[GreenKeys] TT-98 Issue

[Duncan Brown]

Joe,

I have never seen that problem, but I would suspect the governor 
contacts.  R1 is in series with the motor and is normally shorted out by 
the governor contacts.  Only when the motor is going too fast does the 
governor contact open and put R1 into the circuit (to slow down the motor).

The fact that R1 is smoking implies it is getting too hot because it is 
in the circuit all the time, ie the governor contacts are not shorting 
it out.  '

I would clean/burnish the contacts and check that the "governor" action 
that opens the contacts is working.

Good luck & have fun,

Duncan
K2OEQ

(I just finished replacing the SM Bias selenium rectifier in my TT-98D)

On 22-Jul-22 16:23, Joe Clanin wrote:
> Hi Duncan,
>
> I was wondering if you might have any insight into a problem I am 
> having on a TT-98 I'm restoring.
>
> I have the machine cleaned and relubricated to the point where it 
> copies perfectly, however after running the machine for a short while, 
> the large resistor in the attached photo begins to smoke.
>
> This resistor is used in the circuitry of the governor as depicted in 
> the attached schematic diagram. The mechanical parts of the governor 
> all seem to be in perfect working order. I have replaced the 
> capacitors C1,C16,C17 (see schematic) as an attempt to solve the 
> problem, but this has not helped.
>
> There simply isn't much to the circuit. It should be easy to 
> troubleshoot! I am stuck!
>
> Can you offer any insight into this?
>
> Thanks,
>
> Joe