The Museum of HP Calculators

HP Forum Archive 14

[ Return to Index | Top of Index ]

HP-67 read/write head
Message #1 Posted by Jon on 10 Dec 2004, 7:09 p.m.

Hi everybody:

I have an HP-67 that writes but doesnīt read. I think that it is a problem of the head. Sometime ago I read a post regarding the test of this head. I remember that it was tested with a voltmeter. Does anybody know where can I find that information?

Thanks in advance

Jon

      
Re: HP-67 read/write head
Message #2 Posted by Randy on 10 Dec 2004, 8:15 p.m.,
in response to message #1 by Jon

How do you know it writes properly? If you've tested the recorded card in another unit and it works, that problem is usually caused by a bad bypass capacitor across the motor.

You'll find LOTS of postings on the subject in the archives, the easiest way to start is to search for posts by David Smith and Tony Duell. Tony posted an article on 67 internals here: http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/articles.cgi?read=394

At the bottom of the article, he lists the color coding of the head leads, each winding measures typically 50 ohms. If one is open, it will not write properly which lead to my opening question.

            
Re: HP-67 read/write head
Message #3 Posted by David Smith on 11 Dec 2004, 10:14 a.m.,
in response to message #2 by Randy

The bad cap is not the one across the motor. It is a small blue dipped tantalum cap usually located at one end of the reader board chip.

                  
Re: HP-67 read/write head
Message #4 Posted by Jon on 11 Dec 2004, 10:24 a.m.,
in response to message #3 by David Smith

Hi:

I am afraid that the head itself is damaged. I can read 50 ohms in blue-orange wires but the red-yellow widing is open (I donīt measure any value with the voltmeter). Bad luck

I have some HP-41 card readers and I see that the head is just the same. It seems to be glued to the plastic holder. Has anybody tried to use one of those heads in a HP-67?.

Regards

Jon

                        
Re: HP-67 read/write head
Message #5 Posted by Gordon Dyer on 19 Dec 2004, 6:47 a.m.,
in response to message #4 by Jon

When I had the same problem with my HP-41C card reader I used an old broken reader with a good head assembly and swapped it over. Gluing in a head from another machine will be difficult because of head alignment, but worth a try if you have no alternative. I don't know how easy it is to remove the old head from its base, but make some sort of marks on the base or a template before removing the old head to help align the new one. Good Luck!


[ Return to Index | Top of Index ]

Go back to the main exhibit hall