[BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread

[shogami]

First of all.
Which kind of lunchbox do you use ? I had some trouble with a Bento2 with the phantom power. The power board had some problems and the regulator fired up two times.

Second:
You had some solder joints who look really bad.
You should definitely resolder some points (there are lot of joints where you can see the gold solder pads)
95% of problems are poor solder joints.
Also use some isopropyl to clean the pcb.

Hi TillM

I use Radial Six Pack. I have another VP312DI (Rev. C PCB), VP28's and they all power up fine, so I doubt if it's a lunchbox chassis issue.
And thanks for pointing out. I assumed if I tested continuity with DMM, it'd be a good enough connection, but I will definitely look over again and try re-soldering some points.

 

[mhbunch]

OK! long story involving my wurlitzer 120 and sustain pedal/grounding ,but!

Accidentally shot mains voltage into the DI of my 312. now its about 20db quieter than my other 312. (just the DI, mic input works the same).

What did I fry? nothing looks burnt up.

 

[jsteiger]

OK! long story involving my wurlitzer 120 and sustain pedal/grounding ,but!

Accidentally shot mains voltage into the DI of my 312. now its about 20db quieter than my other 312. (just the DI, mic input works the same).

What did I fry? nothing looks burnt up.

Not sure but could be a few things. Which way was the pre/post switch set at the time?

 

[mhbunch]

Not sure but could be a few things. Which way was the pre/post switch set at the time?

I think it was post. Volume is affected both ways tho.

 

[jsteiger]

I think it was post. Volume is affected both ways tho.

Post would go straight into the 2520. Maybe the opamp is damaged? Do you have another you could test it with?

 

[poserp]

Hi! I'm just finishing a build of 2 312DIs + gar1731 opamps. I fired up the first one (haven't done the second yet...) and smoked resistors r14 and r15 on the opamp after applying power. Is this probably due to a fault in my op-amp build or did I do something wrong on the main PCB? If it's an op-amp issue, then I'm probably not the best op-amp builder and will purchase some pre-built op-amps.

Thanks!

 

[TillM]

Op amp is faulty.
Check the directions of the diodes and if you put the BD140 and BD139 in the right direction. Also check solder bridges.
Fire up the 312 without OP amps and check the voltages at the mill max pins where you stack the op amps in.
Where a you live ?

 

[poserp]

Op amp is faulty.
Check the directions of the diodes and if you put the BD140 and BD139 in the right direction. Also check solder bridges.
Fire up the 312 without OP amps and check the voltages at the mill max pins where you stack the op amps in.
Where a you live ?

Thanks! Will do -- I presume that voltages and such should match those in the older 2x assembly guide on the CAPI site.  There's not smoke or anything without an opamp installed (the LED for phantom doesn't light, but I'm certain now that I have the LED wired backwards -- I connected the short pin on the LED to r16), so at least nothing else is frying (yet). Once I have #1 working, I'll finish out the build for #2 (basically done, broke the phantom switch and scratched the front-panel because I suck at assembly. Good thing, I think, that I'm waiting to get one fully-functional first though...).

 

[poserp]

O.k., so I tested resistance across the pins according to the VP2x assembly guide. All resistances were over 200k except for V+ and C -- that measured 9.6k ohms. Is that wrong? It measures that way on both of my boards, so if it's wrong then I have a component misplaced (I put together part layout sheets for my builds, and triple-checked to ensure they were the same and matched the BOM (building Rev D) and such. That being said, perhaps I misidentified a resistor -- I used my ipod camera to zoom in and take pictures so I could work out the color bands, I did a similar thing with the diodes. Perhaps I have a diode in the wrong place?

 

[jsteiger]

O.k., so I tested resistance across the pins according to the VP2x assembly guide. All resistances were over 200k except for V+ and C -- that measured 9.6k ohms. Is that wrong? It measures that way on both of my boards, so if it's wrong then I have a component misplaced (I put together part layout sheets for my builds, and triple-checked to ensure they were the same and matched the BOM (building Rev D) and such. That being said, perhaps I misidentified a resistor -- I used my ipod camera to zoom in and take pictures so I could work out the color bands, I did a similar thing with the diodes. Perhaps I have a diode in the wrong place?

That resistance is correct for this build.

The resistance measurements posted in the VP2x guide are specific to a VP25 or VP26. The VP28 and both VP312 versions are slightly different.

 

[poserp]

That resistance is correct for this build.

The resistance measurements posted in the VP2x guide are specific to a VP25 or VP26. The VP28 and both VP312 versions are slightly different.

O.k., good, thanks! I tried my best to lay out the parts correctly, I really did... I'll check voltages later today to make sure they're correct.

 

[jsteiger]

Hi everyone, just finished putting together a vp312di 51x version and i'm having some problems. i hooked it up to my rack ( capi 11 space and psu ) and upon powering it on +24 and -24 fuses popped... decided to flip the switches on the preamp to 16v and +16 and -16 fuses popped as well... any ideas whats causing this? ( please bear with me, i'm a hardcore noob with this stuff  ;D )

Likely a direct short somewhere on your build. Did you try without an opamp and without a Hi Z Plug-In inserted?

 

[glasscock777]

Likely a direct short somewhere on your build. Did you try without an opamp and without a Hi Z Plug-In inserted?

Just got more fuses in the mail, tested without opamp and hi Z plugged in and no fuses blown... didn't do one at a time though, just with both unplugged. sounds like i messed something up with one of them?

 

[jsteiger]

Just got more fuses in the mail, tested without opamp and hi Z plugged in and no fuses blown... didn't do one at a time though, just with both unplugged. sounds like i messed something up with one of them?

Yes.

 

[poserp]

That resistance is correct for this build.

The resistance measurements posted in the VP2x guide are specific to a VP25 or VP26. The VP28 and both VP312 versions are slightly different.

O.k., got some op-amps assembled by pros and, sure enough, pre #1 had no smoke/fire or any other issues when I fired it up. I'll finish off #2 this week and double-check the audio (didn't have time to listen, only did smoke tests thus far).

 

[Claudio]

This is correct on the VP312DI. The measurements shown in the VP2x Assembly Guide are specific to the VP25 and VP26.

Hey Jeff,

So what would the correct measurements be for the VP312DI? My DMM just goes bonkers when I try to measure the DOA pins as suggested in the VP2x assembly guide.

Thanks,
Claudio

 

[mrmike186]

I just finished a 312DI build and I'm getting no sound at all. Phanton LED comes on when engaged but no mics work. I looked for bridges and heated every joint again but still nothing. I've tried a working gar2525, red dot 2525 and different slots in a BAE 6 slot rack.  I'm hoping something jumps out in these pics.

 

[mrmike186]

Here's a pic of the  Litz output wires.

Everything on the doa sockets tests over 200k except-
"+V" and "C" @ 3.6k
"C" and "O" @ 52.5K
"+V" and "O" @ 57k

If I change the jumper to "output cap bypass"  everything over 200k except-
"C" and "O" @ 0.00
"+V" and "C" @ 3.6K 
"+V" and "O"@ 3.7k

 

[jsteiger]

Hey Jeff,

So what would the correct measurements be for the VP312DI? My DMM just goes bonkers when I try to measure the DOA pins as suggested in the VP2x assembly guide.

Thanks,
Claudio

See the post just below yours. From memory those are right. The VP312 and VP312DI are totally different than the VP25 to VP26 that the old test guide was written for. I do not have a built VP312DI here at the moment.

 

[jsteiger]

Here's a pic of the  Litz output wires.

Everything on the doa sockets tests over 200k except-
"+V" and "C" @ 3.6k
"C" and "O" @ 52.5K
"+V" and "O" @ 57k

If I change the jumper to "output cap bypass"  everything over 200k except-
"C" and "O" @ 0.00
"+V" and "C" @ 3.6K 
"+V" and "O"@ 3.7k

With the output cap(s) bypassed, you should have around 9Ω. You may need to adjust your DMM's range to confirm. This is all correct.