LD90 problem

[mikienorth]

Hello All.

 

I am aware of one other topic reelating to LD90 problems, but almost all that is mentioned is to change the triac.

 

The triac in this case is good (It works another channel when swopped)

 

The channel will not shift from off, even when controlled from the rack. The processor sees the channel (884, which it should be) but nothing is happening. I have checked all the things I have had cause this before, mostly loose connections, but to no avail.

 

There is one thing I want to try which is to connect the power board to the second data link instead of the first, to ensure it is not the data, but I wondered if anyone here, who has performed surgery or maintenance on an LD90 before might have seen this problem before or have any ideas for me to try.

 

And, I do know what I am doing, I have done this before, I am trained and qualified, and old enough before anyone starts to ascertain that. (I'd check too, to be honest)

 

Ta Muchly.

Mike

[Suzette]

I can't help you with an answer but I am working this week in a theatre with LD90's and they have a channel stuck in the ON position, which no-one at the theatre seems to know what to do about... anyone else have any clues?

[danjshelton]

If it's stuck in the On position and the LX Desk isn't giving out the command or it's not set to On from the dimmer control system then the first port of call would be a Faulty Triac (Usually results in channel being permanently on or permanently off).

 

As Mikey said above (presuming the people at the theatre are competent to do this!), the best way to test a triac, before swopping it out, is to swop the cables going into the triac with another channel that is known to be good. That way if this channel stays on then you know it is the triac. There fairly easy to change (depending on the dimmer, never changed a triac on an LD90), and not massivley expensive.

 

Hope this helps.

 

Dan

[AndyJones]

try Tim at stage electrics, he knows the Ld90's off the back of his hand!

[Kazeja]

Ld90 outputs normally fail in 2 ways.

 

Stuck on, change the triac.

 

Stuck off, if lucky, just the opto and a few fusible link resisitors. If really unlucky, tracks may have vapourised as well. Allow about an hour or so to rectify this problem as it requires access to the rear of the power PCB which normally requires the removal of all wires connected to it before it can be pinged away from the heatsink.

 

The above applies to the 8x2K5 dimmers. 4x5K are a different kettle of fish.

[mikienorth]

Fantastic, sounds like I have a fun day ahead of me in a couple of weeks. (I'm off site next week) I'm looking forward to figuring this one out!

[mikienorth]

So, I've changed the triac, and the opto, and still no joy with this one.

 

I'm trying to figure out where to go next, the opto on the channel above gets 169V on pin3, but the opto I've replaced has 0V. Does this mean the capacitor connected to pin 3 may be the culprit? or is something else the matter?

 

Any ideas?

 

Ta.

[Kazeja]

As mentioned earlier, the opto and a "few fusible link resistors" which are there for safety. You say you've done the opto, did you measure the resistors? The one behind the triac needs to be measured with the triac removed.

 

Other thing you may just wish to check is that the terminals have clamped onto the triac legs. I've been to a few sites where the triac has been changed but not terminated correctly resulting in no output.

 

Interested to know what value readings you get.

[Duncan Wood]

Odds are the power device has blown, it's a tpdv840 (Farnell part 9804250). The opto triac can go, but it's normally the power device.