8 Channel, 3U NEVE 1073 completed

[MicDaddy]

Thanks for the heads up JB, I will try with a dummy load on the end of a cable.

The thing that bites my butt is my analog board, with a cable into the pre, no mic on the end, phantom engaged (shows roughly 25.5V between pins 2 and 3) is dead silent, switching on the phantom power.  There may be a very slight almost inaudible change in the noise floor, but it is negligible.

Completely different behavior with my 1290s. 

Sylvain, see attached datasheet for typical LM317, check the IN leg and the OUT leg of the regulator, with reference to 0V.  http://www.fairchildsemi.com/ds/LM/LM317AHV.pdf

 

[sgenevay]

ok thx... but i have no voltage on the 3 legs of the 48v regulator.... even the input leg when the input leg of the 24v regulator has 33,6 v  ... what is situated before the regulator in the ACDC circuit... maybe i burned something else...

 

[MicDaddy]

ok thx... but i have no voltage on the 3 legs of the 48v regulator.... even the input leg when the input leg of the 24v regulator has 33,6 v  ... what is situated before the regulator in the ACDC circuit... maybe i burned something else...

If you have access to the bottom of the board (makes it easier to poke around traces) just follow the traces/components from the Voltage IN leg of the regulator backwards all the way to where the AC comes in.  Have your DMM looking for DC, and if you find a part with a voltage on one side and none on the other, that part is suspect.  I cannot find a schematic and it's hard to follow the traces on the picture.  Diodes sure are suspect, check all of them that are in the 48V circuit.  Check if there's any voltage on the back side of the 120R?

 

[MicDaddy]

I think my dead LED worked over my powerstation.

C1 and C2 are bulged/puffy, and again I have this 60Hz on any channel when phantom power is engaged.

I haven't dug in, to take a closer look at the gobetween, my guess is I have something shorted or screwy in that section which pulled too much current causing the caps to heat and bulge???  Dunno, I can't find a schematic for the powerstation.

The thing still works, both +24V rails look good, and the +48V is still kicking out voltage.
Obviously both caps need to be replaced, but before I cook another 2 I'm going to need to investigate a little closer.

 

[sgenevay]

Ok I talked to Joe last night....
Powerstation and ACDC schematics are available on jlm website in powerstation / ACDC build thread section (2 PDF files at the top of the thread) hope that will help you to find the solution...


Sylvain

 

[MicDaddy]

forgot to install the jumper for the tripler.... 

Have since replaced the 'pump-charge' caps C1 and C2, installed the tripler jumper, set the potentiometer to see +48V.

No more hum on any channel while phantom is engaged.  8)  and now my phantom voltage is a true +48V

I'll chalk up the LED that popped to poor ESD protection (plastic baggies are a BIG no no)

Sounds like creamy butter, if that's an appropriate adjective.  ;D

Thanks you guys for your help!!  Now for this next 4.

Sylvain you and Martin and Desol are INSANE with your 8 channel units 

Sylvain were you able to track down the issue?

 

[sgenevay]

Yeah !!! The 47R was dead... Even if it looked perfect....
I finished my second 8 channel rack. As I sold the first one to a friend who was finally lazy to build it, I changed a bit the front panel... Will post some pictures again soon... Before starting my third rack (I won't stop before having at least 16 ch

best
Sylvain.

 

[desol]

Sylvain you and Martin and Desol are INSANE with your 8 channel units 

I'll take that as a compliment.

 

[California Road]

Hey guys.  I am trying to finish up 2 channels right now, and am having issues with phantom power.  I have gone through this thread many times, but I still have no luck.  I am using JLM go betweens and the acdc power supply.  The pre functions fine with a dynamic mic, but I cannot power a condenser. 

I get +24 and +48 from the acdc, and I get 11 ohms(?) between 0v and chassis ground.  I can post some pics if that is helpful. 

This is my first mic pre build, and I'm not sure where to go from here so any help will be great.

Thanks,

Josh

 

[sgenevay]

Did you check voltage on mic xlr ? Do you find your 48v there ?
If not, it's maybe a wrong wiring somewhere maybe....
Yes pictures would be helpful ofc
best

Sylvain

 

[California Road]

Did you check voltage on mic xlr ? Do you find your 48v there ?
If not, it's maybe a wrong wiring somewhere maybe....
Yes pictures would be helpful ofc
best

Sylvain

I cannot get 48v at the xlr.  With all this talk about grounding I think that is where my error is.  But I'm not sure.  I will post some pics later tonight.  Thanks for the help!

 

[MicDaddy]

Did you check voltage on mic xlr ? Do you find your 48v there ?
If not, it's maybe a wrong wiring somewhere maybe....
Yes pictures would be helpful ofc
best

Sylvain

I cannot get 48v at the xlr.  With all this talk about grounding I think that is where my error is.  But I'm not sure.  I will post some pics later tonight.  Thanks for the help!

With a DMM start at the XLR and work backwards towards the +48V terminal on the ACDC.  It's a short path and should be fairly simple to find where the voltage is getting lost.  Check to be sure all the correct components are in the correct designation on the gobetween.  Check that you have the two jumpers in the correct positions on the gobetween.  Are you using an LED, and if so does it light with the switch on?

 

[California Road]

Did you check voltage on mic xlr ? Do you find your 48v there ?
If not, it's maybe a wrong wiring somewhere maybe....
Yes pictures would be helpful ofc
best

Sylvain

I cannot get 48v at the xlr.  With all this talk about grounding I think that is where my error is.  But I'm not sure.  I will post some pics later tonight.  Thanks for the help!

With a DMM start at the XLR and work backwards towards the +48V terminal on the ACDC.  It's a short path and should be fairly simple to find where the voltage is getting lost.  Check to be sure all the correct components are in the correct designation on the gobetween.  Check that you have the two jumpers in the correct positions on the gobetween.  Are you using an LED, and if so does it light with the switch on?

I do have an LED attached, and it does light when the switch is on.  I went through the path with the DMM and I have 48v unitl the go between.  When the switch is on I dont hav 48V to + or - on the terminal block to the input xlr.

I have attached a few pics of the case layout and one of the go betweens.

Thanks again,

Josh

 

[California Road]

and the go between....

 

[MicDaddy]

Verify that you have +48V at the terminal on the gobetween, the one with the green wire.  If yes, shut off the phantom and just double check that you have good continuity from all three pins of the input XLR, Pin 1 to shield or 0V, pin 3 to -, pin 2 to plus.  Check for any short between any of the 3 pins of the XLR.  Be very sure that your pin 2 pin 3 wire whether if red or blue are correlating with the correct terminals.  It looks like on one side of the JLM you have red as +? and the out side of the JLM red looks to be on the - side??

If this checks good, go over again with a detailed visual inspection for poor/cold solder joints, solder bridge etc.  If no joy, reflow solder joints.  It looks like the electrolytic cap negative leg is towards the smiley which is correct. 


Looking at the furthest to the right, output XLR, you have a red wire (which is typically audio + or hot) terminated to pin 3.  (though I think this is unrelated to your phantom issue)

 

[MicDaddy]

Finally remembered to bring my DMM to the studio and was able to verify the Vintech PSU voltages/pinout.   

1: circuit common/ground
2: Open
3: +24V  (each measured roughly 24.2V)
4: +48V  (each measured roughly 48.5V)

I had +24V on pin 2 vs pin 3. 

 

[danchez]

I've successfully completed 2/8 of my 1073's, very exciting for my first project and these pre's really sound AMAZING. I had a few hurdles along the way (backward caps and a resolder on the input tranny) but for the most part, this ongoing project has gone very smoothly. The power supply was a fun one, the secondary lead of the toroidal met with the 47ohm 1watt next to the terminal blocks, that smell lingered for a few days..... thankfully it only damaged one of the neighboring diodes and replacement of that and the resistor restored phantom power!

Pics coming soon! Thanks for everyone's help and expertise, although I've never posted here before, I've been using a lot of posts from this thread to learn and troubleshoot, so thank you.

 

[California Road]

Verify that you have +48V at the terminal on the gobetween, the one with the green wire.  If yes, shut off the phantom and just double check that you have good continuity from all three pins of the input XLR, Pin 1 to shield or 0V, pin 3 to -, pin 2 to plus.  Check for any short between any of the 3 pins of the XLR.  Be very sure that your pin 2 pin 3 wire whether if red or blue are correlating with the correct terminals.  It looks like on one side of the JLM you have red as +? and the out side of the JLM red looks to be on the - side??

If this checks good, go over again with a detailed visual inspection for poor/cold solder joints, solder bridge etc.  If no joy, reflow solder joints.  It looks like the electrolytic cap negative leg is towards the smiley which is correct. 


Looking at the furthest to the right, output XLR, you have a red wire (which is typically audio + or hot) terminated to pin 3.  (though I think this is unrelated to your phantom issue)

I decided to do a double check of my wiring again, and founf a major issue at the input transformer that solved the phantom issue.  I was shorting pin 2 to ground.  Not sure how I missed that.  But now I am getting a very distorted signal on both channels with phantom engaged, and a perfectly clean signal with phantom dis-engaged.  I have not had a chance to troubleshoot this issue very much, but figured I would throw it out there in case anyone had come across it before.

SOLVED!  Another small wiring issue.  Measure twice cut once right?!  Cant wait to get these in on a session.  Ill post pics when my front panel gets here.

Josh

 

[muffy1975]

Hi guys,

plugging my EZ1290 straight into my work station seems to dull the output of the ez1290. makes it sound closed as opposed to open. is this an output impedance problem endemic with the design of the ez1290? The original pre was often coupled with a neve eq. This would change the output impedance.The output impedance of the ez1290 is 600ohms? right? But the input impedance of the typical DAW is 10k right? Is there anyway of changing the output impedance of the ez1290? How is this done? Does anyone know what i'm talking about?

regards

michael

 

[dmp]

plugging my EZ1290 straight into my work station seems to dull the output of the ez1290. makes it sound closed as opposed to open. is this an output impedance problem endemic with the design of the ez1290? The original pre was often coupled with a neve eq. This would change the output impedance.The output impedance of the ez1290 is 600ohms? right? But the input impedance of the typical DAW is 10k right? Is there anyway of changing the output impedance of the ez1290? How is this done? Does anyone know what i'm talking about?

If you check the schematics I believe the EQ section was inserted before the final output stage in the 1073, etc.  so the final output isn't any different.
My pair of ez1290s do not sound closed when plugged into my soundcard, which have balanced 10kohm inputs.