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baking TKx0 tapes

czunit said:
As one of the few people on the planet who actually *USES* TK50's and 70's as primary backup media I have a few.... thoughts.

First, the weak point in these units is the capstains. Specifically the bearings have had their grease/oil dry out and as a result they drag on the tapes. More importantly the rear one is attached to a tachometer and it is CRITICAL that it does not drag or slip. If they drag they wear the tape and have massive problems with reading (as speed is sensed by that rear capstain)

So you need to remove them and either oil the bearings with light then medium viscosity watch oil (which will re-grease the dried grease) or press out and replace the bearings. If you spin them they should spin freely and spin for a bit with just finger flicks. If the drag or stop immediately they ain't gonna work.

Second problem is tape height is *super critical", controlled by the turns of the nuts on top of the capstains, and extremely difficult to set. However you can mark each nut and count the number of turns exactly to remove it. Make sure to note the position when it's at rest and just before it comes off the screw. Then turn the nuts back on the exact number of turns/fractions of a turn and the drive is in alignment. How can it be not :)

Note: Make sure you remember which nut goes on which spindle, as the marks will be at different places in the threads on the different nuts. Front nut to front capstain, rear to rear, and if there are washers keep the washers with the proper capstain.

When I get a new tape in I run several backups and verifies on it, then I rewind and lift up the head to check for any residue. If I see any residue I junk the tape, it's shedding. No residue=tape goes into the general population box. Keep an eye on the head and which tapes you use, if a tape starts throwing errors check to see if it's shedding, and if so junk that tape, clean the heads and capstains, then check the last tape you used and see if it's now shedding. Go back till you find good tapes, damage can spread from tape to tape.

With that, they're great. I can do things to my system and if I trash the disk I simply pop in an RX01 floppy with bru64k, then do a restore from the tape back to the disk. Never a problem. Also note, the TK70 controller is a lot better than the TK50 and can usually stream backups instead of the endless start/stop of the TK50. And a TQK70 can be used with a TK50 drive.

Have fun!
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My hat is off to you for being able to get these to work. As someone who used these a lot back in the 1980s, I always considered them terrible. Had many problems with them even when the tapes and drives were brand new.
 
antiquekid3 said:
If one had access to a vacuum oven, I would think that would work very well and would allow for reduced temperature if you pulled enough vacuum, yes? Long enough bake time should help reduce air circulation requirements since the pressure is so low. Any idea if this has been tried?
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I played with vacuum chamber with 2 stage pump for AC since I had that and didn't have a baking setup. I tested it on a sticky 9 track tape. Did improve the tape but think still had some problems. It was a while ago so don't remember how long I gave it but suspect an hour or two. Would be good to have a cold trap to avoid contaminating the oil. Vent hose from pump to outside had water condensation so did pull some out. Didn't play further, got baking setup.
 
I've been thinking about the bake-for-shed issue with tapes. I've been doing that a lot, with varying amounts of success. There are some tapes where the oxide has simply detached from the base and will fall off as the tape is despooled. I don't know of any way around that--baking doesn't help--the oxide has already detached and will not re-attach. But that seems to go way beyond the "sticky shed" issue.

However, one issue with baking (my baking times are long >1 day usually), you still havet the problem of the inner wraps of the tape not being treated as well as the outer ones--they're just sealed in too tight. I've been thinking of constructing a setup where the tape is baked as it's slowly despooled. Perhaps fed through a "hot chamber" of dry hot air, or being heated via a controlled IR source. That would ensure that the entire reel would receive the same treatment--a lubrication via a felt wick soaked with D5 could be done at the same time.

I'll admit that it's just an idea at this point...
 
That was the point of having a lot of forced air being blown up the rims, to try to get to the inner layers. You are still going to have to do some pre-processing step before despooling or the binder on the inner wraps is just going to strip off on tapes where the layers have glued themselves together. You should also be watching the torque of the takeup spool. That is an excellent way to tell how badly the layer to layer binding is. I'm sure you've used the trick of seeing how much the first few feet of tape want to stick to the rest of the reel to gauge how sticky the rest of the reel will be. I have a small portable tape cleaner that I use after baking with the blade covered to repack tapes and to tell how sticky the tape still is by seeing how much the takeup spool slows down as it's repacking and to see how much shed is happening by examining the cloth covering the blade. You're the first person to mention long bake times. Even with the forced air, I still bake tapes overnight.
 
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I suppose another approach might be to cut the top flange off the reel in the interest of getting better air circulation. However, most of my customers want the tape returned, so that's not an option for me. 10.5" tape flanges are somewhat flexible, so propping them wider to allow for better circulation might be another tack. I haven't checked to see the limit of this, but widening the space between flanges to 1" might be possible.
 
antiquekid3 said:
If one had access to a vacuum oven, I would think that would work very well and would allow for reduced temperature if you pulled enough vacuum, yes? Long enough bake time should help reduce air circulation requirements since the pressure is so low. Any idea if this has been tried?
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Yes tried with one tape a few weeks ago (CompacTape I).
The tape lead to black residues on the head, all blinking LEDs on the TZ30 and the VMS responding with "fatal drive error".
I tried (40°C/12h) a second run with (58°C/26h) at 1mbar pressure, cartridge door held open.

The black residues on the head had been cured almost but the data was still not readable.

Dismounting the tape revealed following appearance.

1705850835943.png
 
Al mentioned that he uses extra fans in his oven for moisture control. I bake for extended times with silica gel absorbent in mine. I intend to install a hygrometer one of these days--got one, just lazy.
On some 10.5" open-reel tapes, I did verify that the reel flanges could be flexed out to create a larger gap without damage.
 
I used some 1960s reels as an experiment. Of course, they might be sturdier than later ones, given the run-down in quality in the 1980s.
Bad coatings are bad forever-Wabash is bad news, no matter if in diskette or tape form (e.g. MRX). I do my best, but the air turns blue... :(
 
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