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

[spacecho]

Hello Guys,

so i have just put one of these together - with melcor 1731 , fet DI and Cinemag I/O iron.

it all looks good but when doing the resistance test (before powerup) all of the test points gave resistance into the megaohm range straight away(all good) except when probing the V+ to C conection.... it starts with a lower resistance 80k and slowly rises - it got to about 300k but really slowly - has any one had a similar experience when testing?

just thought i'd check before powering up....
cheers

spacecho

 

[jsteiger]

I'm running the passive Hi-Z
Do I still install the 16-24V Hi-Z  Switch?

No, it is not necessary for the passive circuits. You can install it if you ever find the desire for an active alternative. If you are 100% sure you will also use the passive versions, by all means you don't need it.

 

[Winetree]

Is there a parts layout for the Sub D.I. Board.
I didn't realize the diodes would be such a problem.
Only found 2 of the 4V3's. Checked values found 2 groups
one around 610 and the other 750. 4V3 in the 750 range.
what goes where?

 

[jsteiger]

Each relay PCB gets (1) 4.3V zener and (2) 914's.

I have a stuffing guide on the product page.

Here it is. This will clear things up for you.

Hello Guys,

so i have just put one of these together - with melcor 1731 , fet DI and Cinemag I/O iron.

it all looks good but when doing the resistance test (before powerup) all of the test points gave resistance into the megaohm range straight away(all good) except when probing the V+ to C conection.... it starts with a lower resistance 80k and slowly rises - it got to about 300k but really slowly - has any one had a similar experience when testing?

just thought i'd check before powering up....
cheers

spacecho

This should be fine. You are really just checking for a low resistance or a direct short.

Cheers, Jeff

 

[Winetree]

Great got the relay boards.
Where's the info for the SUB-D.I. board. Cap & diode value and layout.
Could make some out with the pictures but not everything.

 

[Winetree]

found the Classic VP312DI Sub-DI.1 BOM in the DOC's you sent.
Great job, thanks.

 

[jsteiger]

found the Classic VP312DI Sub-DI.1 BOM in the DOC's you sent.
Great job, thanks.

Haha. I just sent them again. Thought maybe I forgot. 

 

[geoff004]

sorry if I missed it -
does the fet DI work at 24V?
thanks

 

[jsteiger]

sorry if I missed it -
does the fet DI work at 24V?
thanks

Yes it will and that can be independent of the DOA operating voltage.

 

[geoff004]

thanks for the reply-
got them both done but haven't yet powered them up.
Stuffed with Gar1731s until something else comes in.

 

[ethervalve]

Hi,
Before I attempt to power mine up I just wanted to verify a couple things about the standard 500-series version:
A) Should I just leave sw1; sw2; C2; C3; CR3; and CR4 unpopulated or are there any jumps that need to be installed?

and

B) I just wondering if someone could explain how the J1-1 (DC Block/Cap coupled output|Output cap bypass) three pin header works?

Thanks in advance.

 

[jsteiger]

Besides cutting the card edge connector, you will need to do some jumpering if you are building a VPR version.

You must jumper the opamp V select which is SW2.

You will also need to jumper the V select for the HiZ Plug-In which is SW1 on the DI PCB. The jumper for this goes from the center hole to the right hole (or the 16V hole).

C2 and C3 should not be installed.

CR3 and CR4 should not be installed.

For the J1 description:
The safest place for the shunt is in the DC Block position. This will put the coupling caps in the circuit so any DC offset from the opamp will not get to the 2503 output tranny. When in "straight into the 2520" DI mode, some opamps have significant DC offset which can damage the output tranny. I put the bypass position for those who will not use the "straight into the 2520" mode if they want to have the same circuit as a vintage 312 card.

Cheers, Jeff

 

[ethervalve]

Thanks Jeff! Everything worked perfectly.

 

[jsteiger]

Thanks Jeff! Everything worked perfectly.

Excellent!

 

[bruce0]

Somebody nice gave me a VP312DI kit for christmas!...

I read that I am supposed to stuff the Sub-DI Rev A sub pcb first (posted elsewhere on this board).  However I don't have access to a schematic, parts list or stuffing guide for the VP312DI.  For that matter, there is R14, which doesn't exist on the VP26, but is marked on my circuit board for the VP312DI.

I see above that one poster refers to "Docs" re stuffing the Sub-DI board... Does anyone know where they are?

Maybe Santa needs to write a note to Jeff...

The kit looks great though... nice fit and finish, lovely little attenuator....

 

[bruce0]

Got the BOM, thanks Jeff!

I have another question.  Does anybody know what values resistors R9 and R10 are supposed to be?  The BOM says 750 Ohms, the kit contained 750K.

Actually, never mind.  The Chunger post to the rescue.  His perfect pictures of the boards show that the value on his kit was a 750 Ohm.

 

[jsteiger]

Got the BOM, thanks Jeff!

I have another question.  Does anybody know what values resistors R9 and R10 are supposed to be?  The BOM says 750 Ohms, the kit contained 750K.

Actually, never mind.  The Chunger post to the rescue.  His perfect pictures of the boards show that the value on his kit was a 750 Ohm.

Yes indeed they are 750R. I still have a few "bad" kits out there that were shipped with 750K. If someone finds this, please send me a note so I can replace them for you.

 

[jsteiger]

Bruce,

I get a very high reading no matter which position the switch is in. Do you have a HiZ Plug-In installed? If so, try without it. Any chance of a pic of the rear section of the board from the DOA to the gold fingers area?

Best, Jeff

 

[bruce0]

Jeff:
I updated my previous post with the picture you requested.

Note that when I connect the positive lead to common I get 21K, and when I connect the negative lead to common I get 40K

Also, I went to the back and tested VC to ground on both of the relay cards.  one of them shows resistance, the other is shorted, is that normal?

Note in the picture the HiZ switch is in the 24 position, but it doesnt matter, the switch that makes the difference is the DOA switch.  24v position everything looks fine, 16 V position and I get the higher resistance.


bb

I should also say that when it shows these resistances (V+ to C) they don't show right away, they slowly rise, like there is a capacitor charging somewhere.  But they stop for over a minute at 40K.

 

[jsteiger]

...Also, I went to the back and tested VC to ground on both of the relay cards.  one of them shows resistance, the other is shorted, is that normal?...

Yes. There is a normaled connection in the 1/4" jack that connects VC to Gnd. When a jack is inserted it opens.

Your build looks fine in the pics. The only thing I can think is there may be something on one of the relay boards. Do you have a desoldering tool to easily remove them and investigate?

Best, Jeff