How to Modify/Customize a PA-300?

ProPatriaNeverPassAFault

Silver Supporter
I'm looking to customize the PA-300 that I have a little bit. I have the product manual with the circuit diagram and while my knowledge of electronics isn't the best I'm pretty handy with a soldering iron. I'd like a one-of-a-kind siren for my collection and to turn a lowly PA-300 into something really unique. I'm looking for some help as to how to modify specific components of each oscillator to produce the following:

1) Slower, deeper wail that has that "old-school" sound and a slower wind up/wind down. Looking for something similar to a PA-20 or any of the older sirens, really. WS-222, 224 and 295s all have a sound that like like, ditto for any of the North American Signal Siren Masters or the older SVP SA-400s. I'd like to modify it to become what Wailer would call a musical instrument ;).

2) Slower and deeper yelp. Again looking for an old-school sound. Would also be interested in a tone that's similar to a Powercall Warble.

3) Faster Hi-Lo or something a bit similar to the Priority tone on some PA-300s. I'd be looking for something like a Hyper-Low on a Mastercom.

4) As for the Airhorn, I'm still on the fence. I could go for either a deeper one or one that's a bit like the above-mentioned sirens.

I've stumbled upon an old cache of electronic components. Resistors, transistors, etc. This will hopefully be pretty helpful.

As for modifying the oscillators to change the tone, is it as simple as changing the resistance on a resistor, or is it more complicated than that? I'm also rather concerned about frying the siren or doing some sort of damage to it.

Definitely looking for some help on this one as well as some general info for modifying sirens, such how changing a component in a certain way will affect a tone.
 
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ProPatriaNeverPassAFault

ProPatriaNeverPassAFault

Silver Supporter
Also found this while down the rabbit hole that is YouTube... Might be helpful if you can translate it!

Thank you so much!! That is too cool! Thanks for taking the time to look that up! Looks simple enough, too.

Thankfully, I can understand this Spanish thanks to both French education and government French training, believe it or not. Romance Languages are all pretty similar, but since I don't want to screw this up and because Google Translate isn't exactly spot-on, I'll be double-checking with some good friends of mine from Latin/South America. Problem is, they'll just argue whose dialect is better instead of watching the video. Happens every single time I need Spanish translation. It'll get heated too, as it always does. It has some major entertainment value ;). I'll just moderate their "discussion", as they call it, with the siren.

Only in South America can a heated argument where both people look about ready to kill each other be called a "discussion." Wait, Russia's probably the same. It gets really fun to mess with them by saying that the dialect used by the countries next to their home countries are better than theirs. If you have a death wish, say that the soccer teams from those countries are better than theirs.

Sounds like it's a PA200 you're after!
Yes and no. The PA200's sound would be a definite improvement. Kicking myself in the rear for not getting an earlier one for a steal a few months ago. Ah well. What I'm really looking for is more like a PA-15 Series 1B/C/D or PA-20A Series 2B/C/D sound.
 
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I've located a "silver fox" PA300 & a Director on eBay. There's also a PA201 up in Winnipeg. I'm sure all 3 would be fairly easy to tinker with.
 

Wailer

Veteran Member
Sounds like it's a PA200 you're after!
No, you definitely don't want a PA200. I have one, and it's a high-pitched screamer. :mad: I also have a PA20A series 2E - same circuit, same sound.

There’s a deepness that some early PA300’s have that no PA200 can match. Curious what you come up with in this post!
The silver face and early black face PA300s (pre-1990) have a nice slow rising wail tone. :) Still high-pitched, but I find it more pleasing to the ear than the PA200 and the PA15A 1E / PA20A 2E wail tone.
 
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ProPatriaNeverPassAFault

ProPatriaNeverPassAFault

Silver Supporter
OK, quick update! Maybe I'm biting off more than I can chew, but I want to have a switch for the tone as shown in the video plus a momentary switch for a hands-free type of effect. How I'm thinking about doing this is asking on some electronics boards how I can rig up a momentary switch that's on for 8 seconds or so. Again, kind of like a Jerry-rigged hands-free. I'll attach the circuit diagrams of the PA300 as well as the video and see what the electronics gurus have to say.

I think that it'll need a timer chip, but beyond that, I'll have to see what they say. I'll probably just start with what's on the video then work up to the hands-free type of setup. Past that point is when I hope that the fun can begin and I can find out out to get a nice slow rise/fall to the wail with a deeper pitch. Ditto for the yelp. I don't want to head down the rabbit hole with this, so it'll be a gradual project. My intended goal is a PA-300 with the sound of a PA-15 or PA-20 or similar old-school siren that also has what's depicted in the video that FiremanSketch posted that hopefully has the 8 second momentary switch. Beyond that point. Who knows?
 
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ProPatriaNeverPassAFault

ProPatriaNeverPassAFault

Silver Supporter
Does anyone know what the blue trimmer on the PA300's circuitboard is for? Don't want to go about messing around with it until I know. My guess is the hi-lo speed, but again, I don't want to mess around with things. Fried sirens aren't good for much besides a cool paperweight.
 

MtnMan

Senior Member
Does anyone know what the blue trimmer on the PA300's circuitboard is for?
If you're looking at R57, it is in fact a pitch adjustment, affecting all the siren tones. I was just experimenting with it on an older (ca 1990) PA300, and there's a surprisingly wide range of adjustment, from about 680 Hz peak and hold, up to 1,960 Hz. That gets well into the range of the the early, lower pitch sirens, but to me it sounds odd without reducing the wail rate as well.
 
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ProPatriaNeverPassAFault

ProPatriaNeverPassAFault

Silver Supporter
If you're looking at R57, it is in fact a pitch adjustment, affecting all the siren tones. I was just experimenting with it on an older (ca 1990) PA300, and there's a surprisingly wide range of adjustment, from about 680 Hz peak and hold, up to 1,960 Hz. That gets well into the range of the the early, lower pitch sirens, but to me it sounds odd without reducing the wail rate as well.
Yep, it's R57. Definitely have to play around with that. Also have an older PA300 from the same year and I have to say that 1,960 Hz is really up there. 1,700 sounds pretty good with a Whelen wail, but I'll definitely have to play around with this a bit. I'll just have to be make sure to try and mark where it was originally set. This will be a fun! Thanks MtnMan!!

MtnMan, do you use an oscilloscope when you test these sirens? How do you determine their frequency? I don't have an oscilloscope (yet...), but is there any way to determine the approximate frequency of a siren's tones without one? Thanks again!
 
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shues

Lifetime VIP Supporter
Audacity is a piece of free software that can be used to determine the frequencies of your siren's tones from an audio recording.
 

MtnMan

Senior Member
Hah, I was just recommending Audacity in a PM to Matt. Here's an example of spectrum analysis on a clip of an early PA-15.

Audacity.jpg
 
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ProPatriaNeverPassAFault

ProPatriaNeverPassAFault

Silver Supporter
Whoa! I've never even ventured into that corner of Audacity! I've only ever stuck to the safe confines of waveform view. Had no clue that Audacity could do that. It's a good program, but does have some limitations with certain things. Waveosaur is my backup program. I have a copy of SoundForge somewhere, but I don't know if it does this. Best to stick with Audacity :) !

Audacity was my lifesaver when I used to do a radio show a few years back. The station wouldn't allow profanity. While there isn't much, if any, in funk, soul, jazz or Motown, certain unallowable words sometimes showed up in songs. It's trickier than one would think to clip or muffle a second or less out of a song and then have the edited version sound seamless.

Thankfully, sirens aren't known to use bad language. The only exception would be anything that's said over the PA. That's not the siren's fault ;) . Only other exception would be if one of the Japanese Panasonic or PATLITE talking sirens that they use on their ambulances had some sort of a glitch or was somehow reprogrammed by someone with a sense of humour.
 
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Jasonc

Member
Apologies for resurrecting a long dead thread, but I used to to sell modded PA300's on eBay in the early 2000's before they really started cracking down on LEO items. My most popular mod was installing a red momentary push button just to the right of the rotary switch and jumping either R24 or R26 (can't remember exactly) and this would produce the phaser tone when the button was pressed while the siren was in yelp mode. Sometimes I'd add a low value (10 Ohm) resistor inline to slow the phaser just a tad as directing jumping the resistor made the tone extremely fast. I've also modded them to sound lower and slower like the older PA200's, but I can't recall exactly which resistors I modified. It involves turning down R57 as mentioned above and pulling out a resistor and either replacing it with another trimmer pot or a higher value resistor to slow up the cycle time. It's obviously much easier to do on the older silver PA300's vs the newer SMD units but It can be done regardless. Messing around in the tone generator/oscillator circuit is pretty safe, so there's little chance of blowing anything up as long as you stay away from the output transistors or anything on the power side. It's how I developed my aforementioned mods, so tinker around and experiment and have fun. Just be careful with setting the tones to low as you will fry the output transistors or your speakers. I'll take a look and see if I can find my old notes and schematics, but I'm arid they were lost in a hard drive crash I had 10 years ago. It's been many years since I've messed with modding any electronics so my memory is a bit rusty.
 
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ProPatriaNeverPassAFault

ProPatriaNeverPassAFault

Silver Supporter
Apologies for resurrecting a long dead thread, but I used to to sell modded PA300's on eBay in the early 2000's before they really started cracking down on LEO items. My most popular mod was installing a red momentary push button just to the right of the rotary switch and jumping either R24 or R26 (can't remember exactly) and this would produce the phaser tone when the button was pressed while the siren was in yelp mode. Sometimes I'd add a low value (10 Ohm) resistor inline to slow the phaser just a tad as directing jumping the resistor made the tone extremely fast. I've also modded them to sound lower and slower like the older PA200's, but I can't recall exactly which resistors I modified. It involves turning down R57 as mentioned above and pulling out a resistor and either replacing it with another trimmer pot or a higher value resistor to slow up the cycle time. It's obviously much easier to do on the older silver PA300's vs the newer SMD units but It can be done regardless. Messing around in the tone generator/oscillator circuit is pretty safe, so there's little chance of blowing anything up as long as you stay away from the output transistors or anything on the power side. It's how I developed my aforementioned mods, so tinker around and experiment and have fun. Just be careful with setting the tones to low as you will fry the output transistors or your speakers. I'll take a look and see if I can find my old notes and schematics, but I'm arid they were lost in a hard drive crash I had 10 years ago. It's been many years since I've messed with modding any electronics so my memory is a bit rusty.
I apologize for my lack of knowledge with electronics, but re: jumping the resistors, the resistor was jumped to one post on the momentary switch? What was the other post wired to? This sounds like what I'm looking for.

Re: setting the tones too low and risking damaging the unit, what range or frequency (??; I apologize again) would you say is the red line for getting into risky territory? Certainly not an impossible unit to replace, but I've noticed that they're surprisingly pricey on the bay. As in gouging pricey. Would much rather know when I'm treading into dangerous territory than *ever* risk a fried unit!
 

Wailer

Veteran Member
I've also modded them to sound lower and slower like the older PA200's,
The PA200 was designed to produce fast rising high-pitched wail and yelp tones like the sirens we hear nowadays. I have one that sounds lower in pitch, but that's because some of the components (likely capacitors) are worn out.
 

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