Studer B67 problems.

[backstreets]

HI!

Alright this is weird but at the same time quite good I think.

Disconnected J2, J3 and J5 (even though +24V doesn't go to it). I don't have any J4, to monitor, connector.

And you know what... it still blows fuse F8.

As Michael noted above, the only culprit then is C4. Which is brand new... what?

Questions that pop up in my head are:

- Is it the wrong way? I did put it back the same way as the one I replaced, but when thinking about it... the problem was probably present already before I replaced C4.

Had the dude before me poked around and put it back the wrong way? I was acutally thinking about this when I replaced them. Because C4 is when looking at it put the other way compared to C1, C2 and C3.


But as the Frako cap that looked like an original was put that way I thought it was correct. Looking at the schematic it doesn't point out which leg should be - and which +. How do I figure this out?

I see that the more "advanced" schem. or blueprint does show it, but I can't figure that one out. As both ends of C4 seems to lead back to the rectifer... though one goes back connected to 0V.


Also now when typing I notice that all C1,C2,C3 and C4 are connected the "way" when looking at the more "advanced" schematic...

(Both schematics attached as pics)

It really is the wrong way isn't it?

[backstreets]

Looking back in the log I've written above, the fuse 8 problem started after I recapped the PSU. Meaning I was the one who screwed up

Even after double checking a hundred times... I just noticed that this must be how it's suppose to be... check attached the image and compare with the advanced schem. in post above.

I had put C4 with wrong polarity. BUT it was C2 that was supposed to be that way...

Hope I haven't destroyed something along the way now? :S

Please confirm to me that I've read this correctly now before screwing up anymore.

I guess I just learned a valuable lesson. Take it slow and double check even more to ensure that everything is put the correct way.

I just don't know anymore... I'm confused what's what when there isn't polarity written out in the schematic. Standing by til someone chimes in. Before I replaced the big caps on the PSU three were put with polarity in the same direction (when looking at them) and one was the opposite. I was 100% sure that it was C4 when I did the recapping, but now after inspecting the schematics some more it apparently wasn't. Is attached picture correct or wrong, should C2's polarity be that way or the same way as the other three caps?

Thanks a million in advance!

[Station X]

The positive sides of C1, C3 and C4 should go to the positive terminal of their associated rectifiers with their negative sides going to ground. These capacitors are associated with positive supply rails.

C2's positive side should also go to the positive side of it's associated rectifier. However as this serves a negative supply rail the positive side will also go to ground.

[backstreets]

Ok thanks for your input Station X, As I wrote I stood by til someone replied, in other words I didn't swap C2 around like in the pic. But C4 is rotated so now they all are the same "way" and all + on caps go to + on rectifiers.

I had it running for about 10 minutes. No fuses blown nor any weird smell or anything.

Got scared by the new post you made though so I just turned it off again. Is this correct now?

Ignore PCB attachments above, check the attached pic to this post. That's the current placement I have.

[Station X]

See my edited post.

[Station X]

The drawing in post #24 looks correct. C9 positive is connected to ground. C4 negative is connected to ground and C2 positive is connected to ground.

Just check that the positive lead of each cap goes to the positive terminal of its rectifier.

[backstreets]

Station X, yes then I had it correct. So the 10 minutes I had it running without problems were indeed a very positive thing!

Just have to run it longer tomorrow and start checking the transport functions, motors, putting head assembly back on, check sensors, tape heads etc.

Lots of things left to check and things that might cause trouble, but hopefully not

I'll post back on how it goes of course.

Thanks once again for all help!

[backstreets]

Hi again guys!

Alright, so now I've had it running, on and off for both longer (30min) and shorter (5min) intervals without any problem whatsoever. So power is stable now it seems.

BUT, off to new problems of course

Without any tape loaded, it starts playing and plays about 3 seconds and the automatically stops. This is with the tape sensor blocked with a piece of paper. Behaves the same pressing both rec and play simultaneously and also the same when rewinding or fast forwarding. About 3 seconds and then it stops.

If I take the paper away the play button or any other doesn't stay engaged at all. So it seems the sensor is working.

If I engage Mot. Off (ie. tape dump) and press play, play stays engaged, the supply motor runs and the take up motor stops. Like it's supposed to.

But what about this 3 seconds and then it stops problem?

UPDATE: I GOT IT WRONG! the speed selector changes speed for the capstan like it should. Motors don't change speed but they probably shouldn't either since there's no tape or so on them.

Only one of the speed selection bulbs work, but I've tried to swap it around and it lights up in all speed modes. The bulb is a little delayed though and flickers when button pressed, doesn't light up steadily at once... kinda takes a second or so.

Any ideas where to start the next phase of troubleshooting?

[Station X]

Have you checked that all the power supply lines are reading the correctly? I'm afraid my expertise runs out at this point.

[backstreets]

Gotta go for lunch now, I'll check when I come back. I'll also see how it behaves with tape on then and report back!

About an hour and I'll be back here.

[Michael Maurice]

With no tape loaded and the sensor blocked, the transport also looks for tape move signals coming from the two guide roller, without a tape loaded, there will be no tape move signals and the machine will stop.

The speed of the spool motors are independent of capstan motor speed. The torque (power) of these motors is dependent on the position of the supply and take up arms.

Having established that the transport basically works, you should load a tape, uncover the end of tape sensor and try it.

[Test Card Girl]

Originally Posted by backstreets

Only one of the speed selection bulbs work, but I've tried to swap it around and it lights up in all speed modes. The bulb is a little delayed though and flickers when button pressed, doesn't light up steadily at once... kinda takes a second or so.

This is quite in order: when a speed is selected, the associated lamp only runs continuously when the capstan servo is locked, indicating to the user that all is well and the desired speed is stable. This function also serves as an initial indication that all is not well with the capstan servo of course, if the lamp does not stay lit. Therefore, good practice to make sure all three bulbs are working. Also good practice (tip from me) to deselect any speed when not in use and power is still applied, as this preserves the capstan motor by switching it off.

Looking forward to the next thrilling installment.

Regards

Lucy

[backstreets]

Michael, I loaded tape and everything works in order, what a wonderful start to the weekend!

Station X, didn't measure the test points yet as I had the machine laying down and the multimeter wasn't around. But it's working correctly now it seems. Will of course double check and make sure that everything is reading what it should though.

Thanks for the tip Lucy, I'll better get me some new bulbs for it then. To get them all in working order. Do you have any source for bulbs and how much should I pay for them? I found these on eBay:

http://cgi.ebay.de/Studer-B67-Lampen...#ht_1174wt_907

Priced at 14€ for 6 of them and a 5€ for shipping. So around 20€ total. Whadda think, good or bad price?

Now the following is left.

- Fine tuning tape tension
- Checking mechanical alignment, head block etc.
- I have an order of RMGI Studio Master 468 incoming, so I have to buy a test tape to get the machine setup correctly and realign to NAB eq (it's CCIR now and I don't know if it's correctly done either)

So what do you say... starting with checking mechanical alignment and then the electrical adjustments according to the manual. Order test tape and finish of with calibrating it to NAB eq and 468 tape. And ready to use!

.. did I leave anything vital out?

[SteveCG]

Just out of curiosity: Why change from IEC (35 uSec) to NAB (50 uSec)? Are you having to deal with recordings made on a NAB eq machine - or is it that you are making recordings that will be played on another (NAB) machine?

[backstreets]

SteveCG, no reason other than it would give another EQ curve. And as I will be using the machine for mastering, dumping mixes out to tape and back into the computer the NAB calibrations EQ with slightly cooler highs seemed intriguing.

Though, I read some more about it just this afternoon and it also seem, as the machine does max 15ips (which is all I will be using) I'll get a better signal to noise by staying with CCIR, printing hotter highs.

I didn't realize that switching to NAB would along with the EQ curve of course also affect signal to noise.

So since my last post... CCIR it will be, as signal to noise is of more importance than the frequency change NAB would bring.

[SteveCG]

Thanks for the insight backstreets - as you say, it is a trade-off between S/N and high-level, high-freq handling. Although if you are recording an Operatic soprano in "full flow" then NAB might handle it better!

[Michael Maurice]

I'm glad that its sorted out now. Really you should change C4 for reliability as capacitors do not like to be reverse connected and it may have suffered internal damage.

[TIMTAPE]

Yes as Steve said Eq curves were always a trade off between noise and distortion. In fact they were only a general guesstimate because no one size fitted all programme material or even tape stock.

The advance on these standard playback curves, or the high tech addition to it, was double ended noise reduction which dynamically changed the effective record and play EQ/gain, moment by moment. Sort of an intelligent way of optimising record levels.

[backstreets]

I do of course have to report back here since you guys have been so helpful

I've got it all back together now, replaced the broken bulbs, checked voltages and done all the mechanical alignment. Still need to get an alignment tape though and check the audio alignment.

I've dumped test tones, pink noise and also some drum tracks to tape as a test and it sounds really sweet with RMGI SM468 tape. I'm really happy!

I moved it from the service shop at work to my own studio gear yesterday so it's at the right place now.

The B67 was originally in a ugly custom made rack (not the Studer original rack) which I didn't want to keep, so now I've made some nice oak panels for the sides instead. Still can't decide whether I should "ruin" the panels with handles or leave the sides all wood as it is now. Would be practical to have handles but it looks nice with all wood. I'll upload some pics as thanks!

One problem arose last night though, the play button was kinda weird at first. It responded to play, then it didn't, then responded again and finally got stuck in play mode. CRAP! Didn't have time to check it throughly as it was late, but I if I remember correctly when I had it open one of the springs for the play button was already broken. So I guess it has to do with that, maybe it's just stuck momentarily otherwise I'll probably have to source a new one. Kinda sucks but not much to do about it.

One thing though. Now after all the work I've done to it I have to say that it was much better than getting a working machine to start with as now I know how it works and what does what and when and if it breaks again I have knowledge about it and know my way around it (even though I might need to ask help here again )

[backstreets]

So here follows the pics I promised

Figured out the play buttons problem today, it seems it was just stuck so rocking it back and forth a couple of times solved it. One spring in the button is broken though, so it might very well happen again. I should eventually replace it and at the same time also replace the C4 that I had put backwards, as Michael Maurice suggested.

But for now it's fully working and since I lubricated the mechanics all movement goes really smooth as well. Awesome!

Thanks again for all help!