willp Posted July 23, 2013 Share Posted July 23, 2013 We replaced our zero88 demux with a showtec unit just under a year ago. All works fine except the test function no longer works. Nothing happens when you turn the switch, only way to use it is to disconnect the analogue control leads from the demux unit. Fault still present with demux box powered down. Link to comment Share on other sites More sharing options...
Tom Baldwin Posted July 23, 2013 Share Posted July 23, 2013 Yep, ours does that too. I blame the cheap demux; I assume the Betapack uses a pretty low current test source, so as to protect anything that might be connected to the control input, and the Showtec loads the line down so far that the test function no longer works. I can't see a cheap solution - we just unplug the DIN leads when we need the test function. Link to comment Share on other sites More sharing options...
Light Console Posted July 23, 2013 Share Posted July 23, 2013 I think that is due to one of the eight pins having a voltage on it. I can't remember which now though. Eta. I've had a look at the pin outs and it is pin 7. Pin 8 is the 0v reference, this is required! I think if you remove pin 7s connection then the test switch will work. I find the test inhibit to be useful however, as it stops people playing! Link to comment Share on other sites More sharing options...
DrV Posted July 23, 2013 Share Posted July 23, 2013 Yep, ours does that too. I blame the cheap demux; I assume the Betapack uses a pretty low current test source, so as to protect anything that might be connected to the control input, and the Showtec loads the line down so far that the test function no longer works. I can't see a cheap solution - we just unplug the DIN leads when we need the test function.Cheap solution would be 6 diodes in series with the control signals (anode to demux, cathode to dimmer) so that they can't pull the signals down, only up.Dave Link to comment Share on other sites More sharing options...
pjb304 Posted July 23, 2013 Share Posted July 23, 2013 You would have to choose your diodes carefully to minimise the forward voltage drop. If say your forward voltage drop was 500mV, your maximum brightness would be 95% not 100, whether or not it's an issue depends on the situation. Link to comment Share on other sites More sharing options...
DrV Posted July 24, 2013 Share Posted July 24, 2013 You would have to choose your diodes carefully to minimise the forward voltage drop. If say your forward voltage drop was 500mV, your maximum brightness would be 95% not 100, whether or not it's an issue depends on the situation. Betapack 1 is an S-curve dimmer isn't it? (Happy to be corrected by Keith or other deities!) So the last 5% of control voltage does very little to the output Dave Link to comment Share on other sites More sharing options...
PaulDF Posted July 24, 2013 Share Posted July 24, 2013 When the betapack test switch is turned it connects 10v to each of the channels in turn but it doesn't disconnect the DIN plug, the DEMUX sinks this 10v signal down to around 0v, mine have the same issue but the lamps light up dim so isn't going all the way down to 0v.I just unplug them when using the test switch, I contemplated using diodes to buffer them (which I assume a zero 88 desk has built in) but for the reason mentioned above regarding signal voltage drop I didn't bother - too much like hard work! Link to comment Share on other sites More sharing options...
alistermorton Posted July 24, 2013 Share Posted July 24, 2013 You would have to choose your diodes carefully to minimise the forward voltage drop. If say your forward voltage drop was 500mV, your maximum brightness would be 95% not 100, whether or not it's an issue depends on the situation. Use germanium diodes? Link to comment Share on other sites More sharing options...
timsabre Posted July 24, 2013 Share Posted July 24, 2013 You would have to choose your diodes carefully to minimise the forward voltage drop. If say your forward voltage drop was 500mV, your maximum brightness would be 95% not 100, whether or not it's an issue depends on the situation. Use germanium diodes? The 0-10V signal is not that accurate, you really won't see any difference. Link to comment Share on other sites More sharing options...
boatman Posted July 24, 2013 Share Posted July 24, 2013 I don't see a problem here. You have to be standing at the dimmer pack to use the test switch, so it's just a matter of operational discipline to unplug the DIN connector first. Perhaps a note stuck to the rack as a reminder would be useful. Link to comment Share on other sites More sharing options...
daifuse Posted July 24, 2013 Share Posted July 24, 2013 I unplug mine too, not particularly convenient, but if I've got to access the pack to operate the test function it's no hardship. Link to comment Share on other sites More sharing options...
willp Posted July 24, 2013 Author Share Posted July 24, 2013 Awesome, thanks guys. Test mode is something I hardly use, so I'll be going without. The dimmers are installed in racks with all cable behind so a bit tricky to unplug! Link to comment Share on other sites More sharing options...
dbuckley Posted July 24, 2013 Share Posted July 24, 2013 I unplug mine too, not particularly convenient, but if I've got to access the pack to operate the test function it's no hardship. Call me number three. My pack is actually a Mk 1 plus, which has the faders on the front, and the faders don't work if there is something plugged into the DIN socket. Link to comment Share on other sites More sharing options...
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