I'm trying to add a 3rd cabinet to a 400 system.
Using one sax board the manual says to remove all jumpers in all cabinets and the UR1 resistor on the sax board. Add a ribbon cable from AHU on sax to J4 of 3rd cabinet. I have done this, but the master cabinet will not come on. The PS lights but none of the cards light up, nor the MPD.

Tried unplugging the 3rd cabinet with this configuration and still no main cabinet.

Adding the jumpers back on to make it a 2 cab. system returns all to normal.

Any ideas?? Is it possible the manual is incorrect on jumper locations.

RG
[email protected]

I find nothing about removing UR1 resistor on the 400 cabinet. 128 yes but not 400.
This is a 2 cabinet 400 already? So you added the 3rd to the top and connected MHU to AHU and you do have the correct ribbon cable

From Telrad DigiDoc's

Connect the one end of the 24 inch (610 mm) flat cable (Cat. no. 76-400-0011/3) to connector J2 (AHU) on the middle cabinet SAX motherboard (see Figure 5-21).
6. Slip the flat cable through the cable slot in the top of the middle cabinet.
7. Connect the free end of the 24 inch (610 mm) flat cable to connector
J4 (MHL) on the upper cabinet main motherboard

WARNING
The location of connector J4 depends on the style of the motherboard. However, the function of the connector is the same. Connector J4 is located to the left of connector J3 on the style C-0 motherboards.
Connector J4 is located to the right of connector J3 on the style B-0 motherboards. Make certain to check the location of connector J4 before inserting the cable.

I will attempt to try this again, leaving the UR1 resistor in place. The software is 5x, and in the DBU5 manuel on Digidocs page 5-21. Second paragraph states " Three cabinet system. Remove resistor UR1 from all of the SAX motherboards, as indicated in Figure 5-17, above" The figure also shows the UR1 off. As well as W1-W4.

Is there any difference in the flat cables, other than length?

Thanks

I stand corrected I looked in the DB5 manual and found as you listed. Just make sure you connect into J4 of the upper cabinet. Also in system programming you have to tell the system it will have 3 cabinets.