Stereomour Oops

[Drugolf]

I de-soldered the blue and black wires (the one that extends to HV+ on teh PSB) that extend from the choke and measure resistence.  Both are at 586 ohm.

 

[Paul Birkeland]

That's very good news!

 

[Drugolf]

That's very good news!

Agreed!

I went ahead and pulled one of the 220 uF caps on the PSB and it measured 202uF.  See the following screenshot of the test.  I don't know how to determine if those various numbers for ESR disapation factor  etc are good or bad.

I then also did all the initial measurements of the terminal strip locations per the build instructions manual and all were as they should be.

Then installed the 12AX7 tube and powered it up with Dimm bulb connected and it seemed fine.  Using a 60 watt bulb it was very dimly lit.  200v bulb nothing lit.  12AX7 appeared to light up as it should.

Powered up again with the 2A3 tubes installed.  Didn't go well.  The 12ax7 got way too bright and I also heard a crack/pop noise.  Nothing visually apparent though. 

 

[Tom-s]

Did you install the 2A3's that were installed in the wrong way before?
Or did you install new ones?

 

[Drugolf]

Did you install the 2A3's that were installed in the wrong way before?
Or did you install new ones?

The old ones.  Waiting for new ones to arrive.  So yes, I wonder if it's just the tubes.

 

[2wo]

You mention a 12AX7, that would not be the correct tube. I believe the Stereomour uses a 12AT7...John

 

[Paul Birkeland]

The 12ax7 got way too bright and I also heard a crack/pop noise.  Nothing visually apparent though.

Can you be more specific about what you mean about the tubes being "way too bright"?

 

[Drugolf]

Can you be more specific about what you mean about the tubes being "way too bright"?

I think one of the plates was aglow.

 

[Drugolf]

You mention a 12AX7, that would not be the correct tube. I believe the Stereomour uses a 12AT7...John

Sorry, brain fart.  It's an AT

 

[Paul Birkeland]

A glowing 12AT7 plate is quite unusual.  Can I see some photos of the patched up amp? 

Are you 100% certain that the plate doesn't glow without the 2A3s in the sockets?

 

[Drugolf]

In removing one of the caps on the PT-6 board I damaged the trace pretty bad.  It will either need to be repaired or the board replaced.  I emailed Eileen to see about the availability of a replacement board.

 

[Paul Birkeland]

Those might have ended up with me, I'll have a look in my stash.

 

[Drugolf]

Thanks Paul.  Eileen responded too that you would be the one likely to know if there are any still available at this point.  She is sending me a up grade power cord I purchased so I thought it made sense to see if you still had a board to include in the shipment.
BTW, I tested the 2A3 tubes on a Hickok 800A tester.  no shorts and passed mutual conductance wit numbers that reflect new and the same.

 

[Paul Birkeland]

I did find a small stack of Stereomour I power supply boards, but I don't think I'll be at the office for a week or so.  If you contact me at pb(at)bottlehead(dot)com, we can see if the USPS letter sorting machines can handle a PC board in a paper envelope

 

[Drugolf]

Perfect!  Thanks Paul.