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The Pentax K1000 is a classic, all-manual film camera, and just about the only annoying flaw is that the meter doesn't turn off, depleting the battery over time. Even if you put the lens cap on, it's going to die after months on the shelf. While I enjoy my K1000, in this digital age it certainly does spend most of its life in storage, and last time I put it away, I forgot to take the battery out.

I've been experimenting a lot with studio lighting, using the Cheetah Light V850 system for radio-controlled flash. Since it's all manual and I have the exposure parameters already figured out with my digital SLR, I figured I'd take a few shots with the K1000 even with the battery dead. However, with the trigger on the K1000 hotshoe, the flashes didn't fire.

This surprised me, because the camera has a simple standard center-contact hotshoe, and that's what the foot on the trigger has as well. It seemed like a perfect match. I thought that a) the K1000 battery was only for metering and b) the hotshoe was actually a switch, with the trigger voltage provided by the flash itself.

I have another battery on order, but I'm concerned that there is some other incompatibility with this trigger and that the battery isn't really the problem. Are my assumptions about the way the hotshoe works wrong? Why would the battery matter?

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  • The Cheetah Light V850 is also sold by different companies as as Godox V850 or Neewer TT850. I'm not in any way affiliated with Cheetah Light but am a very happy customer. The price is a little higher but they are US based and offer personal customer service and a quick turnaround in the event a repair is needed (rather than requiring shipment to Hong Kong like the others).
    – mattdm
    Nov 6, 2014 at 12:52
  • Re: Battery drain, as long as the insides of the camera remain fairly dark, this won't be a problem. If you're complaining of a dead battery after many years of the camera being in a closet or similar, you're probably just running into self-discharge. All batteries experience this. It's why the longest battery shelf life spec you're likely to see is 10 years. They're telling you how long the battery will remain in spec despite self-discharge.
    – Warren Young
    Nov 6, 2014 at 13:19
  • @WarrenYoung More like six months. And the battery, as far as I know, was newly made when I got it. (LR44 obtained locally; I ordered SR44 for the replacement. But this is a little off the topic!)
    – mattdm
    Nov 6, 2014 at 13:39
  • I used a K1000 pretty much exclusively for about 3 years, and I might have changed the battery once. All the commentary I see about this issue talks about the lens cap, but the viewfinder can let enough light into the body to turn the light meter on, if the ambient light level is high enough. You need to keep the camera in the dark if you need the battery to last a long time. The best way is to use a case you can close securely, but a closet with a door will do.
    – Warren Young
    Nov 6, 2014 at 21:07
  • It sounds like your trigger isn't thick enough where it attaches to the hot shoe to depress the contact switches under the side springs of the hot shoe mount.
    – Michael C
    Nov 7, 2014 at 11:00

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After some experimentation with my own K1000, I'm confident that it does not use the battery for the flash.

The camera's manual doesn't outright say this, but it does only mention the light meter when it talks about the battery. Wikipedia agrees.

The evidence that convinced me, though, was reading up on the X sync method, realizing that it is just a contact closure, and experimenting with it to find out how it works.

I reasoned that if the camera's internal battery were used for the flash trigger, I should see ~1.5 V between the two contacts, either continuously or momentarily when the shutter is closed. I tested this with a fast DMM and saw nothing.

Then I tested electrical conductivity between the hot shoe and the X terminal. The "ground" contact is connected all the time, and the "hot" contact is connected only when the two switches on each side of the hot shoe are depressed. (The square cross-sectioned sort of toothpick works great for this.) You can see these switches if you look under the little angle brackets that hold the flash on the shoe.

Test Setup

Pentax K1000 hot shoe contact closure test setup

That lead me to try tripping the shutter with my DMM in continuity mode, with the probes across the hot shoe. With each shutter release, the contacts were closed momentarily. The same happened with the X sync connector. (You need a fairly fast DMM to see this. Cheap DMMs generally need more than 1/60 sec to sense a contact closure.)

I assume that this is driven by the mechanical shutter. Two contacts sliding past each other, touching momentarily to close the connection, kind of thing.

All a flash needs to do to sense this is to put a high-impedance voltage on the "hot" pin in parallel with a voltage sensor of some sort. When the contacts close, the voltage source will be dragged to 0 momentarily, which means the shutter just opened.

This is why the camera manual makes a point of telling you that the hot shoe contacts are cold when you use the X sync terminal. Without those switches you see in the shoe, the sense voltage put out by the strobe connected to the X terminal would appear in the hot shoe.

The manual talks about a risk of electrocution. One way I can see that happening is if you have a wall-powered strobe system that's malfunctioned, so that it puts out AC wall voltage to the X terminal. If that appeared on the hot shoe, you could indeed be electrocuted. Such a circumstance wouldn't necessarily damage the camera or blow a fuse.

The comment below tells of another way this could happen, which is probably more likely.

The reverse case — hot shoe to X terminal — isn't as well protected. The X sync contacts are easily bridged by a finger, and the plastic cap is easily lost. I assume this case isn't as worth protecting against since a battery-powered hot shoe flash shouldn't be sending its high-voltage flash power through the hot shoe, but instead a low-power sense voltage. I have not tested that, so just take it as a guess, not a statement of fact.

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    (1) The "meter-only" info is on page 21 of the manual. (2) Old electronic flashes used the firing voltage on the main capacitor (150 to 500 volts), passed through the camera's contacts, to feed the primary of the 4kv triggering voltage transformer. Flash bulb units often (but not always) fed the bulb ignition power through the camera circuits (which could be 120V at light-a-household-lightbulb current on some of the scarier units, though the filament would die almost immediately).
    – user32334
    Nov 6, 2014 at 14:35
  • @user32334: I'm surprised someone would design a flash to put a high voltage across here. It really isn't necessary. It also means the switch inside the camera that closes these contacts has to be fairly studly, if it is to survive the arcing that will happen when switching that kind of voltage mechanically. I've never heard of a camera flash not working any more because the switch contacts had gotten burned away.
    – Warren Young
    Nov 6, 2014 at 14:44
  • With electronic flash, the current was negligible (there is nothing but a capacitive connection on the trigger voltage itself, and the only thing needed at the transformer was enough of a voltage rise to trigger the 4kv pulse in the secondary). But yes, old flashbulb contacts tended to be pretty sturdy. Try to keep in mind that this was at a time when high-voltage consumer electronic circuits mostly meant vacuum tubes; you can't apply today's design priciples to 40+-year-old technology.
    – user32334
    Nov 6, 2014 at 17:59
  • This fits with my belief but still leaves me mystified as to why my trigger didn't work...
    – mattdm
    Nov 6, 2014 at 18:04
  • @user32334: I was referring to the switch contacts that must be in the K1000, those connected to the shutter mechanism. They can't be all that big or heavy, owing to the limited space and spring power available.
    – Warren Young
    Nov 6, 2014 at 18:09

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