Hi Frantisek, I see the light now. I guess with the ZC batteries you just have to test them and replace them very frequently. 1.1V would cause a metering problem. Steve Larson Redondo Beach, California ----- Original Message ----- From: "Frantisek Vlcek" <[EMAIL PROTECTED]> To: "Steve Larson" <[EMAIL PROTECTED]> Sent: Saturday, March 16, 2002 7:12 AM Subject: Re: Which Spotmatic ? Frantisek wrote:
> Friday, March 15, 2002, 2:34:02 PM, Steve wrote: > SL> Hi, > SL> The compensation needed for the difference in voltage (1.35 vs. 1.5) > SL> is about 1/8 of a stop. In my opinion it is not a factor. I made a plate out > SL> of aluminum with a hole in it and put a rubber grommet in it to shield the > SL> negative and positive inputs, screwed it to the baseplate of a Spotmatic II > SL> and applied 1.35V, then 1.5V. The difference on the match needle was > SL> negligible. > SL> Voltage came from a linear 1.1-30VDC 5A linear power supply (home made), > SL> with a transformer you can arc weld with, yes that`s bragging. > > Hi Steve, unfortunately that's a wrong prepared > experiment ;-) > > with your laboratory DC source, you have neglected > one difference between Mercury and Zinc-Chloride batteries: the old > Mercury batteries had much more stable voltage over time, so it did > remain at 1.35V almost to the end of the battery. The newer, ZC > batteries, have 1.5 at the start but much less at the end. That's what > produces the meter problems. Although the difference might not be big > between 1.35 and 1.5, it certainly is between 1.1 and 1.5 or what's > the voltage of full and nearly empty ZC battery. Also, when you tested > at one EV only, you didn't test for meter linearity affected by the > voltage, which might or not might be (dunno). > > It's Pentax's (and many other Japan camera makers > at that time) "fault" that they didn't invest slightly more in bridge > circuitry which would make the whole point of different battery > voltage moot (I am led to believe there is such circuit in the SP. F, > so they did change to it at some time). > > Of course, I may be wrong too :) > > Good light, > Frantisek Vlcek > - > This message is from the Pentax-Discuss Mail List. To unsubscribe, > go to http://www.pdml.net and follow the directions. Don't forget to > visit the Pentax Users' Gallery at http://pug.komkon.org . - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
