M3 flash sync trouble shooting?

[Sax45]

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Hello, I am the new owner of a 1960-61 M3. This morning I received a PC sync adapter so that I can use the M3 with flash. 

Unfortunately when I went to try it, the flash would not fire. The combo I used (Nikon SB-30 + PC-hotshoe adapter) has never failed me on any other PC camera. This morning I verified that it still works fine on every other camera I own that has a PC port.

So obviously, there is something wrong with the camera or something wrong with the Leica-to-PC adapter. How can I go about diagnosing which one is at fault? 

I own a multimeter, but I pretty much only know how to use it test batteries. But I am sure there is some way it can be used to test whether the camera is closing a circuit during exposure?

Thanks!

 

[dg4mgr]

For a first test, you don't need the multimeter. Set up the flash, connect the adapter and Leica cable and close the circuit at the connector you would normally plug into the M3. This can be done using a piece of wire or a paper clip. In case the flash fires, you know the cabling is ok.

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[mujk]

I'm no expert on the M3, but just to check: the left-hand socket is the one to use and the shutter speed the one indicated by the flash symbol (or on M3s with the old shutter speeds 1/25 or 1/50).

You can use a multimeter to to check for a closing circuit by using the resistance (ohm) measurement mode. An open circuit should indicate an infinite resistance. However, the flash control circuit will be closed only for a very short time by the camera, so you may not be able to detect it. Look out for a very brief change in the reading (digital)/needle movement (analog). 

Edited March 2 by mujk

[Sax45]

1 hour ago, dg4mgr said:

For a first test, you don't need the multimeter. Set up the flash, connect the adapter and Leica cable and close the circuit at the connector you would normally plug into the M3. This can be done using a piece of wire or a paper clip. In case the flash fires, you know the cabling is ok.

 

1 hour ago, mujk said:

I'm no expert on the M3, but just to check: the left-hand socket is the one to use and the shutter speed the one indicated by the flash symbol (or on M3s with the old shutter speeds 1/25 or 1/50).

You can use a multimeter to to check for a closing circuit by using the resistance (ohm) measurement mode. An open circuit should indicate an infinite resistance. However, the flash control circuit will be closed only for a very short time by the camera, so you may not be able to detect it. Look out for a very brief change in the reading (digital)/needle movement (analog). 

 

Thanks for the help  both of you.

Yes I was using the left socket with the flash set to the sync setting (thought it should fire at all settings, even if it won't expose properly). I tried with more than one flash and more than one PC cable, all working reliably with other cameras.

I tried plugging the flash into the PC cable, and the PC cable into the adapter. I was not able to trigger the flash by bridging the middle of the adapter to the side of the adapter. I was able to fire the flash by doing the same thing to the end of the PC cable.

I used the resistance setting on my multimeter, bridging the middle and edge of the M3 flash port. It turns out the M3 shows 0ohm resistance for the entire duration that the shutter is held open, not just an instant at the beginning, which is interesting. I was able to read 0ohm both with and without the adapter in place. 

Last but not least, I tried sticking the PC cable right into the M3 port. The M3 port is far too big, but if you hold the cable in just the right way, you can get the center post of the PC cable to touch the center post of the M3 port, and the outer edge of the PC cable to touch the inner edge of the M3 port. Lo and behold, the camera is able to fire the flash!

So it seems like the camera sync works properly, and the adapter is able to attach to the the camera just fine. It seems the issue is that the adapter cannot interface with any of my PC cables. It will be returned and I will try another.

[mujk]

You seem to have located the source of the problem very well. If you are interested you can also use the multimeter to determine whether the discontinuity is in the center or in the outer ring connection by measuring the cable+connector combo end-to-end for each connection.

Edited March 2 by mujk

[Sax45]

Thanks Marcus. I tried that, using a PC cable with the adapter on one end. I probed the center pin of the PC end and the center tube of the adapter end, and found continuity. Then, probed the outer edge of the PC end and the outer edge of the adapter, and did not find continuity. 

So if I follow correctly, the failure to communicate is between the outer edge of the PC end, and the inner ring of the adapter. Any idea how to potentially fix this?

Either way, the eBay seller -- Gary Camera in Indiana -- said they could send me a new one and let me keep the bad one. 

[dg4mgr]

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vor 24 Minuten schrieb Sax45:

Any idea how to potentially fix this?

I have seen flash cable connectors that due to tolerances, easily plug together but the outer conductors don't touch - just one plunges into the other without touching. Maybe this can be fixed by a little bending or compressing the outer ring? 

[Sax45]

That seems to be what is happening. I think compressing the adapter would be impossible as it is very thickly walled, and that might compromise its ability to interface with the camera.

I could try flaring out the PC cable. The problem is those cables work properly now, and I would prefer not to jeopardize their ability to work with other cameras.