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[ajmogis]

I'm having a problem with ATR tape on a Studer A800.  The tape is skewing down on the move sensor roller.  In play mode the tape is buckling out a bit on the bottom edge where it wraps on the roller and it's visibly dragging and squeaking on the tension arm side of that roller.  The weird part is that all other brands of tape work just fine on this machine.  I've checked to see if maybe this was a slitting error in the tape, but when I flip the tape over it is still skewing down on the bottom edge of the move sensor roller.  We've got another A800 here and it is handling the ATR tape just fine.  I've also tried several different batches of ATR tape and it's all doing the same thing.  I've talked to Mike Spitz a couple of times about this and he's doing his best to help me out, but I honestly don't think it's the tape that's the problem.

Here's what I've done so far:

Checked and adjusted the

[Larrchild]

Have the 4 pinch roller sections been off for cleaning lately and not returned in their original order? This is common.

[ajmogis]

The pinch roller segments get cleaned regularly, but they stay on the machine.  This behavior started when we tried to run ATR tape on the machine.  I've since tried shuffling the order of the segments, I've tried inverting them, and I've tried multiple combinations of those two things.  The machine still handles other brands (Quantegy, RMGI) just fine.  The owner of the studio wants to use only ATR because Quantegy isn't being made anymore, and we've had some really ridiculous trouble with shedding from the RMGI stuff.

[Dave Hecht]

Several things to check. First, are the puck sections still pliable, but not sticky? Some cleaning solutions will dry out the puck, or cause damage to the surface. You might try swapping pucks between the 2 machines as a test ( mark the insides w a sharpie to keep the original order). Forget the factory tension settings, I've found the best setup ( assuming the rest of the transport is set up correctly) is 310 gr supply side, 375 gr take up side. This is slightly lower than stated in the manual, but I've found no loss of performance, lowers wear on tape and heads. Have you checked all the bearings in the rollers in the tape path? Check the condition of the surface of the tach roller? Sometimes they get smoothed out and need to be roughened up a bit. A couple of spins through a piece of emery cloth works for that. Last thing to check is height of the elements in the tape path. Proper way to do this is with precision gauges and reference block from Studer( no longer made), although I would expect all tapes to skew to some degree if the heights are off. If you don;t have the guages, you can try adding / removing a shim under the roller to slightly change the height, noting whether adding or removing improves the situation, and fine tuning shim thickness ubtil problem is cleared.

Dave Hecht

[slothus]

What Dave and Larry said but also I'll add I'd beg, borrow or steal a set of Studer gauges, life's too short.

One thing that can be useful is running the machine in play without a headblock on. This can magnify any skew issues around the capstan/pinch roller clamp and also help determine if head zenith is a contributing factor.

One thing I do to determine if the clamp is working as it should is to listen to the demod output of a flutter meter whilst tapping and buggering around with the tape path on the take-up side of the machine. If you have any slippage(shiny capstan or dirty pinch roller) then the flutter filtering capacity of this mechanism is greatly reduced and points to less than optimum performance. This can also lead to tape skew issues very quickly.

I presume this is a machine without a Gizmo mod(gold guide)? The only way I could get one A800 to play nice with GP9 was with an Athan pinch roller and a Gizmo.

And clean the pinch roller again. And again. Then buy an Athan.

Brent Punshon

[ajmogis]

Brent,

Thanks for mentioning head zenith.  I swapped the headstack from the good machine and sure enough, the skew was gone.  The original headstack is the old wide spaced design with split erase heads while the headstack from the "good" machine is the new more compact design, if that might make any difference.

My initial guess would be the top of one or both of the heads is kicking out just a bit too much.

Does anyone have any tips/tricks for adjusting the zenith?  I've never made that adjustment before.

[slothus]

Maybe, maybe not.

What's the wear pattern showing on the heads? What about if you sharpie/chinagraf the heads. Same wear pattern? What's eyeballing across the heads show?

Brent

[Larrchild]

Because there is no fixed guide between the headstack and pinch roller, height of tape path is highly dependent on those puck sections pulling in a straight line. Even backing differences between tape stocks could alter that a little.
If the tape stock that Was working runs down the middle of the head, with just the edge grooves appearing, while the troublesome stock doesn't,  I'd be reluctant to mess with zenith.

[slothus]

I'd agree with that. The bigger issue is frigging with zenith without a known relationship to the reference plane of the deck. The gauges give you this. Eyeballing, rocking the blocks and trial & error don't.

The problem with tape path alignments is due to the electro-mechanical complexities of the entire mechanism (not to mention contributing  variables of tape stock) you often need to suspend logic somewhat. What appears logical at first can prevent you from continuing the search and finding the real cause. The old chestnut of correctly diagnosing problem A by unintentionally creating problem B in an attempt to rectify problem A.

In this instance you're dealing with headblocks of very different designs so it's not an apples/apples behaviour comparison.

Like Larry keeps mentioning, I'd still be considering the pinch roller. Those 4 tyre jobbies are notoriously unstable.

If you really do find you need to tweak the zenith without gauges you'd need to be prepared to screw it up and send the thing off to JRF or the like.

Not trying to tell you how to suck eggs btw, just worth mentioning always...

Brent

[Larrchild]

Yep. Not saying it's not zenith. Just saying that altering the position of it is a big big deal to undo. Makes you want to exhaust all other possibilities first.
Aluminum changes dimensionally much less over 30 years than rubber does,lol,  so logic says start there.
Then there is puck pressure. Add a little with your finger and see if things change wildly.

[Gold]

Is there anything unusual about the Studer gage blocks or will a standard metric set do? How many 0's before the 1?

[slothus]

Ok, third attempt at a reply over the past 24 hours. Dunno if it's my connection or the website or what but I waffle on, press send and the sites gone offline with nothing in the cache...

Paul - The reference gauge is nothing special - 41.05mm in height (representing tape path reference height from the milled reference plates on the deckplate). The early version was cubic, the latter cylindrical. I've had both and the cubic one is the better design.  

On top of this goes the 'tape guidance gauge' or 'head alignment gauge' . Essentially a precision milled rectangular gauge with a fine double beveled edge. There is a version for each tape width. This allows setting height and perpendicularlty of most tape path components and checking head height and zenith (with the headblock on a glass plate).

There are pics and descriptions in the MCH manuals that probably help this make more sense.

There were a few other gauges as well, for tension and cut in and the like. The cut in one is quite obscure actually, it took me a good few years to work out how the damn thing was supposed to be used. Thankfully the same thing can be achieved with a straight edge.

No doubt plenty of people get/got by without these just fine in the real world. But if you want to preserve the precision Studer built into their transports (and minimise tail chasing) they are indispensable. Bad news is they cost a fortune (if Audiohouse still have any).

Brent Punshon

[Gold]

Thanks, I was hoping a McMaster-Carr order might get me close. It doesn't look like it though. I'll try Audiohouse.

[slothus]

Wow, McMaster-Carr where have you been all my life!

Brent

[sodderboy]

Golly, you miss a lot here in a week sometimes!

Maybe I missed it, but did you try playing the tape upside-down?  That is the way to ID a bad cut from the mother roll, and can reveal other tape vs. path issues.
Mike
PS: luv the Athan replacements for all Studer pucks.  Just did some A820's and they breeze again.  Tightwad owner waited until the green pucks cracked at the brass. . .