No Phantom power...

[normandyrocks]

I built an A12 a little while back, but haven't until reacently tried it with a condenser mic. anyway, dynamic mics work fine but I cannot get a condenser mic to work!
I also just built a N72 and it works great with condenser mics using the same cables.
I went through the unit double checking the parts of the circuit that seem to relate to the PP and found nothing amiss. I also reflowed any solder joints that seemed questionable in the slightest! No solder bridges or backwards components that I could find.
what could this be or what do you suggest that I check?
Thanks!
Have a great day!
Norm

[tpryan]

The phantom power circuit is very simple. Refer to the schematic and work your way forward from J7, pin 5 until you find where the 48V disappears.

[normandyrocks]

I checked everything and what I found makes no sense.
I get 48v (actually 46v) on 1 side of r33 and r34 but the side nearest the transformer I do not. R 32 I get it both sides of the resistor. I get it one one side of both caps. nothing at all on the output (xlr)
I removed and tested r33 to make sure it wasnt fried and it tested fine.
I do not understand the role of the caps in the circuit path but the electrolitic cap seems to be positioned the correct way. I don't believe the other one is polarized (?)
Anything you can tell me would be most apreciated!! I am pretty good with soldering, but these are my first projects beyond wiring mic snakes, sound racks and studios.

[tpryan]

Your measurements make perfect sense, though something is definitely wrong. Some more questions:

Did you install the paper insulator under T1?
Did you install a shorting jumper at J3?
What resistance do you measure between the "bottom" of R33 and R34?
What resistance do you measure between the "bottom" of both R33 and R34 to PGND (J7, pin 2)?

Let us know what you find.

[normandyrocks]

Did you install the paper insulator under T1?

yes

Did you install a shorting jumper at J3?

yes, pins 2&3

What resistance do you measure between the "bottom" of R33 and R34?

35.5 ohms

What resistance do you measure between the "bottom" of both R33 and R34 to PGND (J7, pin 2)?

r33 to j7 pin 2 was approx. 62 ohms. r34 to j7 pin 2 was approx. 27 ohms.

I have double checked for solder bridges and found nothing. Clearly I have something installed wrong, but the 48v circuit it so small and to the best of my understanding of it it appears that everything is as it should be.