Zero 88 Demux 48 Fault

[gafferted]

I have a demux 48 which works fine on power up apart from only giving 9v for DMX 255 on a channel.However, after a random time, from a few seconds to several hours the display freezes as seen in this image, all the outputs go to 5v and it doesn't respond to DMX or any button presses.I think the battery has been recently replaced and it certainly appears to test out fine at just under 4v unpowered.The 5v regulator gets pretty hot but I presume this is normal as it has a heat sink attached.I will investigate power supplies, capacitors etc. etc when I get my hands on a scope but in the meantime do any of you clever people have any ideas, or a schematic?

[Edward- Z88]

Hello,

 

Feel free to send us an email at support@zero88.com, or alternatively call our Service Manager Keith Rogers on +44 (0)1633 833101 who will be able to help you.

 

I’m sure Ian Knight will also be along soon as he is also an expert in Zero 88 legacy products!

 

Any queries let me know.

 

Kind regards

Edward

[Stuart91]

Try talking to Zero themselves - they are surprisingly and commendably helpful, one of the main reasons why I continue to buy and recommend their products.

[ianknight]

@Eddie - I'd be looking around the PSU section and checking the 15v Line:- 1. that it's present and is 15v and 2. the physical state of the 100nF capacitors used to smooth it. The output references are all derived from that line - if it's not behaving then you will get only 9v out. Check the output voltage links too - it should be set for 10v running.

 

You don't say if there's negative output cards fitted either - if there are - then try unplugging their ribbon cables and see what happens, whilst the neg cards are fairly simple beasts - if one of their chips is failing, it could pull down lines on the mainboard causing weirdness.

 

You say that you think the battery has been recently replaced... It would be worth checking the tracks around the battery for signs of corrosion, I have had it in the past when I've replaced furry batteries that the leakage has crept along the trackwork under the solder protect and caused issues.

 

Keith will be able to send you schematics but if he's not in the office tomorrow (he gets out and about a lot these days) then PM with your eMail and I'll send all that I've got for the Demux 48.

[gafferted]

Thanks chaps.There are no neg o/p cards fitted.I won't have time until later in the week to investigate further but will email support@Z88 and request diagrams.If I do fix it will post results back here.Eddie

[kgallen]

The 5v regulator gets pretty hot but I presume this is normal as it has a heat sink attached.

It shouldn't be that hot. I had a faulty unit and the 5V regulator was running around 55 degreesC when measured with a thermal gun. After repairing the fault (broken track under the battery as Ian talks about above), the regulator ran cooler, around 35 degreesC. Both of these measurements with no loads on the analogue ports.

 

You can spot a broken track under the battery by checking the supply voltage to the SRAM which should be +5V rather than nearer 10V with a broken track. IC15 pin 28 to pin 14 with issue 4 PCB.

 

Before you contact Zero88, you should find out what issue PCBs you have in your unit so you request the correct schematics.

 

Kevin