Sirius 48 - Problem with stuck channels 1-12 and 37-48

[Candyman]

Hi - I am hoping that you can assist me to repair my theatre's Sirius 48 desk.

 

I recently installed two new batteries in the desk as a 'service' measure as they had started to look a little leaky. The desk was running perfectly fine before this service measure.
The batteries were replaced and the desk power up fine.
Fortunately there is no damage to the boards caused by battery corrosion.
Currently both batteries measure approx. 4.1V after fully charging.

 

About two-three hours after using the desk it started behaving strangely.
First of all, channel 1 intermittently flashed and then turned itself permanently on.
Then channel two did the same thing . . then three . . then four etc.
A kind of 'creeping' fault.
Finally all of the first 12 channels got stuck permanently 'on'. Also, channels 37-48 decided to switch to permanently on also.
After powering off the desk for a few hours, then on again the fault seemed to go away but slowly came back.
Unfortunately, the desk now is permanently in this faulty mode with channels 1-12 and 37-48 permanently on.
The Grand Master works as intended and dims the channels as normal. The A & B preset brightness controls also do the same thing. An 'IPL' check in Super user mode states that 'IPL Running'.

Can you help at all, please, or point me in the right area?
Although the voltage levels on the batteries seem fine, could it be the new cells causing the fault in some way?
I have re-seated many of the chips and wiring loom connectors. Nothing seems to help.

 

Any assistance you can provide would be of great help.

 

Thank you

Christian

 

 

[iank99]

It sounds like it may be the IPL - I'm not sure if the IPL test in SuperUser is "reliable" apart from sensing that there's data happening on the line.

 

I'd be looking at the molex connectors that take the IPL on to the slave card and check that the cables are pushed home so the IDC teeth are doing their job and also that they're on the right way round (if you've had the cards out you may have disconnected them and not realised they're polarity conscious). I would also snag a copy of the Sirius IPL fitting instructions from the download area (PM me if you can't find it) and check you have all the IPL cables in the right place. IPL runs through the DMX I/F if fitted as well - again I can't remember if there's a distinct order to those cables.

 

Is the Desk outputting via DMX or analogue? For the GM to be working, it might suggest that some data is getting through but I'd be surprised if it was consistent enough to control the analogue outputs whereas the DMX card (which sits on the IPL) may just be "commanded" to bring all outputs to Zero via the GM.

 

I suspect it's not a terminal fault from the way it gradually happened (the Sirius is built like a battleship after all!) but something that has happened as you've re-assembled the desk.

[Candyman]

I appreciate the reply, Ian.

 

I have been in communication with Keith this morning, and he has been immense help.
(So nice to deal with a company that you can rely on to give you superb support on your product.)

 

I am satisfied that the IPL is fine, although my research does show that it can be an issue. In past work on the desk, I removed the connectors and soldered the IPL connectors directly on to the board so that this issue wouldn't arise.
I did a continuity test of this cable anyway, and it checks out fine.

 

The desk is both Analogue and DMX, and the theatre uses both systems (hence this is a perfect desk for us).

I agree with what you say - It's a superbly constructed 'Tank' of a beast.

 

I am satisfied that both batteries are fine and operating normally.

I have tracked the problem down to the slave board (the one on the left as you look in from underneath).
The tracking around the battery had very minimal corrosion, and I am happy that it is all in good order (but worth a mention).

 

I don't have a schematic, but logically tracking through the fault, I checked the 4051 analogue multiplexers that take the voltage from the sliders, and pass it in turn to the A-to-D circuitry. There is a problem here, as all the 4051's are giving 5V on their outputs, even though the input sliders are all down (i.e. zero).

 

This is as far as I have got.

 

Chris

[iank99]

Chris - email me iank*AT*centraltheatresupplies.co.uk - I can help with schematics away from here - Ian.

[Candyman]

Thanks, Ian - I have emailed you.

[Candyman]

Fixed!

The fault was the A/D converter (on the small daughter board, the surface mount MAX165BE IC).

My 'creeping fault' description I originally posted must have been this little chip's 'final moments before it bit the dust.

Strangely, the fault did not appear to be anything to do with my battery replacement or the very small amount of corrosion, although a line of circuitry close to the battery does supply the analogue signal to the op-amps on the daughter board.

All it was, was the A/D converter permanently pumping out ‘highs’ to the CPU for all the sliders, and disregarding it’s input which was constantly at a low level (with all the sliders down).

 

My humble appreciation and thanks go to Ian at Central Theatre Supplies for providing the replacement board, and also Keith at Zero88 for his technical assistance on the telephone.

Chris

[iank99]

Chris - glad we could help - another Sirius lives on!