[BUILD] CAPI VP28~500 Series~2-Stage Preamp~Official Support Thread

[jsteiger]

Good back!
Change the burnt resistors of the VP28, verify that everything is in order and we tried with a friend, the two preamps worked very well for now!. If something happened to us and I would like you to guide me, because we are new with this. We had the box turned on and we took out one of the cards to put them in another slot, but when we moved it, PR1 and PR3 burned again, I changed the resistors again and they didn't burn anymore. It could have been caused by the fact that the box was turned on?

Regards!

Burned up 10Rs is a result of a respective opamp problem.

 

[alesjob]

Burned up 10Rs is a result of a respective opamp problem.

But when changing the resistors again, using the same op amp, it no longer burned again. When changing the card while the lunch box was on, that happened, it could have been the cause that the lunch box was on and we changed places like that

 

[jsteiger]

But when changing the resistors again, using the same op amp, it no longer burned again. When changing the card while the lunch box was on, that happened, it could have been the cause that the lunch box was on and we changed places like that

Was the amp properly seated? Classic Audio Products, Inc.

Hot swapping should be no problem.

 

[alesjob]

Was the amp properly seated? Classic Audio Products, Inc.

Hot swapping should be no problem.

Yes sir, it was well placed, after changing the resistors again, nothing burned again, for now

 

[alesjob]

A question.. with how many volts do the transistors BC161 and BC141 work with in the op amps?

 

[PaulSmith]

Hello! I have a VP28 that’s quite low in level to others.
I got the output reading 1.22vAC with gain/fader set to unity and here are the measurements:

1 - 419 mVAC
2 - 1853 mVAC
3 - 1.17 VAC
4 - 291 mVAC
5 - 291 mVAC
6 - 291 mVAC
7 - 613 mVAC
As you can see the TP1/2 are the ones that are quite far off!

Any idea where to look based on this?

Cheers!

May I bump this in case it has been missed!

 

[him chan]

I put my DIY Vp28 into my chassis, The green signal light is keep tuning on even i didn't connect the microphone. And their is not signal pass through. Can anyone know whats wrong with my build.
Thank you so much

 

[Brian Roth]

I put my DIY Vp28 into my chassis, The green signal light is keep tuning on even i didn't connect the microphone. And their is not signal pass through. Can anyone know whats wrong with my build.
Thank you so much

Silly question, perhaps.....Why are the two 2520 DOA modules not installed?

Bri

 

[him chan]

Silly question, perhaps.....Why are the two 2520 DOA modules not installed?

Bri

I am so sorry for it. I am a beginner of DIY Audio. So i need to buy 2 CA-0252 and put it into the fader booster and preamp area?

 

[Brian Roth]

Yes indeed! Module requires two DOA modules, as clearly mentioned on the CAPI website.

Bri

 

[toby.ollisbrownstone]

I've just built my first one of these, and everything works exactly as it should, except the preamp gain has no effect on level? Fader works perfectly though....any guess what could be causing it?

 

[jsteiger]

I've just built my first one of these, and everything works exactly as it should, except the preamp gain has no effect on level? Fader works perfectly though....any guess what could be causing it?

What are the opamps and who built them?

 

[toby.ollisbrownstone]

What are the opamps and who built them?

They're both CAPI 0252 built by myself! I built 2 VP28s and the other one works fantastic!

Further testing today - I switched the preamp/fader DOAs to see if that opamp was the issue and both the preamp and fader gain seemed work great, but the Q8 and Q10 transistors on the dodgy DOA were getting REALLY hot - definitely feels like a problem with that specific op amp