Studer A820 spooling motors stoped

[jtvrdy]

Hi,I have two Studer A820 1" 8 track, one of them when powered yesterday it smelled as something was burning !
... and the spooling motors stoped working
no error messages on the displays
when play is pressed only the capstan is runing few segons and stops
when the FF and RW is pressed the light of the button is on but nothing is moving
Cheked all the fuses, and all the green led of voltages are ok(also cheked with with voltmeter)
cheked the stabilizer cards and the spoling cards and nothing seems burned
any ideas where i can look to find the problem ?

thanks !

 

[jtvrdy]

anyone ?  :

 

[outoftune]

you might wanna try over at electrical audio's forum, there are some studer folks over there, maybe greg will chime in... www.electrical.com

 

[SSLtech]

Does it 'load' tape correctly under tension?

With no tape loaded, when you press and HOLD the stop button, do the reep motors 'creep' slightly?

Keith

 

[jtvrdy]

yes it load tape ,with play pressed the capstan and pinch roller drag tape few seconds and stops because the take up and supply reels don't rotate.
the motors don't rotate with the stop,FF and RW buttons.

 

[SSLtech]

What's odd is that the spool motors have to pull to hold the tape under load...

I can't figure that out.

Keith

 

[jtvrdy]

in fact,  even without tape, the machine "think" that is loaded ...pressing play the capstan and pincroller is runing few segons and stops

 

[pucho812]

We had  the exact same problem with one of our 827 2" machines at work not too long ago. The voltage led's will read correctly and show green yet the machine will not play. IIRC the problem existed with the fact that the soft start section in the PSU had fried. I would go over the PSU with a fine tooth comb and you will find the problem.  We ended up having to replace the whole soft start pcb...


I think it was called soft start....

 

[SSLtech]

in fact,  even without tape, the machine "think" that is loaded ...pressing play the capstan and pincroller is runing few segons and stops

ALL A27's will run the capstan with NO tape loaded... it runs for a lot longer than a fwe seconds, so sounds like your logic is VERY confused.

Instead of just relying on the LEDs, MEASURE the voltages if you can, for a truer pucture.

Keith

 

[jtvrdy]

We had  the exact same problem with one of our 827 2" machines at work not too long ago. The voltage led's will read correctly and show green yet the machine will not play. IIRC the problem existed with the fact that the soft start section in the PSU had fried. I would go over the PSU with a fine tooth comb and you will find the problem.  We ended up having to replace the whole soft start pcb...


I think it was called soft start....

I will check the PSU....

 

[jtvrdy]

in fact,  even without tape, the machine "think" that is loaded ...pressing play the capstan and pincroller is runing few segons and stops

ALL A27's will run the capstan with NO tape loaded... it runs for a lot longer than a fwe seconds, so sounds like your logic is VERY confused.

Instead of just relying on the LEDs, MEASURE the voltages if you can, for a truer pucture.

Keith

measured voltages

5.4(5.6)
24.1(24.0)
15.3(+15.0)
15.2(-15.0)
28.4(+26)
28.5(-26)
48 stab1
47 stab2
47 stab3

 

[Greg Norman]

Those voltages look normal, or at least not totally f-ed.

Can you confirm that the capstan motor is rotating when you hit play?  Tape should have spilled off to the right if the machine is acting like you say. 

With the machine off-

Make sure all ribbon connectors are securely plugged in to all the transport, and control points of the machine.  Reseat them while your there (pull them out then push them back in).   

Reseat all the cards in the control bay (spooling motor driver, MPUs, everyone). 

Unplug and check the power connector on the raw DC power supply for burned metal, or plastic discoloration (this is the Molex connector right next to your AC power connector in the rear of the machine).  Check for overheated connections with the Molex connectors on the two reel drive amplifiers.  We have had intermittent problems caused by this. 

 

 

[jtvrdy]

Those voltages look normal, or at least not totally f-ed.

Can you confirm that the capstan motor is rotating when you hit play?  Tape should have spilled off to the right if the machine is acting like you say. 

Yes that is,the capstan and pinch roller drag tape few seconds and stops because the take up reels don't rotate and there is not tension.

 

[jtvrdy]

thanks Greg !!

I found this,it look like burned...

from the schema it is a PTC resitor Philips 2322 664 16811
measured and has 2.6 Ohm

schema hi res:
http://www.vaporstudio.com/studio/774.jpg

 

[jtvrdy]

anyone kow where I can find this PTC resistor ?
the schema says that I can use one 1.3 ohm 2322 664 16811
or two  2.3ohm 370mA 60V

also this 220uf 100v electrolytic capacitor star leaded is hard to find any ideas ?

thanks,

 

[VertigoRecording]

It seems like you are looking in the wrong area. The circuit board you have posted is the capstan driver and we already
know that the capstan seems to be working. I wouldn't worry about that PTC resistor, check it against the other one right
next to it, do they measure the same? You will probably have to unsolder one leg of each device to be able to read the
value. I think the blue shrink tubing just fell off due to old age. The capcitor is hard to find but I doubt it is bad. I have never
seen a bad one. Since the capstan is working, I would look other places. Try looking at the tension boards that are underneath
the tension arms. You can see them and test them when you lift the deck up. Use a voltmeter or oscilloscope to see if the DC
voltages change when you push the tension arms in. There's a setup procedure in the manual.
Charlie Bolois
Vertigo Recording Services

 

[steved1953]

Hi Josep,

My first post here, so I hope I can make it worthwhile.

I had a very similar experience yesterday with a revox B77. first of all, let me say that whilst I am fairly practical, I have no real electrical/electronics qualifications and little experience.

Anyway, I fired up my little used B77 and noticed that it was struggling to reach speed in play. Then it went up in a puff of smoke. I quickly turned it off and took it apart. There are three capacitors which relate to the spool motors and capstan motor, and one of them looked as though it had overheated (ITT SEL MP 33/3.5/160 A3), although it didn't feel hot. Then I found a component which goes across the "power inlet" to the machine (Rifa PME 271 M 610), which had clearly burnt out and was the producer of the smoke and fumes. My understanding is that perhaps the capacitor failed and went out of spec., and this caused the burnout of the "Rifa" component.

Perhaps, you have a similar problem. See if you can see any round, aluminium bodied capacitors, and see if one of them looks slghtly different near to the contacts. I took an ohms reading (in situ), and the discoloured one read differently to the other two. Perhaps it is supposed to, I don't know!

Perhaps my problem is nothing to do with the capacitor, but the (Rifa) component (whatever it is) is very dead. As an aside, does anyone know where I can get one?

Hope you can sort it out.


Regards,


Steve D.