Old C Bus 1, 4 Channel Relays and Power Supplies

I have been asked to investigate a old C Bus job that I have very little documentation on which is locking up networks randomly for a period of time and sometimes returning to normal mode. The LEDs on the switches usually start flashing in this fault mode.
I Know step 1 is replace all power supplies.
I am getting 42-43 V from these old units.
I have 6 networks with a backbone and Network Bridges.
The only clock available is on the old Network Bridges.
I believe the high voltages have damaged some switches over time but these can be very hard to pinpoint.

I was wondering if the old C Bus 1, 4 channel black box relays draw current from the network.
Is there any other traps I need to look out for.

Thankyou

 

Hi Frantic,

I have attached the two manuals for you, one the PSU and the other is the RVF relay with the specs you asked for.

42-43v is obviously way too high and would cause the C-Bus comms signal to be crunched by the lack of 'headroom' on top of the DC waveform. This could cause certain units exposed to the highest DC voltages to drop off the network which would explain the flashing units (though they also flash when they're dead!!). Once the power is back within limits, correctly burdened and clocked, I think you should regain links to most of your units. Some may require a reset.

Look at the C-Bus Diagnostic log in Toolkit and you will probably see the network having issues like stuck transmitters and other timeouts.

Many switchplates the age of the RVF dimmers (~15 years in some cases) are prone to failure anyway. Toasting them with DC is not helping of course

The relay draws 18ma from the C-Bus network.

As for traps/tricks, there's probably many others will add, but here's mine.

• Work on the core network first and get it operational and then work out through the bridges.

• It's easier to take your own modern PCI than to trust that the one you might find on-site will easily link to your laptop, it also lets you move it between the separate networks more easily to see the other side of the bridges.

• Also, just watch the C-Bus cable trace colours and understand where your C-Bus +ves and -ves are. Many of the really old sites I have come across were wired up using an eclectic mix of colour combinations. The most common wrong-un was blues together / oranges together. Knowing this will be important when terminating the new PSUs and any required replacement units. Of course, if the wrong pairing is in place, you will have a choice as to whether to just continue or re-terminate but it gets sticky when you are terminating your RJ-45s for the new units.

• Take a copy of the C-Bus Diagnostic Utility with you to help you understand what's happening on the networks when onsite.

All the best,

Brad

 

Thanks a lot for the detailed info Brad.
The color code they have used on this site is solid Orange and Brown for + and the pairs for -.
I will change out the power supplies first and then work my way through the rest of the issues as the arise.

Thanks again

Mark

 

Hey - we had an installation of C-Bus One in the Clipsal Padstow NSW office, and it would go flakey occasionally.

We changed out the power supplies but there was still random stuff happening. Eventually we traced it to some of the original 2000 series push buttons. We replaced a few at the furthest part of the network and it all came good. Oddly, the switches seemed to be OK when they were on the test bench.

In the olden days there was no Pink Cable or even a consistant colour code. many contractors didn't undertand about the pairs and twists, which didn't help. Many of the sites got wired in standard (Cat 1?) telephone wire, and even in bell wire. These weren't twisted as tightly as Cat 5 so they often suffered more from noise being injected into the comms.... which might have been OK at the beginning but as the Power Supply capacitors start failing they add more noise and the comms grinds to a halt.

I'd recommend splitting the network up (adding clocks or whatever temporarily) so you can see smaller chunks and isolate the issues easier.