Monday, December 11, 2017

Aftermarket Stepper Motors for Icom IC-756 Auto-tuner

This may be old news, but just in case, here it is... I just repaired the auto-tuner in my IC-756 (not a pro version). One of the motors failed. I found a procedure online for repairing the motor, but also decided to try an aftermarket replacement motor. The OEM part number from Icom was MP28GA, and their new # for their replacements is MP24ZA. This happens to be the same replacement part used in some Yaesu auto-tuners, their part # is M2190023. The Icom part costs about $35 + shipping, the aftermarket part is $4.95 + shipping. Looks to be the same part, except that the aftermarket part has a brass output shaft vs. plastic on the OEM. 

This looks to be the same motor used in several Icom HF rigs as well as Yaesu. I bought the aftermarket motor from https://www.adafruit.com , and it is their item #918 and cost $4.95 each. The plug is slightly different, but I was able to slice off a piece of the plastic clip from the socket on the tuner PC board and it snapped right on, but you could simply replace the connector from the original tuner motor...the wiring colors match perfectly. 

There's a great Youtube tutorial on how to repair the original stepper at:

http://youtu.be/UdY6RhNOCWg

 
 Comparison of back side of stepper motors...

 Comparison of front side of motors...

 
 Tuner is under this board...

 Board remove, exposing metal cover on tuner...

 Metal cover removed, stepper motors seen in lower RH side of pic. Remove screws from tuner, lift it up, loosen screws on motor coupling, and replace the motor. Very easy!
 

UPDATE, 2/2/2019:

I got a message from Jim Durham, and wanted to add it in before I lost it. This is a link to a stapper with a 1/64 gearbox ratio, and seems to tune a bit more smoothly than the units I use. Mine are still working fine, but this looks like it might be a better choice. Here's the link:

https://www.amazon.com/Diymore-28BYJ-48-Valve-Stepper-Motor/dp/B01J3KV3B2/ref=sr_1_1?ie=UTF8&qid=1518217311&sr=8-1&keywords=stepper+motor+12+volt+4+phase




Dave WB4IUY
http://www.WB4IUY.net