Whelen tail strobe acting erratically

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Jason Koiter

Filing Flight Plan
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JayKoit
Looked for a thread on this subject but couldn't find one...

I have a '51 PA-22 with an old Whelen red/white strobe mounted atop the rudder. Today during pre-flight I noticed it still flashed, but about half as frequently, and not in a consistent rhythm...

My guess is the power supply (or transformer in the power supply) is on it's way out, but wanted to confirm that before I searched for a used replacement part, so if anyone can let me know that would be great.

I know, I know -- it's easier to replace with the LED version, but I'm trying to make it to my checkride without spending a lot on parts (and dropping that $700+ will clean out my DPE checkride fund). I'm almost there, I have one more night of dual work to go, hoping I can get this remedied economically with my IA and get things wrapped up.

Thanks
 
Might just be poor/dirty connections. I've found that ground connections are usually the place where stuff like this happens.
 
Daleandee said:
Might just be poor/dirty connections. I've found that ground connections are usually the place where stuff like this happens.
Click to expand...
Worth a look, I'll check those connections tomorrow...the flashes still seems to be the same intensity, just less of them per minute (and sporadic)
 
I agree with “ connection “issues.

Specifically if you are relying on the greasy Rudder Hinge Pins to provide a

good ground. You really want a bonding strap somewhere . They do

disappear.
 
If you take the lens off and the flash tube is black at one end of the tube it's time to replace the bulb also it is hard on the power supply and will cost you more than the bulb to replace.
 
brien23 said:
If you take the lens off and the flash tube is black at one end of the tube it's time to replace the bulb also it is hard on the power supply and will cost you more than the bulb to replace.
Click to expand...
I'd start here as well. I've experienced similar issues with strobes (although not a tail-beacon), and it was a failing bulb.
 
brien23 said:
If you take the lens off and the flash tube is black at one end of the tube it's time to replace the bulb also it is hard on the power supply and will cost you more than the bulb to replace.
Click to expand...
If it were me, and I determined the flash tube was bad, I'd install an LED.
 
Thanks everyone, I'll check the bulb and the ground and see what I find.
If a replacement part is needed, I may be able to get a bulb or power supply used for under $100 to get by for now, then I'll upgrade to LED at my annual in November.
 
An old circuit breaker or strobe switch can do this, too. Their contacts become oxidized and present resistance, lowering the supply voltage. And the only way to prove that is to measure the voltage at the input wire at the powerpack, with the powerpack connected and turned on. You might have to peel a bit of insulation off the power wire to get at it. While you're in there, peel a bit off the ground wire and look for voltage between that bare wire and a clean spot on the airframe. ANY voltage at all implies a bad ground.
 
Dan Thomas said:
An old circuit breaker or strobe switch can do this, too. Their contacts become oxidized and present resistance, lowering the supply voltage. And the only way to prove that is to measure the voltage at the input wire at the powerpack, with the powerpack connected and turned on. You might have to peel a bit of insulation off the power wire to get at it. While you're in there, peel a bit off the ground wire and look for voltage between that bare wire and a clean spot on the airframe. ANY voltage at all implies a bad ground.
Click to expand...
Thanks for the tip, Dan. I'll check that too.
 
So I started with the easiest troubleshooting first: I disconnected and re-seated the wire connectors for the strobe at the bottom of my rudder, and also manipulated the switch in the panel back and forth about 15 times, and the strobe is now functioning as it should -- for now :)

Thanks for the feedback, if issues reappear I now have multiple other things to test to find the problem.
 
I’ve seen bonding straps at rudder/ fin.

Not sure if factory.
 
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