studer a820 won't load tape

[nielsk]

a friends A820 2" will suddenly not load tape, pressing stop or play does nothing (it should load tape), it worked perfectly yesterday...all motors work, lifter motors work (it will move lifters with a edit command) all p/s voltages look perfect. I switched out the transport mpu and interface card with borrowed working ones, no go. It seems like the photo sensor is working, the board with all the led's on it under the deck changes w/ the sensor...any ideas or know a studer tech who may have seen this before?

 

[Greg Norman]

[quote author="nielsk"]a friends A820 2" will suddenly not load tape, pressing stop or play does nothing (it should load tape), it worked perfectly yesterday...all motors work, lifter motors work (it will move lifters with a edit command) all p/s voltages look perfect. I switched out the transport mpu and interface card with borrowed working ones, no go. It seems like the photo sensor is working, the board with all the led's on it under the deck changes w/ the sensor...any ideas or know a studer tech who may have seen this before?[/quote]
Are all the fuses ok, and power supply status leds on?
What does it say on the 2 lcd screens?
See if "console remote IF" is enabled.
Did you restart...er cycle the power?

 

[nielsk]

yes, yes, and yes...no errors reported on screen, not in rem if or remote..all voltages read perfect
when it is turned on the stop button light flashes 10 times then stops. It should flash untill tape is loaded then light solid.....

 

[pucho812]

Never did much with the 820's only the 827's. I know they are similar.

Is the tape threaded properly?
If so is the tape sensor working?

Check the tape tension in the soft menu's.

do you have a service manual for it, if not you can download one from studers ftp site.

 

[nielsk]

yes, yes & yes...there is no troubleshooting guide that addresses this in the manuals, and if it wont go into a "load" condition, the tension can not be checked......

thanks

 

[Greg Norman]

What happens when you press the stop button with no tape on board?
What should happen is the reeling motors move slowly (to draw tension to loose tape), and brake solenoid clicks.
If you press the fast forward button the take up motor should rotate slowly, and reverse button, supply motor turns.
If the reel motors move like I stated, you may have a problem with the light barrier sensor (tape end sensor). It can still be malfunctioning with the red light working. I don't think that is it though.

Is there any condition in which you see the reel motors moving (by themselves)?

FYI-
If you have swapped any MPU cards: Make sure the eproms are of the same software version. Having incompatible software can freeze the machine. I know your problem was before you swapped anything.

 

[pucho812]

have you tried hitting the reset buttons on the cards? Might have to dump the memory and load in the default settings.

 

[Michael Tibes]

Sometimes the IR light sensors in the tape path get dirty and create funny stuff.

Michael

 

[sodderboy]

EDIT: re-read the thread, and since all LED's are OK, it can still be that card under the display. When unplugged, you will have no transport access, but if it is loading the PS in any way, tape will load if it is disconnected.
And is there any synchronizer connected?



If any of the voltage LED's are out, then the usual problem is that one of the cards has a bad de-coupling cap. It is usually one of the cards under the deckplate. You remove a ribbon (machine off!) and power the machine. Do this until all rails (LED's) come-up.
The #1 offender is the 2200 on the parallel card just underneath the display.
This is simplistic, but it is the case in 90% voltage rail problems in the 820/827.
Mike

 

[nielsk]

I have not yet been able to get at the machine again and try cleaning the tape "present" led / photo sensor (with a mirror..)... I can not find any table in the manuals that expains the indications of the red led's on the board under the photo sensor(under deck lid), there is a ladder of them and they do display something...
all voltages present and measure good, the green led's on the power supply indicator board are all nicely lit up...

 

[Greg Norman]

[quote author="nielsk"]I have not yet been able to get at the machine again and try cleaning the tape "present" led / photo sensor (with a mirror..)... I can not find any table in the manuals that expains the indications of the red led's on the board under the photo sensor(under deck lid), there is a ladder of them and they do display something...
all voltages present and measure good, the green led's on the power supply indicator board are all nicely lit up...[/quote]
I think you are talking about the pinch roller gate (mounted beneath left side of the transport). You can find out about that on one of the 820 manuals on the studer ftp site.
ftp://ftp.studer.ch/Public/Products
The leds will show tach pulses of the reeling motors, tachometer, capstan, and some other statuses.
I would assume it is a blown cap, but that usually shorts out a power supply rail.
If you have a chance, you might want to swap the spooling motor driver board, and spooling motor control board in the mpu/control card bay.
After that, you might have to search for some shorted caps, and burned connectors.

 

[pucho812]

check the soft start in the PSU cage. Ours went out a while back on our 827 and caused a whole list of problems yet all the voltage led's were green meaning they were o.k.

 

[nielsk]

Results, no tape:


Hold stop: both motors slowly spin.
Hold forward. right motor slowly spins
hold rewind. left motor slowly spins
hold play: the same as stop

 

[SSLtech]

Niels,

Are you at the machine now? -I'm calling your cell phone...

Keith

 

[Greg Norman]

The fact that the motors are moving is a good sign.
Can you perform the light barrier/tape (opto) end sensor adjustment as described in section 3, page 6 of the manual (3.1.2)? If the machine thinks there is no tape loaded, it won't let you do anything.

 

[nielsk]

Once I figured out that this machine (it is a very late production #) has a opto board as used in the 827 instead of the one in the manual, I was able to make sense of it, and it tests fine. I was able to obtain a loaner opto board from an 827 to substitute, but have not been able to try it yet.
Can the machine fire up as normal and all power rails test fine if the soft start is having problems?

 

[pucho812]

IIRC it can it was a wile ago when it went. When our soft start board went all looked fine until we tried to get a tape going. would try and play it but would stop almost instantly.

 

[nielsk]

Well, it can not be the soft start, the power supply was replaced and the new (?) one is the early model with no soft start board.....I have a borrowed set of motor driver boards I will switch out, there is not much left to try (every connector checked, all control circuitry confirmed with known good cards)

 

[nielsk]

Thanks to some very good nudging in the right direction by Charlie, (& all the other listers who helped) I have found the problem at last! The take up side tension sensor board is the culprit.... it looks like oxide dust has been collecting on it over the years (through the tiny slot in the cover plate), and shorted out the little interface board. I have a working loaner board in while I troubleshoot the bad one....store this one in the databanks....