AA764 Champ diy bug help!!!!!

[goldstache]

Hello,
Just finished wiring up a blackface champ (no trem).
And it sounded awesome upon firing up. All voltages are within spec.  Plays for 10 minutes then starts to duck in volume then starts distorting and audio ceases.  I power off and almost immediately power back on and it repeats this bug.
I'm using a hammond 270BX PT
550V CT @50maDC

And a Hammond 125CSE OT
I'm using Yellow 8ohms @5k
And Black 0 volt
On secondary side.

Here is the catch
I'm also running an EM80 magic eye off the plate of the 6V6. 
It's working flawless and is tapped off its own RC filter. 
I'm cool as far as filament requirements.
What am I missing?????
Help. 

[goldstache]

Well my PT only supplies 2A of 5v filament for rectifier 5y3
Do you think this is not enough for the 2A the rect. needs????

[Willabe]

Hi GL and welcome!

1st off, a 5Y3 only needs 2A@5vac so that's fine.

I think it's either your 6V6(?) is right on the edge of 'red plating' and in a little while your pushing it over it's limit or you might have a bad solder joint that after a little time is heating up and is making a bad connection.

To check if the power tube (6V6?) is 'red plating' play the amp with the lights off in the room and watch if you can see the tubes plate start to turn orange and/or red. If so turn off the amp!

Then you have to either get a tube that will handle that amps set-up or you will have to increase it's cathode (K) R.   

Or 3'rd and maybe 1st, try disconnecting the magic eye tube and see if that fixes it.


                  Brad          

[goldstache]

Thanks willabe!!!
Found the issue!  I wired the PT secondary to wrong heater of 5y3.
Switched pins voila' No More Problems!

Newb mistake
Tip top now thanks!!!!!
Rect was only getting 1.5 Volts before I switched wires now I've got 5.3v across heaters!!!!

[Willabe]

Thanks?   

I missed it, YOU found it!


We all make mistakes and learn from them, good job!


             Brad