| Studer A-800. No Power at all. Suggestions? [message #340886] |
Tue, 13 May 2008 02:46  |
 Robomatic
Messages: 25
Registered: May 2008 |
Member |
|
|
|
Hi. I am working on a Studer A-800 MK111. When I turn on the power switch, the machine wont come up. No blinking stop light, nothing at all except the tape position lcd on the top of the machine. I checked all fuses on all power supplies and they are all fine. I think it is in safe mode where the power supplies wont come on because of a faulty voltage somewhere. Most of the post's that I have read have the stop light blinking. I have no lights at all, basically nothing. Any help on the areas that I can check first would be of great help before I get the manual out and tear the machine apart. By the way what does the 8 uf phase capacitor do. Maybe that is the problem? Thanks.
|
|
|
| Re: Studer A-800. No Power at all. Suggestions? [message #340974 is a reply to message #340886 ] |
Tue, 13 May 2008 10:12  |
Dave Hecht
Messages: 332
Registered: February 2005 |
Active Member |
|
|
Just to make sure I'm following you, when you say no power at all, are you referring to just the transport? Are you getting lights in the meter bridge? When you say tape position lcd, do you mean the led display at the right front of the machine?
If you've got meter lights and the locate display, try a quick test. Close the head shield and rotate one of the tension sensors by hand. The capstan should spin and the sync deviation led above the locate display should light. If they do, your stop light bulb is burned out. Just replace it, or not. The machine will work fine without it.
If the capstan doesn't spin, and you don't get the led, try swapping the bulb from another function to see if you get the flashing bulb. If you do, repeat the above test, see if the light comes on with no flashing. If the light continues to flash during the test, you've most likely got a blown transistor on the MDA.
See how far you get and report back.
Dave Hecht
|
|
|
|
|
| Re: Studer A-800. No Power at all. Suggestions? [message #341154 is a reply to message #340886 ] |
Tue, 13 May 2008 20:59 |
Dave Hecht
Messages: 332
Registered: February 2005 |
Active Member |
|
|
Did you check the fuses with a meter, or just visually? If the mains fuse (on the spooling motor psu) is bad, the transport wont light up, but the meter bridge should. If that fuse is good, and every thing is dead, try checking all the psu connections. Along with the ac inputs on the back (looped from the spooling motor psu to the audio psu's, then the expansion rack), there is a connection from the spooling motor psu to the electronics psu. You have to remove the mda to get at this cable, but if it's disconnected, it will kill all voltages at the stabilizer card. If the +24 volts is missing, the other supplies won't come up, so double check that fuse & rail at the stabilizer. Also, exactly what are you seeing on the led display?
Dave Hecht
|
|
|
|
|
|
|
| Re: Studer A-800. No Power at all. Suggestions? [message #341734 is a reply to message #341699 ] |
Thu, 15 May 2008 14:59 |
ssltech
Messages: 2185
Registered: May 2004
Location: Florida (previously UK) |
Platinum Member |
|
|
Check the power transistors on the Capstan MDA. -It's not just a "board" as such, it's a cube-like 'Block' of heatsink, with lots of big power transistors in there.
Measure them to find the bad one. -While you're in there, get any large cobs of dust out, and check the heatsink thermal grease isn't too dry on the rest of the transistors, or you'll be back in there again very soon. -Look for brown, crispy overheated wires and molex connections, and replace anything that's been hot or become brittle.
Keith
| MDM (maxdimario) wrote on Fri, 16 November 2007 21:36 |
I have the feeling that I have more experience in my little finger than you do in your whole body about audio electronics..
|
|
|
|
|
|
| Re: Studer A-800. No Power at all. Suggestions? [message #341983 is a reply to message #341915 ] |
Fri, 16 May 2008 09:59 |
ssltech
Messages: 2185
Registered: May 2004
Location: Florida (previously UK) |
Platinum Member |
|
|
If you measure a short between collector and emitter on any of the heatsink-mounted transistors, that's DEFINATELY going to cause the flashing stop lamp.
Keith
| MDM (maxdimario) wrote on Fri, 16 November 2007 21:36 |
I have the feeling that I have more experience in my little finger than you do in your whole body about audio electronics..
|
|
|
|
|
|
|
Members
Search
FAQ
Register
Login
Home
