Simplex 4005 Help

There is an electronic circuit breaker circuit in the power supply that could be tripped or damaged. That should cause a “Signal Power Trouble Input” condition on the panel.

Here is a test procedure for the signal power circuit. Use it even if the “Signal Power Trouble Input” condition is not present.


• System Trouble

• Signal Power Trouble Input

• Panel in Trouble


• Cause is Associated with the Power Supply

• Signal Power Trouble Input 28-7 Main Supply Overcurrent


• See below for possible solutions:

1.) With trouble condition displayed press the Right Arrow Key to verify the trouble point as 28-7.

2.) The Signal Power from Signal +24V and OV are compared through the Power Distribution Board fuses F1 and F2 to a comparator to the CPU.

3.) Check Detector Power on CPU TB-1 terminals 1 & 2 for 24V. This is Resettable Detector Power.

4.) Check the voltage on the right hand Power Distribution Board TB-1 terminals 3 to 5 and terminals 4 to 6, both should have 24VDC. This is Signal Power voltage from the power supply. If there is no voltage check fuses F1 and F2 on the power distribution board.

5.) Check the voltage on the right hand Power Distribution Board TB-1 terminals 1 to 5 and terminals 2 to 6 both should have 24VDC.

6.) If you do not have 24VDC on the Power Distribution board TB-1 terminals 3 to 5 and 4 to 6 and the fuses are good, but you have 24VDC on TB-1 terminals 1 to 5 and terminals 2 to 6, then the OV Signal on the power supply is not turned on.

7.) Go into the programming and make a change in the CFIG (Change: a label or point), and save the CFIG. Check the voltages again. This is intended to provide the system CPU with a Restart signal and the chance to reset internal system software flags.

8.) If steps 1 to 6 fail in identifying the cause of trouble replace the power supply.

Is there supposed to be wires in that 6 screw terminal block?

When a 4005 is new from the factory there were no wires connected to that terminal strip. Whatever wires are there are left from the installation the panel was removed from.

Okay I’m not getting any power from the resettable detector power

Or do you think since I’m having a trouble on the one signal circuit that the panel is canceling all operation on that card all together??

There is only one circuit on the power supply that can shut down all of the signal power outputs when it is tripped. I would disconnect the wires going to your signals and place 10K resistors on the two circuits you are using. Then follow steps 6 and 7 in the test procedure. If the voltages come back on test the NAC operation with just the resistors connected. If the DET PWR voltage on the CPU and the voltages on the distribution board terminals do not come back on the power supply probably is damaged.

The voltage on the nac card will only go up to 17ish

Is that 17ish volts in standby or alarm? It is normal for the standby (supervisory) voltage to be lower. The NAC card has two 24 volt sources coming to it. The supervisory voltage is from a different 24 volt circuit than the signal power used to sound horns in alarm mode. So there can be supervisory voltage in standby mode but no signal power when in alarm mode.

You have to recheck at the DET PWR terminals and the terminal strip on the distribution card. Those voltages are sourced from the signal power circuit that has the electronic circuit breaker that can shut it off.

That 17 is alarm voltage is for the circuits without any horns or strobes on it. The circuits with horns and strobe on it is 0 all together

With only 17 volts available on unloaded circuits in alarm, my best guess is that the power supply is damaged and needs to be replaced. Sorry.

I know this post is a couple weeks old, but may I just say that is very funny.

My name is also Ryan, and I too have a 4005 that has an issue with its power supply, and Retired STR-SG just helped me troubleshoot that as well. Thankfully mine works; I just have a persisting ground fault that won’t clear unless I replace the power supply.

We’re kind of on the same boat!