[GreenKeys] Model 14 keyboard adjustment

[Ralph Mowery]

That loop driver may work for some of the ‘modern’ but for the model 15 and older you need at least 75 and more like 120 volts minimum to operate the magnets for the printers. This has been discussed many times before for the reason of a high voltage loop.  The higher voltage does help keeping the oil burnt off the contacts.  The contacts are going to have lots of bounce to them but the bounce is not much concern to the mechanical machines. 

 

The magnet coils have to be wired so they are ‘in phase’  with each other.

 

Ralph ku4pt

 

 

From: greenkeys-bounces at mailman.qth.net [mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of Eric Moore
Sent: Sunday, August 06, 2023 9:06 AM
To: Gerry Block
Cc: Greenkeys
Subject: Re: [GreenKeys] Model 14 keyboard adjustment

 

https://deramp.com/downloads/teletype/Model%2015/loop%20interface%20board/Schematic%20Rev%20A.pdf

 

Verified the printer loop at 60ma. The keyboard loop runs at 15V, not sure on the ma, but not sure it matters much as it just opens and closes without driving any coils or similar.

 

I am fairly certain my issue is the contacts somehow. I see voltage (and continuity) up to those contacts, but despite cleaning fairly extensively with contact cleaner, they are still too high resistance. I am going to try some sandpaper today and see what is what...

 

-Eric

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