Gossen Pilot / Sixtar with slow needle.

Discussion in 'Classic Manual Cameras' started by christos_theofilogiannakos, Nov 19, 2013.

  1. I don't know if this is the right place to ask, but "classic manual cameras" was the closest, so here it goes:
    I was recently given a vintage Gossen Sixtar (Pilot in the US) light meter. I already have a Lunasix, but the Sixtar appeals more to me because of the smaller size. The readings seem to be fairly accurate, but the needle is quite slow to settle to its final resting point (in excess of 10 seconds). It moves quickly to a certain area of the indicator panel, then it very slowly drifts to finally stop at least one or two stops from where it showed originally. The Lunasix needle responds almost instantly, so I wanted to know if this is normal.
     
  2. The Pilot meters I have (a broken Pilot and a non-broken Pilot II) are selenium meters (no batteries) and very simple indeed. They do not behave this way. I also have a couple of old Sekonic CdS meters that resemble the Sixtar, and they do not behave that way either.
    Meter movements can bind if the needle gets a little bent and contacts the face or crystal, even lightly, and also if the meter bearings get loose or the tiny hair spring that returns the needle gets kinked. A meter will usually respond well to input even if it's binding, but in order to respond well to input the needle return spring must be extremely weak. You can check if the problem is mechanical or electronic by shaking, inverting, or tapping the meter when it hangs up. If the needle flops back to zero, it's likely a mechanical problem with the meter movement.
     
  3. Unless I'm grossly mistaken, there seems to be some confusion as regards designation. The Pilot indeed is, as indicated by Matthew, a selenium meter which does not need batteries. But the Sixtar is not the European name for the Pilot; it rather is a Lunasix-style device, and of course it does need batteries. So, the first step should be to ascertain whether you have a selenium or a battery-operated meter.
    If the former, in addition to Matthew's suggestions you must be aware that the needle's movements are powered by the external light, and thus even with a meter in perfect working conditions cannot possibly be as fast as in a Lunasix (but 10 sec. is much too much). If the latter, checking the batteries and cleaning their compartment is an obvious step.
     
  4. Assuming this is indeed a Sixtar (not a Pilot/Sixtino). Needle movement is especially slow at the low end of each (low/high) range. This seems to be caused by the internal response of the CdS photoresistor. In the case of the low end of the high range, this can be overcome to some degree by briefly depressing the side button that switches to low range: the CdS element will be briefly exposed to a higher flux of light, and, returning to the "high" (default) range, will converge more rapidly to a stabilized reading. Also do check (against a known good photocell or silicon TTLmeter) that readings are accurate with whatever substitute for a mercury battery that you are using.
    The Sixtar is a good exposure meter, usable to lower light levels than a Selenium cell. Enjoy!
     
  5. Thanks for the quick replies! The US name for the Sixtar was Super Pilot, so this is my mistake, it is not a Pilot. I am using a fresh alkaline PX625 cell, but I haven't touched the calibrating screw at the back and the readings are off by 1 stop approximately, I guess this is easily corrected. It's just that the needle behaviour is strange and doesn't seem to be a mechanical problem, more like a problem with the CdS cell as suggested by Bernard Lazareff. I plan to use it with my Yashica D TLR, so speed of response is not such a great deal, at least it is relatively accurate for the time being.
     
  6. I've had a Super Pilot for about 35 years and it still works perfectly.
    And I have a Pilot 2 from the same era that still works fine because it was stored away in its case fro many years.
    Pilot 2s show up on ebay frequently. I bought a new one about a year age. Works perfectly.
    Try the Wein zinc cells for the battery.
     
  7. Cadmium Sulphide (CdS) cells have a "memory" and react slowly in general. After metering a high value and changing to low light, it will take considerable time for the meter needle to reach its final position. I still have a Sixtar but have not used for many years. I have no battery at the moment. I would say the behaviour of yours is probably normal. In those days people did not need much persuasion to switch to Silicon Photo Diodes.
     
  8. There are adaptors by CRIS and by my friend Frans de Gruijter to use 1.5 V Silver Oxide cells instead of 1.35 V Mercury cells. The adaptors correct the voltage.
    http://www.mediafire.com/view/?iar6oztje34owme
    Ferdi
     
  9. Not sure about this meter, but on all meters I have seen the adjustment screw on the bottom does just adjust the zero position of the meter needle, it can not be used for calibration. But of course the zero position has to be set properly prior to calibration.
    Also, it is NOT possible to use a meter designed for a mercury cell with an alkaline cell, even if you compensate for the voltage difference. The reason is that the voltage of an alkaline cell is everything but constant over time, it will drop from an initial 1.55V to around 1.4 V after some time. A mercury cell has constant voltage over its lifetime and the meter circuitry needs a constant voltage.
    You may use a silver oxide cell in proper format (if available), its voltage is higher (1.55V) but it is constant over time so the meter can be properly compensated. Or use a hearing aid battery in 625 format, it has almost the same voltage (1.4V) as a mercury cell but will last a few months only (independent of time of usage).
     

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