Frequency Gage wrong at startup

[Toolslinger]

So at startup on my 802a, the frequency gage is pinning itself to the right. Conditions are cold. We're in the teens most days when I get out there. Unit is dry, under a tarp that is on the hoops on a 116a3. Humidity is pretty low.

First few times it caught me off guard, and I dialed the RPMs down until it was right around 61hz (no load), but it really sounded like it was running slow. After it ran for several minutes, I'd come back, and the gage was reading low, so turn up the RPMs to 60 (loaded by now), and it sounds right then.

Finally brought the Fluke with me this morning. It's hitting 61hz on startup, but the gage is still pinned right. Since the Fluke said I was good, I left it alone, and again after several minutes, I checked again, and the meter was right on.

Has anyone run across this before? Should I be expecting something to fail shortly?

 

[kloppk]

Sounds like the Frequency Transducer is on its way out.

 

[Toolslinger]

Well, that's utterly logical... At least it isn't buried too deep.
Naturally that's one of those things I can't use from the 813a carcass...
Far from the end of the world.
Thanks!

 

[BeStihl]

Mine seems to swing between 1Hz higher than actual to dead accurate when the temperature changes. I think it reads higher on 80 degree days and spot on when around 40 degrees, but it has never pegged that far off. I was instructed to set it at 61.5Hz no load with a fluke and monitor it from there, that has been great advice.

 

[Toolslinger]

As long as it's putting out 60ish +/- 1 or so I'm not going to bother with it. The gage is nice as a reference, but for most of the use it see, it doesn't matter, the heater will run just fine for now.
The Fluke is all knowing, and I trust it.

 

[Scoobyshep]

These are a known pita. Take that transducer and gauge and throw it as far as possible. There are many line voltage frequency gauges out there (if you look hard enough, one what requires no adapter) that are far more robust.

Sent from my SM-S908U using Tapatalk

 

[LuckeyD]

The Frequency Transducer when new seemed to work at -20° during testing. Testing was done at white sands, and at the cold room in Aberdeen MD. I found in the field under normal cold conditions it does funny things as you have indicated. I took one apart, but it took too long and thawed out while taking it apart. I found very small amounts of water droplets inside. Humidity will coat it and after starting this seems to go away as it runs. One member mentioned line voltage freq units and these are inexpensive, but if you want to keep it OEM, recommend two things:
1. drilling a small weep hole, being very careful not to penetrate the box as you break through. This seems rare, but it was recommended by others several times. Keeps the thing going longer.
2. Take that box and put it in your oven at about 100-120° for about an hour and a half. When cool enough put it in a plastic bag sealed until it is cold enough to handle and re install. Should have worked out moisture and it should work again.

 

[Toolslinger]

That makes sense. Something is just sucking in a little moisture, and then dries out with the power flowing through it.

My preference would be to keep it OEM if for no other reason than the schematics, and troubleshooting info would be right. In addition, I really don't want cheap gages involved. To me, they wouldn't look right, and I'm not sure how much faith I'd have it it. I did find some nice Hoyt line voltage, analog gages that would likely drop right in, but ruggedized Hoyt, and cheap don't really run together.

This would have to be a summer project, or after I get #2 back together and running.