[BUILD] CAPI Dual VPR & 51x Floor Box PSU~Official Support Thread

Since the wires are disconnected, check the windings on the toroid's secondary for shorts. MAKE SURE there is no live AC connected to the PSU. FYI, these readings will be less than 10Ω. Keep in mind you are looking for a direct short.

Hi Guys,

I'm assembling  a VPR PSU. everything went fine, but now I'm kinda stuck with measuring the voltage values at step 38 of the build manual...

in stead of getting values close to what's on the pcb i get the following:

I cant seem to get the reading of the 16v terminals lower than 19.33 volts.
The values on the 48V terminals are 63Volts.

Also the values measured from the toroid do not match the spec sheet:
Red are both at 15V
Orange both -7.8V
Yellow both 15V
Green both -4.2V
Black both 44V

Mains is 230 Volts

Anyone who can help me out?

When measuring the ACV at the inlet header, there is no ground reference so your DMM probes go one to each of the colors from a winding. For example; black probe to 1st yellow secondary lead, red probe to 2nd yellow secondary lead.

Can you post a few pics of the PCB so we can see all of the resistors?

here 2 pics of the PCB, hope this is clear enough

OK the R's look correct. Did you see my note about measure the voltages at the AC inlet header?

when measuring the ac inlet per color, all give values around 25,5 Volts, except for the black ones,  which are  73 Volts

Zamoht said:

when measuring the ac inlet per color, all give values around 25,5 Volts, except for the black ones,  which are  73 Volts

Click to expand...

Hmm that's very high. Can you check your AC source? Next maybe post a few good pics of the primary wiring to the mains switch and voltage select switch.

I think i'Il might be needing a new  DMM, as the source from the wall measures 330 volts in stead off 220-240..
I check with another DMM on this tomorrow.

(and if that's the case, the psu might have been working properly after all )

Zamoht said:

I think i'Il might be needing a new  DMM, as the source from the wall measures 330 volts in stead off 220-240..
I check with another DMM on this tomorrow.

(and if that's the case, the psu might have been working properly after all )

Click to expand...

Wow could be. Maybe try changing the battery?

I had the same idea of changing the battery. Everything works fine now.

Really was not expecting that hahaha!  :-[

Thanks for thinking with me

Zamoht said:

I had the same idea of changing the battery. Everything works fine now.

Really was not expecting that hahaha!  :-[

Thanks for thinking with me

Click to expand...

Gosh, good news! All is well that ends well 

I hope this may help someone in the future as well.

Hi Jeffrey,

Just finishing the 51 Floor Box PSU, kit is very nice indeed.

I just have a problem with 48V: I can't get  more than 20V, and everything  seems to be all right around there. I got 54v on th toroïdal AC 48V, i got 70 V on the  input of the TL 843.
Have any idea???

Thank you very much,

Yves JAGET

Hi Jeffrey,

Just finishing the 51 Floor Box PSU, kit is very nice indeed.

I just have a problem with 48V: I can't get  more than 20V, and everything  seems to be all right around there. I got 54v on th toroïdal AC 48V, i got 70 V on the  input of the TL 843.
Have any idea???

Thank you very much,

Yves JAGET

Are the  resistors R1 and R2 flipped with each other?

No, R1 - 150R      R2 - 5,11K

Is the 48V reg too tight and partially shorting thru the sil pad? If you look at the schemo, there is not much past the reg. Can you look close and make sure the 48V reg is the correct part/label?

Yes i will Jeffrey,
tomorow i will have a deep investigation on that.

Thank you,

I just finished my third module build today, and when I went to test I got no sound. My eleven space rack was also loaded with a VP28 and VP312 (both worked fine yesterday). After troubleshooting a bit I realized none of my modules had audio, and that my rack wasn't passing +16v. I then check the PSU and the +16v terminal comes out at 0.006v.
Thoughts on what might have happened, and what action I should take?

Additional things I noticed:
- the signal light on my VP28 was flickering, and there was a rhythmic ticking when i monitored it (this is when I realized it wasn't just the new module).
- the VP312's transformer was a little warm (never took notice, so could be normal)
- no smells, or signs of component damage.
- phantom switches light up.

Is it a 18-pin 51x rack or 15-pin VPR rack? Maybe a bad opamp on the last module knocked out the 16V rail?

jsteiger said:

Is it a 18-pin 51x rack or 15-pin VPR rack? Maybe a bad opamp on the last module knocked out the 16V rail?

Click to expand...

Its the VPR.

What does a knocked rail entail?

Thanks, Jeff!