Just bought a Studer 902 console. Would need some advice with recapping.

[Larsson]

Hi guys.
We recently bought this beauty to our studio:


It has 22 mic/line/tape mono channels, and 2 mic/line/tape stereo channels.Everything with balanced inserts, and 4 stereo busses.
The stereochannels have the "stereospread" function, wich i got to say is pretty amazing  .

It is in need of some recapping and maintainance. Some faders are a bit scratchy. Two channels are only working when sending signal to the busses in PFL. I´ve checked both fadermodules and inputmodules so the problem seems to be in the wiring in the console somewhere. Has anyone experienced this problem?

One mono eq is sounding distorted and hums alot when engaged. Two of the buses are making wierd noises, and a couple of line in´s does not pass audio. Also one buss isnt even between left and right.

Does anyone have experience in working on these consoles and got any advice for recapping? Whats the best startingpoint? PSU and mastermodules? What about changing opamps (mostly 5532´s) to something "better" or just putting in new 5532´s?

Thanks! // M

 

[pucho812]

I have never been one to mess with 5532/5534's, only replace when the opamp is dead and only replace with another 5532/5534.  They are a well done low cost opamp.  Recap as necessary. Does the PSU  need a recap? IS it causing hum or any other issue?  doesn't sound like it so no need to recap that yet.  As far as recapping, on each channel replace all the electrolytics as those dry out over time. The rest of the caps replace as necessary. On the studer FTP, you can get the service manual and schematic. It will help you out a lot.

As a far as channel working only with PFL you may have a problem in the channel as in an opamp out,etc. Since it is a broadcast console it may require some jumpers that are not installed or need to be removed.  I doubt the problem is in the internal wiring snakes. That would be the last place to look and even then it is more likely be a  broken wire at a connector then in the wrong splace. when those were made Studer was Studer and not Harmon kardon so the quality was good. 

 

[Larsson]

I have never been one to mess with 5532/5534's, only replace when the opamp is dead and only replace with another 5532/5534.  They are a well done low cost opamp.  Recap as necessary. Does the PSU  need a recap? IS it causing hum or any other issue?  doesn't sound like it so no need to recap that yet.  As far as recapping, on each channel replace all the electrolytics as those dry out over time. The rest of the caps replace as necessary. On the studer FTP, you can get the service manual and schematic. It will help you out a lot.

As a far as channel working only with PFL you may have a problem in the channel as in an opamp out,etc. Since it is a broadcast console it may require some jumpers that are not installed or need to be removed.  I doubt the problem is in the internal wiring snakes. That would be the last place to look and even then it is more likely be a  broken wire at a connector then in the wrong splace. when those were made Studer was Studer and not Harmon kardon so the quality was good.

Thanks for the reply!
Thats what i thought also about the opamps.  I really like the sound of the console and would like to keep the original sound. I did read a post from Jim Williams at GS where he recommended a different opamp to get rid of offset capacitors in the audio path. That made me curious. I thought of modding one of the stereochannels to a more clean sounding "masteringchannel". But..I´ll keep the 5532/5534´s and change to new ones where necessary.

I´ve got a 580 page manual and the PDF-file so I have some interesting reading ahead 
The PSU and stabilizers seems to be working fine.
Are there any electrolytic capacitors that stands out from the rest rest or could i pop in any high quality capacitor?

I will start checking the connectors in the slots as the modules are passing audio if i put them somewhere else.

 

[pucho812]

Jim williams got his start with guitar amps then moved on to other things which was good for guitar players. I know a lot of people who all say the same thing if you want it to sound  sterile then do what Jim williams suggests. While I don't doubt he knows a thing or two, The end result leaves a lot to be desired. Something I have heard a lot lately and even more so with those who had him do the work at great expense. 500 dollars  a stereo buss/master channel?

Danger will robinson Danger.

 

[zamproject]

nice catch 

I'm Studer user too (but more used with older series x89) this company made great desk!!!
i have the same "stereo spread" in my 289 stereo modules, don't know if the 900 series use same design for this purpose but it is (for the moment, compared to all other tools I have) the only "phase enlarger" I can use in a good and musical way, all other just made my brain flip off.
Have the 900 stereo channel XY/MS input matrix ?

Be careful when recaping, i find the 80' 90' studer PCB easy prompt to break track when working on it (have this on eurocard balancing unit, i think you have some in your 902)

I' going the same way as Punco for 5532/34. Also could be some issue with PSU when changing large OPA quantities

 

[audiomixer]

You might want to do a frequency response measurement before mending something that's not 'kaputt'....

dried coupling capacitors would have a negative / noticable effect on LF response. you could check mic / line in to direct out / aux out / master out and compare with Studer specs.

Arta / RMAA / and quality soundcard would be an adequate tool, but make sure your setup is linear beforehand of course.

- Michael

 

[jensenmann]

These desks are great IMHO. I would not bother with swapping chips. Certain persons do suggest swapping because they make a living out of it.... With other desks there might be reason to change chips because the circuit design is less than stellar. Not so much the case with Studers. These are very well designed with no corners cut.
As others already mentioned take your time and a very good desoldering tool to recap it since the PCB traces are very - and I mean extremely - sensitive. Lifting or breaking soldereyes will happen even if you are very careful. Definitely start with the PSU since a healthy PSU is a lifeinsurance for the desk. Renew all thermal grease and double check the rectifiers.
There´s a tantal cap in the logicsection of each channel which may cause a short to ground hence loading the supply voltage of the channel down. Make sure to replace these.
It will not do any harm if you increase the capacity value of all electrolytics which are in the audiopath, btw.

 

[Larsson]

These desks are great IMHO. I would not bother with swapping chips. Certain persons do suggest swapping because they make a living out of it.... With other desks there might be reason to change chips because the circuit design is less than stellar. Not so much the case with Studers. These are very well designed with no corners cut.
As others already mentioned take your time and a very good desoldering tool to recap it since the PCB traces are very - and I mean extremely - sensitive. Lifting or breaking soldereyes will happen even if you are very careful. Definitely start with the PSU since a healthy PSU is a lifeinsurance for the desk. Renew all thermal grease and double check the rectifiers.
There´s a tantal cap in the logicsection of each channel which may cause a short to ground hence loading the supply voltage of the channel down. Make sure to replace these.
It will not do any harm if you increase the capacity value of all electrolytics which are in the audiopath, btw.

Thanks for the replys everyone!
Haha I get it. I´ll leave the good ol´5532´s inside. Lets say an opamp IS broken. Is there any way of telling if its an opamp or cap thats gone bad? Im thinking broken opamp - no sound / distorted. CAP - Wierd frequency response, hum and wierd noise?
Thanks for the advice on the PCB traces. I have soldered alot but then on modern PCB:s and some home etched.
So the electrolytics are not there for any filtering duties? Just DC blocking? How would larger caps be better? Sorry for the noob question..

nice catch 

I'm Studer user too (but more used with older series x89) this company made great desk!!!
i have the same "stereo spread" in my 289 stereo modules, don't know if the 900 series use same design for this purpose but it is (for the moment, compared to all other tools I have) the only "phase enlarger" I can use in a good and musical way, all other just made my brain flip off.
Have the 900 stereo channel XY/MS input matrix ?

We were looking at a 389 before but went with this because of the equalizer. That is a nice looking console  8)
My first impression of the desk is great (especially compared to our old tascam M600). The stereo spread is really nice if you use it carefully! I have noticed though that it makes the HF band in the EQ go crazy as one channel gets louder as i increase gain. Yes it has XY/MS. Thats a nice feature!

 

[jensenmann]

Coupling caps act as a highpassfilter together with the inputimpedace of the next stage. If you increase their capacity the cutoff frequency will go down. These desks were made at times when there was no significant information happening below 40Hz. Today this has changed to let´s say 20-25Hz. On top of that every filter creates phaseshift. This can be audible, today even better than back in the days due to our better monitoring systems. Moving the cutoff frequency far out of the audioband will lower phaseshift. This translates into cleaner lowmids.

 

[pucho812]

easy to tell if an opamp is broken, it's not working As much of a joke as that is to say to find that out best to scope out the unit with tone and measure...

 

[zamproject]

We were looking at a 389 before but went with this because of the equalizer. That is a nice looking console  8)
My first impression of the desk is great (especially compared to our old tascam M600). The stereo spread is really nice if you use it carefully! I have noticed though that it makes the HF band in the EQ go crazy as one channel gets louder as i increase gain. Yes it has XY/MS. Thats a nice feature!

What is your point with x89 series EQ??? sound nice with inductor
The steeped freq and boost/cut make it "recall friendly" especially when you have 24 input...
I have nice result using MS input for a BX20 return (only when sending mono signal to the reverb), can be use in lot of other creative way other than MS mic recording
but of course 900 series have more features, better routing more aux etc...

 

[Larsson]

What is your point with x89 series EQ??? sound nice with inductor
The steeped freq and boost/cut make it "recall friendly" especially when you have 24 input...
I have nice result using MS input for a BX20 return (only when sending mono signal to the reverb), can be use in lot of other creative way other than MS mic recording
but of course 900 series have more features, better routing more aux etc...

Well no point concerning the sound. Its a killer EQ  However not as flexible as the 900 EQ with 2 Q´s and more bands etc..
Nice idea, BX20 is on my "must have" list.

Coupling caps act as a highpassfilter together with the inputimpedace of the next stage. If you increase their capacity the cutoff frequency will go down. These desks were made at times when there was no significant information happening below 40Hz. Today this has changed to let´s say 20-25Hz. On top of that every filter creates phaseshift. This can be audible, today even better than back in the days due to our better monitoring systems. Moving the cutoff frequency far out of the audioband will lower phaseshift. This translates into cleaner lowmids.

Well thats true. So your suggestion is to move the cutoff frequency as low as possible or should i aim for say 20hz? Thanks.

 

[jensenmann]

To lower phaseshift you´d have to go way lower than 20Hz. The cutoff frequency is depending on how many circuit stages are in the signal path. They are in series. So you´d need to design the cutoff frequency of a single stage very low since they add up. 1Hz may be a good target for that.
The additional benefit is that distortion in the electrolytics is lowered, too. But I´d not get too scientific with that. Whatever increment of capacity you chose will be an improvement.

 

[Larsson]

To lower phaseshift you´d have to go way lower than 20Hz. The cutoff frequency is depending on how many circuit stages are in the signal path. They are in series. So you´d need to design the cutoff frequency of a single stage very low since they add up. 1Hz may be a good target for that.
The additional benefit is that distortion in the electrolytics is lowered, too. But I´d not get too scientific with that. Whatever increment of capacity you chose will be an improvement.

I´ll try to fit in as much farads as possible then within a reasonable price. Thanks Jensenmann!

 

[natrecstudio]

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