[MRCA] ART13 bypassing autotune circuit

[Ian Gallimore]

Please note: my new email address is va3oda at gmail.com

On Mar 16, 2025, at 6:58 AM, Doran Platt via MRCA <mrca at mailman.qth.net> wrote:

> I missed a salient point in the original post. 15 amps far exceeds the total current the transmitter draws at any time. With autotune running, filaments on, relays engaged... about 9 to 11 amps. If the motor is smoking, sounds like a locked rotor situation. Either the motor is frozen or the autotune drive shaft is frozen or jammed. Before proceeding, that must be addressed.  Recall also that one winding is always excited to overcome stiction and to ensure it's operable at altitude (temp).  One mod is to add some diodes so as to excite the motor only during channel change. I think I would be inclined to remove the lower front cover, un- solder both the motor windings and then check the ccurrent.Then, ensure the drive shaft is not mechanically  stuck. Be careful, however, of the motor reversing relay and spring switch behind the PTO autotune assy.  It can be damaged if the drive shaft is turned beyond the normal stop points. 
>   
> Jeep K3HVG 
> On 03/15/2025 10:55 PM EDT JEFF CICCONE via MRCA <mrca at mailman.qth.net> wrote: 
>   
>   
> folks. another ART13 Ive been working on has a bad autotune motor . Drawing about 15 amps, no filaments lit and some smoke coming from the motor. I killed the power right away. Has anyone bypassed the autotune circuit to make the set work without needing the autotune circuitry?  thanks Jeff N2IA 
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