[BUILD] CAPI VP2X~500 Series~Preamp Kit~Official Support Thread

[Newton In Orbit]

Hello, I built a pair of Rev A VP26's wayyy back, like at the start of this thread. Later bought and built a bunch of other preamps, and these kinda sat for a while. I used to use these on mono guitars, like one on one amp, the other on 2nd guitar player, or with a JDI for bass.

Recently, I put them on snare drum, and noticed there is a phase or polarity issue. Was driving me nuts, as I was checking cables, moving mics ad nauseam etc trying to get stuff in phase.

I did some googling and found two pdf files labeled option 1 phase fix, and option 2 phase fix.
What I need to know I guess, is where was the original issue? Was it that the primary or secondary of the input trafo was flipped, or the primary or secondary of the output transformer was flipped? Trying to see which is the better fix, and that looks like it maybe the one outlined in the "option 1" pdf.

I must have built these, continued on with my life and missed the bulletin that there was a mod to fix this issue.

Thanks in advance for any help,
John

 

[jsteiger]

Hello, I built a pair of Rev A VP26's wayyy back, like at the start of this thread. Later bought and built a bunch of other preamps, and these kinda sat for a while. I used to use these on mono guitars, like one on one amp, the other on 2nd guitar player, or with a JDI for bass.

Recently, I put them on snare drum, and noticed there is a phase or polarity issue. Was driving me nuts, as I was checking cables, moving mics ad nauseam etc trying to get stuff in phase.

I did some googling and found two pdf files labeled option 1 phase fix, and option 2 phase fix.
What I need to know I guess, is where was the original issue? Was it that the primary or secondary of the input trafo was flipped, or the primary or secondary of the output transformer was flipped? Trying to see which is the better fix, and that looks like it maybe the one outlined in the "option 1" pdf.

I must have built these, continued on with my life and missed the bulletin that there was a mod to fix this issue.

Thanks in advance for any help,
John

Wow that was a VERY long time ago. About 15 years or so. Option #1 is the best as that is where the mistake was made.

 

[Newton In Orbit]

Thanks Jeff. Yep. I bought a 3124 soon after that, and these didn't get used as much. Please disregard email I sent you, and thanks for the reply. Will do the jumpers on the input.
Appreciate it!

PS, all a blur now. Everything was a very long time ago!

 

[Hanz]

Hey everybody. I have built 9 VP26's, and one of them has a little bit of a tremolo oscillating noise in the background. Also, the pad switch makes a loud crackle, louder than the other VP26's I built. So maybe the problem is in that area? I have checked and reflowed all solder joints and also tried a different opamp. I've added a WAV, you might have to turn it up a bit to hear it. Any ideas what it could be?

 

[mkerlin]

Completed my first CAPI kit. Went together relatively smoothly except for one detour I took due to my own carelessness. Anyway when completing the "preflight" check between any of the DOA sockets and the Output socket my meter is showing an open circuit. I have continuity at the socket off several of the rails so I don't think the socket is in play. I've searched over the board several times and I'm scratching my head. Any tips to narrowing this down would be appreaciated.

 

[leaf]

This was my experience as well. But when I inserted the DOA and inserted it into my rack, it worked perfectly. If you haven't already traced the audio as described on the first few pages of this thread, you might want to do that first. That gave me confidence that it was all going to work once the circuit wass completed by inserting the DOA and providing power.

Here are my measurements from the preflight stage which Jeff told me looked fine. He said we are mainly looking for direct shorts at the preflight stage.

Preflight stage: Most read 0.L MΩ. but -V and +V = 4.3 MΩ. C and O = 2.79 MΩ

Good luck!

 

[mkerlin]

Ok, so I built a VP26 and 0252 OP amp. Popped it in my Purple Sweet 10 and lights all start blinking. Not good. Bought a VP26 and 0252 from Trace Audio cause I was going to buy another VP26 kit anyway so I got one that I know would work for troubleshooting comparisons. Also bought an extension card kit. Prebuilt unit works fine. Tried my OP amp in the prebuilt VP26. It works fine, so my first OP amp build checks out!! Connected my VP26 with extension card... probed CR2 and CR1 and get no +16V/-16V DC. I assume I have a short somewhere but I've gone over all my soldering twice. I've also compared my board to the Trace board and their damn similar except the Trace has the Litz. I'm could really use a couple next steps tips. Thanks...

 

[mkerlin]

Ok, so I built a VP26 and 0252 OP amp. Popped it in my Purple Sweet 10 and lights all start blinking. Not good. Bought a VP26 and 0252 from Trace Audio cause I was going to buy another VP26 kit anyway so I got one that I know would work for troubleshooting comparisons. Also bought an extension card kit. Prebuilt unit works fine. Tried my OP amp in the prebuilt VP26. It works fine, so my first OP amp build checks out!! Connected my VP26 with extension card... probed CR2 and CR1 and get no +16V/-16V DC. I assume I have a short somewhere but I've gone over all my soldering twice. I've also compared my board to the Trace board and their damn similar except the Trace has the Litz. I'm could really use a couple next steps tips. Thanks...

UPDATE:: After examining the prebuilt unit everything checked out. Soldering was as good or better EXCEPT for the Mill-Max sockets. The prebuilt had MUCH more solder than mine. I tried to match it and once I did this, and also touched up C5 everything works now, including my first try at the OP amp. Time to play around with this unit.