Hello everyone, I have an issue with one of my 4904-9136 strobes and I was hoping someone here familiar with the flash circuit could provide some insight.
First off, I am knowledgeable in electronics and troubleshooting down to the component level. I have a lot of test equipment including a full featured digital multimeter.
I currently have a Simplex 4010, 4005, and 4001 panel.
My 4001 is a basic demo setup with one detector, one pull, and one signal, this strobe. I know there’s debate going on about whether the 4001 outputs filtered DC on the NAC or FWR. I believe it’s filtered DC, and the problem is that the filter capacitor dries out over time and causes the output to be FWR.
I just replaced the capacitor on mine. However, before I did so I noticed this strobe would no longer flash when in alarm and the panel was putting out NAC power. The strobe used to flash on steady coding as well as coded.
I believe this strobe either failed due to age or because of being powered by FWR. My question is what exactly is the failure mode of running one of these from FWR input power? I have disassembled the strobe so I can access the circuit board to do some inspection and troubleshooting.
To me these seem pretty simple. Like a camera flash for example, a large capacitor is charged up to a high enough voltage and then is discharged across the xenon flash tube, which ionizes the xenon thus producing the flash. In the case of the strobe, there’s a component marked “T1” which to me looks like a high voltage coil or transformer, similar to a high voltage tripler in early solid state TV sets. The wire coming out of the top of this component goes to the anode electrode in the flash tube. I’m assuming the large capacitor dumps it’s charge into the primary side of this transformer and then when the magnetic field collapses it produces the high voltage pulse which is what drives the flash tube (or the transformer might just be an ignition transformer to strike the initial arc across the tube) along with an oscillator circuit and associated components to keep charging the capacitor back up after each discharge. This repeat of the cycle produces a repeating flash with constant input power. (steady NAC output, strobe constantly charges and discharges) I see a crystal on board which may drive this oscillator along with a few transistors.
The main capacitor that fires the flash tube checks good in the uF range. I see a few diodes, some other ceramic capacitors, resistors, the high voltage transformer, a few transistors and misc. components. Everything visually looks good and I tested a few diodes and whatnot and they all check okay. I’m assuming one component has failed, either open or short. I noticed that checking across a strobe’s terminals with my meter set to resistance, a working strobe measures somewhere in the high meg ohm range across it’s input, somewhere between 30-40 meg. However, this failed strobe reads lower at around 7 meg. So something is definitely wrong.
It’s just curious to me how FWR can damage these circuits.
Thank you ahead of time, I’d appreciate any insight on this topic.
-Dylan SimplySimplex