My Evo-8 decided to start behaving exactly as described in the first post here, not powering on and blinking the various LEDs in an unhealthy fashion. I've pulled the circuit board, and am gradually fixing things as I find them.
Most of the connectors on this board have tiny little fuses on most signals, to protect against Bad Things. These little grey coloured devices are all numbered with the prefix "FB". So first I went around checking every one of those, on both sides of the board, with my ohm-meter. Each of them should read zero-ohms, unless the fuse has blown. All of mine were fine.
Next thing to check, if the mount is not powering up, is the +5V regulator which powers much of the on-board stuff. Here it is, component U5 circled in RED:
The one on my board was labelled as a GH18H, which is a version of the AMS1117-5.0 regulator commonly used on all sorts of stuff. You can test it by powering the board from a +12VDC power supply through the DC jack, and turning the switch on. For this to work, the small 2-pin connector from the switch, and the 3-pin connector from the DC jack need to be plugged in. Nothing else has to be plugged in.
The pin-out of the regulator is as shown:
Turn the power switch on. Use a volt meter and measure the voltage between Ground and the +12V pin -- it should be around +12V, but anything from 7.5V and up is fine for now. Mine read about 12V exactly.
Then measure the voltage between Ground and the +5V pin (or the tab), which should read at least 4.8V and no more than 5.1V. If not, it needs to be replaced. Mine read 0V, so I knew it was dead, or there was a short on the output side somewhere. Not seeing any smoke, I figured it was dead.
I have a bin full of that kind of stuff here, so I removed the original regulator and swapped in a regular AMS1117-5.0 in place of it. The mount now powers up, shows the battery charging briefly (it was already fully charged), and the hand-controller mostly works on my mount.
Next, I tried slewing the mount from the hand-controller, and discovered the AZM motor at the base of the mount is not working. So I swapped connectors between it and the ALT motor, and then the ALT motor was not working. So the two motors and their cabling are actually fine, and the problem is on the main circuit board.
The obvious place to look is the L293DD motor driver chip. I could probe the inputs to see if it is being given the correct signals from the onboard micro-controller. If so, then the L293DD will need replacing. Or I could just replace the chip anyway, and then see what happens.. haven't decided which yet.
Edited by mlord, 17 October 2022 - 02:19 PM.