Martin Destroyer Help...

[Insanity]

I have been given a couple of Martin Destroyers to try and fix for a friend. One of them was an easy fix, the mirror array had fallen out, after a good clean up it's good as new...

The second one is the issue, I think the stepper motor drivers have failed... It starts up and the steppers go to their centers and the bulb lights, but after that, nothing moves with either a DMX signal or through the sound activated mode. It looks like all electronics are all on one board...

So, I was just wondering if anyone has any experience with these? Or knows of a secret hidden stash of these boards cheap

Any help appreciated
Mark

[shrad]

pictures of the drivers would help

especially the H-bridge driver chips if present, their part number should tell if they are of the feeble breed

(they should look like a very wide TO-220-ish housing on a heatsink)

these H-bridge drivers tend to blow an internal diode and usually let the stepper behave erratically

[Insanity]

Thanks for the super quick reply... I thought I would just test the water before I started taking pictures, I'll get some posted shortly...

I'm afraid my electronics knowledge is pretty rubbish, so if it involves rebuilding circuit boards or anything tecchie, then my friend will be getting his Destroyer back as is

Mark

[Insanity]

Here you go, it's not a pretty sight

Mark

[shrad]

ok, the driver in question is the ULN2803 IC next to the stepper connections

according to its datasheet here: http://pdf1.alldatasheet.com/datashe...I/ULN2803.html you can access each internal diode on pins 10 (common cathode) through 17

with a multimeter in diode test mode, you can test each diode by placing the black probe on the pin 10 and then the red probe on each other pin to 17

if there is a blown diode, it will indicate either a short circuit (close to zero) or an open circuit (no measure), and if the diode is good it will indicate between 0.4 and 0.8

if there is a blown diode, you'll probably have to replace the ULN2803 which is really cheap

if the problem comes from somewhere else, you may check the voltage between pin 3 of the voltage regulator and the ground (the regulator is the black transistor-like device with a mounting plate left of the fuse)... if it delivers the same voltage as your working unit the problem comes from the power supply, then we will surely be able to diagnose it

if you feel uneasy about the practice of electronics, no worry, it's easier than it looks, especially because the devices which are most probable of being blown are through-hole components

all you would need to have to work it out, if the problems are simple (and it will suffice in most cases) is a small soldering iron (25~30 watts), a desoldering pump, a multimeter and some 0,8mm solder with resin core

a good exercise for beginner practice would be to gather old boards and try to solder/desolder components to acquire decent soldering skills, then you should be able to replace any through-hole component

if you think you want to give it a try, please tell, I think many people here will be glad to help and direct you in the good ways

[Insanity]

Wow!!!!! Thanks for the detailed instruction, just what I needed

I'll have a look at some point this week when I get a moment....

Thanks
Mark

[heroic]

If you're not comfortable doing it yourself then buy the new parts and take the boards and parts to a local TV repair store- the kind that fixes TVs on site. They will do it for you for a few bucks.