I have gotten an impression (not backed up by analysis yet) that various models used for CRITICOM applications (intelligence) were fully perforated as well as being 7.00 instead of 7.42. 

Why? I do not know, but the A B C model nomenclature may simply mean different applications and not progressive improvement. 

Nick England K4NYW
www.navy-radio.com


On Wed, Jun 4, 2025 at 9:45 PM Duncan Brown <duncanancy@earthlink.net> wrote:
Daniel,

At least according to the documentation, the Navy used both chadless and full perf on both the TT-192, TT-292 and TT-253 series.  There were modification kits to add the vacuum chad removal, but it is not clear what they were replacing.

What is strange (to me) is that they started out chadless and then went to full perf in later models (TT-192, -192A, -192B were chadless; TT-192C was full perf.  TT-253/UG was chadless and A-D models where full perf.  TT-292/UG was chadless and TT-292A was full perf.)  Does this imply a problem with the chadless tape?

Interesting that both of our TT-253As are chadless, although the LPRs could have been changed out at some point. What model reperf is in you TT-253A?  I have a LPR13XXX in mine.  i can't find anything about it.

73,

Duncan
K2OEQ


On 6/2/2025 11:49 PM, Daniel Jones wrote:
I wonder if the navy used both Chad and Chadless in these units.  My TT-253A has the chadless Reperf.  

Looking at the case I wonder how they dealt with the chads in units with the full punch.  

If you need more print heads let me know I have 50-60 still on hand from the batch I made a couple years ago and I can throw a few in an envelope for you and send them your way.  

Daniel

Daniel



On Jun 2, 2025, at 19:54, Duncan Brown <duncanancy@earthlink.net> wrote:

 Is there a document that lists all the different M28 reperf "LPR" models and  what is different about each?

I'm working on a TT-253A (thanks to Nick!) that does not have a standard reperf in it.  The TT-253A is supposed to use a LPR53AWA (full perf, tape feed out, backspace).  What is in this unit is a LPR13XXX (chadless, tape feed out, no backspace). The unit punches fine (after I re-hooked up a spring in the Selector Magnet area), but can't check the printing yet due to missing print hammer (one on order from Nick).

In checking out the "Tape feed-out" function - the tape feed-out solenoid operates (and buzzes) and the ratchets turn but no tape out. I think this is the version that tape-out is suppressed by incoming message (there is an arm going up towards the SM armature), but can't see why it is not releasing the function clutch when running closed.  

Also confusion between different manuals about whether the tape feed-out solenoid is supposed to operate on 115V AC or 115V DC.  1963 vintage manuals (eg NAVSHIPS 94456) show TT-253A using LPR53AWA reperf with solenoid L5850 (TC # 274); 450 ohms; 115VDC. Wiring diagrams show the LTRK5 base with a series resistor & diode and parallel capacitor to supply the 115VDC. But this LTRK5 base has the resistor & diode replaced by wires and the capacitor removed.  

I thought that the removal of the 115VDC parts could have been a later modification. (Besides the change of LPR unit, this TT-253A had the power & signal lines soldered directly to the blue Amphenol 16 contact ribbon connector!) (I've ordered the mating connector)

Then I got a hold of the NAVELEX 0967-LP-616-7010 (APR 79) manuals and they show the LTRK5 base and LPR53 wired for 115VAC!! 

I'm getting confused!

The reperf in this TT-253A is a LPR13XXX, with a tape-out solenoid #252 and measures 200 ohms and it does not look like any of the drawings in any of the manuals. (Pictures enclosed)  I've read how the tape-out mechanism is supposed to work, but had trouble following it, especially in that my unit seems different from what the manuals are talking about.

When I energize the solenoid, the timing ratchets rotate, but nothing else happens.  I've tried pushing & pulling (gently) the various levers in the area, but nothing trips the function clutch. I'll put in the parts to put DC on the #252 solenoid, but I don't think it will affect the tape-out.

This dissertation was partly just to get my thoughts & facts together, but if anyone has any ideas about the tape-out mechanism, I'd like to hear them.

Thanks,

Duncan
K2OEQ
<LPR13XXX tape-out side.jpg>
<LPR13XXX tape-out top.jpg>
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