Convert FWR panel to filtered DC?

Can it be done for a hobby system? I have a bit of electrical/electronics engineering knowledge which made me start wanting to tinker with it. My first thought was to put a filtered power supply in place of the transformer for whatever voltage the transformer is supposed to put out, that way the AC wave is already done with and we don’t have any of the FWR nonsense. I might be crazy, but does this sound like a feasible thing to do?

I PM’d Destin (thesdx) a while back about doing something similar to my MS-4. From what I can remember, he said that he knew of a few people who fried their panels trying to do this.



The PM isn’t in my inbox anymore, so unfortunately I cannot reference it. If he’s still around maybe he can weigh in on this.

I have a MS-9200UD and I would not want to fry that guy. I’ve seen MS-2’s pop up on Ebay for $30 so if I get a little more info I might try to convert the MS-2.

Are we using the same eBay? When has an MS-2 been only $30?


I always like to say “If it ain’t broke, don’t fix it”. That being said, I wouldn’t try doing anything to a good panel. FWR can be a pain in the neck sometimes due to the “noise” it makes and its incompatibility with some devices, but you risk destroying your panel. Even with a bit of knowledge, fixing something with SMD components can be near impossible without the right equipment.

Not sure, I remember looking for my panel and I saw an MS-2 new in box for $30.

I’m not planning to do any SMD rework, but my first thought was to basically replace the transformer with a filtered DC supply.


If you accidentally cook something, fixing it may require that. Though it is an idea, I wouldn’t try it. Risk VS Reward.

You might try adding a capacitor between the + of your NAC and the + connection of the device you want to receive filtered DC. As long as your A/V signal is polarized (and only AC signals are not), you cannot reverse-charge it during supervision, and since it would only supply the 1 A/V signal you don’t have to worry about working it on to the panel somewhere/somehow. Unfortunately, the MS-2/MS-4 has an on-board rectifier which is designed to take the signal from the transformer and turn it into FWR. If you had a schematic you could replace the filtering capacitor with one that has a larger capacity and get a much smoother signal, but again, you risk damaging the board.

Also note that any of my solutions proposed would void any warranty, fire code, NFPA guideline, UL listing, etc, etc, that may have applied to the system so don’t do it in a professional install.

NFPA my a$$ since this is a hobby system.



What kind of cap value am I looking for? 1000uf?

Do you intend to use Simplex devices on your panel? Most devices run just fine on FWR.

Probably a TrueAlert eventually, but I was thinking about running older mechanical horns like a 450D, Simplex 9219, 7002T, etc.

The only devices you’d have to worry about would be the TrueAlert and 9219 then. The mechanical horns will run, but will sound raspy.

Yeah but I want the mechanical ones to run smoothly. It might just be a dumb thing but I want them to sound nice.

Another option is to use a NAC panel, although it may be around the same price to get different conventional panel that outputs filtered DC.