[GreenKeys] Model 33 progress (II)

[Brad]

I've finally gotten around to hooking my Model 33 up to a computer (one of
my SWTPC 6800s).  When I left it, I had it mostly working (many thanks to
Wayne!).  A few glitches included one or two characters that don't come out
right consistently (L comes out as M usually, for example), a tendency when
plugged in/running for more than 30 min for output to suddenly become
gibberish (and return to normal after a 1-2 hour cooling period) and of
course my hardened platen which can't move paper.

 

To address the last one, I was looking at something like this: 

 

http://www.mgchemicals.com/products/cleaning-products-for-electronics/cleane
rs/specialty-cleaners/rubber-renue-408a-408b

 

Don't know how you guys feel about that particular one.  Seems like it would
do the job.  My platen isn't cracked or broken, just really smooth and has
almost no grip.

 

I don't have a fix for the 'overheat' problem - I suspect it is the larger
of the two caps in the machine - but I don't have enough skill to test.  I'm
going to order a brand new replacement and see what happens.  Resistors, etc
all seem ok.

 

The character problem seems to be something local.  If I hit L, which to the
SWTPC means Load, the 33 will produce an M but the machine pauses just like
it's supposed to when trying to load something in.  If it were actually
sending an M I ought to be able to start entering a memory address to look
at, but it freezes the console as it's supposed to and I can't do that.
Also, if I run a test program that produces every character the 6800 can
send out, L comes out exactly as it should.  I'm thinking this is just
something sticking in the printer - when it's running a string of characters
at high speed I think it gets just enough momentum to fire out an L, whereas
typing individual characters isn't sufficient.  The fact that the machine
seems to think I'm sending an L even when it prints an M locally suggests
the encoding system on it is working fine.

 

Apart from that, there are some other 'bugs' - my paper tape reader is
missing its power supply (I am ready to buy if anyone comes across one), and
the punch is definitely not putting out everything like it's supposed to.

 

Thanks again to everyone including Wayne who helped previously to get it to
this point!


Brad

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