[GreenKeys] [Bulk] TT-4C We have action!

[Jack]

Greg,

 

Good job! There's a lot of us Greenkeyers who have been following your

initiation into the wonderful world of TTY's!

 

Jack K0TTY

Kansas City, MO, USA

 

 

 

From: greenkeys-bounces at mailman.qth.net
[mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of Greg
Arnoldussen
Sent: Sunday, July 15, 2012 8:56 AM
To: greenkeys at mailman.qth.net
Subject: [Bulk] [GreenKeys] TT-4C We have action!

 

With the assistance of my friend we managed to "manufacture" a DC
voltage of 105 VDC for the loop supply.  The transformer we had handy
had the choice of inputs of 400V or 230V and outputs involving
combinations of 55 and 60V on two windings.  By hooking in 240 VAC to
the 400V input we then chose 60V + 60V on the output and used a large
capacitor with diode to rectify to DC.  As I have since learnt, AC is
quoted as RMS but DC is at peak current and the difference between the
two is about 1.4.  Therefore 120 VAC is not the same as 120 VDC, it is
actually closer to 170 VDC.  Therefore, as the mains 240V was going
into 400V that was a factor of 0.6 so that brings 170 VDC back to
about 100 VDC.  Indeed, when I measured the output it came to 105 VDC,
not quite 120 V but it seems to be OK (read below).  If required we
can re-configure to achieve 140 VDC but I thought to play it on the
safe side.  Also the breadboard is safely housed in a plastic box, and
the transformer has no exposed wires.

 

Upon connecting to terminals 1 & 4 I got nothing on the milliammeter
despite turning the line knob, yet the multimeter was reading 105 VDC
across them. Yes I had blown a fuse.  Just in case the original fuse
had been blown previous to me buying the machine I tried another (250
V 0.12 A) and it blew too (these fuses have a very fine wire and it is
quite difficult to see - checking with the multimeter resistance
confirms if it is OK).  At this point I measured the rheostat attached
to the line increase knob and worked out that at maximum resistance it
read 2500 ohms which was exactly correct.  Just one problem....silly
me had the knob turned fully clockwise and effectively offering no
resistance!  This is why fuses exist - to stop idiots like me blowing
things up!  I know a few people here on greenkeys have already told me
to do the exact opposite of what I did, including the manual, but for
some reason I took "line increase" as an increase in resistance.
Nevermind, I still had an extra fuse so THIS time I turned the line
increase knob fully COUNTER-clockwise, turned on the loop supply and
slowly backed off the resistance by turning clockwise.  Low and behold
the needle on the meter started rising and I stopped it at 60 mA with
the switch to "DC".

 

At this point I started the motor and the TAT TAT TAT noise ceased
with just the (much quieter) whirring of the motor left.  I set the
range to 65 and adjusted the armature until I could get the keyboard
to type.  It all works perfectly!  Every single key works including
the BELL and STOP key.  The BREAK key starts the motor after pressing
STOP.  The only thing I noticed (and this may be because it has been
so long since I used a manual typewriter) was that it felt a bit
clunky - I doubt I could type as fast on the TT-4C as I can on this
laptop, however because the pictures in the manual are very difficult
to see there is a good chance I have not fully lubricated every
component.  I have also tuned the motor.

 

So all in all a very productive weekend.  After completing the clean
up and lube of both machines I will hook them up and see if I can get
them to communicate.  The final step will be to connect to the PC and
supply a feed when I have an appropriate interface available...I have
already had a lot of emails from everyone concerning this and I will
be relying on more advice in time to come as I can see this as being
the most challenging of all.

 

Thanks to everyone for your help this weekend (Steve, Duncan, Don, Jim
and anyone else, my apologies if I have forgotten anyone).  Much
appreciated, thanks again.

 

Greg in Wangaratta.

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