Lightmaster XLS problem

[PJKBTS]

Hello, I am having some technical difficulties with tthe lightmaster XLS.

The problem that is occuring is.

Whilst in preset mode after about 10 or 15 mins the whole desk will stop working and all the LED lights above the faders will come on permanantly.

The only way to it is to unplug it from the mains and start again.

There are no other problems with the desk that I can find, in all other modes it works fine.

Any help would be greatly appreciated.

Thanks.

Patrick

[KWR88]

That sounds like the internal battery has failed and you are over voltaging the RAM.

Please contact me on the e-mail address below for further details.

[jes]

Hello,

I have a similar trouble with my old XLS.

As seen on other topics, I measured the voltage from the internal battery and I got

- 4.18V without power supply, the same with the electric cord connected

- from 7.30 to 7.55V when switched on, with variation until 6.10V

 

The desk can work about 10 mins and freeze with, at least, two visual effects

- only the green leds are on and the voltage is 3.92V

- ALL leds are on, and the voltage varies from 6.40 to 6.50V.

 

Any help or suggestion will be appreciated.

 

Regards

Jean-Etienne

[iank99]

It might well be the processor has failed or one of the RAM chips - it's quite an old desk now and sadly those components do have a finite life.

 

I suspect you'll need someone with a lot of patience to swap out components to get it working.

[jes]

Thanks for your reply.

I know that it is an old desk (verification date on electronic circuit is 11/95), but we use it about three times a year with some very old dimmers, and, of course, it went wrong just before ths show.

 

I think it would be very helpfull If someone can send me the circuit diagrams and measurement points

 

Regards

Jean-Etienne

[jes]

Hello,

we have changed the internal battery at the beginning of May and the voltage is now 4.3 volt without variations.

Since,

- the desk has run ceaselessly during 3 and a half days without any error

- we have made a small light show of 4 hours

- we have made two lights trainings

 

I think that the repair is good and the is quite reliable now.

 

I think also think that we can change all chemical condensers (~15) and the three voltage regulators to have a longer life.

Any advice about that last point will be appreciated

 

Regards

Jean-Etienne

[iank99]

Good to hear you managed to keep it alive

 

Changing the electrolytic capacitors might be an idea - the voltage regulators should be ok unless you know the desk has been subjected to a mains spike. Electrolytic capacitors can dry out sometimes with age and then cause problems - if you have the time, then it can't hurt.

[kgallen]

Certainly electrolytic capacitors can "dry out" although I'm not sure I'd go about changing them unless you see a problem, they look aged or you know they've had a an over-voltage event. I don't see any value in swapping out the voltage regulators unless you think they are damaged. At 20 years of age maybe I'd be more concerned that the data retention of any non-volatile digital storage devices (EPROMs and the like) is well down the statistical tail of the expected retention life. Such devices of that era often had guaranteed retention of 10 years, and 20 year retentions were more unusual (generally military grade components). I have these 'worries' with my own Demux48 of a similar age! Other ICs of that era are built from a relatively large geometry silicon process, and failure modes due to electromigration were not the reliability concerns we now have with the ultra-deep sub-micron processes we use on today's digital devices.

 

Maybe for now, "If it ain't broke, don't fix it!" (NiCd batteries excepted, but you've replaced that one).

 

Kevin

 

ETA:

 

If you do change the electrolytics, I'd recommend ensuring a good margin on their voltage rating. If you can physically fit the replacement to the PCB, choosing one at double the voltage rating is always good for reliability, and a minimum rating of 16V is always a good rule-of-thumb even on 5V supplies.