High Freq Noise in NEVE 5106

[opacheco]

Hi to everyone,

I am in the repair, restoration and  mod process a NEVE 5106, that was used in ESPN and this was send totally dissemble at all!!....it was a hard work to place every module in place and clean because this console was retired of operation several years before of the purchased....it was stored for some years too!!.....well this is the best part of this history only!! because I found it have a very rare high freq noise (6 or 7 kHz )  but this is audible in the mix level or line level. 
After of some test in order to determine the module or the location of the problem by stratification process , am thinking the problems could be  with the power supply because the noise is within any stage of the mixer (main outputs 1, 2, 3, 4, mono output, aux Ouputs, DIrect output of the each channel, mixing board output seccion in every summing Ouput...) .

I  have add some pic of the console and noise showed I my oscilloscope for the +24 Volt DC supply but this noise is the same in another's outputs  DC voltages. This console have a hiss noise but I don't  know if this noises normal because I don't know how to determine this.

Any advise in order to find the origin of this noise will be appreciated at all!!......

https://drive.google.com/open?id=0B7bi3Ftmem8rcjFIbTkwRWpONDg

https://drive.google.com/open?id=0B7bi3Ftmem8rZmFZeERfcFlfaDQ

https://drive.google.com/open?id=0B7bi3Ftmem8rSXFhRGtCNW10V1U
Thanks https://drive.google.com/open?id=0B7bi3Ftmem8rSXFhRGtCNW10V1U

Thanks a lot,
Opacheco.

 

[pucho812]

If there is noise everywhere, it's a safe bet that it comes down to the power supply....

Start with  as minimal as you can have hooked up, 1 channel strip and the master section use that as your test set up. If you can get that working with low noise, then you can start to add in more channels.

 

[radardoug]

You haven't told us what level the noise is at. Please measure noise level with ref to the consoles '0' VU output and also tell us what that level is.
Is the noise on group outs or the stereo mix?
Is the unit using the Neve standard power supplies?

 

[opacheco]

If there is noise everywhere, it's a safe bet that it comes down to the power supply....

Start with  as minimal as you can have hooked up, 1 channel strip and the master section use that as your test set up. If you can get that working with low noise, then you can start to add in more channels.

pucho812, thanks a lot for your response and  comments.....I have pull out all the channels except one in the mixer and left the master section, I have test from the direct output of this channel too and the noise is there until.......

Opacheco

 

[opacheco]

You haven't told us what level the noise is at. Please measure noise level with ref to the consoles '0' VU output and also tell us what that level is.
Is the noise on group outs or the stereo mix?
Is the unit using the Neve standard power supplies?

Dear radardoug, thanks for your response. The NEVE have its original KINGSHILL power supply. ....here some pics

https://drive.google.com/open?id=0B7bi3Ftmem8rQk51VTlkQ3pTMzA

https://drive.google.com/open?id=0B7bi3Ftmem8razdPRUF3V2x3dEk

https://drive.google.com/open?id=0B7bi3Ftmem8rZmFZeERfcFlfaDQ

Please see the picture with a screen capture for the oscilloscope noise measurements in the +24V DC only but in the rest of DC voltage is the same situation .....please look at and let me to know.

Opacheco

 

[opacheco]

Someone have the PSU and PSU REGULATOR schematics for this Kinghill PSU??

Opacheco.

 

[radardoug]

Do you not have a proper noise meter? You are wasting your time if you dont have proper test gear.

 

[opacheco]

Do you not have a proper noise meter? You are wasting your time if you dont have proper test gear.

I have osciloscope and multimeter only (and another basic equipments).......I think that is suficent for, do you?
Did you see the noise wave form in the picture??...It show the wave form of the noise, Vpp.

Opacheco.

 

[pucho812]

the o-scope and DMM will do you just fine for faulting finding this and such.

 

[opacheco]

the o-scope and DMM will do you just fine for faulting finding this and such.

Think so!!
Opacheco

 

[radardoug]

Seriously? How can you measure noise without a proper noise meter? You need to know what the signal to noise is, not just guess it.
When Neve were commissioning these, they would make a complete set of measurements on every one.
Yes, you can use your scope and multimeter for basic faultfinding, but thats all. You cant make serious measurements without test gear.
So why are you saying the desk is noisy? How do you know? You have no idea without measuring it what your signal to noise is.

 

[pucho812]

While I understand what you are saying doug, that an AP or something of that ilk would be ******* brilliant right here, he does not have access to one.    If the scope  is picking it up there is a problem, you do not need an AP for that.  In any console there is acceptable noise and not acceptable noise.  I high doubt that when new the console performed that way...
the DMM and the scope  will get him sorted on this...

 

[radardoug]

No, he has given us no figures, so we cant tell what the noise level is. The scope indication is meaningless without ratiometric measurements.
You can buy an HP 334 on Ebay for a couple of hundred bucks, very good noise meter, you can read to - 80 and do distortion figures as well.
It is just insulting to Rupert  to be restoring a Neve and not have accurate measuring capability.

 

[opacheco]

Seriously? How can you measure noise without a proper noise meter? You need to know what the signal to noise is, not just guess it.
When Neve were commissioning these, they would make a complete set of measurements on every one.
Yes, you can use your scope and multimeter for basic faultfinding, but thats all. You cant make serious measurements without test gear.
So why are you saying the desk is noisy? How do you know? You have no idea without measuring it what your signal to noise is.

Dear radardoug,
Your pout is valid if we are doing a laboratory analysis but the noise is obious; check the oscilloscope pictures, you don't need a more specific noise analysis because the oscilloscope show a clear freq between 6 and 7 kHz!!.....and residual noise too!

In other hand, I was checking the PSU and its regulator and find some Zener  diodes open in the control board section inside (MR4 Zener diode 1N283).

https://drive.google.com/open?id=0B7bi3Ftmem8rSENfZGVka042V0U

https://drive.google.com/open?id=0B7bi3Ftmem8rLUVVYlNKbWtJWlU

I will change these parts and let you know if this  solve the noise. Sometimes the eyes works so well in the electronics repair process!


Thanks a lot again
Opacheco.

 

[radardoug]

Sorry, you have not quantified the noise.  You have no idea what the signal to noise is. Do you have a digital workstation? You can use that to do noise measurements too. Signal to noise is measured in dB as the difference between the operating level and the noise floor. You need to know the operating level and then you can work it out. But since you are obviously so expert I am wasting my time here trying to point you in the right direction!

 

[opacheco]

Sorry, you have not quantified the noise.  You have no idea what the signal to noise is. Do you have a digital workstation? You can use that to do noise measurements too. Signal to noise is measured in dB as the difference between the operating level and the noise floor. You need to know the operating level and then you can work it out. But since you are obviously so expert I am wasting my time here trying to point you in the right direction!

Dear radardoug,
I am here because have resolved some problems with help of all of you no for figth with anybody or search for who care the real true!!...please clam down man, take it easy!!....I appreciate so much your point of view but sincerely I don't want to measure the noise level but to solve the origin of the problem, that's it!!....the noise is there for any gain of the mixer (mic or line input)
I am so sorry for to led this controvert theme......it's no my intention ; my intention is to find the origin of the problem.

For other hand, I changed 10 Zener diodes and I am ready for test.....and if everything is ok I will to proceed to MEASURE THE NOISE behind the data of the service manual.
The Zener diodes MR3 were open in all regulator boards for the -15, 15, -25, 25, 48 volts and the MR4 and MR5 in the -25 and 25 boards are over heated.

https://drive.google.com/open?id=0B7bi3Ftmem8rRVVhakJNSzNaVXc

Thanks a lot!
Opacheco

 

[pucho812]

now we are on to something. component failure. The next step if possible would be to figure out why the failed? heat over time?

 

[opacheco]

Well guys everything look ok now; no high frequency noise at all and less residual noise too!!.......that was very instructive to me too, but the Zener Diode was the origin of the problem, I can't  figure out whay this failure!! but I could conjecture an abrupt raise of voltage supply of the control board (transformer secondary  of 36volts) cause this don't have any protection for a failure of this!!

I will do a thing more: I WILL MEASURE THE NOISE FIGURE in order compare to the spec of the NEVE mixer data.

Thanks a lot for the comments and help....you are the best!!
Opacheco

 

[opacheco]

These are the plots before and after of the change of MR4 Zener diodes

Before
https://drive.google.com/open?id=0B7bi3Ftmem8rSXFhRGtCNW10V1U

After
https://drive.google.com/open?id=0B7bi3Ftmem8rOEJjcG9ZWWJmdFU

Opacheco

 

[radardoug]

So not much difference then. Pity you dont have a noise meter.