82161A Mini cassettes



#7

Hi,

As all of you 41'ers probably know, such scarcy item are really difficult to find (even impossible if you don't have an oversized budget)... the last 3 I saw on e-bay were offered at $25 each (no sale).

I've got 4 non working of'em and would like to know if anybody has found a suitable magnetic tape to rewind it.

I've found out that the shell is fairly easy to open without severe damage, though this is no allways needed to "refill" it with new tape, unless the original tape has been broken inside. Apart from that the rest of the task is simple: cut a 24m long magnetic tape, make two centered and small (<1mm) holes 20cm away from both ends, and join the ends to the leading celluloid tape with standard (prefferably thin) adhesive tape. That's the theory...

The question at this poit is: Which brand-model cassette type is suitable for managing the magnetic density grade required by the 82161A's read/write heads?

I'll start testing this weekend and will tell the results in here... Unless some of you has already found a good answer and share this info with me/us.

Again thanks, and have a very nice weekend!


#8

I rebuilt some with some tape from some surplus tape cartidges that looked a lot like DC100's. They were not marked with any recognizeable markings. I would try using some of the lowest density data tapes I could find with a matching tape width. More modern tapes use a harder to magnetize media. I have also heard of success using mini-audio casettes but have not tried them.

#9

Most of the time the problem with these cassettes is not the tape, it's the pressure pad. This consists of a layer of felt on top of a foam pad, and the foam decays with time.
I wrote an article on repairing this fault (and other faults I'd found with the cassettes) for Datafile (HPCC club journal). I'd be happy to e-mail the LaTeX file for this article to you, or upload it to a suitable site.
As regards a source of tape, it's the same width as normal compact cassette tape (a normal audio cassette splicer is ideal for rejoining the tape to the leader in the 82176 cassettes). Waht about trying the tape from some of those
digital cassettes that were used about 10 years ago?


#10

Hello,

Thanks a lot David and Tony for your comments/suggestions. BTW Tony, it'll be very interesting to read your previous experiences and comments about the issue, pls e-mail me when you can.

As I promised, here comes the results of my "Tape experiments":

Regarding the length of the tape, I used my audio tape recorder timer to count the 8min 44sec. needed for the task.
This is the result of calculating how much time a standar tape recorder needs to run 24'384m (80feet) between the holes, plus 2 x 25cm extra tape to reach the leaders at both ends.

I've also wound the old defective HP tape into a standard audio tape shell... and of course played it!! The saturation is farily high >+8dB!!
(I'm sure that my neibourghs' son is still wondering where the hell have I got this amazing new beat!!!! ;-)

Then conected an oscilloscope to the phones output and took a look... It's a 1'85Khz. (approx.) carrier with phase/amplitude modulation, as stated in the 82161 manual, separated in brusts and silences of 1'16s/0'6s ratio (approx.).

Translating this into 82161's read/write speed of 9inches (22'86cm) it results in a 8'9KHz (approx.) carrier. Those are "approx." due to the 82161's constant ANGULAR speed while standard audio tapes runs at 4'75cm. constant LINEAR speed.

I decided to made my first attempt with a CrO2 TDK tape as I assumed a standard FeOxide tape would have some difficulties in handling the required saturation level and Metal tapes trend to be highly abbrassive.

Cutted the tape, made the holes in their corresponding places with a 0'8mm drill bit, taped the leaders, wound it back into the HP Mini Cassette shell and insert it into the drive.

NEWM 256.... and... IT WORKS!!!!!!!!!! ;-)

Some WRTP's, DIR's and READP's to make a first reliability test and everything seems to be OK.

Hope this help someone to recover his/her old (and unusable up to now) Mini Cassettes.

Thanks again and bye for now.


#11

I've just sent you the article by private e-mail. Feel free to post it on a web site etc.
Thanks for the info on using normal CrO_2 tape in these cassettes. If I ever get a cassette with damaged tape I'll give it a go.
I wonder if the tape hubs could be made from the ones in mini- or micro-cassettes? If so, then you could make up some 'tapes' using such hubs and audio cassette tape, and then load them into an HP cassette shell, and then read/write them in the 82161.
This would not be very convenient, but it would be better than having no tapes at all.


#12

I've just received and red your article Tony, a good job I must say, and plenty of ideas to fix the cassettes. Really useful.

I'm of course trying to get an 9114 Disk Drive, but they're also quite scarcy... I'll keep on seeking.

Regarding the question about using commercial micro-cas hubs I can tell you that it is not possible as the holes (whit the six inner pins) is much wider then the ones in the HP 82176 so they wouldn't even engage in the drive.

Thanks and regards from the Canary Islands.

P.S. Please excuse me for my grammar "crimes" :-)


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