27 channel dmx board issue

[diyer]

Over Christmas I noticed that one of my dmx boards wasn't operating correctly, I finally got around to having a look at it today.
When I connect a dmx signal to it, it goes crazy randomly flashing lights, if I then remove the dmx, it freezes the currently illuminated lights even if they are partially dimmed.
Can anyone shed any light on a possible problem? Is it fixable, or shall I bin it?

 

[i13]

Not sure why the lights are randomly flashing but check that

• the start address switches are all working
• test mode isn't selected
• the CAT5 plugs are all working

These are things that can happen or stop working.

The 27 channel boards don't turn off the lights when the signal stops. It is normal for them to continue outputting the last signal they were sent.

 

[diyer]

Test mode not on, connections ok, the address is correct, but I haven't tried removing the dip switch and bridging the address. I'll do that next
Busy watching the cricket with a beer at the moment, you have to get the priorities right....

 

[i13]

It is just that the CAT5 plugs can get damaged and so can the dip switches. You could probably just test on the back of the board with a multimeter to see if the dip switches are working.

 

[diyer]

DIP switch continuity - ok
Board runs on test function - ok
DMX signal at board - tested ok with my LED thingy
Run a new program with 1 as start address - fail

 

[David_AVD]

What is the DMX source ?

Have you tried sending data to it via da_DMX or da_E131 ?

 

[diyer]

Me thinks that I have more than one issue here, I installed another dmx board and although the dmx light is flashing it won't work. My tester is telling me that I have lost either dmx + or - as the bi colour LED is now one colour only.
I tried another cable - same result.

I'm using a Enttec open DMX, could it be at fault? I updated to Win 10 pre Christmas, I think the driver is ok as I used it over Christmas with no problems.
I tried da_DMX, nothing happened.

 

[AAH]

With da_dmx it should detect the open dmx dongle. Assuming that it does then click on the "open port" at the top and it should start streaming data out of the dongle. If you can measure the dc volts between the D- and D+ then as you fade up and down with the "single" fader which fades up all channels (in the start-end range) you should see a variation in the voltage.

 

[diyer]

Thanks Alan,

The da_DMX shows the DMX Open as FT232R USB UART

Fading varies the voltage from 2.6 to 3.8v

 

[diyer]

I just opened the da_DMX again and the DMX Open box is blank and I get an error message

 

[AAH]

Not sure what's up with the message as there has been a few bugs through the different versions and da_dmx particularly doesn't like the dongle being removed while it's "open" and streaming data. Try unplugging and replugging the dongle and doing a re-scan. When you pump data out with da_dmx do you get the same flickering or is it stable? Also is it possible to measure the d- and d+ past the 27 channel board to see if it's possibly something with the connectors?

 

[diyer]

Thanks for the input.
When it's being dimmed by da_dmx it's ok, but put the controls to zero and it starts randomly flickering.

 

[AAH]

Is the flickering only occurring when all faders are down to zero? Is the start address consistent and stable? You can check this by setting the start address and then fading up 2 channels separated by a few channels and confirming that they stay at the level they are meant to be and no other channels flicker at all.

 

[diyer]

I'll try what you have suggested, however I have connected up a DMX36 to the same lights and DMX cable with no issues

 

[diyer]

I had another look at this board, I traced the DMX signal to the first IC (SN75176BP), as I am an absolute beginner with a scope i didn't really understand the scope traces but I had a feeling that the IC might be the issue. I found some on eBay, cheap enough but I had to buy 10.
They arrived this week and as I had some spare time today I swapped it over and retested, success! 8)