Forerunner Cable VS 4 Pin

[Rob Fulton]

Is there any difference in "Forerunner Cable" and 4 pin dmx? I'm running into issues with some forerunner scrollers.

 

[RonHebbard]

Is there any difference in "Forerunner Cable" and 4 pin dmx? I'm running into issues with some forerunner scrollers.

@Rob Fulton I'll begin by stating I'm NOT personally familiar with your scrollers, their power supplies or their cables.
That said: At one point there were three popular manufacturers of scrollers all utilizing XLR 4 contact connectors and very similar cables with each manufacturer wiring their cables and connectors differently and INCOMPATIBLY.
First thing to know, scroller cables typically contain four insulated conductors configured as a comparatively heavier gauge twisted pair to carry power and a comparatively smaller gauge twisted pair to distribute DMX. Sometimes only the data pair is shielded while sometimes the overall cable is enclosed within one overall shield. Sometimes the shield is bonded to the XLR's shell, while sometimes the shield is connected to the negative side of the power supply which may, or MAY NOT be bonded to ground and / or the XLR's shell. One manufacturer placed their power across contacts 1 and 2 with their DMX data across contacts 3 and 4.
Another manufacturer went with data on 1 and 2 with their power across 3 and 4.
A third manufacturer connected negative power and an overall shield on contact 1, DMX on 2 and 3 with their positive power on contact 4. You don't have to look at the possibilities for too long to appreciate how easily you could release the 'magic smoke'.
I don't believe I've ever met what you're calling: "4 pin DMX", 3 contact and 5 contact, yes, 4 pin no.
Also, I wouldn't recommend using scroller cable to extend your comm's headset from its belt-pack.
Bottom Line: Label and keep track of your scroller cables as they may be incompatible while appearing the same upon a quick glance.
Toodleoo!
Ron Hebbard

 

[Amiers]

There is no 4 pin DMX.

There is 4 pin Comms. And yes that would potentially be bad.

Look at your manual to find out pin voltage and measure pins accordingly.

 

[icewolf08]

Wybron Forerunner units use standard 4-Pin accessory cable. Only the ColoRam and CXI required different cable as the power and data pairs were non-standard. Not only that, but the data passed from a RAM power supply is proprietary to Wybron whereas the data passed from a Forerunner supply is DMX.

While 4-Pin is not technically “DMX cable” one pair still does carry DMX data and needs to meet the DMX spec.

 

[RonHebbard]

Wybron Forerunner units use standard 4-Pin accessory cable. Only the ColoRam and CXI required different cable as the power and data pairs were non-standard. Not only that, but the data passed from a RAM power supply is proprietary to Wybron whereas the data passed from a Forerunner supply is DMX.

While 4-Pin is not technically “DMX cable” one pair still does carry DMX data and needs to meet the DMX spec.

@icewolf08 Can you speak to the needs and cabling of Rainbow scrollers which were imported from Europe, Sweden perhaps, then cloaned by a North American importer / distributor?
Toodleoo!
Ron Hebbard

 

[derekleffew]

Is there any difference in "Forerunner Cable" and 4 pin dmx? I'm running into issues with some forerunner scrollers.

https://www.controlbooth.com/threads/4-pin-scroller-cable-rules.20437/

First, let's obliterate any reference to the term "4 pin DMX." ...

 

[Stan Longhofer]

Wybron Forerunner units use standard 4-Pin accessory cable. Only the ColoRam and CXI required different cable as the power and data pairs were non-standard. Not only that, but the data passed from a RAM power supply is proprietary to Wybron whereas the data passed from a Forerunner supply is DMX.

While 4-Pin is not technically “DMX cable” one pair still does carry DMX data and needs to meet the DMX spec.

Are you certain about this? Looking at the manual for my Coloram II power supply unit, it states "The cable used in the Coloram System is the same cable which is used in the Forerunner System and may be referred to as either Coloram cable or Forerunner cable." Later it specifies that pins 1 and 4 are 14 gauge (DC power and ground while pins 2 and 3 are 22 gauge (data - and +).

 

[icewolf08]

Are you certain about this? Looking at the manual for my Coloram II power supply unit, it states "The cable used in the Coloram System is the same cable which is used in the Forerunner System and may be referred to as either Coloram cable or Forerunner cable." Later it specifies that pins 1 and 4 are 14 gauge (DC power and ground while pins 2 and 3 are 22 gauge (data - and +).

I see that. Everywhere that I am worked with RAM and non-RAM devices everyone had separate cable. However, the spec seems to be the same, but you sure are not supposed to connect RAM devices to non-RAM PSUs (or vice versa). So, aside from RAM being proprietary data protocols, I don't know why they put the big warning about damage due to interconnection unles the polarity of the PSUs are different. Interesting.

I mean, color scrollers: the best terrible invention ever.

 

[Stan Longhofer]

I see that. Everywhere that I am worked with RAM and non-RAM devices everyone had separate cable. However, the spec seems to be the same, but you sure are not supposed to connect RAM devices to non-RAM PSUs (or vice versa). So, aside from RAM being proprietary data protocols, I don't know why they put the big warning about damage due to interconnection unles the polarity of the PSUs are different. Interesting.

I mean, color scrollers: the best terrible invention ever.

Just looked at the Forerunner manual. It looks like the cables are identical, but what runs across the 14 gauge wires is reversed. The Forerunner uses pin 1 as the ground and pin 4 as the 24 volt DC source.

In short, the cables are interchangeable, but the power supply units are not.

 

[Kelite]

< In short, the cables are interchangeable, but the power supply units are not. >

Yep. Plain and simple.

 

[Duncan Milne]

I just happen to have an Apollo scroller manual here (I've got some scrollers, but no PSU). It states that Apollo PSUs are compatible with Forerunners (and Spectra-Q, Chroma-Q and Rainbow) but not Coloram which seemingly has power reversed. Apollo pinout is 1: 0V DC; 2: DMX-; 3: DMX+; 4: +24V DC; and shell earthed.

 

[DELO72]

Also- the resistance of the wires & the shielding material inside the outer jacket is often key in both DMX cables and Forerunner. Cables are not interchangeable just based on wire gauge as you can get signal bleed or loss if certain ones are not properly shielded or unshielded (whatever is required). I would buy the actual Forerunner cable, unless you know the exact Belden (or other reputable cable mfn) code for the 4 wire cable itself that is used, and want to solder your own using the correct cable type.


**edit note- Thanks Ron for catching my Belkin/Belden brand name mix-up!**