Mesa V-Twin Problem

[Pmelius]

Not building this pedal, but I have one and it's frying power supplies, I think!

Was playing it the other day, and all of the signal cut out.  LED's and switching still work, but no signal when engaged.  Still bypasses signal.

I measured the output of the power supply, and it's only 3vAC.  So, I order a new 12vAC power supply.  (Measured it first, 14vAC) Plug it in, it works for a few minutes and then goes dead.  I measure the new power supply, 3vAC.

Anyone have a clue what might be causing this?

Here is a schematic.  I understand that this was made by someone not-affiliated and is known to have a couple oversights.
https://schematicheaven.net/boogieamps/boogie_vtwin.pdf

[Groovenut]

It could easily be a shorted tube heater or plate. Pull the tubes and check the power supply voltage. If it stays where it's supposed to, you have a bad tube that will need replaced. It's probably best to replace them all/both if this is the case.

If the voltage still drops without the tubes in, there's another shorting component.

My money is on the tubes though.

[Pmelius]

Should have mentioned that I tried two new tubes with the same issue. When I get the new PS, I will try this though.

The real issue now is that I have two fried power supplies haha.  I ordered a third from Amazon, do you know of a clever way to protect the PS from any damage coming from the pedal so that I can continue to test this with the new PS and not fry it?

[Pmelius]

I should specify that when I'm talking about the power supply, I mean the wall wart that supplies the pedal with 12vAC from the wall, not the internal power supply section of the pedal.

[GibsonGM]

You could test for shorts.  Anywhere that power "goes into something", you can check from there to the other power terminal to see if it's shorted.    You can find the internal ground, and use that for your " - " while you probe with the " + " at IC power pins.    Make sure unit is unplugged when doing resistance tests, LOL! 

Easiest thing to do is first check the resistance across the main power input to the circuit.   If it is VERY VERY VERY low ohms, it tells you there's a short.  Low but rising resistance = a cap is charging.    You can test across the heaters this way too (pull a tube, what  resistance do you read between pins 4 & 5?).    A tube heater is only going to show, say, 20, 30 ohms, so expect this, it is not a short.   If both tubes are out, then expect no connection (unless a short!).   

Why don't you try that and post back what you find?  There is no reason something in the POWER section of the circuit couldn't have fried, either.  The rectifier, etc.    First things first...

[PRR]

That rig could be pulling over 1 Amp. (There's 0.3A of heater, a 12VAC:HV transformer of unknown losses, and some other stuff...)

What was the current rating of the warts you have been smoking?

[Pmelius]

That rig could be pulling over 1 Amp. (There's 0.3A of heater, a 12VAC:HV transformer of unknown losses, and some other stuff...)

What was the current rating of the warts you have been smoking?

Well the Mesa PS was rated for 1 amp and that's the rating of the Jameco brand one that I replaced it with

[Pmelius]

You could test for shorts.  Anywhere that power "goes into something", you can check from there to the other power terminal to see if it's shorted.    You can find the internal ground, and use that for your " - " while you probe with the " + " at IC power pins.    Make sure unit is unplugged when doing resistance tests, LOL! 

Easiest thing to do is first check the resistance across the main power input to the circuit.   If it is VERY VERY VERY low ohms, it tells you there's a short.  Low but rising resistance = a cap is charging.    You can test across the heaters this way too (pull a tube, what  resistance do you read between pins 4 & 5?).    A tube heater is only going to show, say, 20, 30 ohms, so expect this, it is not a short.   If both tubes are out, then expect no connection (unless a short!).   

Why don't you try that and post back what you find?  There is no reason something in the POWER section of the circuit couldn't have fried, either.  The rectifier, etc.    First things first...

Gonna try this tonight! Thank you!