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1. 07:51 AM - Re: Tach needle wobbles (A. Dennis Savarese)
2. 09:08 AM - Re: Tach needle wobbles ()
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| Subject: | Re: Tach needle wobbles |
Mark is right on the money. This is a very common problem with the tach
generator on the M14. Do exactly as Mark has described and very likely
you'll solve the problem.
A. Dennis Savarese
334-546-8182
www.yak-52.com
On 3/23/2021 1:11 PM, Mark Bitterlich wrote:
> There is a common problem with the Tach Generator plug, on the Tach
> Generator itself that might be causing your problem, especially if
> both Tach gages are doing the same thing.
>
> Take the cannon plug off the Tach Gen and carefully take it apart.
> Desolder one wire at a time, pull it out, heat and then tap solder cup
> in plug. Then reinsert the wire and resolver with quality rosin core
> solder. Repeat process for the other wires.
>
> Caution: Be extremely cautious with the shield to reinstall it
> properly as well. Failing to do so will result in EXTREME radio noise.
>
> Mark
>
> P.s. Not a guarantee, but this is the first place to start. Unhooked
> one Tach gage at a time also might be worth observing.
>
> -------- Original message --------
> From: Penco <osipenco@gmail.com>
> Date: 3/23/21 12:47 PM (GMT-05:00)
> To: yak-list@matronics.com
> Subject: Yak-List: Tach needle wobbles
>
>
> Hello,
>
> I'm encountering an issue with my RPM gauge on a Yak-52. It wobbles. I
> tried tightening everything on the engine pickup and it seemed to fix
> the trouble but after a few minutes of warmup, the wobble is back.
> Though nothing seems to have loosened up after I shutdown the engine.
> Do you guys have an idea where it might come from ?
>
> Below are the videos of the effect.
> First one a couple minutes after start, second one after about ten
> minutes of warming up.
>
> https://streamable.com/ojz5d0
>
> https://streamable.com/vd4zex
>
> Cheers,
> Alex
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=501064#501064
>
>
Message 2
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| Subject: | Re: Tach needle wobbles |
It could also be the air pressure regulator valve popping-off, unloading the
compressor, with the rear drive bevel gear backlash (shared with the tach
generator) causing the needle to twitch in sync.
Which would explain why it happens after 10 minutes or so into the flight
when the main air pressure has been recharged back to 50 bar.
Simple test is pump the brakes to lose some main air pressure and see if the
twitch stops . and returns when back to 50 bar again.
Hope this helps.
Rob Rowe
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