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

[corgan4321]

I'm in process putting a pair of 312DIs together and cannot figure out how to get the small NKK switches on the sub PCB to line up with the front panel.
I followed the instructions to shim the trim pot with the PCB board so it's lifted 1/16" up. As you can see in the photos attached, the pots seem to line up with the push button switches well and I think I've installed everything else correctly?

Can't wait to hear it!
Thank you

 

[jsteiger]

I'm in process putting a pair of 312DIs together and cannot figure out how to get the small NKK switches on the sub PCB to line up with the front panel.
I followed the instructions to shim the trim pot with the PCB board so it's lifted 1/16" up. As you can see in the photos attached, the pots seem to line up with the push button switches well and I think I've installed everything else correctly?

Can't wait to hear it!
Thank you

The Bourns pots need to be dry fitted to the PCB/L-bracket assembly and then soldered from the top to hold them in place. Visit the very first post of this thread. The PCB under the pot body was for the original solder lug AB pot not the Bourns pots. There should be enough info in the first post to get you there.

 

[corgan4321]

Hello,

I did do the dry fit for the bourns pot as indicated in the first post. You mentioned that the bottom T pot shim directions were for the original solder lug version, are you suggesting that th new version I have should be soldered directly to the board, contrary to instructions on the PCB?

 

[jsteiger]

Hello,

I did do the dry fit for the bourns pot as indicated in the first post. You mentioned that the bottom T pot shim directions were for the original solder lug version, are you suggesting that th new version I have should be soldered directly to the board, contrary to instructions on the PCB?

NO! Do not solder directly to the PCB.

 

[corgan4321]

Very well, then it seems I've followed all the instructions correctly.

I'll reheat some pads on the two pots to try to get them to move enough where all the components fit in their places.

 

[jsteiger]

Very well, then it seems I've followed all the instructions correctly.

I'll reheat some pads on the two pots to try to get them to move enough where all the components fit in their places.

If everything was done correctly then all should drop right in.

So the mini toggles are not lining up? Are they tight and flat to the PCB? Nice and perpendicular? If so they should work no problem. There is some tolerance in the front panel holes to allow for some slight variations.

 

[corgan4321]

Correct, the mini toggles are off by 1/16"
They are nice and tight and perpendicular to the PCB.

If everything was done correctly then all should drop right in.

So the mini toggles are not lining up? Are they tight and flat to the PCB? Nice and perpendicular? If so they should work no problem. There is some tolerance in the front panel holes to allow for some slight variations.

 

[jsteiger]

Correct, the mini toggles are off by 1/16"
They are nice and tight and perpendicular to the PCB.

You do have something else off then that's hold things up.

 

[boji]

Ensure there's no gap between the satellite pcb and the main pcb when soldering.  Best to pinch together boards while soldering.

for mine there was a tiny bit of offset but with a little front plate wiggle/finessing the nkk's should pop right in.  Post a pict of the front with the face plate off around that section and I'll compare it with mine.

 

[boji]

Actually on second look, in your pict, I see some light coming thru those two pcb's...

 

[Kman79]

On my Rev D BOM - I see that caps C10 and C11  are optional.  From all of the pictures of builds I can see in this thread it looks like everyone used them.  Why are they optional and any pro's and cons to use them.

 

[jsteiger]

On my Rev D BOM - I see that caps C10 and C11  are optional.  From all of the pictures of builds I can see in this thread it looks like everyone used them.  Why are they optional and any pro's and cons to use them.

They are AC coupling caps to block any DC offset from the opamp to the output transformer. Just put them in and use the shunt jumper to bypass them if you want. BUT if you ever use the DI in "Post 2622 Mode" you will want them in circuit as there is a higher than normal amount of DC offset in that situation.

 

[GrievousAngel]

Anyone noticed this before?

I run my VP312DI-51x in 16V mode due to the +/-16VDC rack I am using it in. Anyways. ... with this 312DI the T-pad Output has no effect on the output level. Sounds good, etc. The Stepped Gain control works as expected as it controls the output level, even though the T-pad as no control of the output.
Suggestions?

With the VP312DI in 16V mode would the FET DI option work OK? The related info specifies 24VDC.

Thanks

 

[jsteiger]

Anyone noticed this before?

I run my VP312DI-51x in 16V mode due to the +/-16VDC rack I am using it in. Anyways. ... with this 312DI the T-pad Output has no effect on the output level. Sounds good, etc. The Stepped Gain control works as expected as it controls the output level, even though the T-pad as no control of the output.
Suggestions?

With the VP312DI in 16V mode would the FET DI option work OK? The related info specifies 24VDC.

Thanks

All HiZ Plug-In options work fine on either 16 or 24V. That will have no influence over the t-pad. I would look for bad solder joints. Does the Polarity switch decrease the volume drastically?

 

[GrievousAngel]

I have a completed VP312DI-5 however when I power it up for initial testing, I noticed a few issues.

1. 600z T-Pad Attenuator does not control the output, i.e., unit stays at the level the input gain switch selects where Full CCW is 0 gain right? When I step CW signal gets louder as expected, but the output attenuator has no effect.

2. A1 test good in my DOA/Op Amp test rig.

3. If I set my signal generator (NTi MR Pro outputs a consistent balanced signal level due to its feedback circuit design) to 0dBu at 400Hz, as expected the 312 output voltage indicates when the Gain is stepped. The MR Pro displays the actual input impedance seen when looking into the 312 input circuit. Appears OK. MR Pro also displays the relationship between the Input XLR Pin 2 and Pin 3. If the 312 Input is fed a balanced signal, and all is OK, the graphic indicates signal halfway between Pin 2 and Pin 3. It can also move hard to P2 or P3, indicating if unbalanced and polarity. I'm telling you this as the 312 appears to be OK input-wise.

4. I have measured the 312 output levels at +24dBu up. Knowing the input signal level (0dBu), when activating the -20 PAD, the output drops somewhat as expected.

5. I have gone over both Xformers, PBs and the two relay circuits (RLY1 and RLY2). All appeared OK.

6. I would venture to guess that a high percentage of 312DI build issues, stem from the relay circuits. Those two relays determine the signal flowing or not flowing. Relays being located on daughter PCBs, potential failure-points would run with PCB-PCB header pins and if solder joints are solid. I did go over both relay circuits. Seems OK.

That is about as far as I have gotten. Ideas and suggestions needed.

Thanks

 

[GrievousAngel]

All HiZ Plug-In options work fine on either 16 or 24V. That will have no influence over the t-pad. I would look for bad solder joints. Does the Polarity switch decrease the volume drastically?

I did noticed that at least once, when engaging Polarity switch, it either lowered the output or killed it. When disengaged, output came back.

If A1 is at unity gain, Is it likely the input signal feeding into T1 (due to the Pri:Sec winding ratio) would have a signal boost noticeable at the output? What conditions would have to be in play for the Attenuator T-Pad to pass signal but with no control? Depending on Gain Step position, the output can be somewhat large up to maybe 24dBu! I have never seen this type of failure symptoms before. Have you?

I just posted a reply prior to this reply. So I won't repeat it all. Thanks Jeff

 

[GrievousAngel]

All HiZ Plug-In options work fine on either 16 or 24V. That will have no influence over the t-pad. I would look for bad solder joints. Does the Polarity switch decrease the volume drastically?

Jeff, I found the problem with my 312DI. One of the T-Pad pin terminal (B section outside pin) was folded over when I installed it. I didn't notice it when soldering. It apparently 'hot' wired the T-pad to FCW.

Thanks for your help. Later Billy

 

[andYz00m]

Hey there. Putting a pair of these bad girls together.

I have a question regarding how to connect the phantom LED, switch and R16.

On the board there are two points for the led, but one also says (R16 vertical) and in the schematic it shows them in series. In the first page of this thread there are recommendations for Rev B and C but not D.

Second question, for SW1 and SW2, if Im doing a VPR build, I just jumper them correct?

Its late and my brain hurts.

Halp.

 

[hasanova]

Hey there. Putting a pair of these bad girls together.

I have a question regarding how to connect the phantom LED, switch and R16.

On the board there are two points for the led, but one also says (R16 vertical) and in the schematic it shows them in series. In the first page of this thread there are recommendations for Rev B and C but not D.

Second question, for SW1 and SW2, if Im doing a VPR build, I just jumper them correct?

Its late and my brain hurts.

Halp.

Check picture in post #338 for LED connection:
https://groupdiy.com/threads/build-...ect-official-support-thread.40821/post-903991
To answer your second question: yes, see detail of Rev D overlay

 

[andYz00m]

Check picture in post #338 for LED connection:
https://groupdiy.com/threads/build-...ect-official-support-thread.40821/post-903991
To answer your second question: yes, see detail of Rev D overlay

Great, thank you!