open filament, try measuring resistance between pins 3 and 4 of the tube with the tube out of the circuit; it should give a low resistance value.

Now with the right tube 48 volts on pin 3 are sure to kill that filament! Maybe you wired it to the MOSFET's pin 2 instead of pin 3? Another possibility is that the MOSFET's pin 2 and 3 are shorting out?

cheers!

 

[Nonchalance]

I definitely wired to pin 3. How do I test if the MOSFET is shorting out?

I can't get a resistance reading on 3-4 on either of the tubes. I guess I blew one and the other was damaged during shipping.

Well this project failed, haha.

Is there another way to test the rest of my circuit without the tubes? I want build it right at least.

Thanks for all the help guys. I really appreciate it

 

[tomb]

Quote:

Originally Posted by Nonchalance /img/forum/go_quote.gif I definitely wired to pin 3. How do I test if the MOSFET is shorting out?

Your next line below answers that.

If you measure zero resistance between the pins. Quote:

I can't get a resistance reading on 3-4 on either of the tubes. I guess I blew one and the other was damaged during shipping. Well this project failed, haha. Is there another way to test the rest of my circuit without the tubes? I want build it right at least.

You can go through a methodical resistance measurement around each part - or junction measurements referenced to ground, also referenced to the schematic (write down the numbers on a copy of the schematic). In so doing, you can at least compare the readings for the two channels - they should be the same. At points where they're not, chances are that's a problem. Quote:

Thanks for all the help guys. I really appreciate it

One thing I'd try is to put more electrical tape on some of those junctions. It looked like in your pics that there many chances for shorts - especially if the amp got knocked down a few times. It seemed like those Panasonic FC cans were touching part of the power socket, for instance (an electrolytic's wrapper is not sufficient insulation) - but that could've been the camera angle. Good luck.

 

[Nonchalance]

Ok I sorted out a bunch of wires and now I'm getting light and crazy readings. Maybe I'm not as screwed as I thought I was.

~44.5 V at pin2 on both MOSFETs and at the 48V marking on the schematic. ~44V at the right tube pin 3, tube lights up a lot. ~18V at left tube pin 3, barely light, mostly in the middle, and I get sound out of this one. I know the tubes are working because both got sound on the left socket, just a buzzing on the right side where the voltage is nuts.

 

[kuroguy]

turn it off before you waste that really bright tube. you are running 44 volts through a 19 volt filament. I bet the tube won't last more than a few minutes at that rate.

 

[Nonchalance]

I know, I took some measurements and put up some music then took the tube out so it doesn't burn out. It was on for ~30 seconds total.

 

[hitman47]

OK, I already managed to screw my amp up again... I finally got the casing more or less done and was running it with my PC as source, so I lifted it onto my desk which has a massive metal frame and there was a huge spark from the casing to the metal frame and now only one tube glows when I turn it on and there's no sound coming out at all. Any ideas as to what might have gone wrong?

 

[ethan961]

Quote:

Originally Posted by kuroguy /img/forum/go_quote.gif turn it off before you waste that really bright tube. you are running 44 volts through a 19 volt filament. I bet the tube won't last more than a few minutes at that rate.

I believe it is rated for 100V, so there should be no worries. TomB didn't warn me of it (I am having the same problem) and I believe it is on one of his sites at DIYForums.org.
The tubes normally run at half voltage, so I wouldn't be worried.
I can't currently check the resistance on my amp but I still cannot see anywhere there might be a short. I might get some pics up when I get home tomorrow evening.

 

[ethan961]

Quote:

Originally Posted by hitman47 /img/forum/go_quote.gif OK, I already managed to screw my amp up again... I finally got the casing more or less done and was running it with my PC as source, so I lifted it onto my desk which has a massive metal frame and there was a huge spark from the casing to the metal frame and now only one tube glows when I turn it on and there's no sound coming out at all. Any ideas as to what might have gone wrong?

Something must have shorted to ground, possibly damaging something.