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[slothus]

Rob,

The lubrication for sintered bearing Studer capstans (pre 1988)is Kluber Isoflex PDP65. Studer and Kluber both recommend not mixing oils if you want the capstan to last its full life and stay in spec. Unfortunately PDP65 can only be purchased in 1L containers for about US$168. There are some places selling Kluber constant OY68 as a substitute for Studer capstan lubrication but Kluber told me specifically not to mix the oils.The Constant OY68 would be fine if all traces of PDP65 were eradicated (impossible without major surgery). I do know people who've mixed the oils though...

If the Capstan motor has a red label it's a post 1988 capstan (A820 and beyond) that uses Kluber Constant GLY 2100 liquid grease. These versions can find their way on to A800's if the original has gone back to Studer under the capstan exchange program.

www.klueber.com

As far as the tants (blue on the record card)I'd say try a channel and see. It will prevent spontaneous combustion if nothing else. Just for the record the orange caps you see are Philips Solid Aluminium, not tants. These do not need replacing.
The repro pre-amp cards are worth doing (under the deck plate inside the sheet metal box) as are the axials inside the sandwich at the back of the card cage, although you need to be feeling adventurous to do these.

I've compiled a list of A800 parts/lubrication references that you're welcome to if you want to send me your email. Very incomplete but some useful info nonetheless.

cheers
Brent Punshon

[Dave Hecht]

Rob,

 Don't know where you're located, but you can still get some spares from Studer in LA. Call Frank Rodriguez at 818-920-3279. Studer sold the remaining A800 parts to a company called Audiohouse, http://www.audiohouse.ch. They may also have the capstan oil available.

As for the caps, the tantalums rarely fail, and I wouldn't do a wholesale replacement of them. For the electrolytics, if you don't have any symptoms such as bad low frequency response, I'd leave them as well.

Dave Hecht

[slothus]

I would agree with Dave in leaving the tantalums.I've never bothered. You will find varying opinions on this though.

Also, just for the sake of completeness I failed to mention there is also a 3rd Studer capstan motor that uses a permanently lubricated sealed ball-bearing (no re-lubrication required). These can find their way into A800's, again, if the motor was exchanged under the capstan motor exchange program (still running through Audiohouse at about a grand). I have no idea whatsoever but would presume this is reasonably rare.The identifying part number is 1.021.352.82 for this one.

Brent Punshon

[Robomatic]

Hi guys.. Thanks for the info about the lubrication. I will definately get some. I am still at a stand still with the stopping flash light however. I replaced the faulty transistors in the MDA and the machine still has the flashing stop light? I may have missed a bad transistor but I dont think so. I will check them again. Do you recommend taking them off the heatsink to check?  Maybe the head protector switch is faulty? I measured continuity across the terminals on the switch and also measured 13 some odd volts DC on the one lead, reference to chassis ground. I re checked RCA411 (out of curcuit) and it comes up good. Other than those things and having the proper voltages on the stabalizer board (which I do) are there any other ares that I have missed? If not, I think that the MDA must have another transistor out on it that I have missed, or blew when I powered the machine up today.

Thanks for the help on this,

Rob.

[Larrchild]

Is the light bulb that is used for the tape sensor in the head stack on?

Also, the microswitch under the head stack has a small metal flap that can flip over the wrong way, and the stack can still be mounted.

[Robomatic]

There are two lights to the left of the heads. Are those what you mean? I think they are on when I power up the machine. I know one is anyways. The micro switch that you are talking about I think is the head sheild protect switch. That is the one that I was looking at. I know if that isn't working the stop light will flash. The MDA transistors are cold to touch, so I think I may still have a problem in there. Is there anything I should be testing inside the spooling motor supply on the back left of the machine? The connector looks snug at the top of the MDA board.

Rob.

[Dave Hecht]

Rob,

 Are you getting the flashing light with tape on the machine, or are you just testing without tape? If you're testing without tape loaded, are you turning one of the tension sensors as well as closing the head shield? The light will continue to flash if the machine gets no tension indication.

 A few other things to check. As Larry mentioned, check the position of the actuator for the head switch. You can also jumper the switch for test purposes, which will let the stop light come on with a bad switch. Since you've had the MDA out, double check all the connections. Also, if your machine has the slew limiting mod (a cap in parallel with the spooling motor connections), try removing those - if one is shorted it could leave the machine in safe mode.

Dave Hecht

[Larrchild]

Ok, well if you have light shining up at the head stack then the sensor lamp is good. It will sit there and dumbly blink if it burns out. So, as Dave mentioned, you need both tension arms taut and tape against the head. If it got all that, then it's still more trouble.

Moving the head shield toward the head should produce a faint, but audible click from the "shields-up" switch. If not, check the switch.

[Robomatic]

Hi guys. I am getting the flashing stop light with and without tape threaded on the machine. With the tape threaded, I am making sure that the tension sensors are taunt and the head shield is up. I do hear a clink when I move the head shield up and down. The only light that I see is to the left of the headstack. I will check the MDA connections and transistors and get back to you. I dont recall seeing a cap in parallel with the spooling motor connections, so I dont think this machine has that mod.

Rob.

[slothus]

You only need to nudge either tension sensor out to about 10 degrees and with the headshield closed you should hear the capstan spin-up (if the top jumper is in the top position on the tape deck IF card) and the stop light go solid. There is a definate click of the microswitch when the shield is brought up.

The tape end switch bulb doesn't effect this at all (if the bulb is good - like Larry said!). It only affects the counter. When the bulb is out (and Q7 shorted and Q8 emmitter cut on Command receiver card) the counter will continue to count while the move sensor turns (like when tape is spooled off). When the light is on and there is no tape loaded the light is reflected in the mirror back to the detector and the counter wont turn over.

If you find a further problem in the MDA it's best to replace pairs of power transistors as they'll last longer with some matching. Short of a jig, at least replace with pieces bought at the same time or from the same batch.

Brent

*Sorry guys I was half asleep when I wrote this post. I've corrected it, sort of. Lesson learned....

[Dave Hecht]

Rob,

 Along with re-checking the MDA for another bad transistor, double check all connections, make sure nothing is loose. You don't have to desolder the transistors to test them , but you will need to pull the wires from the pc board to isolate the individual transistors. Also, try jumpering out the head shield switch. I've had those go bad before.

Dave Hecht

[Robomatic]

Thanks Dave. I took the MDA sink out again and pulled all the connections form the PC board. All the transistors came up good. I put it back in the machine. Still had the flashing stop light. I may have something intermittent on the tape deck interface board on the front of the machine. I snugged up the blue connectors on the back and the capstan motor came on and the pinch roller came into the capstan shaft.(tape treaded on machine) I had a solid stop light for a while but still no transport functions? After a few minutes of trying to find the problem I was back to a flashing stop light, no capstan? Intermittent connections? Dirt? I will jumper the head switch tonight. Red and black wires together I'm assuming. We are definately making progress.

Thanks for the help.

Rob Deacon

[Robomatic]

Jumped the head switch tonight. No luck, still have no capstan/ transport. I can hear & see the capstan trying to go, but stops after a second when I turn on the machine. Could it be the MPU card or one of the other cards on the front?

[slothus]

Is there a jumper in the top position of the Tape Deck IF card? Have you reseated all the cards in the top bay? Do you see the software revision info when you turn the machine on?

Brent

[John Monforte]

Sorry to jump in late here. I've been out for a while.

There are many reasons (a dozen? -twenty?) that a Studer will not permit operation, shut the transport down, and indicate this to you by blinking the STOP lamp. Thus the lamp is a symptom, not the problem. Unfortunately, the machine provides no information about the source of the unsatisfactory condition.

You can go to the manual which will help show you the various sources to the logic circuit that controls the protection and you can start checking them each out one by one. It can be tedious, I'm afraid. If you are tricky, you can fool the protection circuit by eliminating the fault circuit inputs to see which gets the lamp going - just don't try to run the machine! Once you have found the disagreeable section, you can then start to address its problem.

I had one that turned out to be a card that had a modern upgrade that was not shown on the schematics and it gave a fault indication to the machine even though the circuit was functional. That one was tough! Usually, it is not too hard to find.

I must pause for a moment of perspective. This is not a beginner-level problem. Please take a long look at that 30 amp power cord, those powerful motors, and the wire wrapped microprocessors. Contemplate the current levels, torques, and voltages involved. Scan through that four-inch-thick manual. Think about those precision components that were expensive when new and are now hard to find. Then think of what could happen if you make a mistake.

I don't know your level of experience, but if you are looking for something to fix and gain some electronics knowledge on, this isn't the place to start. Not that I am trying to discourage you, but this is the very top of the pyramid in studio gear when you consider the electronic and mechanical complexity ivolved.

Of course, if you are confident to proceed, we will all try to help - even though it would be far easier for any of us if we were there with our own hands on it.

Meanwhile, I'll keep reading and cheering for you. I hope it works out.