Studer A820 "motor supply voltage low" error

Hi,
I have a Studer A820 2track 1/4,when it power up,first appears a message with no errors detected and
after few seconds "motor supply voltage low" error is displayed, the spooling motors don't work..no play, FF or RF
Checked the fuses all are ok, all green led on.
measured voltages:
+5.5 (+5.6v)
+25.5 (+24v)
+14.8 (+15v)
-14.8 (-15v)
+25.8 (+26)
-31.5 (-26) how can correct this voltaje?
+48.1
-48.1
50.9
already recapped the stabilitzer 1.820.832.00 card and the spooling motor supply 1.820.777.84 but same erro diplayed...
any help where i can look?

thanks,

Also noticed some hi freq noise 8k-10k( mechanical ,no audio) that seams comes from the zone of the stabilitzer card....

anyone?

Hello,
Your Question is  difficult to  answer  without to see  Schematics. Did You  measure the Voltage direct at the Motor ?
If  there is a  Motorcondenser You could  check him for  leakage or short. The Voltages for the Logic, Relay,s, Audio ,Lamps  seem to be ok. The -26V  should be -31,5 V , has this  Voltage  anything to  do with the Motor? Is there a Trimmer on the Card  to adjust this Voltage ?
Sorry this is all i  can  say but  maybee it s  a good Idea to post your Problem in a more Tapemaschine related
Place  like this one
http://www.tapeheads.net/forumdisplay.php?f=68
or  a special Studer Forum, its german , but I think it s possible to post in english
http://forum.studerundrevox.de/viewforum.php?f=7&sid=229d4f75773aee7953f2a65970c637b7
Good Luck !!
Greatings,
Lothar

http://www.vaporstudio.com/studio/1.820.833.00.jpg
changed:
D101,D102 (BYV32-200)
C101,C102,C103,C104,C105,C106
R102,R103,R101,R104 checked, are ok

still  +25.9V and -27.1V without load ...

Hello,
Where  do You measure ?  At the Testpoints ?
Did You check  the  Motorcondenser ? I am quiet sure there is one. If You have less Voltage with the Load of the Motor , it could be that the Condenser is leaky. The Card is a stabilisation  Unit, so You should have the same Voltages with or without Load, I think. What happens If You connect a resistive Load of maybee  500 Ohm  instead of the Motor ? Do You still have the Voltage Drop ? If so You  may have a Problem with the Card, You should measure the Currentflow during this Test , if You have enough Power.  Replace or check  Q 2  if  not. I wouldnt touch R 101/104  because You have enough Voltage without Load and You may unbalance the Voltage . When You have no Voltagedrop  and enough Power, the Problem is on the Motorside . Sorry, I am not a Studer Expert and I may talk rubbish. Maybee someone can chime in and can help.
Good Luck !
Greatings
Lothar

Check all the parts on the secondary of the switching transformer, especially the electrolytic caps.

Hello,
I thought Your Problem is the low  Voltage of the Motorsupply Card. The stabilitzer Card  should supply 26 Volt and You have 25,9 Volt, that s ok I guess , if You have Current. Can You  post the Schematics from the Motorsupplycard ?
Greatings

I agree, I think your problem is on the Spooling Motor Supply PCB 1.820.777 (on our 1/2"). Maybe a leaky transistor or triac.

the schematics
http://www.vaporstudio.com/studio/1.820.777.84.jpg
the 22000uF is new.
actually there are three problems:
the low spooling motor supply voltage
the -31.5V should be -26v
and the high freq "ringing" of the stabilizer

Hello,
First  check or change C 15 , if leaky You have a Voltagedrop.
it could be that one or more Bd 900 Powertransistors or the internal Diode is faulty.
This Part is easy available and cheap, You can find them here
http://www.henri.de/bauelemente/bauelemente-aktive/transistoren/bd/13966/bd900-p-darl-transistor-diode-80v-8a-70w-hfe-750-to220.html
They are all parallel so they don t need to be  matched, i think.
The Optocoupler  DL. Q 1 and the Bridge  DZ 1 are also  Canidates to fail.
Do You have a extender Card to measure  something with the Maschine  enabled ?
The Controlvoltage for the Motor seems to have a own Plug. What Happens if You disconect  the Motor. I ask  again, is there a Motorcapitor directly at the Engine ?
Did You already measure the Current of the stabi Card.?  It s good to solve  one Problem  after the other.
Greatings
Lothar

thanks Lothar
I will check the points that you suggest.
sorry no extender card...
there is not any capacitor at the motor, the motor is connected through "spooling motor drive amplifier" 1.820.775.81
http://www.vaporstudio.com/studio/1.820.775.81.jpg
I am thinking how to measure current of the stabilizer but don't see a simple way to do it because of the multipin plugs...

Hello,
Without a extender Card it s difficult to fix Your Problems. I would try to get or borrow one. You can also DIY one. I think it s a  must have if You want to fix and service Your Tapemaschine. How to make one is discussed here for example.
http://groupdiy.com/index.php?topic=56557.0.
The Current of Your Stabicard can be measured if You lift the outputside of R 104 and put a Meter between  this Point and its formal Place or at the Connection from the Card to the Multipin Plug.(with 2long Cables, because of the absence of the Extendercard.) or if You have Access to R 104 measure  under Load the Voltage before and  after the  Resistor (against 0V) , subtract  them  ( the Voltagedrop  After the Resistor )and calculate. I=U/R.    ( You  need  to know  the Value of  R 104 )
At the Motordriveamp I would check  C 22/23/24/25.
Do You have technical Support at Your Place?  Maybee it would be good to contact a Tapemaschine or better a Studer Expert.
I think now You are good prepared to contact a Tapemaschine related Forum and get a more specialized Support.
Sorry, this is all I can say, because I don t know anything about Studertapes.
All the best ,good Luck and Greatings.
Lothar