[GreenKeys] TT-4C start-up progress

Sat Jul 14 21:05:29 EDT 2012

Greg,

Sounds like you are making progress!!

Before operating the units, make sure that the shipping locks are 
removed (para 2-6 in the -12 manual)

As Steve stated, you need a "loop supply" or "Battery" to control the 
printing.  Some TTYs include a loop supply, but the TT-4 did not.  It 
relied on the equipment it was connected to (wireline modem or "radio 
modem" = Terminal Unit = FSK converter) to provide the current to 
operate the "Selector Magnet" (dual solenoid on the left side).  With no 
current in the Selector Magnet (meter on the front panel reads zero), 
the unit will "run open."  You can simulate the selector magnet being 
energized by gently pushing up on the back end of the lever (armature) 
with your finger.  This should stop the "tat-tat-tat". By quickly 
releasing and then pushing up on the armature repeatedly, you should be 
able to get the machine to cycle and print some random characters. You 
need to do this quickly - you are simulating 22 millisecond pulses.  
This is a simple test to show basic operation when you don't have a loop 
supply.

The Loop supply should be about 120VDC and be able to supply 60 ma. Put 
an ohmmeter on terminals 3 & 4: it should read about 2000 ohms. If not, 
adjust the "Line Increase" control on the front panel.  Now when you 
apply 120V across the terminals 3 & 4, the current will be I=E/R 
=120/2000 = 60 ma.  Figure 2-7A shows the typical hookup for two 
machines.  For testing one machine, just jumper terminals 1 & 4.  
Remember, everything is in series (loop supply/battery, keyboard, 
selector magnet, Break key). When you get to the point of having another 
signal source (eg ITTY), you will need to key the loop with an 
optocoupler or fast relay by putting it in series with the loop also.

Don't worry too much about the motor speeds now.  The TTY signaling is 
asynchronous, though the motor speeds have to be somewhere near the 
same, especially on a noisy circuit.  But for test purposes and with a 
good signal, some speed variation is acceptable.  I have copied 67 wpm 
signals with no problem on a 60 wpm machine ( going the other way might 
not have worked as well)

To adjust the motor speed, first you need to get the knack of the tuning 
fork. You hit the palm of your hand with it and then look through the 
slot at the running motor.  You should see three blurry spots that are 
rotating slowly in one direction or the other.  The idea is to get the 
spots to stop moving.  You do this by grabbing the white shaft sticking 
out of the motor and pushing or pulling it to change the motor speed to 
where the spots stop moving. (a very slow drift is OK)

Have fun,

Duncan

On 13-Jul-12 23:12, Greg Arnoldussen wrote:
> I spent most of my nights this week cleaning the first of my two 
> TT-4Cs, serial number AW-176 (with the other being AW-247).  I chose 
> the one with the surface corrosion - a white crystalline deposit which 
> was removed using fine sandpaper, a toothbrush and simple green, 
> taking care not to allow any of the debris to fall into the mechanism, 
> where possible I wedged in a cloth underneath to help.  I decided it 
> was far better not to take apart this machine to the point where I 
> could have trouble getting it back together again (even by following 
> the manual).  I still have more cleaning to do.  The removal of the 
> paper guard on the rear really helped with accessibility.
>
> This machine is already well greased but I oiled the felts and turned 
> the motor by hand and all of the components respond without complaint. 
>  The fuses seemed OK.
>
> I purchased a 240 to 115V transformer and plugged in the machine, the 
> earth strap is designed to connect to a wire which ends up connected 
> to a post in the ground (for Army field use) but as the best earth I 
> could use is the earth pin of the socket itself I have used that.  It 
> is not pretty but it does the job for now and I will have to purchase 
> modern proper US style plugs (retaining the original plugs of course).
>
> I switched on the unit with no effect.  I tried the break switch with 
> no luck.  I tried striking some keys and no good.  I put the cover 
> back on to see if the light worked and yes it did, so that told me 
> power was getting in.  Nonetheless, I still could not get the motor to 
> work.  I replaced a fuse without luck.  I removed the TT from the base 
> and turned it carefully onto its side to remove the electronic circuit 
> cover at the rear.  It is amazingly clean as if it was made yesterday. 
>  Nothing looked leaky and cables were not loose.
>
> Last night my electrical engineering friend (a very cluey guy)came 
> around and after an hour or so worked out the relay beside the bell on 
> the right hand rear corner of the machine was open, its normal state 
> is closed.  When we closed the relay and started the motor everything 
> fired with a steady "tat, tat, tat" noise.  This is good!  We tried to 
> understand why the relay was open.  The only way to close it was by 
> hand, and we figured that either (a) the machine had been 
> decommissioned and this was a safety step or (b) a remote TT had 
> opened the relay and only a remote TT can open it again.  Personally I 
> thought the BREAK switch should engage the motor as stated in the 
> manual, but it did not work when I tried, perhaps someone might know? 
>  I struck a few keys but nothing typed, maybe this has something to do 
> with the armature setting or jumper settings. Despite reading both op 
> and service manuals it is still a whole new world to me and I have to 
> remind myself I am dealing with fifty year old technology!
>
> I do not want to run this machine too much yet before I am confident 
> everything is working internally with grease and oil. So I am now 
> going to go over the lubrication schedule next and to synchronise the 
> motor with the tuning fork (I am have trouble with this, I think the 
> procedure requires a fairly fine turn of the screw).  All in all a 
> very successful week.
>
> PS.  Where do you guys source rolls of  paper from?  I got some 
> strange looks from the office supply shop.  Fax paper is not the right 
> paper I told them.
>
>
> cheers,
>
> Greg in Wangaratta.
>
>
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