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

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jsteiger

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Error in BOM or KIT capacitors

I'm building CAPI VP28 Rev. B. A problem has arisen with capacitors C14 and C5 which are given in the BOM as 68pF and 82pF.
The only 2 capacitors I have left which have not been placed are an NC 441J and an NC112J.
Can someone help here?
/D
There is no error. The printing on those caps is very small and not super crisp. If you look close with magnification, what you think is 112 is actually 82. Not sure where you are seeing 441 but odds are that is a 68pF. I have nothing here that would be labeled 441.
 

dubbySwords

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There is no error. The printing on those caps is very small and not super crisp. If you look close with magnification, what you think is 112 is actually 82. Not sure where you are seeing 441 but odds are that is a 68pF. I have nothing here that would be labeled 441.
My mistake, I knew I was getting old but now I know I'm up there :)
Thanks.
/D
 

RekStudio

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Jul 15, 2022
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Guys - quick question: I had to pull the brown transformer lead and unfortunately could not desolder the tiny hole so I soldered back to the top of the hole. Is this going to be a problem?
 

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RekStudio

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Newbie here: Seems like my first 2 VP28 builds went successfully. Quick Question...

I notice in an earlier thread Jeff says: "Lowest gain setting is knob to 7:00. Highest gain setting is knob at 6:00." Is this also true for the Channel Fader?

My rotary knobs currently stop at 11/12:00 on both so I imagine I need to realign this to have the stops at 6/7:00. Can someone kindly confirm?
 

jsteiger

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Newbie here: Seems like my first 2 VP28 builds went successfully. Quick Question...

I notice in an earlier thread Jeff says: "Lowest gain setting is knob to 7:00. Highest gain setting is knob at 6:00." Is this also true for the Channel Fader?

My rotary knobs currently stop at 11/12:00 on both so I imagine I need to realign this to have the stops at 6/7:00. Can someone kindly confirm?
Same for channel fader. -20 is the lowest setting and +12 is the highest. There's a big blue hashmark dividing where the switch stop is at.
 

WillDuc

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Jul 25, 2018
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Hi guys,

I'm having a problem with a VP28 unit i built myself. When i am in line mode, pad engaged, there seems to be a substantial increase in the high end when i run tracks through it. I set up Q clone using my daw to verify that and it turns out that when the pad is engaged in line mode, there's kind of a high shelf (see picture). When i am in mic mode though, the frequency response stays flat whether or not the pad is engaged.

Is this something normal ? If not, where should i start as for as troubleshooting ? Bad solder joint, wrong capacitor or resistor value etc...

Here are my test points :
TP1=101mV
TP2=698mV
TP3=1,241V
TP4=305mV
TP5=305mV
TP6=305mV
TP7=642mV
XLR output = 1,233V

Regards,
 

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Tommmes

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Dec 27, 2021
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Hi,

Building a pair of VP28’s. I tested the CA-0252-DIY in a other module (VP26) and 2 of them work fine. The other two are distorted(MEGA). Followed the guide step by step and measured all resistors before putting them in. Diode are in correctly. Transistor all seem to be in the right space aswell.

Where should I begin the trouble shooting?

Edit: Aah excuse me, after some extra inspection I messed up the orientation of Q7. I feel extremely stupid. Should I order two new ones?

Question number 2; I had the working VP28 with the good Op Amps running for sometime (in Line mode) with some music running through it. Everything was working fine. Then I started messing around with the gain knobs and my PSU started to catch on fire. (I test in a open Bento 2, for easy access). The Module seems to be fine.

Any guesses what the hell I did to start the fire?

Thanks for the time.

Kindly, Tom
 
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