BA123 Side panels and Stuck TK50

Douglas Taylor dj.taylor4 at
Wed Aug 31 10:10:06 CDT 2016

On 8/30/2016 4:54 PM, shadoooo wrote:
> Hello,
>> The same cabinet has a TK50 and I foolishly put a cartridge into it and
>> now it won't come out.  It is called being 'stuck'.  How do proceed to
>> get this TK50 cartridge out?
> Error 'stuck' means that the tape has been "glued" to the head because 
> of the effect
> of the tape binder being converted to adhesive due to age and moisture.
> You can remove the cartridge in this way:
> - pull the drive out of the machine
> - carefully unscrew the metal cover over the internal reel and the 
> head to expose it
> - slowly insert a paper sheet between the tape and the head, in the 
> same direction of the tape, to detach it without damage
> - slowly rotate the front motor (from bottom side) in way to rewind 
> all the tape from the back reel to the cartridge reel
> - detach the tape leader if necessary
> - now keep the electromagnetic cartridge unlock mechanism pressed, and 
> remove the cartridge from the drive
> A tape in this condition of striction is probably unusable anyway, 
> unless you back it up a little in an oven,
> but even so it could be readable just for a couple of hours

I removed the drive from the MicroVax and took off the metal cover on 
the TK50.  There was about 1/2 inch of tape on the takeup reel and it 
moved freely.
The documentation on bitsavers told me what I should have known in the 
first place.  The Green and Red lights indicate the health of the drive.
When the drive first powers on the red light should be on during a brief 
diagnostic test, then the red light should go out and the green light 
should come on indicating that the drive has passed internal tests and 
is ready.  My TK50 never lights the green light and before I cleaned it 
out the red light would blink indicating an internal fault.
Geez I hate these things.

The Bitsavers doc had a section for bench service and interpreting error 
codes, does anyone know how to get these codes?   Is there a PDP11 or 
VAX diagnostic that reports these codes?  Can you get at them from ODT 
or the VAX console?

I still would like to rewind the tape and remove the cartridge, but it 
looks like a difficult task to rewind by hand.

>> Also, the TQK50 controller never saw the drive and I was wondering if
>> the PROM's (after 30 years) on the board lose their data?
> Well, I never seen an UV-EPROM loose it's data, unless the erase 
> window cover is missing and the memory exposed to the sun light.
> Andrea

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