[GreenKeys] Re: teletype M33
gil smith
[email protected]
Mon, 01 Jul 2002 22:10:04 -0700
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)
;-----------------------------------------------------------