Beepre2 filament voltage 0 vdc help [resolved]

[Kurthaudio]

Hello all,

Short version: assuming everything populated correctly and windings of the PT-9 are wired correctly…….0VDC on power test means bad regulators……right?

Long version: this is my second attempt at the BeePree 2. Having built many audio kits in the past with success I flew through the build in an impatient attempt to hear this bad boy ASAP. No voltage checks, little reading of directions, and little attention to detail. This resulted in a completed preamp with a very loud hum/ buzzing from my speakers with very little audio. After going back trying to find what I screwed up I found several mistakes. Out of impatient frustration I threw it in a box to deal with many months later.

Now is that time. I’m currently laid off so have plenty of time to go through this and do it right. I started by desoldering and cleaning up every single joint. This took me a full day in itself. So now I’m basically starting from scratch. Not wanting to eat an entire humble pie for a second time I’m measuring every component, double checking, and reading the very well written directions step for step. I’m at page 39 witch is testing the filament voltage I’m getting 0 VDC. I have verified to my satisfaction that everything is installed properly on the board. I’m also satisfied that my twisted pairs from tab 12/13 and 14/11 respectively are wired and soldered correctly. Does this mean I fried the LT764 regulators?

If so, I may have some extra regs stashed away somewhere around here. Are there any suitable replacement you would recommend?

Thank you in advance for any help. Really appreciated!! Mike

[Paul Birkeland]

On the regulator PC board, there are two pads on each half of the board up front that have nothing connected to them.  What DC voltages do you get between those pads on each side of the board?

You haven't provided enough information to determine if anything is wrong with the regulators.  I would not do anything with them just yet.

Also posting some photos of what you've built and what you're looking at could also be helpful.

[Kurthaudio]

Thanks Paul,

I’m getting 8VDC on each set.

[Paul Birkeland]

OK, and with no wires connected to the output terminals that go to the 4 pin sockets, you are seeing 0V?

It would be pretty unusual to have this set of circumstances.  Often regulators that fail will short out and you'll see all that voltage on the output.  The 1764 also has a lot of built in protection circuitry, so that ought to help as well.

What faults existed in the construction of the filament regulator boards previously?

[Kurthaudio]

Yes sir, 0VDC with No wires connect. The only wired going to the board are the A/C wires from the tranny.

I’m getting 6.5 VAC from those wires.

The board is now as it was the first time. I just double checked everything and it all appears correct so I left it alone.

I’m getting 260VDC from the high voltage supply for whatever that’s worth.   

[Paul Birkeland]

Can you tilt the board up to show the solder joints on the bottom?

[Kurthaudio]

I must have damaged the through plating of the board eyelet. I’m getting 8 VDC measured from the bottom of the board.


Is 8.1 VDC is a little high?

[Paul Birkeland]

Yes, it should be just about dead nuts on at 6.3V on the regulated output. Still, I wouldn't rush to replace anything just yet.

[Kurthaudio]

Ok, so any ideas what to do about 8 vdc instead of 6.3? Or should I just leave it and move on?

[Paul Birkeland]

Yes, can you post some photos of the soldering on the bottom of the PC  board?

[Kurthaudio]

I soldered the wires into place and ran them to the solder tabs next to each tube socket. Took another voltage check…….6.3vdc on the money?.?.?.  This eyelets must have been damaged and putting the wire through made a better connection? Whatever the case the problem seems to have salved itself.

Thanks Paul, without your advice I would of most likely replaced those regulators and still had the same problem.