TTY 33 - Finally - UPDATE

Rick Bensene rickb at
Sat Jul 4 10:58:02 CDT 2015

Happy Independence Day to USA readers, and good day to all others,

I found out what the problem was with the tape reader on the 33ASR Teletype.

This morning I had some time to do some diagnostics.   It appeared that reader trip contacts that are triggered by the cycle clutch were making contact just fine (thanks for the recommendation to check this first). 

However, there was no sign that there was any current flowing through the contacts, and there was no sign that the reader solenoid was activating.  

So, I started backtracking, and found the tape reader power supply circuit board.   There's a 1/2 Amp Fast-Blow fuse on the board that I tested right away.  It was open.  

I inspected the fuse under a microscope, and there was no sign that the fuse was blown...the filament looked intact.  I then found by jiggling the fuse around, it would intermittently show continuity.    There was absolutely no sign that the fuse had blown due to an overcurrent condition -- it was more like the fuse had some kind of mechanical fault.  

So, I grabbed a 1/2 A SB fuse out of my parts bin and installed it, and powered up the Teletype.  Put a tape in it (STARTREK listing from OS/8 BASIC), and started the reader.  It immediately started reading the tape and printing out the program listing.    

Good stuff!

I have subscribed to the GreenKeys list, and am waiting for approval, which probably may take a little extra time due to the holiday.  

I need some ribbons, paper, and a new pad for the printhead hammer, but figure I should easily be able to find pointers to sources for these on the GreenKeys list.

Now to see if I can find out how to make a facsimile of the tape reader control gizmo that DEC used to allow the PDP 8 to control the paper tape reader, so I can get this terminal properly interfaced to the 8/e.   In the meantime, I'm going to hook it up to the Altair 8800 for a little immediate nostalgia.

Thanks to all.


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