Princeton Tectonics Depth Gauge Adjustment

[duckbill]

I have here a Princeton Tectonics wrist-mount, altitude compensating, adjustable depth gauge, but no manual. How does one go about zeroing or compensating for altitude?

My guess is:
1) Loosen small screw (vent?)
2) Turn large screw to zero the needle
3) Tighten small screw.

Could somebody in-the-know please tell me if this is correct or otherwise set me straight?

Also, should the vent(?- if it is) be open during air travel, or would that be totally unnecessary?

[nemrod]

My Tekna guage which is similar I think has a seperate screw--thumbwheel for zeroing the needle. The altitude vent should remain screwed in all the time in my opinion unless you vent for adjusting. Since I have never dived at an altitude sufficient to warrant venting so I never have. The depth following needle should be reset to about 10 feet each dive--don't keep it shoved down on top of the depth needle.
The most accurate guages I have are the similar Oceanic, the Tekna is number one and the ScubaPro heluim gauge 0-500 feet is number three, all threee are very accurate. My old Voit hangs in there pretty good too. The Tekna, Oceanic, ScubaPro and I think your Princeton have expanded scales so they are easy to read, they are diaphram operated with obviously an air filled case.
I would not vent the case in a humd area as it may result in fogging.
James

[duckbill]

Thanks James.
I've never heard about not resetting the following needle against the main needle before. Does that only apply to gauges with no needle stop- the ones that make more than one revolution?

I also have one of the ScubaPro helium filled units. Is the screw in the center of the crystal the vent? I guess the needle itself is not adjustable on that one. Once the gauge is vented and the pressure equalized, if the needle is off, the needle is off. Is this correct?
And I guess I can also assume that the portion of the gauge between the face and the crystal is not helium filled, or venting would ruin that feature. So, what is helium filled?

Is anyone familiar with adjusting the Princeton Tectonics gauge in particular?

[nemrod]

Hey, I bought my Tekna and Oceanic long ago and stupidly lost the instruction books but I am positive that it was stated not to jam the depth needle with the following needle. neither of these guages have a stop btw. I think they do not want you to preload the needle and also it could interfere with zeroing the needle. As I said, two of my guages have a zero adjustment. I don't see this feature on the ScubaPro which I got on ebay without instructions. I am assuming the screw in the crystal is for altitude adjustment on the ScubaPro. Now, why do I need to zero the Tekna and not the ScubaPro?
The Princeton guage is a nice guage, do you have a pic?
James

[duckbill]

nemrod said:

I don't see this feature on the ScubaPro which I got on ebay without instructions. I am assuming the screw in the crystal is for altitude adjustment on the ScubaPro. Now, why do I need to zero the Tekna and not the ScubaPro?

That's a good question. Sometimes the needles on gauges end up off the mark. I'm not sure how. But the needle on my ScubaPro is nicely on zero.

nemrod said:

The Princeton guage is a nice guage, do you have a pic?

The easiest way to show it is by referring to Dan's which is for sale here about three quarters of the way down the page:
www.vintagescubasupply.com/access.html
I was hoping he might have access to a manual and chime in, but I'll bet the manuals are few and far between. This gauge is usually advertised as "vintage", but it sure doesn't look like a vintage model. I wonder what time period they come from.
I'll try to post a picture of the back side where all the adjustment features are located.

[duckbill]

Here is the back side. The adjustment screws are in the dark recesses near the arrows- large screw to the right ("Calibration Screw"), small screw to the left ("Altitude Compensator- Must be closed"). The other screws attach the band to the gauge, I think.

[nemrod]

OK, that is different from what I thought and really neat too. It seems to me that the calibration screw is like my thumb wheel for setting the needle to zero. The compensator screw is used to vent to ambient and then closed and KEPT closed. I would not open that on an airplane. It might not hurt it but I don't think it needed to do so and if you forget to close it then their goes a beautiful guage. The question is do you rezero after venting? I would think so. That is why I assumed the Tekna had the large thumbwheel.
Manuals and boxes get tossed, heck, I did the same thing, who would have ever thunk I would be sitting here 20 years latter yacking on about some old guages. Plus what I did not toss my mother and then later my wife did! Frankly I am lucky I have not been tossed out as well!
James

[admin]

Hi Terry;
I just noticed this thread today- sorry- I don't spend as much time as I would like on my forum! The Princeton gauge is probably the finest analog depth gauge ever made. I have several of them, both in feet and in meters. I also have one sold by Scubapro, with a black background, Scubapro logo and marked in meters. These Princeton gauges are one of the few gauges that are "serviceable", meaning they can be opened up and repaired. I took one of mine to several watch shops to see if they could open it. None could figure it out. So I did it myself. The back unscrews like a fine watch. I built a tool that attaches to the six small screws that hold the gauge to the wrist band. Then I used a strap wrench on the front portion and the back unscrewed. If you've seen a few of these gauges, you will notice that the rivet to the right of the 14 ft mark sometimes turns dark or black. This is corrosion starting and the case probably leaks. There are a couple of 0 rings inside that should be replaced to make them air tight again. Unfortunately, they are metric 0 rings and I haven't had time to track them down.
Terry and James, I'd be glad to send you a Xerox copy of the instruction manual if you want.
Dan

[duckbill]

Hi Dan,
I'm just checking in on the forum and I see your offer on the manual xerox.
I'm getting toward the end of my holiday travels now, but I am VERY interested in the information. I'll get back to you when I get home.
Thankyou.