Show me your tubes

[MartyB]

Nyuk. nyuk...

Hey has anybody gotten Stephen's Sopht to work?  I've tried  it with a homebrew layout/pcb but but it needs debuggin" ,    so I'm buggin.

mARTYB

[slajeune]

Hi Marty,

I have a few people that have built all of the Sopht amps (even the ruby tuby).  What seems to be the issue?  Which model / version are you trying to build?

Thanks,
Stephane.

[MartyB]

Hi Stephane,

 Sorry about misspelling your name.  Had a couple Mardi Gras drinks tonight.  It's the 12u7/12aL8 - the same one  the guy built in the blue project box that you have posted on your site.  I think there's a version after that.  Could my power supply be a problem?  I'm using a 1 amp 13.5v wall wart.

MartyB :wink:

[slajeune]

Hi Marty,

Ok, it's the 12AL8, ok.  Version 2 is probably the best one (the latest one simply has too much gain and doesn't as good thru speakers).  First thing to check is voltages on all pins of the 12U7.

You should have something similar to (take these as ballpark voltages).  These voltages assume pin 4 to v+ and pin5 to ground for the heaters.

pin1: ~10V
pin2: 0V (probably slightly negative)
pin3: 0V
pin4: 12V
pin5: 0V
pin6: ~10v
pin7: 0V (probably slightly negative)
pin8: 0V
pin9: not connected to anything

Also, what are the symptoms (i.e. no sound, garbled sound, heaters not lighting up, etc..).

Cheers,
Stephane.

[MartyB]

Stephane, or anyone else who's built his Sopht:

Here's my pin voltages on 12U7:

1: 6.7v
2: -0.3
3: 0
4: 13.1
5: 0
6: 4.2
7: 0
8: 0
9: 6.5 -  this seems wrong.

 This pin isn't connected to anything.  The tube is NOS bought from Tubesandmore IIRC.  Is this an internal short?  My neg ref was the gnd trace on the pcb.

MartyB

[Luap]

I'm right there with you Marty,
I've recently moved my 12k5 Sopht amp to a new enclosure. This time I built my own simple RC PSU. (pulling my hair out) ...as far as I can tell it would need some sort of regulation to work right? So  ...I just ended up using another SCSI switching supply (works great).

It's a head scratcher for me,  kept thinking there was some bad component. Since it powered up fine on batteries as well as the PC unit.

-are your filiments lighting up?

-you might want to power it up on batteries just for a sanity check (running B+ on a seperate cell)

The filiments and B+ have very different current draws... I'm still strugling with this current rangling (at least I think that's what it is).

Luap