Yashica Electro 35 FC auto mode shutter speed repair

spl · Jan 11, 2022

I have a cute little Yashica 35 FC. It may never be a truly excellent camera but it IS compact and feels really nice. Shutter doesn't work in auto mode as described below in point 5. Can anyone tell me how to fix the symptoms I describe. I have intermediate repair skills and have disassembled Pen FT / OM1 and Yashica Electro 35 GTN, so I may be able to make the fix if it's not extreme.

Current camera condition:

1) Powered by 2xLR44 by addition of spring to battery compartment, voltage is 2.8 and should be good for this camera. Battery check is good. Mechanical condition seems perfect. Optics clear, viewfinder good to excellent. Focus distances are credible.

2) Camera appears to function correctly in flash mode, and would probably take a correct flash picture now (Guide number dial untested but appears to operate and moves with focus as expected Very beautiful) but the shutter clearly slows down to a visible speed probably 1/30, but only when batteries inserted, defaults to fastest otherwise so the shutter mechanism is not totally borked and the electronics are still alive in there.

3) Electronic self timer works.

4) Over exposure red arrow appears to work when pointed into the light on high ASA. Also the slow/yellow light lights up on flash only, but this may be hard wired as the shutter speed is fixed for that mode.

This is what is specifically wrong:

5) On auto mode the 'slow' light is inoperative ('Over' seems to work per point 4) and the shutter deploys at (looks like) fastest speed.

I'm going to check under the top for dislodged wires etc, but there isn't as much info for the FC as other Electro 35s.

Anyone know how to progress would be grateful.

shutterfinger · Jan 11, 2022

A LR44 battery is marked 1.5V. A new LR44 will read 1.55V to 1.56V. 2 LR44 batteries will read 3V to 3.2V.
Anything below 3V may not run a camera as the batteries will not supply enough current to operate the electronics.
Full auto mode requires the most from a battery. Battery check on a camera only tells you there are batteries with some power in the camera.
If you were to measure the batteries in the camera with the shutter button depressed in Auto mode you would see the voltage from from 2.8V to 2.5 V or less.

spl · Jan 11, 2022

I wish that were the solution but it doesn't pan out on experiment

I just now tried 2 fresh lr44, 3.2 volts. Symptoms are unchanged. I measured the voltage as the shutter button goes through its three stages:

Beginning: 3.1 - 3.2 volts
pressed down to 'over' stage: 2.6 volts
pressed further to 'slow' stage: 2.5 volts (Yellow light doesn't illuminate at all even though it should)
then shutter releases at fastest speed and voltage stabalises to 3.1 after a few seconds even with button held down.

When the camera is set to flash the same observations are made except that the orange Slow light illuminates.

I considered that despite the freshness of the batteries their internal resistance might be a problem, so I wired up an mb102 power supply at 3.3 volts and put the camera through the sequence again. The observations are unchanged but this time the voltage never dropped below 3.25 because its running off the power supply.

shutterfinger · Jan 11, 2022

Sequence of problem solving Batteries, battery contacts/wires to circuit boards, shutter switch contacts, circuit components.

spl · Jan 12, 2022

shutterfinger said:
Sequence of problem solving Batteries, battery contacts/wires to circuit boards, shutter switch contacts, circuit components.

I found a teardown guide for the Electro 35 GSN. It scared me. I was hoping to find one for the Electro 35 FC. I have read it's a different camera inside.

extraniamiento · Jan 12, 2022

I have a Yashica 35 CC (I believe it is quite similar to the FC internally) which has some problem with the electronics (it doesn't fire consistently at the same speed, some times clearly overexposing others underexposing), while the arrows themselves light up as expected. I fully opened the camera and cleaned contacts but I think some component may be failing. The circuit also looks very complex so no idea what to do about it. There's a diagram for the metering system somewhere (at least for the other Yashica's) if you are into electronics. It would be really cool to understand the circuit for these specific cameras and be able to find the component that needs replacing.

spl · Jan 12, 2022

Absolutely agreed @extraniamiento. The circuits themselves are not extremely complex they're just 1960/70s non IC boards with resistors, capacitors, transistors and contact wipers. On paper they look simple enough. Tearing down the Yashica Electro 35 GSN looks like an ordeal, but I suspect the FC is a simpler camera inside. My questions would be:

Start with the lens and inspect contacts therein? or go straight to the body and inspect the circuit board? There are also contact wipers in the body. Resistors are unlikely to fail in a battery device, but finding which transistor or capacitor to replace may require removing the board and part desoldering it, and possibly a trip to a friend who is more expert in these components for diagnosis of the board.

And I'm not sure there's any point in gutting the camera without a teardown guide and a circuit diagram as you can't assume the problem will be visually identifiable or the camera will come apart without damage in the absence of a service manual or ever fit back together again. (Lesson learned in the past!)

The teardown guide for the 35 GSN describes the circuit and connections of the coloured wires and the layout of the wiper contacts. Ironically I might be able to teardown the GSN though it is scary complicated, but I have no such guide for the FC.

extraniamiento · Jan 12, 2022

Yeah, I'm sad for my CC since I would attempt a more in depth repair if I had more information, but the CC's are not very common. If I were in the US I would maybe try Mark Hama, he probably knows these cameras inside out.

As you mention, though, there aren't many things that can fail and I don't think there are many transistors/capacitors to inspect. But since this is all analog circuit and the specific components are not made anymore it would be hard to know how a working circuit should behave. BTW, this post looks to be made from someone who really understands the circuit (and there are various diagrams there), but it is sadly for the other series of electros with the double rod, which does not apply to the CC/FC

extraniamiento · Jan 12, 2022

I found some manuals on ebay. Too expensive for me to justify it, though. But would be cool if someone bought it and shared it.

spl · Jan 12, 2022

extraniamiento said:
I found some manuals on ebay. Too expensive for me to justify it, though. But would be cool if someone bought it and shared it.

That link would cost me an extra $30 in shipping and more for duty and vat because I live in EU. I would definitely consider buying a digital copy at a reasonable price. I'll try contacting the Yashica company but it's a long shot.

extraniamiento · Jan 12, 2022

Yeah, I would prefer a PDF anyway.
Good luck! Please report back =)

shutterfinger · Jan 12, 2022

There is a Electro 35 service manual and other Yashica SLR manuals for free download at https://learncamerarepair.com/productlist.php?category=2&secondary=39

spl · Jan 12, 2022

shutterfinger said:
There is a Electro 35 service manual and other Yashica SLR manuals for free download at https://learncamerarepair.com/productlist.php?category=2&secondary=39

Thank you @shutterfinger. Actually this is where I sourced the Electro 35 GSN teardown guide, I was just too lazy to find the link. There is an impressive array of manuals there but not the FC.

There is a circuit diagram there that is just labelled "Yashica Electro 35 Unit Type 35" I wonder does this apply to the FC? I'd be astonished if it were the same honestly given the differences between the cameras. I may poke my head into their Facebook group.

shutterfinger · Jan 12, 2022

This page http://www.yashica-guy.com/ may be of help. Check the rescue link.
Reading on line the FC and CC are very similar but with different lens and are not similar to the Electro 35 and G variants.

YE35FC · Mar 31, 2022

Hi there!

I just created an account to reply because I had the same issue with my recently acquired 35 FC. Measuring the shutter speeds using my phone cameras slow motion function, I found that even in total darkness (photocell covered), the shutter speed never went below 1/100. In direct light, however, it did go up to 1/1000. In flash mode, it was pretty much exactly 1/15. This led me to conclude that the camera was still capable of running different shutter speeds, but the metering was faulty. After some disassembly of the lens, I was able to access the CdS cell as well as some metering circuitry (I have attached a sketch of that circuitry). The CdS cell is in parallel to a 6.3 kOhm resistor. When turning the aperture ring to the flash setting, sliding contacts switch from the CdS cell to a 160 kOhm resistor. Thus, a resistance of 160 kOhm across the CdS cell should correspond to a shutter speed of 1/15. However, even in total darkness, the CdS cell never went above 10 kOhm, which led me to conclude that it was faulty. Unfortunately, I was not able to find any information whatsoever about its specification, or what a suitable replacement may be. So I just went with a PDV-P8103, since it was in stock at my local electronics store. Replacing it successfully fixed the issue for me, and the camera now runs shutter speeds of several seconds in darkness, as well as 1/1000 in bright light, as it should. However, the metering is most likely off by a few stops now, since the new CdS cell doesn't fit the specs of the original one. I have yet to measure the exact shutter speeds under different lighting conditions to verify.

I hope this was helpful nevertheless! Let me know if you have any more questions.

spl · Mar 31, 2022

Oh @YE35FC That's a fascinating observation. I completely disassembled this camera and measured the resistance of the CDS cell under various conditions but I never considered it was faulty. It gave different readings in different light and I did not yet draw a graph of resistance vs light. I will use my lux meter to do that eventually.

I guessed that one of the discrete components, probably a capacitor, was malfunctioning and I ripped out all the electronics from the camera leaving behind the CDS cell, microswitches and shutter release coils. I am currently in the process of installing a seeedunio microcontroller in there to do the metering and control the shutter using the preexisting open and close coils. Should be finished in a month or two, it's a slow burner.

Of course if the CDS cell is also bad in that its readings don't stay consistent or are otherwise unsuitable then I have spares and it doesn't really matter what spec I use because I'll be programming the response curve into the microprocessor myself. I chose the seeedunio because of its size and because the power board can automatically charge and discharge a LiPo battery so the whole assembly will be USB charging and should get a roll of film on one charge. The camera will look the same and operate the same with the possible addition of a buzzer and vibrator and the battery check button will turn into a backlight exposure compensation button.

For your case though you might just replace the parallel resistor with a tiny rheostat and when you get the value right order a 1% tolerance resistor for a permanent fix. Aaaah ... the adventure.

extraniamiento · Mar 31, 2022

Very interesting @YE35FC
I too suspected something wrong with the electronics but couldn't figure out what. But it would make sense that the CdS becomes faulty. Replacing it could also be easy although I wonder about the proper sensibility to allow working in the expected ISO range.
If you have a light meter and you already can measure the shutter speed, I would try to use a dimmable light and point it straight at the cell and try different EV values. There's supposed to be a couple of pots on analog cameras where you can tune the meter response. I imagine it is similar to other non-CC yashicas and there may be information on how to do this. If you manage to get something usable please report. I have the CC laying on a shelf without expectation of getting it fixed.

YE35FC · Mar 31, 2022

@spl that sounds like an awesome project! I love the idea of having a 50 year old camera with modern electronics.

Thanks for the tip about replacing the parallel resistor! I hadn't even thought of that. I will give it a try and see if I can get everything dialed in correctly.

extraniamiento · Mar 31, 2022

YE35FC said:
Hi there!

I just created an account to reply because I had the same issue with my recently acquired 35 FC. Measuring the shutter speeds using my phone cameras slow motion function, I found that even in total darkness (photocell covered), the shutter speed never went below 1/100. In direct light, however, it did go up to 1/1000. In flash mode, it was pretty much exactly 1/15. This led me to conclude that the camera was still capable of running different shutter speeds, but the metering was faulty. After some disassembly of the lens, I was able to access the CdS cell as well as some metering circuitry (I have attached a sketch of that circuitry). The CdS cell is in parallel to a 6.3 kOhm resistor. When turning the aperture ring to the flash setting, sliding contacts switch from the CdS cell to a 160 kOhm resistor. Thus, a resistance of 160 kOhm across the CdS cell should correspond to a shutter speed of 1/15. However, even in total darkness, the CdS cell never went above 10 kOhm, which led me to conclude that it was faulty. Unfortunately, I was not able to find any information whatsoever about its specification, or what a suitable replacement may be. So I just went with a PDV-P8103, since it was in stock at my local electronics store. Replacing it successfully fixed the issue for me, and the camera now runs shutter speeds of several seconds in darkness, as well as 1/1000 in bright light, as it should. However, the metering is most likely off by a few stops now, since the new CdS cell doesn't fit the specs of the original one. I have yet to measure the exact shutter speeds under different lighting conditions to verify.

I hope this was helpful nevertheless! Let me know if you have any more questions.

By the way, did your camera turn on the red/orange lamps when changing aperture and pointing to light/dark areas? Mine does but does not change shutter speed, that is why I didn't suspect the sensor itself (I thought about some transistor or the timing capacitor).

YE35FC · Mar 31, 2022

extraniamiento said:
By the way, did your camera turn on the red/orange lamps when changing aperture and pointing to light/dark areas? Mine does but does not change shutter speed, that is why I didn't suspect the sensor itself (I thought about some transistor or the timing capacitor).

It turned on the "over" lamp when pointing at something bright, but not the "slow" lamp in darkness. "Slow" only came on in flash mode. So it does sound like the problem is something else in your case. Does the shutter speed change to 1/15 when in flash mode?

extraniamiento · Mar 31, 2022

I have a Yashica CC. AFAIK there's no flash mode. Although I understand than there's a pin which is pushed when something is connected to the PC port the shutter is fixed at 1/30. I haven't tried that, but it is a good idea.

monopix · Apr 1, 2022

extraniamiento said:
I have a Yashica CC. AFAIK there's no flash mode. Although I understand than there's a pin which is pushed when something is connected to the PC port the shutter is fixed at 1/30. I haven't tried that, but it is a good idea.

Yes, there is a pin and it often gets stuck in the pushed in position. Usually needs the top removed to free it up.

Yashica Electro 35 FC auto mode shutter speed repair

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