Bronica ETRS AE repair

[adam m]

I recently picked up a Bronica ETRS camera and AE-II prism and have been working through the autoexposure flow charts in the service manual. In a few places, the manual describes how one of the leaf switches, the "display" switch, should be deactivated by a half-press of the shutter button. I cannot for the life of me understand how this is supposed to happen from the depictions in the manual nor the camera in front of me.

In the relaxed state, the display switch should be active, the memory switch should be active, and the sub-switch should be inactive.



In the half-depressed state, the display switch supposedly is to become inactive, potentially along with the memory switch, while the sub-switch should be active. In my camera, only the sub-switch becomes active during a half-depress, while the display and memory switches stay active and only become inactive during shutter actuation.



I'm basing my understanding of what the shutter button is supposed to do from Page 18 of the ETRS service manual, where it (albeit a little unclear) seems to describe the display switch becoming inactive during a half-press.



However the more direct description of the behavior comes from the AE-II service manual where one of the remedies describes ensuring that the display switch becomes inactive during a half-press of the shutter button.



Am I missing something here? I can't seem to find any way that the lower rocker arm should be moved during a half-press of the shutter. It's further difficult to intuit what should be going on as the illustrations in the service manual don't line up exactly with the actual parts that interface with the switches in my camera.

Edit: I did go back and watch this video, and it seems the display switch doesn't deactivate on his camera either. Is it the documentation that's wrong?

 

[reddesert]

What problem are you trying to address?

I'm not sure that I have a working ETRS AE prism, but the principle of operation is that the meter and display are switched on by a half-press of the shutter button, like most cameras. The text of the repair manual seems nominally backwards from this logic. Whether this is due to a wording issue, using "on" to mean "closed," or some subtlety of how the circuit works, is unclear. The service manual doesn't have a full schematic so it is not clear how the switches interact, but there is a troubleshooting flowchart.

The ETRS uses a set of easily accessible contacts at the front of the body & prism to communicate all power and information to the prism. So it is possible to diagnose some issues by removing the prism, putting a voltmeter on the contacts, and measuring voltages when the body is wound, shutter half pressed, etc.

 

[adam m]

I actually can't remember what the original issue was when I was chasing this down. The "display" switch in this context would be some secondary behavior caused by a half-press of the shutter button, as there is actually a second switch that goes closed with a half-press, as one might expect. I went down the rabbit hole though because of some weird volt readings I was getting at parts of the flow chart.

So far as I can tell, the ETRS body itself seems to function mostly electronically correct, but at the same time it's hard to tell because I've determined my AE prism is electronically damaged beyond what the service manual can repair. I would need a full schematic at this point to go any further, or to give up on this particular prism and bite the bullet for a new one if I truly wanted AE.