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Martin MX-4 scanner issue

partyanimallighting

Oct 22, 2012
330
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Oct 22, 2012
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330
Hi wizards, I need a little feedback on an issue I'm having with a Martin MX-4 scanner. I acquired four of these very old discontinued units (Circa 1999) and each one had issues that I have resolved after troubleshooting them one by one. The major issue I've encountered was malfunctioning TILT motors caused by faulty drivers but I resolved this by removing the old ULN2803A drivers and installing new drivers on new IC sockets. If the problem re-occurs, it'll be a simple swap out in the future. One unit however, has me baffled. I've gotten functional PAN, TILT, COLOR and GOBO but the SHUTTER continues to act erratically. So far I've done the following:
1. Replaced all ULN2803A drivers
2. Removed the SHUTTER motor, opened it up and checked but there are no visible problems.
3. Swapped out the SHUTTER motor with the COLOR motor (all the motors carry the came number) and the COLOR functioned fine and the SHUTTER problem continued.
4. Checked all six leads on the SHUTTER motor wire harness for continuity. All fine.
5. Checked all solder traces on the PCB for continuity from the motor terminals to the ULN2803A drivers, then from the drivers to the ATMEL AT90S8515 microprocessor and all the traces are fine.
Having done all this, all that's left for me is to assume that the microprocessor is faulty so I'll have to source a new (secondhand) PCB. Hence I'm throwing this out there for you gurus to take a look at before I commit to trying to replace the PCB.

Any feedback will be greatly appreciated.

Party Animal!!Martin MX-1 PCB 004.JPG Martin MX-4 Schematic.jpg PCB Terminal Layout.JPG
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
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Jan 21, 2010
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25,510
Presumably you've traced the shutter control back to a pin on the microcontroller.

There is a small, but finite probability that this lead of the microcontroller either wasn't soldered, or the solder joint had fractured.
 

kellys_eye

Jun 25, 2010
6,514
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Jun 25, 2010
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6,514
Change C116 (10μf) - decoupling straight across the μP power lines. Could be transients causing it.
 

partyanimallighting

Oct 22, 2012
330
Joined
Oct 22, 2012
Messages
330
Hi (*steve*), I traced the lead from the shutter control from the harness pins back to the ULN2803A driver pins with the driver installed in the IC socket from the top of the driver pins with good continuity. The same goes with the leads from the driver back to the microcontroller. Good continuity there also. kellys_eye, I changed the C116 and this didn't resolve the issue either. Microcontroller issue??:confused:
 
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