Re: RS-485 Question (Troubleshooting)


mpm wrote:

Well, here's the update (after several hours working today..)

It's a Strand model 300, which they don't make anymore. (8 years old)
It does use DMX512. I scoped the bus and nothing coming out the XLR's
on the back.
Programming looks good.

On the dimmer packs, I shotgunned all the LTC485 transceivers, but (of
course!) that did not help.
So, I un-did all the screws and plug-in jacks to peek at the bottom of
the board for lifted traces, etc..
No problems there.

Did a continuity check on the cabeling - everything looked good there
too.
I was able to control the lights manually (panic mode), and also dim
them with the analog controls.
So, it looks like the dimmer pak might actually be repaired now - even
though I can't test it.
(I wish I had another DMX transmitter of any sort..!!) Do they have
test gear for this??

So, back to the 300 controller. Opened it up, took out the XLR card,
and starting looking back "earlier" in the circuit.
Low and behold, just in front of this output card, I can see the data
every time I move a slider...!!

So, it looks like the daughter board has a problem. It's a simple
circuit, but too much time to trace out by hand. Also, the parts are
surface mount, etc.. You know the drill.


I used to do a lot of surface mount rework, under a stereo
microscope. After having a palsy in my right eye, and nerve damage in my
left arm I'm not sure I would be able to do it, anymore. I routinely
hand soldered 288 pin packages with no problems.


There are surface mount components labeled D1, D2, etc, and some
marked Z1. I'm guessing these are diodes.
The seem to meter out OK in-circuit, but that might not mean too
much. My guess is the protection is blown on this board, and that
what's killing the comm-link to the dimmer pak.

Either that, or I am about to send back the wrong component to the
repair depot. ;?


Are the supplies all working to that board? It may be fused, or a
separate supply to provide some isolation to the other boards.



BTW, email me & let me know what part of Florida you're in.


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