Hi all,
Maybe this is more in the ATM section, but since this thread is active, I figured I'd post here.
I've owned three Tak mounts over the years: EM-10 (sold), EM-200, and an EM-1s. In general, they ROCK! Absolutely wonderfully made. I've taken apart the RA on the EM-200 and one axis on a Tak Sky Patrol... the machining job is INSANELY good. Really better than it has to be. I've taken apart Vixen mounts before and it's clear as day the Taks are machined to higher tolerances.
Anyways, for this post I wanted to share a motor drive rebuild I did for the EM-1s.
I've owned the mount since 2022. I started with a 6" mak on it (about 12 lbs) and as expected it was rock solid. I normally use a 5" APO (~22 lbs with accessories) on the em-200 and always assumed that it would be too much for the em-1s, so I never even tried it. Back in the day when I had the EM-10, which is nominally a bit stronger than the EM-1, I found it just marginally acceptable with the APO at high power.
Inspired by another post here on CN, just last fall I tried putting the APO on the EM-10 for the first time (after having them in the same house for years!). And, guess what, it has been OK! Between 1 and 2 sec damping after a tap at high power. Not perfect, but usable by my standards. It's on a Berbelach Planet tripod, which is probably what made it a bit steadier than the EM-10 on the stock Tak tripod.
So lesson 1: The em-1s on a strong tripod can be a wonderful mount, carrying something like 30% more than the stated capacity of 17 lbs.
Then, of course, just weeks after I made this happy discovery, the old motor controller died. No motion, no LED lighting up. I looked into finding a replacement board, but that seems impossible. Plus, the mount only moved at 2x or 0x sidereal when you pressed the hand controller buttons, which was really testing my patience.
So I did a little research and bought an Adafruit Trinket microcontroller board. It's Arduino compatible and really tiny to fit in the small cavity. Then alongside a TMC2208 stepper driver, I put together a new controller that runs at sidereal by default and +/- 5x sidereal with the hand controller. I would have preferred 12x or 16x, but that's as fast as the motor would turn! The gear ratio is insanely high: 24 steps / turn on the motor x 500:1 internal gear reduction x 2.5:1 external gear reduction x 144 tooth worm gear x 2 microsteps minimum for the TMC 2208 driver. That's almost 7 steps per arcsecond!! I guess Tak REALLY didn't want anyone to see ticks at 1000x while tracking...
I also added an LED polar scope illuminator while I was at it. Also, now it runs on 12v DC with center pin positive like everything else.
I was planning on using the original EM-1s motor housing cover, but wanted to add an on/off switch (the original setup had the switch on the batt pack). So I used some scrap 3mm polycarbonate sheet to make a new window. I wasn't planning on it, but the transparent cover actually allows me to forego the on/off indicator LED, since I can just see the insides! There's a cool purple LED on the Adafruit board itself. At first I wasn't sure this was a feature or a bug, but I actually REALLY like it! Gives it some air of modernity and excitement.
All and all, took a couple of days of messing with it to work, but glad to be using the wonderful EM-1s again.
Clear skies!
Roger