[BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
- Thread starter jsteiger
- Start date
Help Support GroupDIY Audio Forum:
Ah ignore my last post turns out all good after going over the board again.
All works well but one strange issue remains however, which is only present when grayhill up full. There seems to be a strange oscillation sound/high pitched screech on the DI input when I flick the DI -10db mini toggle. The sound occurs as the switch is transitioning annd I can make it sustain for as long I hold the switch in between the two positions. The sound goes lower in pitch as I turn down the bourns pot. I feel like I’ve already gone over every joint a few times but can go again if we think it’s a bad joint.
All the best!
All works well but one strange issue remains however, which is only present when grayhill up full. There seems to be a strange oscillation sound/high pitched screech on the DI input when I flick the DI -10db mini toggle. The sound occurs as the switch is transitioning annd I can make it sustain for as long I hold the switch in between the two positions. The sound goes lower in pitch as I turn down the bourns pot. I feel like I’ve already gone over every joint a few times but can go again if we think it’s a bad joint.
All the best!
rauri76
Member
Hola Comrades,
Long time lurker, first time poster...
I just built two CAPI VP312DIs... One totes works... the other ...the 1/4" DI on the front works... but the XLR part of the VP312DI does not... 48v LED doesn't light up and no signal out from VP312DI ...
verified by racking the VP312DI in my CA500R8 connecting both a dynamic and condenser mic = nada. Also routed audio out of DAW through the pre (via USB CA500R8) = nada
I know it's not my 500 rack, been using it for almost a year and all slots 100% work.
Looking at my handy work on the failed VP312DI ... no visible scorched or burned bits or bobs...
...very odd that the 1/4" DI on the front works just fine but not the XLR in/out half of the pre...?
searching this thread so far, hasn't illuminated anything yet...
Not my first DIY project (2 DIYRE color palettes, 2 Lola Pres, 2 CAPI LC40s, about a dozen DOAs).
Sincerely appreciate anyones time and suggestions.
Happy Holidays!
Long time lurker, first time poster...
I just built two CAPI VP312DIs... One totes works... the other ...the 1/4" DI on the front works... but the XLR part of the VP312DI does not... 48v LED doesn't light up and no signal out from VP312DI ...
verified by racking the VP312DI in my CA500R8 connecting both a dynamic and condenser mic = nada. Also routed audio out of DAW through the pre (via USB CA500R8) = nada
I know it's not my 500 rack, been using it for almost a year and all slots 100% work.
Looking at my handy work on the failed VP312DI ... no visible scorched or burned bits or bobs...
...very odd that the 1/4" DI on the front works just fine but not the XLR in/out half of the pre...?
searching this thread so far, hasn't illuminated anything yet...
Not my first DIY project (2 DIYRE color palettes, 2 Lola Pres, 2 CAPI LC40s, about a dozen DOAs).
Sincerely appreciate anyones time and suggestions.
Happy Holidays!
Last edited:
Ricardus
WILL SOLDER FOR FOOD
Start by uploading hi-res pics of the tops and bottoms of all the boards.
rauri76
Member
Attachments
rauri76
Member
Having a doozy of a time getting jpegs to stick the landing here...
rauri76
Member
rauri76
Member
Thank you in advance for any tips or insights.
rauri76
Member
- I've A/B'ed my working VP312DI and the failed VP312DI side by side, visually checking each resistor, capacitor, diode, Litz wire... checking for any possible reversed/wrong polarity...any resistors in wrong place... every part seems to mirror my working VP312DI...
- I've double checked each solder point looking for cold solders and/or solder jumps... found one dubious solder point where I clipped too close to the PCB, however verified there is plenty of solder for solid connection on the top side of the PCB...
- ...waiting on shipment of a 500 series extender...
- ...and I guess next step is to research this thread and how folks started poking at their VP312DI with a multi meter to troubleshoot...
- ...stare at the schema like a Eureka moment will materialize...
- ...otherwise I'm gonna guess there is a failed component somewhere in the XLR signal path...
rauri76
Member
taking notes from the thread...
#56
If it's not passing a mic signal and the DOA is known to be good, I would first check the PK2 relay to make sure that with no 1/4" jack inserted, pins 8 and 10 get coupled to the input transformers primaries. With a ground signal present at PK2's VC pin, the rear mic in will be couple to the 2622. When a 1/4' jack is inserted, the normal of the sleeve's contact is broken/opened which disconnects the ground from PK2's VC pin and switches the relay to the HiZ Plug-In as the source for the 2622's input.
If all of that is good, you will have to look at the output section. That is very short and sweet really but I would make sure it is not a solder joint on either the Mute or Polarity C&K switches.
#84
Well, like I said, there will probably be no magic bullet or smoking gun fix. When having trouble like this the "pot shot" approach to finding and fixing will most times never work. The only way to find and solve is systematic and methodical.
First, common sense things with the opamp. Is it a known good solidly built opamp? Who built it? Has it been verified good in another working device? Is the voltage switch set incorrectly for the opamp installed? I never test a freshly built preamp with a freshly built opamp. Too many variables.
From there, you will need to follow the schematic like a road map. You can follow signal from the input up to the opamp with no opamp installed. When in mic mode, does injected signal get to the first relay board? Does it get past it? Keep following all the way to the opamp.
When inserting a 1/4" jack, the rear relay will switch to DI mode. Follow the signal throughout the DI signal path as well.
This may seem like a frustrating time, but the rewards when you can systematically follow signal thru an entire device and find the culprit will be very rewarding. It will only make you a better builder as well.
#85
All of the things I am about to post can be deciphered by looking at, reading or following the schematic. This will become a necessity with the amount of kits you build if it's not already. Good troubleshooting skills will out weight good build skills any day. No matter how good a builder one may be, there will always come a time when you need to sort out an issue.
So, think it may be the t-pad? Easy. Let's bypass it and see what happens. By looking at the skiz we can see that the t-pad follows the 2503 output transformer. Desolder the Blue and Orange leads from the 2503. Temporarily solder them to an XLR or whatever means you need to monitor the output. Again from the skiz, Blue will be + and Orange will be -.
What are the results? Same issues? No sound and opamp heating up? I think we have ruled out the t-pad.
In a general studying of the 312 schematic, what would happen if the 2503 is bad? What if the primaries are shorted within the x-fo? Very rare but shit does happen. Again, in following the skiz, the DOA's output would be directly shorted to ground. Not good. Would probably cause a very fast over heating of the opamp. Maybe next you should desolder all the leads from the 2503 and measure DCR to see.
What is DCR between the following: (again, that damn schematic is the key!)
Red to brown?
Blue to green?
Yellow to orange?
Violet to gray?
Make sure your DMM is set to properly measure resistance under 100 ohms. Let us know what you find.
Last thing to mention, before I would have gotten to the above, I would have injected signal and followed it all the way thru the preamp. Where it stops would be the area to look. If the above holds true, things would be fine up to the DOA's input. Would be a great help to yourself if you could verify this. You will be thanking me for it one day down the road.
#113
You can beep for continuity between the A+ pin and the O+ pin (mic mode). Next would be the B+ pin to the O+ pin (DI mode). This info is on the skiz. There is just enough room where the 90 degree header comes out of the relay PCB to get your probe tips in. If this relay is not flipping with the plug going in/out of the DI jack, it's either a problem on the PK2 relay build or the control signal which can also be followed on the schematic. You must have DC applied to the main board for this to work.
#115
The relay in question that selects what input goes to the 2622 (mic or HiZ Plug-In) is PK2 that is situated more in the center of the PCB just behind the input transformer.
PK1 routes the DI input signal to the HiZ Plug-in or to the post 2622 position. You need to flip the mini toggle on the front to get this relay to active/deactivate. This can only happen with a plug in the DI jack.
#119
Well, I can't think of any reason why the mic in won't work then. If the relay PK2 board is fine, then the only difference between the output of that relay card from DI mode to mic mode, are a few inches of PCB traces and the gold fingers #8 and #10. Is this maybe an issue that lies between the card and the mic? Meaning rack or outside cabling?
#121
Well, many things are not making sense here. My suggestion is to pull both relay boards and make sure they are working right. I test them on a breadboard. 98% of all problems on a VP312DI build are related to those little relay boards.
If Pre 2622 DI mode works, mic mode should also work.
... gonna try swapping out the DOA and HiZ Plug-in PCB from the working VP312DI into the failed one... just to rule that out...
... otherwise Jeff repeatedly points toward incorrect diodes on the relay PCBs... So I'll have to double check those little suckers...
#56
If it's not passing a mic signal and the DOA is known to be good, I would first check the PK2 relay to make sure that with no 1/4" jack inserted, pins 8 and 10 get coupled to the input transformers primaries. With a ground signal present at PK2's VC pin, the rear mic in will be couple to the 2622. When a 1/4' jack is inserted, the normal of the sleeve's contact is broken/opened which disconnects the ground from PK2's VC pin and switches the relay to the HiZ Plug-In as the source for the 2622's input.
If all of that is good, you will have to look at the output section. That is very short and sweet really but I would make sure it is not a solder joint on either the Mute or Polarity C&K switches.
#84
Well, like I said, there will probably be no magic bullet or smoking gun fix. When having trouble like this the "pot shot" approach to finding and fixing will most times never work. The only way to find and solve is systematic and methodical.
First, common sense things with the opamp. Is it a known good solidly built opamp? Who built it? Has it been verified good in another working device? Is the voltage switch set incorrectly for the opamp installed? I never test a freshly built preamp with a freshly built opamp. Too many variables.
From there, you will need to follow the schematic like a road map. You can follow signal from the input up to the opamp with no opamp installed. When in mic mode, does injected signal get to the first relay board? Does it get past it? Keep following all the way to the opamp.
When inserting a 1/4" jack, the rear relay will switch to DI mode. Follow the signal throughout the DI signal path as well.
This may seem like a frustrating time, but the rewards when you can systematically follow signal thru an entire device and find the culprit will be very rewarding. It will only make you a better builder as well.
#85
All of the things I am about to post can be deciphered by looking at, reading or following the schematic. This will become a necessity with the amount of kits you build if it's not already. Good troubleshooting skills will out weight good build skills any day. No matter how good a builder one may be, there will always come a time when you need to sort out an issue.
So, think it may be the t-pad? Easy. Let's bypass it and see what happens. By looking at the skiz we can see that the t-pad follows the 2503 output transformer. Desolder the Blue and Orange leads from the 2503. Temporarily solder them to an XLR or whatever means you need to monitor the output. Again from the skiz, Blue will be + and Orange will be -.
What are the results? Same issues? No sound and opamp heating up? I think we have ruled out the t-pad.
In a general studying of the 312 schematic, what would happen if the 2503 is bad? What if the primaries are shorted within the x-fo? Very rare but shit does happen. Again, in following the skiz, the DOA's output would be directly shorted to ground. Not good. Would probably cause a very fast over heating of the opamp. Maybe next you should desolder all the leads from the 2503 and measure DCR to see.
What is DCR between the following: (again, that damn schematic is the key!)
Red to brown?
Blue to green?
Yellow to orange?
Violet to gray?
Make sure your DMM is set to properly measure resistance under 100 ohms. Let us know what you find.
Last thing to mention, before I would have gotten to the above, I would have injected signal and followed it all the way thru the preamp. Where it stops would be the area to look. If the above holds true, things would be fine up to the DOA's input. Would be a great help to yourself if you could verify this. You will be thanking me for it one day down the road.
#113
You can beep for continuity between the A+ pin and the O+ pin (mic mode). Next would be the B+ pin to the O+ pin (DI mode). This info is on the skiz. There is just enough room where the 90 degree header comes out of the relay PCB to get your probe tips in. If this relay is not flipping with the plug going in/out of the DI jack, it's either a problem on the PK2 relay build or the control signal which can also be followed on the schematic. You must have DC applied to the main board for this to work.
#115
The relay in question that selects what input goes to the 2622 (mic or HiZ Plug-In) is PK2 that is situated more in the center of the PCB just behind the input transformer.
PK1 routes the DI input signal to the HiZ Plug-in or to the post 2622 position. You need to flip the mini toggle on the front to get this relay to active/deactivate. This can only happen with a plug in the DI jack.
#119
Well, I can't think of any reason why the mic in won't work then. If the relay PK2 board is fine, then the only difference between the output of that relay card from DI mode to mic mode, are a few inches of PCB traces and the gold fingers #8 and #10. Is this maybe an issue that lies between the card and the mic? Meaning rack or outside cabling?
#121
Well, many things are not making sense here. My suggestion is to pull both relay boards and make sure they are working right. I test them on a breadboard. 98% of all problems on a VP312DI build are related to those little relay boards.
If Pre 2622 DI mode works, mic mode should also work.
... gonna try swapping out the DOA and HiZ Plug-in PCB from the working VP312DI into the failed one... just to rule that out...
... otherwise Jeff repeatedly points toward incorrect diodes on the relay PCBs... So I'll have to double check those little suckers...
rauri76
Member
Verified the issue is not the DOA or HiZ Plug-in PCB (swapping both from failed unit to 100% working unit and vice versa confirmed) ...
I also double checked the tiny eye straining print on the diodes for both relay boards... cross referenced the relay PCB overlay...
1N749 (4V3 Zener) is in correct polarity/location and so are both 1N914's...all good there...
Verified the 1/4" DI still works as well as the Post 2622, -10 and LPF switches... but still no XLR in/out signal...
While waiting for my 500 extender card/cable to arrive...
...Might it be worth de-soldering both relay boards > swapping PK1 (DI relay) with PK2 (CA2622 relay) > solder and test..?
...or just be patient and wait for the extender to arrive and test the pins with a DMM on PK2..?
Last edited:
rauri76
Member
Going off post #387...
"Relay testing:
Unit connected to power
PK1 / next to DI jack:
B+ O+ beep when no plug is plugged in
A+ O+ beep when plug is in and the mini toggle is at Post 2622
B+ O+ beep when plug is in
Clicking audible when "post" switch is flipped
PK2 / next to input transformer:
A+ O+ beep when in mic mode
B+ O+ beep when plug is inserted (no matter where "Post 2622" is)
Clicking audible as soon as tip of plug is inserted and touched sleeve contact of the Neutrik
So that's that, seems like the relays all work as they should"
... and a complete lack of understanding what I'm doing... I aimed to mimic this exercise and I conducted continuity tests on the relays PK1 and PK2 with the following results...
PK1
O+ and A+ = beep
1/4" cable inserted into DI
O- and A- = beep
O+ and A+ = beep
PK2
O+ and A- = beep
O+ and A+ = beep
1/4" cable inserted into DI
O- and A- = beep
O+ and A- = beep
O+ and A+ = beep
with PK2 disconnected from power no 1/4" cable plugged into DI
VC and B- = beep
VC and O+ = beep
my results do not seem to mirror Fritzmyname's post #387 results... which doesn't seem positive and what my continuity tests results reveal... I haven't the foggiest.
Ultimately my guess at this point is that PK2 is faulty or a component therein... and I surmise it might be best to write Jeff and see if I can purchase a PK2 relay ensemble should he be able to part with one.
tgs
Well-known member
- Joined
- May 30, 2013
- Messages
- 80
I have a 312DI (rev C) where the output dropped to near-nothing. Pulled it out yesterday to start trouble-shooting, which turned into a very easy task since C10 had ballooned up significantly. I swapped it out and I'm happy to report that the preamp is now performing as it should again. Out of curiosity though: what might have been the cause of this? It didn't feel like the obvious thing to break (apart from it being an electrolytic).
tgs
Well-known member
- Joined
- May 30, 2013
- Messages
- 80
Thanks Jeff, I'll measure that to see what I'm dealing with. The cap was rated higher at 16V and the one I put in now is even 20V. I have one more that I built at the same time, maybe that one is next.
Admittedly they are a bit old by now, I think I built them more than 10 years ago.
