Demux 48

[djzub]

Hi to everyone!

There is a problem with this device, just recently it has started to behave strange.

When I power up this device on the display it shows 001, after some time lights go crazy and start to flash and on display also digits flashes, afterwords the display shows 012 and all lights are fully on! So all the shows are spoiled and this make me mental...

Any ideas what to look for?

thanks in advance.

[kgallen]

Looking at the 8 Nov 2006 entry on here http://zero88.com/forum/topic/3850-problems-with-demux48/ looks like you have the same problem.

 

The problem with that one was a flat battery, so looks like the mempack needs replacing in yours.

 

I must check ours one day before it leaks...!

[KWR88]

Would agree on this all indication battery is starting to fail. Would check it asap incase it starts to leak as the could make the unit ber

[kgallen]

Replacement battery page is here:

http://zero88.com/support/index.php?/Knowledgebase/Article/View/546/280/replacement-battery-information

 

3.6v, 150mAh Varta Mempac

[iank99]

I must check ours one day before it leaks...!

 

That's going to end up on so many gravestones you know

[djzub]

Thanks for all your replies!!! I have been told that the new battery has been ordered.

Hopefully this one will end my torment...

[kgallen]

As I'm here again, here are some sources for the battery:

 

http://cpc.farnell.com/varta/3-v150h/battery-ni-mh-mempac-pcb-3-6v/dp/BT00152

 

http://uk.rs-online.com/web/p/coin-button-rechargeable-batteries/0422393

 

http://uk.farnell.com/varta/55615603940/battery-nimh-tht-3-6v-150mah/dp/279353

 

I'm not convinced by some of the dimensions reported on the CPC site. As I'm ordering one, I'll check it and correct this entry if it turns out wrong. In the mean time, I'll press the "order" button then IanK can come along and let me know I've ordered the wrong one...

 

ETA The CPC part above is the correct one.

[kgallen]

Recording for future reference...

 

When replacing the battery, make sure the PCB trace under the battery is intact and not corroded. Worth checking the continuity to the SRAM pin 28 from the battery positive terminal. The supply across the SRAM (pin 14 VSS, pin 28 VCC) should measure the same as VBAT. With the unit powered, if the voltage is above VBAT then suspect a break in the VBAT track. I measured nearly 10V with a good battery but this track broken. Fortunately the SRAM (and a 74HC00 NAND gate also on VBAT) survived the experience somehow.

 

Thanks to Keith for assistance fixing one - that's another DEMUX48 rescued from the scrap heap.

[iank99]

I've never had to scrap one!

 

It's one of the sturdiest bits of kit after the BetaPack 1.

 

If the battery has put on it's winter jacket and it's spread to the PCB - ensure you clean as much of the corrosion as you can, I repaired one unit and then 18 months later got it back because corrosion had spread under the solder resists. If the track looks really bad - it might be worth severing it and linking with some hookup wire.

[kgallen]

Hi Ian,

 

When I found the problem I thought straight away - I bet Ian would have told me to check that track!

 

This was a unit from a well known auction site. It looks like a previous user had replaced the battery (it was an Ni-MH) but looks like they hadn't realised the old one had damaged the traces under it. This had me fooled for a while as the battery looked new (no fur jacket!) and the battery voltage was within range (3.7V) for a powered on and powered off unit. Keith got me to check the SRAM supply at its pins which was way out at a scary 10V - which would relate to the charging supply from the +15V rail via the 2k2/1N4148 - but without the battery acting as the voltage clamp. I eventually removed the battery as I wanted to check all continuities with it out of circuit and voila instantly saw the track. Buzzed it all out and realised this was the problem. I cleaned it all up thoroughly then used some mod wire to reinstate the connection. The other traces looked ok. After that we were up and running.

 

The only annoyance is I should have got the thing cheaper as it was sold as working - well it did power up - but with the 012 error code on the display!

 

Still all's well that ends well!

 

Thanks,

Kevin

[iank99]

That'll be £99 one then - I asked if they knew whether it had been serviced & had the neg output cards fitted and they didn't know but offered me a 14day money back warranty.

 

It would have been handy as slave stock but limited without the neg kit - the one card I did have, I ended up fitting to CTS's demux before I left

[kgallen]

I can confirm - not "serviced" (whatever they would mean by that) and no neg output kits!

 

I'm sure the warranty would have been a bit pointless. They looked like a cash converter outfit and more likely to put it in the bin than have the skills to fix it I would suspect...

[iank99]

They looked like a cash converter outfit and more likely to put it in the bin than have the skills to fix it I would suspect...

 

You discovered my USP...

 

I rescued an Alcora off eBay the other week - it arrived in a poor state as someone had tried to fix it but all the bits were there - only two faders failed. I now have a nice 12/24 channel Go button slave desk to loan for repairs - just one button slightly melted due to carelessness with my soldering iron

 

There seems to be lots of Alcora/Elara on eBay just now - silly money being asked for some too