trying to diagnose strange phantom issue

Hi there,

I'm a relative newbie to electronics, but this problem is extra weird.

It's a hamptone jfet kit, finished, and sounding great except for no phantom on the right channel. Here are some observations so far:

1. There's only 40.3 volts when the switch is engaged. When the switch is out it's 48.0.

2. Tried swapping the switch out with another, but the same deal.

3. The supply is delivering a handsome 48v.

3. On the good channel, I'm getting 48v on pads 1-4 of the input transformer (wired 1:8).

4. On the bad channel, I"m getting 32 (or so) volts on the amp side of the 6.8k resistors, but NOTHING on the other side of them.

5. I tested all resistors.

6. This sucks...I thought I did such a good job this time.

:green:

Mainly, I'm kind of hoping somebody's seen this "switched-in" drop in voltage.

Thanks so so much,

kelly

Is this with or without mics plugged in?

Make sure that you haven't accidentally grounded the input transformer primary. If it has a centertap, let it float.

hey...

as far as a mic goes...dynamics are fine in both channels, similar gain, etc. It's just condensers on the right channel...no sound.

I just repositioned the input transformer a tiny bit off of the board, reheated the connections, and no luck. Is there some other way I could be sending it to ground?

??

Thanks, Dave, for getting back so quick...

kelly

???????????? :roll:

So yes, Dave...it does look like the input trasformer pins 1-4 are grounded, but I don't know why. What I did notice is resistance on the good channel between pins 1-4 and 5-8, and no resistance when measuring the same pins on the bad channel trasfo.

I've lifted the transfo, reseated to make sure it's not touching the pcb. When I lifted it, I measured resistance...between pins 1-4 to the grounding pins 6,7,8 and there doesn't appear to be an internal short.

I'm feeling dumb...what part of an input circuit (xlr to transfo to 6.8k to switch) would send short the transformer?

Is it worth swapping a different (same turns ratio, cinemag) trasformer in to see if it's a bad transformer? Could I have overheated it soldering? Strange.

NO!

Thanks for steering me to the tranny, Dave. That's what it was...I swapped in a cinemag cmmi-8 I had sitting around and voila.

Again, thanks..