Does anyone know the pinout of the external power connector on the Pentax 645N?

[digital_archivist]

My 645n is occasionally intermittent, so I bought a Power Cord 645 with the intent of powering it from an external source (i.e. bunch of lithium batteries) to see if it helps. If it does, I'd guess the problem is in the internal battery holder and watch for a replacement.


Thanks!

 

[Hassasin]

Just one sure this is the 645N? The original 645 had internal connection issues between grip and body, would not trigger constantly, but in every case I had to deal with it, using external battery pack solved it, so the issue was clearly somewhere between internal battery power/trigger switch path. It's a fairly common issue and when 645s were aplenty, they sold cheap.

 

[Hassasin]

This is what you really needed. Power cord itself is adding a lot of work to what you want to try. And this is a very useful accessory if you shoot in low temperatures.

Pentax 645 remote battery holder

 

[Hassasin]

to see if it helps. If it does, I'd guess the problem is in the internal battery holder and watch for a replacement.

I'm not sure what you by "watch for replacement". Battery holder itself should be easy to meter if power is on the pins. If the problem is what original 645 had, the issue was past the holder, somewhere between holder connection terminal and trigger switch. This was bypassed by applying external power source.

As at some point my 645 stopped going intermittent I did not go deep. But also power grip on original 645 is removable, not the case on the 645N. So in the case of 645 you could actually replace the whole grip, on 645N that's an internal job.

 

[Hassasin]

BTW, the battery holder of 645N was much better built than original 645, which was ageing badly, susceptible to low temperature material fatigue, etc. I have the NII, so that is same as in N, much sturdier holder and I can't see how holder itself has failed. Unless you can see clear signs of contact corrosion or other damage.

 

[digital_archivist]

All good things to know - thanks! I didn’t realize the battery holders changed between the 645 and the 645n. I’ll keep digging for the real issue.

 

[Hassasin]

One other thing you might want to try is remote cable (vs. remote power set up). This might better indicate where the problem is. If remote fires shutter consistently it would farther support the idea issue being in the grip, between battery connectors and trigger switch. Event mechanical cable might show a different behaviour.

 

[digital_archivist]

It’s an odd sort of intermittent; sometimes I’ll shout an entire roll with no issues. Sometimes, the shutter will fire just fine, but there’s an approximately three second delay before advancing to the next frame. Fresh batteries don’t make a difference.

 

[ant!]

I have a spare external battery holder (same as in link above, have two and need only one), works for 645 and 645n (but the actual battery holder is the 645 one in these packs). I'm am in Canada, not sure if this is making sense for you. Message me in case you are interested and I am sure we can figure something out...

 

[digital_archivist]

Message sent. Thank you!

 

[ant!]

So, finally got the time to measure this (massive ice storm knocked out Montreal, plus Easter days...).

I measured the external battery holder with 6 fresh AA (1.5V each, without measuring them). The result is 9.5V, so they are simply chained together. No idea what the minimum voltage is for used batteries. Same voltage on the battery holder and the cable pin which gets inserted into the camera when using the external battery holder.

Polarization: See the images here

 

[Hassasin]

The problem has always been internal, at times the holder has clear signs of contact corrosion, but that is too obvious to miss. As @ant! just showed, batteries are in series, but while I don't know what the minimum voltage is to still run P645 as designed, I do know the camera runs on same set of batteries for quite a few rolls of film. Whatever Petnax says in specs is pretty close in normal condition.

The issue here is with 645N though, but possibly, internally, Pentax made no changes in how they knitted everything together. All I can think of is to open up the grip and look for any signs of contact problems.

 

[yurihuta]

Not sure if this would help but Jaron Ball has repaired three 645N bodies for me. Might be something easy to take a look and see if this is normal within your battery grip.

Pentax 645N No power & Erratic functions Repair info - Burned out inductor & Bad Negative Bat Switch

 

[digital_archivist]

Good idea! Thanks for the suggestion!