[GreenKeys] 404 OPM Speed for TT-4/TG

[Duncan Brown]

Pete,

I will check our stock at the AWA (Antique Wireless Association - not 
to  be confused with Amalgamated Wireless Australia) Museum when I am 
there on Tuesday.  I know I have extra gears, but don't know offhand if 
there are any 404 opm gears.

All mechanical TTY machines can receive over a +/- 10% speed variation, 
using the Range Control to adjust when the selector magnet reads the 
data.  So your TT-4 can copy 66wpm with the 368 opm gears (just turn the 
Range control down to about 20), but of course you will need the 404 opm 
gears to transmit 66 wpm.

You could also try increasing the motor speed by about 10% while still 
using the 368 opm gears.  I don't know how increased speed would affect 
the life of the motor or brushes.  But since the unit was designed to 
work 24/7, and as long as you only use it a few hours a day, I wouldn't 
think it would affect its life significantly.

Good luck & have fun,

Duncan Brown, K2OEQ
USASA    31J30

Antique Wireless Association
  Communication Technologies Museum
    Asst. Curator, Commercial Equipment
(also chief TTY op & repairman)

i-Telex: 212503

www.antiquewireless.org

AWA Youtube channel: 
https://www.youtube.com/channel/UCX55peBhzeX1qps_VYXdLBA

Virtual AWA Museum TTY Tour: https://www.youtube.com/watch?v=TpB6jM90VV8



On 3/8/2026 6:17 AM, Peter Leonard wrote:
> Hello all,
>
> I need a gearset for a TT-4/TG to operate at 404 OPM / 66WPM / 50 
> baud. I am happy to exchange a 368.1 OPM / 60 WPM / 45.45 baud set and 
> a 600 OPM / 100 WPM set. The TT-4 manual states that the 368.1 OPM set 
> is normally fitted and the 404 OPM set is held inside the machine. My 
> machine is fitted with a 368.1 OPM set holds a 600 OPM set.
> I am located in Adelaide Australia and am happy to pay parcel post 
> both ways.
>
> Kind regards,
>
> 73 Pete   VK5XP
>
>
> Peter Leonard
>
>
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