Pentax MX Battery/Light Meter Issue

KidA · Sep 30, 2016

A couple years ago, I purchased a Pentax MX for my girlfriend and has been working fine. Once her original batteries died, I replaced them with two 357s and they only lasted a month - and the month did not come without problems: the meter would only work when it wanted to. Now she's in Florence and replaced her batteries (she wasn't able to tell me on our short conversation) with different ones. She brought it to a camera store and they told her the 357s were not the batteries to be used. Anyways, the meter worked for a few hours and after that, the meter started to show that all exposure settings were overexposed. Any of you know what's going on here?

Les Sarile · Sep 30, 2016

357 batteries are fine. Loosing meter is an electrical contact not being made and can be simple such as the battery cover needs cleaning to something else internal in nature. Of course the battery is only needed for the meter so if she can estimate exposure - and she's using color negatives with huge exposure range, she can still take pics easily particularly in outdoor daylight conditions.

As with all older cameras, a CLA may be due.

KidA · Sep 30, 2016

Thanks.

Yeah, I gave her a little run down on how to use sunny 16 and she's getting the hang of it. She had some time to practice - guessing first and checking with the light meter after and she's ususally within a stop. She'll be fine for now.

GRHazelton · Sep 30, 2016

I hope the MX works out for her. I have three of these lovely little cameras, and they all seem to eat cells voraciously. I've had one worked on by a supposedly competent local firm; I told them to keep it as long as need be to cure the problem, but it still goes through cells in a very few weeks. Now, the problem developed after I'd used this particular camera for several years with no problems. l bought it used. There is a tiny switch which can be seen after removing the base plate, it is supposed to open the meter circuit when the rapid wind lever is returned flush against the body. I've checked the switch with a VOM and it does open the circuit but it still eats cells.

Does anyone out there have a similar problem, and a solution??

Dan Daniel · Sep 30, 2016

There is a ribbon cable that passes over the pentaprism. I had one opened up and this cable had developed a crack, breaking a couple of wires. So the switch under the bottom plate isn't the only potential problem area.

For a truly knowledgeable answer, contact Eric Hendrickson at http://pentaxs.com/ He's seen it all, including all the small internal changes Pentax made in the MX production run.

If she has a smartphone she can get an app to use it as light meter as a backup and safety check for learning sunny 16. Also Fred Parker's ultimate exposure computer write-up can be a good explanation on metering and sure helped me relax on thinking that I needed to meter every shot five times. http://www.fredparker.com/ultexp1.htm

Les Sarile · Sep 30, 2016

I have two MX's and one had a non-working meter that cleared up by cleaning the battery cover. They both work perfectly and I can't even remember the last time I changed batteries in either.

Chan Tran · Sep 30, 2016

I think it has a short circuit somewhere rather than bad contact.

John Koehrer · Oct 1, 2016

^^^ That's more likely.
If I remember correctly(or not) I believe the correct battery
is the MS76, They're also labeled S76 and are silver based batteries rather than alkaline.

wiltw · Oct 1, 2016

John Koehrer said:
^^^ That's more likely.
If I remember correctly(or not) I believe the correct battery
is the MS76, They're also labeled S76 and are silver based batteries rather than alkaline.

A LR44 battery has the same size, shape and case as an SR44 silver oxide battery and even provides the same 1.5 volts. However, the silver oxide battery can last up to to four times as long! The high quality silver oxide battery might cost a dollar or two more, but it may be the difference between changing batteries once per year versus four times per year! But the 357 is indeed SILVER, same as S76!

georg16nik · Oct 2, 2016

Silver Oxide (SR44 and analogs) batteries give a constant voltage over their entire life, while Alkaline (LR44) batteries allow the voltage to drop gradually. Pentax MX is kinda famous for having meter issues of various kinds and I know from experience that the 2 MX of mine measure incorrectly with LR44 but about OK with SR44.

Pentax MX Battery/Light Meter Issue

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