federal , smith & wesson siren amps

Thread Starter


Joined Feb 9, 2018
Greetings, I was starting to clean up and I ran across these old police siren controllers i wanted to do something with.
Federal signals PA-20A
Smith & Wesson Model 800
I've spent some time messing with them and all the siren functions work, wails, horn, bleeps, so that tells me all the time/signal generators and those functions are fine. the federal is pretty old school no ic, the s&w is one whole green 80s ic board, only about 3 caps, 2 transistors, and one giant transformer donut on top i guess.

1) main problem with the s&w(s) is the pa microphones don't seem to work. There are 4 wires to the mic handset and I re-soldered what was loose (pretty sure to the right pads based on the two i had, see pic blue wire) but I still just get nothing, a static click when you push the talk button tells me something is getting power or connecting but not full signal? do mics themselves go bad? one had the red and black wire contact loose, i just glued it back next to the cone. Can you rebuild them? or just splice another handset? i would refer to fix and keep it authentic

2) one of the units i also start to get a low level but noticeable crackle/static/groan after about 5 minutes on, unaffected by what mode you're in or gain adjust.

3) the federal also pa mic handset not working (but there is a ext jack), but i can't get enough volume to even hear if the handset is clicking or what. the sirens are a whisper with the same 100w speaker that the s&w will blow your ear out.
manual (and schematic) along with troubleshooting page says try changing main 3 transistors, which I did with spare used ones here, a little better and cleaner but still just as quiet. there is this 4th smaller transistor Q9 maybe if i remember but i don't have a spare here. should I order that or is the problem with something else not enough power like the transformer

4) troubleshoot page also says relace the two tant caps (C9&C11 i think) next to mic selector switch if no mic pa/radio. any other ideas on where to start or what to do. i know elec basic and have done some limited computer board stuff but have no clue on audio equipment. Thanks for all your help in advance
Download - Federal Signalwww.fedsig.com › resource-document › filement.


Last edited: