Diversitronics Luma Power strobe 3000w strobe light No DMX

[Ed Kaz]

Hi,

 

     I have 3 Luma Power strobes that do not respond to a DMX signal. I think the DMX chain had a "Master/Slave" switch set to Master and not a DMX channel and blew something out in the strobe?

I was wondering if it is worth fixing and where one can (if possible) find parts? 

Thanks

Ed

[indyld]

Worth fixing, if the ancient Atomics that I'm still keeping alive are anything to go by.

I don't know the unit, but if it's a single board like the Atomic then you are looking at component level repair or a replacement board. I've no idea if you can get the latter but a call to the local distributor will probably tell you.

[timsabre]

Unlikely that incorrect master/slave would cause this but it's not unusual for a DMX receiver chip to fail (in general, I don't know this fixture either) . There are only a few types of chip used by everyone, the usual device is an 8 pin RS485 transceiver 75176 or SN75176. It's usually easy to locate by tracing the incoming DMX signal. Spares available on eBay or from Farnell etc

Edited November 12, 2021 by timsabre

[indyld]

As Tim mentions, it's not unheard of for the 485 chip to fail with or without intervention. One way that they get killed is by someone confusing the DMX chain with the audio or comms system and the result being significant DC voltage on the signal lines. 

 

[Tomo]

In a lot of fixtures the DMX transceiver chip is an 8-pin DIP in a socket, so dead easy to swap - just make sure you get it the right way around!

There are a few different types, so best to replace like-with-like.

Usually something like £2-3 from Farnell et al.

[Ed Kaz]

I took one of the strobes apart. There is only 2 socketed IC on the board. Would the MC3405OP the chip I am looking for???

[Tomo]

Yes. Technically it's an RS422/423 driver, but for receive there's basically no difference.

Check it's got power first, though - I'd suggest pulling it and measuring between pins 16 (VCC) and 8 (GND), should be 5VDC.
If that's failed then sort out the 5V rail first!

[indyld]

That Motorola chip is a transceiver, am sure the boffins here can give you some more details about the circuit design.

 

With my diagnosis and repair hat on, you have not yet described the details on what the unit DOES do in order to eliminate other problems. So, before sourcing and fitting a new chip (if you have some working units, you can always swap it out from a known good one), I would just confirm that there are not any other symptoms that lead a path to a wider fault.

And also check Pin 16 has a supply voltage and that pin 8 has a ground connection.

 

Edit: Ha, Tomo beat me too it.

Edited November 13, 2021 by indyld

[Ed Kaz]

Thanks for all your help !

Voltage good....Ordered replacement chips to try.

 

Ed