ZB8-8 card issue

Hey all, I have this IRC-3 with a ZAS-1 card in slot P5 (upper card slot) and a ZB8-8 acting as a NAC in P6 (lower card slot). The issue in question is this:

The NACS appear to be active when the panel is not in an alarm state but when the panel trips into an alarm it’ll cut power off to the NACS. It’s outputting 26.6VDC and appears to be pulsing the output almost? It will not power any strobes but powers horns. It appears to be operating the NAC’s in reverse almost. Outputs/zones 1 through 6 are the NAC’s and I’ve tried all 6 but all act the same, 7 and 8 are resistored out. I’ve even tried swapping CM cardcages as well but it still does not fix this issue. Connecting a device to it will put the corresponding NAC into a restore state but immediately goes back into an open state even with a EOL resistor at the device. All the outputs are labeled as follows “Horns 1, strobes 1, horns 2, strobes 2, horns 3, strobes 3” so they are programmed to be a NAC. Is there any way to possibly fix this issue?

Check your power supply feed for the ZB-8 . If memory serves me there is a port on the main board that it comes in on. It is sounding like the supply is dropping out for some reason if it is effecting all outputs. But, it has been 15 years since i have worked on that model.

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I assume the main PSU that’s connected to the CM1N? Or something like the APS8? Looking at the Riser inputs on TB3 on the CM1N only bottom riser A is connected. Do B and C also need to have power supplied in order to operate? Sorry I’m not too well rounded with these old systems. I’ve noticed jumpers for zones 3 and 6 are jumpered in positions B while the rest are A if that might indicate something. If you need me to provide photos I can.

If this is an exiting system then your riser inputs should be configured already. I would use a DVM on DC for the riser input and verify the voltage when the system outputs are active. if the 24 dc drops out during alarm you either have a bad device or the power supply cannot support the power needs of the circuit or the power supply can longer support the current needed.

This system was taken out of a large school a few years back but I unfortunately didn’t obtain the wiring diagrams along with it. Essentially just using context clues on how this may have been wired. There’s sharpie mentioning 4 and 6 but terminal 4 connects to the top riser and I don’t wanna potentially break the ZAS-1 on it. I measured the riser voltage when setting it into alarm and it stays at 26.7dc while the outputs go from 27.7 to 0 when triggered into alarm. I also swapped PSU’s all together but the same issue returns. I assume the ZB8 is just dead?

Also if you need me to I’ll provide photos of how it’s currently wired up.

So iti is sounding like you are seeing the supervisory voltage which I believe comes from the cmn side of things. When you go into alarm it switches over to the riser so what you can do is set the panel into alarm verify there is no voltage and no riser connected. Then use your DVM on ohm and meter 1 leg on the output and 1 on a riser input until you see the which riser is being use. Do the same for the other leg they should be paired up.

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Found the outputs! It’s riser C and just measures 0.01/0.00 with nothing on it. Would it be clear to hook 24vdc back onto it?

Sounds like it the point to connect to