Zero 88 DMUX 48 "012" fault

[spotblaster]

I have been asked to check out a couple of redundant Zero88 DMUX 48's with the hope that one of them can go to a local village hall drama group. They were made in 1999 and had little use before sitting in a cupboard for a number of years.

 

So I changed the battery and cleaned the pcb in the first and powered it up.

 

It didn't do the usual display test sequence but went straight to displaying "012". All the outputs were at 100%. Applying DMX put the "received" led on but no control.

 

So moving on to the other one I changed the battery and applied power.

 

Eureka! This one did the display test sequence ending up on 001. Applying DMX put the "received" light on and the unit worked.

 

Well for a while......

 

Then the display flickered. All the outputs came on at 100% and the display showed - yes you guessed it "012"!

 

This made me think it could be a common fault and others may have had the same thing happen.

 

Anyone else seen this?

 

Any ideas?

 

Many Thanks in anticipation.

 

 

David Ashton.

[DrV]

Have a look at http://zero88.com/forum/topic/7105-demux-48/

 

It's important to clean up any corrosion very thoroughly and check continuity to the SRAM chip as described.

[kgallen]

Yep, as I describe on that Zero88 forum entry you're likely to have a corroded open circuit PCB trace under the battery. If I remember correctly there weren't any convenient vias to solder mod wire to, so unfortunately the best approach is to unsolder the battery and fix the track there before refitting a new battery.

Kevin

[ianknight]

Also...

 

Depending how long the corroded battery has been left on the PCB - the acid can eat along the tracks that run under the battery "travelling" under the solder resist. I've repaired a couple of Demux 48's before now where corroded tracks were a couple of inches away from the battery and needed 'creative' repairs.