[GreenKeys] Re: teletype M33

Tue, 02 Jul 2002 07:37:18 -0600

I haven't worked on a 33 for probably 23 years.  Burnt selector magnet driver
boards were typical.  Seems like when ever i'd get a different machine or board,
even it showed the discoloration.  Could be an intermittant there which is giving
false info on down the line.  If it were a 28 i'd probably be looking at one of
the clutches on the main shaft.  WIthout a 33 to even look at, and i haven't seen
one for a long long time, i suspect you've got a good start on where to look.
ALso make sure the print wheel is lined up properly on its shaft or you'll get un
readable characters.  It may need to be taken apart and cleaned if it appears
gummy.  Good maintenance manuals or a good local tech could be of great help
here.  Wish i could remember more.  Also as an added note, most all the
adjustments on the 33 are "bend till its right" types as i recall.  Don't make any
till you definately know what it is your affecting before you bend it.  bend and
pry.   arrrrgggghhhhh.....I hated them things.  28's forever.

Larry

gil smith wrote:

> Hi Scott:
>
> I copied this to the greenkeys teletype email group -- you may want to
> join.  I'll forward any responses to you in the mean time.  I haven't
> looked at the 33 in a while (and I have been swamped lately), so hopefully
> someone on greenkeys recognizes your machine's symptoms.  I'm not sure why
> you would see two chars when a key is pressed, let alone the same two.
>
> Did you do any oiling/greasing on your M33 yet (not with WD-40 I hope)?  If
> not, you may just have something sticking in the mechanism.
>
> I also found un-soldered power resistors on the selector-magnet-driver
> board in my 33 -- it's a shi**y pcb design, with no thermal considerations
> at all.  I did the same thing you did, repair with buss wire and solder.
> This board amplifies the 20-mA input to 500-mA, I believe, for driving the
> typing mechanism.
>
> gil
>
> At 04:10 PM 6/30/02 -0400, you wrote:
> >Hello Gil,
> >
> >I finally got around to trying out that asr-33 teletype that I got
> >back in March ... of course it appears to have a problem. I
> >thought that I would describe what I have done and what I see
> >in the hopes that you might be able to offer me some pointers...
> >
> >The tty powers up ...the motor spins just fine. I can put the tty in
> >local mode and start typing ...but only two characters, regardless of
> >which keys I press, are printed (and because of the ribbon or an
> >alignment issue I can't quite read what the characters are ... just
> >enough to tell that they the same). So the printhead activities when
> >a key is pressed, and the carriage advanced after I turned it on for
> >the first time. But when it got all the way to the right ...it will not
> >return ...it's stuck at the right.
> >
> >I think that's because the actual keys that are pressed are not the
> >actual characters that are getting sent ...including the 'Return' key.
> >
> >I decided to load up the paper tape in the punch and turn it on ...and
> >sure enough, either all holes get punched (regardless of the key pressed)
> >or all but one hole gets punched for some of the keys. Only two ascii
> >patterns appear on the paper tape regardless.
> >
> >In doing some research, I think (but really have little clue) that the
> >problem might be with a little board called the 'Selector Magnet
> >Driver' circuit. It is mounted in an edge-connector socket on the right
> >hand side of the tty ...just under the removable top-mounted plate. It
> >seems that this card drives the appropriate selector 'bits' for the correct
> >character ...but I am not really sure.
> >
> >The card is quite burnt in this ...the parts (power resisters in particular)
> >look like they get quite hot when the tty is running. Some of the traces
> >were lifted right off the board ...and some of the solder joints were
> >disconnected. I repaired the board with heavy gage wire (used some
> >resistor leads) and pretty heavy solder joints prior to firing up the tty for
> >the first time ...but I wonder if the board was somehow damaged. Of
> >course, I'm still not sure that this board has anything to do with the
> >problem that I am seeing....
> >
> >Do you have any recommendations? Am I way off track?
> >
> >Thanks Gil ...
> >
> >
> >Best regards,
> >
> >Scott
> >
> >----- Original Message -----
> >From: "gil smith" <[email protected]>
> >To: "Scott LaBombard" <[email protected]>
> >Sent: Sunday, March 31, 2002 12:52 AM
> >Subject: Re: teletype M33
> >
> >
> >> Hi Scott:
> >>
> >> At 07:02 PM 3/30/02 -0500, you wrote:
> >> >...I have several Imsais and Altairs and others ...most
> >> >all of which can talk quite nicely to the asr-33. I'm looking forward to
> >> >getting everything operational.
> >>
> >> I'd love to see some pics;  do you have a web site up?  Never played with
> >> an Imsai or Altair -- my first PC was an Apple II that a few of us cloned.
> >>
> >>
> >> >...do you happen to have working paper tape reader -
> >> >punch ...without an attached/integrated teletype? I think that the correct
> >> >term for what I am looking for is '7 layer' ... or more specifically
> one that
> >> >supports ascii
> >>
> >> I think you mean 7-level, or 7-bit ascii, though the ascii machines from
> >> teletype (33, 35...) could use parity or mark as desired, so the data was
> >> 8-level (ie: 8 holes across the tape, and 8-bits per character
> >> transmitted).  The only 8-level machine I have is a 33asr, with integrated
> >> tape stuff.  I need to fix a thing or two on my 33 yet.
> >>
> >> There are standalone tape-punches like the BRPE, but I don't recall a
> >> standalone reader.  There is an external punch/reader for the M43, but I
> >> don't know what the interface is.  It's pretty compact though.
> >>
> >> In 5-level baudot stuff, I have an M14-KTR keyboard typing perforator, an
> >> M14-TD transmitter-distributor (or tape reader), and an M28-TD reader.  I
> >> can punch 5-level tape with the M14-KTR and read it on the M28-TD.
> >>
> >> You will be able to punch and read 8-level tape on your M33 anyway though.
> >>
> >> Resist the temptation to use WD-40 to lube anything -- it is a
> >> shellac-based gunk designed for water-displacement (WD).  After the light
> >> solvents evaporate, the goop left behind is nasty.
> >>
> >> I use 3-in-1 oil for light linkages, a 30W (or 20W or 10W) non-detergent
> >> automotive oil for heavier oiling, and an automotive lithium grease for
> >> cams 'n stuff.
> >>
> >> Probably a good idea to put a scope on the power supplies -- old capacitors
> >> can dry out and no longer filter properly.  Also look at any power reistors
> >> on the boards;  I found a couple that had virtually de-soldered themselves
> >> (poor heatsinking on the pcb layout).
> >>
> >> gil
> >>
> >>
> >>
> >> ;-----------------------------------------------------------
> >> ;  vaux electronics, inc.             480-354-5556
> >> ;  http://www.vauxelectronics.com     (fax: 480-354-5558)
> >> ;-----------------------------------------------------------
> >>
> >
> >
> >
>
> ;-----------------------------------------------------------
> ;  vaux electronics, inc.             480-354-5556
> ;  http://www.vauxelectronics.com     (fax: 480-354-5558)
> ;-----------------------------------------------------------
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