8 Channel, 3U NEVE 1073 completed

[0dbfs]

Hey Punkrocker,

Not sure but I see it looks like you have paint scraped off by the PSU where the regulators appear to be connected to the chassis for heat-sink. Are the tabs shorted to chassis or isolated from chassis?

Cheers,
JoBu

 

[punkrocker]

Hi JoBu,

Yes the paint is scraped off but I don't think anything is shorting because then the PS would not be working right? Everything thing is functioning perfectly, and the pres work great with dynamic mics, its just the phantom power that's not working. Would the paint being scraped of somehow affect the phantom power? Sorry, like I said this is my first time with DIY.

 

[0dbfs]

The tabs of the regulators normally carry a voltage. They did on a build I recently had opened up. If they short to chassis then you have a short circuit which would theoretically make it fail sooner rather than later. Maybe turn off the power and measure for continuity between the regulator tabs and chassis. If there is continuity, make sure there is none before turning it back on.

Perhaps the ACDC is different. What regulators is it using?

Cheers,
JoBu

 

[punkrocker]

The tabs of the regulators normally carry a voltage. They did on a build I recently had opened up. If they short to chassis then you have a short circuit which would theoretically make it fail sooner rather than later. Maybe turn off the power and measure for continuity between the regulator tabs and chassis. If there is continuity, make sure there is none before turning it back on.

Perhaps the ACDC is different. What regulators is it using?

Cheers,
JoBu

Ok I just checked and there is no continuity between the regulator tabs and the chassis. This means nothing is shorting correct? The regulators are 2 LM317 and 1 LM337. Like I said a few posts ago, I'm getting +48v on the mic input pins 2 and 3 but it's not powering the microphones. Perhaps it's a faulty mic input jack? However, I guess that wouldn't make much sense because it works fine with dynamic mics. Any advice is greatly appreciated .

 

[0dbfs]

You have good GND on pin1? Can you confirm that the mic works? What mic is it?

Best,
JoBu

 

[desol]

0v is floating at 10ohms from GND on the JLM supply.

Do you have continuity between 0v on the ACDC and pin1 of the input xlr?

 

[0dbfs]

You can also use a phantom powered DI with an led to test for phantom on the end of a mic cable. Do you something like that or a "phantom tester"? If so, you could also unhook everything in the chassis except the parts required to get phantom. Ie; disconnect the preamp boards and test for phantom power with the di/test-plug to help identify where the fault is.

Best,
jobu

 

[punkrocker]

You have good GND on pin1? Can you confirm that the mic works? What mic is it?

Best,
JoBu

How do I test for GND on pin 1? Sorry for the newbishness again . Yes the mic works, it's an SM7b.

0v is floating at 10ohms from GND on the JLM supply.

Do you have continuity between 0v on the ACDC and pin1 of the input xlr?

Yes I have continuity between 0v and pin1. Is this good or bad?

 

[0dbfs]

Sm7b is a dynamic mic isn't it? Is that the mic you are using to test for phantom?

Cheers,
jb

 

[punkrocker]

UPDATE: SOLUTION FOUND

Wow I feel like an idiot right now :. Turns out that the cable I was using to connect the mic to the pre wasn't passing phantom power. Swapped the cable and everything works great (not to mention sounds like gold!). Thanks everyone for helping out a newbie!

Sm7b is a dynamic mic isn't it? Is that the mic you are using to test for phantom?

Cheers,
jb

Yes sorry I meant I used that mic to check to make sure that audio was passing through so I could verify it was strictly a phantom power problem.

 

[0dbfs]

Awesome! Feed her good music and lots of it.  She'll prolly like that best

Cheers,
jobu

 

[desol]

Yes I have continuity between 0v and pin1. Is this good or bad?

It's good. You should measure 10ohms when you try continuity from 0v to GND(case).

Regardless, enjoy your new pre.

 

[sgenevay]

If u test ACDC board with ohmmeter, u will see that the 4 holes are linked together (normal) on all versions  (and yes linked to the hole labeled "case").
And on new versions, the 4 holes are linked to the "screwed pin" labeled case (sory for my English again). Joe made new screwed version of the board to make an easier way to link that point to the ground (with a wire).
That means that this point HAS to be linked to the ground by any way (metal standoffs or wire to screwed point or wire to any "case" point).
Why ? ... Cause for me this is the only way to have your 10 ohms between your 0v point and any ground point....
And if u haven't those 10 ohms, your ground wiring is not correct so there is a problem...
Hope my explanation is clear ;-)
best.

Sylvain.

 

[sr1200]

My theory on the matter was the metal standoffs are too wide and are touching something else.  Being that i dont have different diameter standoffs, it was just easier to use nylon standoffs and let the wire do the ground work.

 

[sgenevay]

Sure.... Nylon is ok as soon as u have wire.... ;-)

 

[punkrocker]

If u test ACDC board with ohmmeter, u will see that the 4 holes are linked together (normal) on all versions  (and yes linked to the hole labeled "case").
And on new versions, the 4 holes are linked to the "screwed pin" labeled case (sory for my English again). Joe made new screwed version of the board to make an easier way to link that point to the ground (with a wire).
That means that this point HAS to be linked to the ground by any way (metal standoffs or wire to screwed point or wire to any "case" point).
Why ? ... Cause for me this is the only way to have your 10 ohms between your 0v point and any ground point....
And if u haven't those 10 ohms, your ground wiring is not correct so there is a problem...
Hope my explanation is clear ;-)
best.

Sylvain.

Ok great thank you that makes much more sense. I will link it with a wire and test for ohms. And your English is fine. I see you're from France, I don't speak French at all so your English is certainly better than my French!

My theory on the matter was the metal standoffs are too wide and are touching something else.  Being that i dont have different diameter standoffs, it was just easier to use nylon standoffs and let the wire do the ground work.

Thats a good point I wouldn't be surprised if that was what was happening.

 

[MicDaddy]

Got cases in from Dan, starting to get things laid out. 

One note regarding the trim-pot.  I ordered 51AAD-B28-D15L from mouser and they won't fit the allotted hole in Dan's panel (1/4"), so be aware, I know this pot was mentioned earlier in the thread.  It feels great but just won't fit. 

sr1200, any chance off the top of your head do you remember the hole you needed to drill for the panel mount trim pot you used? 

Any suggestions on how to drill this 1/4" hole out a tad bigger without tearing the aluminum front panel all to hell?

 

[sr1200]

I had made my own front panel from FP express.  I can find out tomorrow what the diameter of the hole i used was when i get in the office.  (i have the FPE file there)


  Usually with a drill press, if you bring the bit down slowly it works itself into the existing hole.  With the press off bring the bit down to line it up, bring ti back up, fire the press up and bring it on down.

 

[erikb1971]

Hey All
Just about ready, just wiring the acdc in external box... but I got some small questions.

1. In attached picture you see the instructions forwiring the acdc. I have added in grey the lay out of my power inlet. Bottum one is front, top one back. A,B and C are the soldering points. A is ground, that one goes to the case, and to the screwed hole (eerrmmm...) labeled case. But it also has to be connected to pin 2 of the 4 pin xlr connection between acdc and 1290 to link both cases together right?

2. Wich ones from violet and yellow wires from the transformer have to be connected to B and C and why? (I mean mean not why they need to be connected, but why wich one to wich?)

3. From what I understand, black and red wires from transformer are just connected together and go nowhere right?

4. Last one,on subject of grounding. Some of you seem to have grounded the 1290 pcb's with a wire directly to the case. Is that needed?

Kind regards

Erik

 

[sr1200]

This is my FPD front panel for anyone that was interested.  Has cut outs for VU meters, trim pot, JLM go between w/ 48v indicator and gain.

http://www.meirecords.com/BJ/21073.fpd