[GreenKeys] TU-170

[Duncan Brown]

John,

For something of the age of the TU-170, it is not likely that they used 
an active current limiter.  Somewhere in the loop circuit, you will need 
a 2K, 10 watt, power resistor to limit the loop current to 60 ma.  If 
there is not one in the TU-170 (hard to miss) then you will have to add 
one externally, in series with the TTY.

Good Luck & have Fun

Duncan
K2OEQ

On 10-May-20 15:00, John, W9DDD wrote:
> Good afternoon all,
>
> I'm expecting a TU-170 to arrive here Wednesday.  I managed to find a 
> copy of the manual on-line.  So I'm checking what the connections will 
> be and I'm a bit confused about the loop supply connections.
>
> I appears to me that they expect a loop current setting resistor 
> external to the TU-170, but I don't see that referenced any where in 
> the manual.  It doesn't appear to me that MJE340 is operated in a 
> current limiting mode, but then I took that course last century and 
> forgotten anything past Ohm's law.
>