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

[jsteiger]

Eddie

As mentioned in the email, I would look at the nonworking Pad switch. Try reflowing the solder to that switch. That fact that it is not working is a big clue!

 

[entresolmusic]

I will try that tonight Jeff, yesterday I didn't had time.


Thanks for the quick answer.


Eddie

 

[dipfrik]

Hey,

i finished my 1st VP312DI but no sound at all. 48V works fine with a mic including the LED.
I started with with the quick Startup Testing Procedure and the problems are there

Here my readings with no opamp and not connected to a power source:

-V and +V = 0
-V and C = 0
C and +V  = 4.7k
C and O = 6.2M
V+ and O = 6M
-V and O = 0

Everything should be way over 200k or?

OMG

Thanks for any help, Sven

 

[jsteiger]

These look OK for a VP312DI.

Eliminate any possible, rack, cable, mic, converter etc problems first....then DOA's.

 

[dipfrik]

Everything external is fine here. I can switch to my JLM or OV560 with the same setup and they are running as expected.
What are the next steps? Measuring the +/-V and C sockets with connected power and they are +/-16V as expected.

Can i test with JLM99V op amp to see if the problem is there? I don't think so or, because they are working from 24-34V or?

btw. permanent VPR mode added.

Thanks, Sven

 

[dipfrik]

i'am building on the Rev C.1 PCB

 

[jsteiger]

You can test with those opamps. Scroll thru this thread. Almost every conceivable issue has been discussed here previously.

 

[dipfrik]

OK the Zener Diode on PK2 was wrong positioned.
Now i hear the PK2 relay switching when i put a jack into the HiZ Jack. Still nothing comes out.
Should the Mic audiopath with a "good" PK2 working or can the whole audiopath with a wrong Zener in PK1 still be a problem?

Thanks, Sven

 

[dipfrik]

When should i hear the PK1 relay clicking?
Actually when i'am on 48V and put a jack into the HiZ, the 48V are away and if i'am remove the jack from the HiZ the 48V are coming back.

Again no audio at all.

Thanks, Sven

 

[jsteiger]

Check both relay builds. They are usually the problem with most folks.

 

[dipfrik]

Yes, i will definitely do that!

Thanks, Sven

 

[technoteo]

Here is a couple of vp312 just finished.

it just took me 6 hours to finish both units and GAR2520!!

ah...BTW they sound fantastic!!

 

[Matt D]

My VP312 has been doing nicely for a couple of months now.  Then about a week ago the DI stopped working. The pre was at my band practice space so I haven't had a chance to look at it until today.  When I opened it up I noticed right off the bat that C12 has exploded.  It looks like it's in correctly polarity wise to me but perhaps I messed it up.  My first question is: Are the exploded cap and non-functional DI possibly related, or am I dealing with two separate problems?  The pre passes signal with the blown-up cap.

 

[Matt D]

Here is the cap.

 

[Matt D]

Did I miss anything hard wiring the SW2 connections?  What else could douse that cap to blow up other than a reversed polarity?

 

[Matt D]

Also, in the meantime can I run the pre in "output cap bypass mode" to bypass C10?

 

[Matt D]

As you can see in the pictures, I had the blocking cap in/out connector on incorrectly.  Running in cap bypass mode.  The DI works fine.  Still wonder what it was that made the cap blow up....

 

[jsteiger]

Typically, if that cap sees a voltage near or above it's rating it will blow. It almost looks like a bad leaky cap, not one that exploded but who knows. I would not run the pre in cap bypass mode without measuring the DC offset. Do you have a way of doing that? The pre will need to be on the bench flat in front of you while under power to check the DC offset.

 

[Matt D]

Thanks for the reply.  I have one of your ribbon cable/extender card units so setting it out flat on the bench is no problem.  Where should I take the measurements?

 

[jsteiger]

Set your DMM to read DC voltage. Red probe to the top of R9 and the black probe to a good ground reference point like where the phantom LED is connected tot he top of the pushbutton switch.