Pentax Spotmatic Meter Help

[Phoenix Phil]

Hi,

I just purchased a Pentax Spotmatic today and the meter is behaving incorrectly. I made the mistake of putting in a new battery backwards (plus side pointing outward). The needle moves up and down and seems to meter correctly but just in the opposite direction.

After realizing that something was wrong, I flipped the battery (plus side pointing inward). Now the meter doesn't respond at all. What have I done? bang:

Phil

 

[Andrew Touchon]

Hi,

I just purchased a Pentax Spotmatic today and the meter is behaving incorrectly. I made the mistake of putting in a new battery backwards (plus side pointing outward). The needle moves up and down and seems to meter correctly but just in the opposite direction.

After realizing that something was wrong, I flipped the battery (plus side pointing inward). Now the meter doesn't respond at all. What have I done? bang:

Phil

Is your meter switch on the front of the camera in the up position?

 

[OldNick]

As I recall with my Spotmatic SP, there is usually a plastic ring used to properly position the battery. Do you have this in place? If the switch is moved up and the meter still doesn't work, I would check to see if you are getting proper battery contact.

Jim N.

 

[Phoenix Phil]

Andrew: Yep, the SW is in the up position. The meter responds when the battery is in the wrong configuration.

Oldnick: mine didn't have a plastic ring but I have tried wrapping some black electricians tape around the battery to position it. Still nothing works.

I also found a Spotmatic F manual online and it has the battery plus facing the cap and away from the body, which is opposite to how it is stated in my manual.

I have verified that the meter matches an old Super Pilot meter; the Spotmatic just operates backwards. It indicates "+" when it is underexposed (and the manual states that "+" should be overexpose).

Thanks for the responses.

 

[OldNick]

I just pulled out my Spotmatic SP and checked the meter movement. When the lens is wide open, the needle is on the upper, + side of the notch. As you stop down, the needle moves down until it passes through the notch and moves toward the - indication.

Jim N.

 

[Phoenix Phil]

Hi Jim N,

Can you tell me which way your battery is inserted? Plus side in or plus side out? And also what battery are you using?

Thanks
Phil

 

[OldNick]

Hi, Phil,
On mine, the plus side goes toward the camera, which I guess you would call plus side in. The battery, which I obtained from a local camera dealer, is apparently made in China. The package is marked S400PX BP. It appears to be used as a replacement for E400N, RM400R, and V400PX. On the battery itself, it is marked S936S VINNIC Silvercell. I paid $3.80 for this one in July 2005.

Jim N.

 

[Phoenix Phil]

Jim thanks for the information.

Also, I figured out the problem. I purchased a 389 replacement battery which I learned from other forums that it fits perfectly. It does fit perfectly but I suspect that physically it doesn't match the orginal mercury battery.

I finally put the plus side in since that is supposed to be how it works. I then wrapped black electricians tape around the edge of the battery so that it would not touch the camera body. I suspect that the original mercury battery did not have the plus part of the battery extended to the edge of the battery like the new silver oxide batteries do today.

I then put a piece of 24 gauge wire on the other side of battery (facing the battery cover). I did this since I figured the battery negative was not making good contact with the battery cover which also connects with the camera body. In my earlier attempts with this configuration, the battery negative was not making contact with the battery cover so the meter would not work. Basically, the 24 gauge piece of wire serves the same purpose of a spring.

The meter now responds in the expected fashion. I thought I would write up all of this in case others have the same issue. In the future I think I will go with a slightly smaller battery (386 or 382?) so that can use a rubber ring as a spacer instead of electricians tape. Also, I plan on to put a bit of solder on the battery cap to build up the metal to make good contact with the battery negative side.

Thanks for everyone's help on this subject. I hope it helps others in the future.

 

[Andrew Touchon]

Jim thanks for the information.

Also, I figured out the problem. I purchased a 389 replacement battery which I learned from other forums that it fits perfectly. It does fit perfectly but I suspect that physically it doesn't match the orginal mercury battery.

I finally put the plus side in since that is supposed to be how it works. I then wrapped black electricians tape around the edge of the battery so that it would not touch the camera body. I suspect that the original mercury battery did not have the plus part of the battery extended to the edge of the battery like the new silver oxide batteries do today.

I then put a piece of 24 gauge wire on the other side of battery (facing the battery cover). I did this since I figured the battery negative was not making good contact with the battery cover which also connects with the camera body. In my earlier attempts with this configuration, the battery negative was not making contact with the battery cover so the meter would not work. Basically, the 24 gauge piece of wire serves the same purpose of a spring.

The meter now responds in the expected fashion. I thought I would write up all of this in case others have the same issue. In the future I think I will go with a slightly smaller battery (386 or 382?) so that can use a rubber ring as a spacer instead of electricians tape. Also, I plan on to put a bit of solder on the battery cap to build up the metal to make good contact with the battery negative side.

Thanks for everyone's help on this subject. I hope it helps others in the future.

This battery will work in a Spotmatic without modification: http://www.bhphotovideo.com/bnh/con...915&is=REG&addedTroughType=categoryNavigation

 

[OldNick]

Andrew,
That battery is identical to the one I am using, though mine was sold under another brand name. It does require the plastic ring to keep the proper parts in contact to make up the circuit. I would advise Spotmatic owners to keep the plastic ring when replacing the battery, in case one has to use a battery not sold with the proper ring.

Jim N.

 

[Andrew Touchon]

Andrew,
That battery is identical to the one I am using, though mine was sold under another brand name. It does require the plastic ring to keep the proper parts in contact to make up the circuit. I would advise Spotmatic owners to keep the plastic ring when replacing the battery, in case one has to use a battery not sold with the proper ring.

Jim N.

Mine also has the plastic ring on it. I think the ring came with the battery.

 

[Kim Coxon]

Hi,
The S400PX cells sold are generally a 395 silver cell with the collar. On their own the 395's are about 1/6 of the cost so it is worth swapping the ring over. Because of the difference in chemistry the polarity on silver cells appears different. On a silver cell the case is + and the stud -. On mercury cells it is the other way round. With the Spots, I find the 395's work perfectly well without the collar.

You may want the check the witing under the base plate. If this is corroded, it could give you the sutoms you describe.

Kim

 

[tedwhite]

Phil, I think you are on the right track. Replacement batteries (always use 1.55v silver oxides or Wein zinc/air) may not be the same width or thickness as the original, now unavailable, mercury batteries.

The Wein batteries work OK but don't last long, maybe six months, but the silver oxides will last two to three years. The trick is to buy one Wein (they come with a little O ring) and use it until it tanks, then toss it but save the O ring for use with the silver oxides.

To insure contact, clean the camera side of the cap thoroughly, then very slightly and very gently, pull the contact tang located at the bottom of the battery well up just a tad.

The meter system in Spotmatics consists of a bridge circuit, which is good as it's fairly indifferent to battery voltage variations.

Sometimes, with a newly installed battery, the needle will initially fluctuate wildly - or not work at all - but eventually there's a handshake and all is well. I find Spotmatic meters to rarely be more than 1/2 stop off a handheld meter.

What Spotmatic do you have? The SP or the F? A great site for data on your camera is the Yahoo Groups Pentax Spotmatic Forum.

As you use your camera, feel free to ask me questions. I've been using them since 1963 on virtually a daily basis.

Ted