Schindler elevator main controller board always gets hardware error 2

[Proximus]

The main controller board BP 304 has its IC chip burned in the relay board. Its history was that, there was an intermittent stop or it will flash a " tripped" event. Then after several power reset, it will return to normal.
Then one time, it just stopped, then after resetting the power, a burnt smell came, and we found out this IC was damaged and burnt. Then we tried to replace the whole assembly (power,relay, IO boards). When we power-up, immediately, an IC got burned, and showed hardware error. Please advise on how to mitigate this faillure.

 

[jraef]

That would be worthy of a phone call to Schindler.

The first thing I would suspect however would be a crossed wire somewhere putting current on the IC circuit that is not supposed to be there. In my exposure to elevator system controls years ago, I came across numerous design decisions that would be considered very inappropriate for industrial control systems. One of those is that they use TTL logic level signals out to sensors in the field and connect them directly to the IC circuits with no inter posing relays, or isolation. So one crossed wire can easily take out an IC chip.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[Proximus]

Thanks jraef. Same as we suspect that a stray voltage and current is passing through that board. This elevator has been running for more than 10 years without major failure and we have not modified any wiring. Could there be 24Vdc short circuits, from push buttons etc, because before that happened, there was always a "safety circuit tripped" alarm?

 

[itsmoked]

To burn ICs often you send a higher voltage into them then they are designed for. Look for a way for that to happen.

Find the inputs of the IC that zorched.
Trace them across the circuit board to which external input they each go to.

Then if you can safely do it, hook a voltmeter to the logic ICs ground and then probe the all the inputs.

It's likely you will find one that has a high voltage landing on it. If the IC is logic it is likely only good for 5Vdc so if you see 24Vdc on the input there's the problem.

You should also switch the voltmeter (DMM) to AC volts as a very likely problem is 120Vac has somehow made it to the inputs.

Keith Cress
kcress -

http://www.flaminsystems.com