Computer issues tonght.LOL.. Just got a vintage setup in the mail tonight and have a question. Princeton Tectonics bottom timer, do these have a reset? Console mount only one knob. Appears that it winds in the clockwise direction. When the pressure switch is pushed the timer will run. Tryed pulling up and pushing down, nothing. Would think that there should be a way to reset to zero but not sure. Don't think I would really trust this timer but it is rather nice. Any info appreciated.
Princeton Tectonic Bottom Timer
- Thread starter smithrjd
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That silver ring on top (the one with the straight slot screw in it) has to be pulled out like the knob on a watch. Then you can rotate the hands back to zero. Don't be bashful, put a little rear end behind it, and it will work. It took me a week to figure that out when I got my first one. Furthermore, do no be paranoid about it keeping time. It is mechanical. Wind it up, and time it vis-a-vis your watch, and see if it keeps time. If it keeps time, then you can use it. If you do not want to use it, then sell it to me, my girlfriend could use a reliable bottom timer 
I have used them for years with 100% reliability. The O ring will stick, you need to pull up on the silver knob, sometimes spin it a bit and pull again, it will pop up, when it does you can set it back to zero. Then push it back down and wind the mechanism. Simple, works good. Thing is it records total bottom from 10 feet depth until you return to 10 feet depth so since actual bottom time is until you begin your direct ascent you may need a watch also to mark your bottom interval and ascent.
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rstofer
Contributor
My NAUI tables mirror the USN Tables, bottom time ends when you begin a direct ascent to the surface. There are other ways to do it and some are very workable.
Another thing I miss with the PT Bottom Timer is no rotating bezel to mark elapsed time but nonetheless I have found then useful to this day. I have several. N
rstofer
Contributor
From the 1987 NAUI Table:
So they clearly point out the difference in the ABT definition between NAUI and the U.S. Navy tables.
From the 1989 NAUI Table (current, I believe):
It is interesting to note that neither version requires a safety stop. The 1987 version allowed an ascent rate of 60 fpm while the 1989 version lowered it to 30 fpm. PADI is still 60 fpm but they recommend/require a 3 minute safety stop at 15'.
Richard
LOL, vintage being pre-73, my NAUI tables say USN on them and are from 66. What they did in the modern era, I dunno. I mostly use--shhhhhhhhh---either the 1980's PadI tables that are the same as the original Navy Tables or the actual Navy Tables from the 66-70 CR edition of the New Science of Skin and Scuba.
I use the 60s era tables with bottom ending upon beginning of direct ascent. Many tables now have variations and have also adjusted the bottom times. I prefer the original tables and original useage and then I add an appropriate safety factor. The tables that include ascent into the bottom time cheat you bottom time and then on top of that they have shortened the bottom time, 90 feet for example, on my NAUI/USN table bottom time is 30 minutes until beginning a direct ascent at 60FPM. Since ascent is off gassing why should it be included into bottom time except as an additional safety penalty mechanism? No, sorry, just me, my opinion, I don't agree with the concept of including ascent with bottom time. Now, with today's slow ascent rates, deep stops, safety stops etc that were NEVER a part of the tables or a common practice, is ascent always off gassing, perhaps it makes sense to include it as bottom time in which case your PT Bottom Timer would be perfect?
The USN tables diver at 90 feet for 30 minutes, ascent beginning at 30 minutes direct at 60 FPM, total dive time is 31.5 minutes. With your modified tables I think dive time at 90 feet is surface to surface 25 minutes on a square profile with a 30 fpm ascent rate and a 3 minute stop (stop not included in BT) so the ascent portion is 3 minutes from 25 for a actual time on bottom of only 22 minutes. TT surface to surface is 28 minutes including the safety stop. That is a huge difference. No, I think I will stay with the original tables, add an appropriate safety factor and stop.
So, now, me, for that 90 foot dive, 30 minutes on the bottom max, (adjusted as needed for safety factor), 60 fpm to 60 feet, 30 fpm to 10/15 safety stop for three minutes give up to 30 minutes actual time on bottom, 2.5 minutes to safety stop (approx) and then three minutes in stop for a total surface to surface time of 35.5 minutes.
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I use the 60s era tables with bottom ending upon beginning of direct ascent. Many tables now have variations and have also adjusted the bottom times. I prefer the original tables and original useage and then I add an appropriate safety factor. The tables that include ascent into the bottom time cheat you bottom time and then on top of that they have shortened the bottom time, 90 feet for example, on my NAUI/USN table bottom time is 30 minutes until beginning a direct ascent at 60FPM. Since ascent is off gassing why should it be included into bottom time except as an additional safety penalty mechanism? No, sorry, just me, my opinion, I don't agree with the concept of including ascent with bottom time. Now, with today's slow ascent rates, deep stops, safety stops etc that were NEVER a part of the tables or a common practice, is ascent always off gassing, perhaps it makes sense to include it as bottom time in which case your PT Bottom Timer would be perfect?
The USN tables diver at 90 feet for 30 minutes, ascent beginning at 30 minutes direct at 60 FPM, total dive time is 31.5 minutes. With your modified tables I think dive time at 90 feet is surface to surface 25 minutes on a square profile with a 30 fpm ascent rate and a 3 minute stop (stop not included in BT) so the ascent portion is 3 minutes from 25 for a actual time on bottom of only 22 minutes. TT surface to surface is 28 minutes including the safety stop. That is a huge difference. No, I think I will stay with the original tables, add an appropriate safety factor and stop.
So, now, me, for that 90 foot dive, 30 minutes on the bottom max, (adjusted as needed for safety factor), 60 fpm to 60 feet, 30 fpm to 10/15 safety stop for three minutes give up to 30 minutes actual time on bottom, 2.5 minutes to safety stop (approx) and then three minutes in stop for a total surface to surface time of 35.5 minutes.
N
As Slonda828 suggested just pull hard on the top knob to engage the reset mechanism...then it is a simple matter of resetting to zero. But, if your timer is of the older flavor and has a plastic knob rather than the silver knob be very careful. A hard pull will result in the knob pulling completely out and may damage the very fine spline in the top of it. If yours does have the plastic knob work it up slowly by prying with a fine screwdriver until the 0-ring loosens a bit and then carefully exercise it up and down until it moves easily.
BTW, you have a good device there....I have been using them since 1980.
Place PT timer in water for a few minutes. Then press down on the silver knob and rotate gently back and forth so as to wind the clock spring. Then lift up on the knob while slowly rotating. If it does not come up, press it back down, rotate the knob a little and try to pull up again. Repeat until it comes up. It may be stubborn if not used recently. Brute force should not be required and I have yet to need to pry one up but my fingers did turn blue on one but properly selected curse words and threatening gestures may be helpful in frightening the device into compliance. Liquid 100% food grade silicone is a good lubricant for the O ring but do not spray it with aerosol cans as the plastic case may not appreciate it.
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Well after using a screwdriver gently to wedge the knob up (silver metal) I did get it pull up. Still does not want to reset. Clicks like winding in the clockwise direction, turns a little bit counter clockwise then jams. Still runs though, perhaps best retire this one. Too bad as it has a very nice scratch free lens.
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