Mac500 tilt problem

[aziz]

so due to the lockdown I have plenty of time on my hands so started to go thru the broken pile at the end of the lockup.Started to go through 6 mac500s and now left with two that are not doing anything on the tilt.Motors,wiring and drivers are all ok,checked the current sense resistors and the readings are the same as the ones on the working pan side.Anything else I can check

[IRW]

so due to the lockdown I have plenty of time on my hands so started to go thru the broken pile at the end of the lockup.Started to go through 6 mac500s and now left with two that are not doing anything on the tilt.Motors,wiring and drivers are all ok,checked the current sense resistors and the readings are the same as the ones on the working pan side.Anything else I can check

 

When you say they are not doing anything on the tilt, do they seem to have any power to the tilt motors, or do they just swing in the wind?

[indyld]

Agree to above: more detail needed on the symptoms.

[aziz]

1585142451[/url]' post='581808']

Agree to above: more detail needed on the symptoms.

 

Yeah there is no power to the motors,if I swap the tilt connector onto the pan on the motherboard,there is power and moves correctly Obviously putting the pan connector on the tilt side does nothing.I've seen pan and tilt problems where they don't move put there is power on the motors and others that the movement is jerky and lacking torque

[indyld]

So, if I read this right: Swapping the pan and tilt connectors on the main board points to an issue on the mainboard itself and you have also swapped the stepper driver chips and proved the tilt chip is actually OK? Then surely the next thing up the line is Vcc and motor power to the driver IC, followed by continuity on the logic drive line(s)?

 

Have you found the service manual online for more info? It's there somewhere.

Edited March 25, 2020 by indyld

[aziz]

1585158701[/url]' post='581814']

So, if I read this right: Swapping the pan and tilt connectors on the main board points to an issue on the mainboard itself and you have also swapped the stepper driver chips and proved the tilt chip is actually OK? Then surely the next thing up the line is Vcc and motor power to the driver IC, followed by continuity on the logic drive line(s)?

 

Have you found the service manual online for more info? It's there somewhere.

 

Yeah seems to be a problem on the board somewhere,I'm comparing continuity on the tilt side of things to the pan side,I'm a bit useless when it comes to following circuit diagrams and a bit wary of where I'm sticking my meter probes especially when powered.Reading a old thread here on blue room points the blame on the 1k5 sensing resistors but they appear to be ok.Maybe it's tracking somewhere after corroding as these fixtures were laid up for a long time

[DrV]

The sense resistors should read 0.5 ohms not 1k5. There are four 2r2 in parallel.

[aziz]

1585161915[/url]' post='581818']

The sense resistors should read 0.5 ohms not 1k5. There are four 2r2 in parallel.

 

My old fluke 79 iii isn't the best these days but was showing 0.8 which is the same on the pan resistors

[DrV]

1585161915[/url]' post='581818']

The sense resistors should read 0.5 ohms not 1k5. There are four 2r2 in parallel.

 

My old fluke 79 iii isn't the best these days but was showing 0.8 which is the same on the pan resistors

Close enough!

[indyld]

If you prefer to do dead testing with a MM then I would blip around the stepper driver IC pins in diode mode with red probe on GND. Compare to nearby known-good chip. Motor looms disconnected.

 

It may give you an area to look next. Corosion is a possibility on older fixtures for sure.

[aziz]

Thanks everyone for suggestions so far,will probably give it another shot tomorrow