Whelen Air Horn - Popping Noises

Lunixor

New Member
Hi all,

I recently acquired a Whelen PAP112 Air Horn & PA Amplifier that I've installed in my vehicle. Unfortunately, I've noticed a couple issues that I can't seem to figure out a cause for.

Whenever the PAP112 unit turns on or off (via key ignition power), a loud 'pop' noise can be heard from the speaker. It is very noticeable and somewhat annoying. The air horn itself functions fine.

Similar thing occurs when keying the microphone - an audible popping noise both at the start and end of push-to-talk. I've noticed that when the mic is plugged directly into the unit it's not as much of a problem, but when using the 10' extension cable (from trunk to cabin) the noise is much more audible.

From what I can find online, these are generally not normal noises for most siren amplifiers. Is there something wrong with my PAP112 unit? It is the older model and I would guess it is 10-20 years old if that plays in as a factor.
 

Jennifer Rose Towing

Established Member
A previous Whelen siren I had would give that same tick, clap or pop when turning on or off. The off noise was a bit quieter then when switching on. I never thought twice of it, thought it was normal. The siren was a 295 something. Keying the mike gave a light noise too but much much quieter then the power switch.
 
OP
OP
L

Lunixor

New Member
I have the unit grounded to the chassis behind the passenger kick panel, so I'm not sure if grounding would be the issue
 

d119

Member
I'd be looking at capacitors on the unit, especially if it's that old. Generally capacitors are used for filtering and containing voltage spikes, which is what you're getting. Might be time for a trip in to the manufacturer, or someone who does bench-level electronics repair.
 

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