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Studer 903 problems
Old 6th April 2013 | Show parent
  #31
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Studio ManCave's Avatar
 

Quote:
Originally Posted by 12ax7 View Post
.
...Well, at least you've got the caps outta the way.
I'll bet you find the culprit soon.

(Sounds like you're on the right track.)
.
Thanks for the support!!
I sure hope to find it soon, should be recording a band next weekend...
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Old 7th April 2013 | Show parent
  #32
Lives for snowflakes
 
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Quote:
Originally Posted by Studio ManCave View Post

CR output does not work.
[...]
I sure hope to find it soon, should be recording a band next weekend...
As problems go, that's a much better one than many others you might possibly have had with the thing.

...At least (if need be) its possible to do a workaround for your upcoming session.

It looks as though if you keep poking around, you'll find the place in the circuit where audio stops passing to the next stage.

...Then just find out WHY.
.
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Old 7th April 2013 | Show parent
  #33
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Ike Zimbel's Avatar
 

Quote:
Originally Posted by Studio ManCave View Post
No.

CR output does not work.
See my last post:
"...Since all the outputs actually work(except the CR out of course)..."
Hi Tomi,
Are you sure the module is getting all of its power supply voltages? I have docs for a 963 and I see that on its CR card, there are three PTC self re-setting fuses that the +/-15v and 6v supply go through to get on the card. IF there is a short on the card on any of those voltages (if your desk has similar circuitry) the fuse will go open...and sometimes they just go bad. So, you should take the module out and see where the power comes in. If it goes through PTC's, you should measure across each one with your DMM and see if they show continuity or a few ohms resistance. Alternately, if you have an extender board, or you can pull some adjacent modules so you can access the CR module, you can try and take some voltage readings and see if you are getting power on to that module when it is in the desk and powered on.
It would be helpful if you can post a schematic and / or a picture of the module.
Best,
Ike
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Old 7th April 2013
  #34
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Thanks,

I did check the voltages to the module a couple of days ago and they were all within 0,2V of what they should be. I measured this at the connector, though I didn't check what the opamps were getting... But I'll do that today as soon as I get to the studio.

12ax7:
I have a soundcraft 6000 all hooked up and working as well so even if I don't get the Studer fully working, at least I can use it as a front end so I'm ok as far as the next session is concerned.


Here's the CR unit schematics, if you want pictures as well I can post them later today.
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Attached Thumbnails
Studer 903 problems-crunit.jpg  
Old 7th April 2013 | Show parent
  #35
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I realized that the picture was resized... Here should be a higher resolution one:
https://www.dropbox.com/s/goo914z4vgoae2c/CRunit.jpg
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Old 7th April 2013 | Show parent
  #36
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Ok, some news... I just blew the +-15v rail...

I accidentally shorted the +15v to ground and now it´s putting out just under 4v. Well I guess I just have to take this as another learning experience and dig deeper to the innards of Studer.

Hopefully all the power rails are protected with a fuse so I wouldn´t have to start soldering but I guess we´ll see...

The CR unit problem has to be postponed for now.

I´m sure I´ll keep coming back for questions though, so please bear with me.
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Old 7th April 2013 | Show parent
  #37
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I take that back!!!

Just turned on the console to measure the voltages and they were back to wher they should be!!! The -15V rail was -14,8 and +15v rail was +14,8!!!

Pheooow!!

Lesson learned. So now back to the original problem.
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Old 7th April 2013
  #38
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That's the "self-resettable" fuses doing their job. I just took a look at the schematic. You really want to make sure that the -6v and -24v supplies are getting to the module. They are responsible for turning on all of the FET switches in the signal path (the J-112 transistors). If those aren't functioning, there's no way any signal will come out.
Best,
Ike
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Old 7th April 2013 | Show parent
  #39
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I measured everything again and at the connector all the voltages are within 0,2V from the target so they seem fine.
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Old 7th April 2013
  #40
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Did you check the +/- 10v rails to the VCA's? If those VCA's are out of action you are completely dead in the water. Likewise, you need to see that the VCA control voltage and CR vol signals are getting to the module via connector "P-6"
Best,
Ike
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Old 8th April 2013 | Show parent
  #41
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Again, thanks Ike!!!
You know, those were the only voltages I didn't check. I must have overlooked them, though I did check the -6V rail on P6 connector.
What kind of voltages should I be getting from the CR VOL and VCA CONTROL pins?

I don't know how I missed the 10V rails.

This is only my second mixer that I'm working on. The first was my Soundcraft 6000 which I recapped complitely and fixed a couple of things.
I've also built a couple of discreet preamps but this mixer is totally something else and if I can get this thing up and running I'm pretty proud of myself.
After all, I´m just a singer and a sound guy...
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Old 8th April 2013 | Show parent
  #42
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Ike Zimbel's Avatar
 

Quote:
Originally Posted by Studio ManCave View Post
After all, I´m just a singer and a sound guy...
Proving, once again, that the singer always ends up with the sound guy !

But seriously... where is the actual CR pot / fader located? This could be something simple, like a connector being disconnected from the CR control.
Best,
Ike
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Old 8th April 2013 | Show parent
  #43
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Quote:
Originally Posted by Ike Zimbel View Post
Proving, once again, that the singer always ends up with the sound guy !
True, true.

The actual monitor volume control is just a pot on the CR unit itself. I´ll check the 10V rails tomorrow.

It's 4am here so I better get some sleep, another busy day tomorrow. I've been upgrading my computer at the same time so between the mixer and the comp
I´ve been pretty occupied...

Later,
Tomi
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Old 8th April 2013
  #44
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Hey, I´m back at the studio.

My schematics are actually different from the ones on the net in that they are not showing the +-10V rails in connector P6... Everything else is the same.

I also measured the pins 27 and 28 of P6 and there was nothing.

My schematics also do show the 10V rails going to the VOL and BALANCE pots so it seems I am missing the 10V rails which is why I´m not getting the signal.

Here´s a picture of the pinouts in my paper schematics. Looks like we´re getting somewhere.
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Attached Thumbnails
Studer 903 problems-wp_000851.jpg  
Old 8th April 2013
  #45
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Interesting. Maybe there was a non-VCA version of the CR module that was originally fitted to your desk. You can quickly generate an almost +/-10v signal by clipping two very new 9 volt batteries together so the + of the 1st clips into the - of the 2nd. That centre connection (where they clip together) will be your 0v point while each of the exposed contacts will be either + or - 9.xx volts, depending on which contact it is. No idea if that will provide enough voltage and current for the VCA's, but it's a quick and easy test...
Best,
Ike
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Old 8th April 2013 | Show parent
  #46
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I´ve been tracing the 10V rails on the PCB and at the P6 connector pins 27 and 28 are terminated. Also when I measured there was no voltage coming in to those pins.
And it seems that the 10V rails to the pots and VCA 1 is also terminated in the middle of the PCB...

I can see 2 discrete small PCB´s which I assume are the VCA´s.

There sre 2 VCA´s in the schematics so I would think my board has them as well?
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Old 8th April 2013 | Show parent
  #47
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Ok, I´m getting -10V and +10V to the pots and the VCA?!?!
Also the VCA´s are getting the 15V supply ok.

I have no idea where it is coming from but it´s there...
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Old 8th April 2013 | Show parent
  #48
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If I understand right, the actual source selector switch controls relays? If that´s the case then I think I should start looking at that?
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Old 8th April 2013
  #49
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Ike Zimbel's Avatar
 

Yes.
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Old 9th April 2013
  #50
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Studio ManCave's Avatar
 

I think I´ve got it.

There are 3 relay card slots under the desk but only 2 cards installed... Looking at the diagram under the desk there are supposed to be 2 "RELAY 5/1A" cards and 1 "RELAY 4/2A" card installed but there is 1 "5/1" and 1 "3/1" card insted.

I was going through the manual and these are the relays that switch between the monitor input sources.

Looks like I have to go for a hunt... Damn.

EDIT:It seems I´m also missing the monitor amplifier card. This is the last circuit the signal goes through before hitting the CR out connectors in the back.

Could I bypass tha Monitor amp card and just hard wire the output of the CR unit to the CR output Connector? It´s already balanced so I thought why not just bypass the card position alltogether...
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Old 9th April 2013 | Show parent
  #51
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12ax7's Avatar
 

Quote:
Originally Posted by Studio ManCave View Post
I think I´ve got it.

There are 3 relay card slots under the desk but only 2 cards installed... Looking at the diagram under the desk there are supposed to be 2 "RELAY 5/1A" cards and 1 "RELAY 4/2A" card installed but there is 1 "5/1" and 1 "3/1" card insted.
Quote:
Originally Posted by Studio ManCave View Post
It seems I´m also missing the monitor amplifier card. This is the last circuit the signal goes through before hitting the CR out connectors in the back.

Could I bypass tha Monitor amp card and just hard wire the output of the CR unit to the CR output Connector? It´s already balanced so I thought why not just bypass the card position alltogether...
Hmmm...

For those of us following along at home, is it possible for you to post the manual you're using?
.
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Old 10th April 2013 | Show parent
  #52
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Studio ManCave's Avatar
 

Quote:
Originally Posted by 12ax7 View Post

Hmmm...

For those of us following along at home, is it possible for you to post the manual you're using?
.
The manual is like 500+ pages, so I really can´t give you that. But you can find the 900 series manual here:
ftp://ftp.studer.ch/Public/Products/...g/900/Manuals/

Mine is just a paper version of that.
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