Demux 48

[KidNation]

my demux battery leaked on the PCB but at the time it was still working. i cut out the battery and cleaned up the mess and now the screen is stuck on 12. does the demux need a battery to function? thanks

[kgallen]

Yes it does since the battery regulates the voltage to the static RAM chip, whose supply will otherwise rise to around 15V when it should be 5V.

Also you'll probably find that at least one of the PCB tracks under the battery has been eaten away so you'll need to reinstate the connection with some mod wire. Sometimes if the damage is bad these can be unrepairable though. Depends if you caught it quickly enough.

There are some threads from me or Ian Knight on this somewhere on this Forum. I'll try to find...

If you want a repair considered, then Ian is your man for this kit: http://www.serviceguy.co.uk/zero88-legacy-service-repair/

 

ETA: See this one for a start:

 

[iank99]

Kevin's correct - the acid seems to creep along under the solder resist - depending how long the old battery was left in-situ, the more damage has likely been done I'm afraid.

There are some fine tracks near the power supply molex on the main board that seem especially susceptible to corrosion - I had to scrap a Demux 48 because too much had been eaten away and it wasn't worth the time to try and get it sorted