KevinE Posted March 21, 2009 Share Posted March 21, 2009 Hi, I have a Zero 88 Rackmaster 260 which wants to put out around 100V (on load) all the time on each of the 6 channels. Ive turned all the preheats right down, and according to the manual, unplugging the fader desk will kill the preheats and take the output to zero..which it doesnt. The thing is, it's on all 6 channels..which are discrete channels with their own power supplies etc shared in pairs. have I got a full set of faulty boards here, or am I doing something wrong? kev Link to comment Share on other sites More sharing options...
Wrighty Posted March 22, 2009 Share Posted March 22, 2009 Sounds like a problem with a reference voltage somewhere, or possibly the entire low voltage supply. I would've thought the outputs should have pre-heat applied even without a desk plugged in, but I can't say for certain whether that's the case or not. A mate of mine has one of these so he might be able to check if it's not buried under a pile of gear. Link to comment Share on other sites More sharing options...
adamharman Posted March 22, 2009 Share Posted March 22, 2009 A mate of mine has one of these so he might be able to check if it's not buried under a pile of gear. Cheeky f*****, I'm not that untidy! It's in the workshop at the moment awaiting repair as one channel has died. Seems strange that it's doing it on all 6 channels, because as you say, they're in pairs that are pretty much independent. Maybe a problem with the ground connection of the control signal between the boards? If that's floating then it could do strange things. I'll have a poke inside mine later. Only other thought - I assume you've got some load on it? Leakage through the triacs and filters will give you a meter reading on the outputs even with the channels down. Edit - typo Link to comment Share on other sites More sharing options...
Wrighty Posted March 22, 2009 Share Posted March 22, 2009 ** laughs out loud ** :P I'll leave this one for you to look at then, Adam! Link to comment Share on other sites More sharing options...
KevinE Posted March 22, 2009 Author Share Posted March 22, 2009 I assume you've got some load on it Yeah, I'm using 100W light bulbs at the moment. The manual definitely states that the preheat is switched off if no desk is detected plugged in. The dimmers are buzzing so I assume they're being told to fire from somewhere...and 100V is alot for a preheat anyhow! This is one of those desks that puts 20V out to power the desk and requires 0-10V back from the faders for 0-100%. When you unplug the desk, pull-down resistors take the input to -1V which turns the channel off completely. Plugging in the desk takes that -1 back up to 0V which enables preheat. Link to comment Share on other sites More sharing options...
adamharman Posted March 22, 2009 Share Posted March 22, 2009 Got mine in bits in front of me now... I can't see anything that should affect all 6 channels. Have you tried unplugging the control cables from the dimmer boards? If that doesn't stop it then you may well have the same fault on all 3 boards. Only other think I can think of - and this is probably an insult to your intelligence, but I'm running out of ideas - the channel test buttons aren't pressed in are they? I'm reading about 120v on mine with them in. One of the zero88 boys will probably be along tomorrow and offer some useful advice. Link to comment Share on other sites More sharing options...
KevinE Posted March 22, 2009 Author Share Posted March 22, 2009 the channel test buttons aren't pressed in are they? Link to comment Share on other sites More sharing options...
Wrighty Posted March 23, 2009 Share Posted March 23, 2009 Problem solved? Link to comment Share on other sites More sharing options...
KevinE Posted March 23, 2009 Author Share Posted March 23, 2009 I'm embarrassed to say, yes. The 'channel test' buttons arent marked 'test', they're marked 'channel 1' and 'channel 2' etc all the way across. Thanks Adam, yes my intelligence was insulted, but I deserve it and I take it like a man. :) Link to comment Share on other sites More sharing options...
adamharman Posted March 23, 2009 Share Posted March 23, 2009 This is true. The front panel labelling isn't as comprehensive as it could be..... Other than that, they're good dimmers. Nothing too complicated to go wrong, 4 screws to get the cover off and everything is there in front of you. There's not many dimmers that you can change a triac and have the thing reassembled inside 2 minutes from start to finish! Link to comment Share on other sites More sharing options...
KevinE Posted March 24, 2009 Author Share Posted March 24, 2009 I agree, I like them! The one I have here has had a demux IEC power lead tapped to the main input busbars which are fused at 60A! Much easier to work on than the last rack units I overhauled which were Multiform, though they were nice quality too. One down, 13 to go. http://common.zero88.com/public/images/RM260.jpg Link to comment Share on other sites More sharing options...
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