Yashica GSN shutter problem

john neal

john neal

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Hi,

I have been working on a GSN recently that is now driving me mad!

The pad has been replaced, as has the capacitor which is now an unmarked tantalum bead (these were done before I got the camera). I have managed to fix an intermittency on the sliding contacts and got the film wind / shutter cocking sequence back in the correct order, but I still have an annoying inconsistency in the shutter.

This is particularly noticeable at f16 in low light. If I select f8 with a yellow light, changing to f11 will produce a shutter time that is about twice f8. However, if I now select f16, the shutter sits open for an absolute age, normally until I get tired of timing it and decide to change the shutter. I noticed that sometimes at f1.7, the shutter does not open correctly, particularly with a red light.

Further, sometimes when I have a correct exposure (ie no lights) the shutter misfires, often twice in a row. Looking throught the lens at an even light source suggests that the shutter is either firing at something faster that 1/500, or it is not opening fully (my old eyes can't quite determine which).

Does anyone have any idea where I should be looking for the source of this problem - is it a sticky shutter (it looks clean), the capacitor, the IC, or an intermittent power supply?

Any ideas most welcome.
 
I wonder if its a power problem? Since it seems intermittent and sometimes
it fires at 1/500(default speed) Maybe the wire from the battery holder is
corroded. Not sure what battery/method you are using for a replacement
battery. I used a coil spring and tape around a smaller 6v battery and never
had any problems.
 
Thanks for the input guys.

I'm inclined to think it is not the battery - the compartment is clean and all wires look to be sound. I'm using a brand new 4SR44 with a conical compression spring and the test light works all the time and is bright.

I'm leaning towards the shutter and or aperture contact rings - having done some more tests today in bright light, I have had a range of wacky results at f16 from underexposed at 1000asa while f11 was over (really!) to 2 seconds at 400asa to 1/500 at 25asa.

I guess the lens has to come off......................

More later.
 
jon_flanders said:
Are you sure the pad has been replaced correctly? Does it clunk when you advance the film?
Click to expand...

Jon,

The pad is fine - I had it all apart and checked - it's in great shape. I don't get a "clunk", I get a "click" - ie the secondary shaft is definitely hitting the pad on wind-on.
 
GSN Shutter Update

GSN Shutter Update

I am a little further forward with this, but still stuck!

Since the shutter blades are clean and dry, but I still have a problem with exponential increase in exposure between f11 and f16, I started wondering about the tracks inside the lens housing (see Mr Feurbacher's website), but have cleaned them and the sliding fingers, to no real effect. I also cleaned the track under the resistor chain around the aperture ring.

Interestingly, the f16 problem is now fully reproducible - it ALWAYS gives a huge increase in exposure at f16, rather than only sometimes - hmmm, very interesting! So, I decided to take resistance readings from the resistor chain, but do not know what the values should be, so it has not helped much. They run as follows, staring at the top (f1.7) 1.7, 2.2, 2.2, 1.6, 0.9, 0.5, 0.18, 0.4 - all in Ohms

I'm a bit worried about the penultimate resistor as the value does not seem consistent - it sometimes measures 0.18 Ohms, sometimes 180 Ohms. I don't think this is my meter or measuring technique, and I have no idea why that happened, but it would explain the situation if it has gone bad in some way - does anyone have standard figures for the resistors?
 
Ha! I think my problem is the same as yours!!! I just looked at mine last night. I *DID* remember a clunk a long time ago. I've taken the top off so many times. BTW, I STILL don't know what the "PAD" thing is. Someone tell me that later. But here's how I fixed mine. Sometimes, the shutter 'sticks'. I have to press really hard. Then I remembered something from the Tomosy book.

Remove the bottom plate. And DIRECTLY under the shutter, there is a pin. The PIN may be hitting a hook. Unscrew the pin until the hook is next to it. After you press the shutter, the pin goes down and the hook will latch to a grove. This is what makes the "clunking" noise.

That's it!

Eric
 
Update

Update

Right!

I have spent so much time on this and it's still two steps forward, three back 🙄

Following advice here and on the classic repair forum, I have now checked the shutter blades (clean & dry) and resoldered all the connections on the resistor chain connected with the aperture ring. Yes, stupid boy, I forgot that I can't measure resistance while the part is still in circuit (doh!). Anyway, since f16 was causing the problem, logic suggested checking the last resistor in the chain. I removed it and it measures 1.14 Ohms (so what?). I substituted a piece of plain wire to see if it made much difference to the f11 shutter speed - interesting! At a 2 second exposure @ f11, I now got around 3 seconds @ f16, probably explained by the fact that the resistor value is relatively low anyway. So resistor back in and I get 4 seconds - whoohoo!

This sets me to thinking and I decide to check the solder joints on the pc board with the (already) replaced capacitor on. Lo and behold, one or two dry joints and the capacitor has a small crack at the top of the -ve leg. Next move is swap the capacitor, but it is unmarked - following conventional wisdom, this is usually 2.2 or 3.3 microfarad. Tried both these values, but ended up with a completely random shutter (arrgghh!), so original back in until I can get some other values to try.

Wait a minute! It's all working PROVIDING I have all the screws in that hold the meter circuit in the body - wow! (I wonder if there is a return path through the frame?) So I put it all back together and give the shutter a good few dozen tries at different asa figures and the difference between f11 and f16 is just about double every time - go to bed a happy boy 😀

Wake up this morning and show her indoors how clever I am only to find that the shutter is as random as ever (grrr!). So I'm back to square minus one!

I'm starting to think that the IC is dodgy and only works correctly when it is warm - ie above a certain temperature - this is backed by the fact that the loger held the body this morning, the better it worked.

Anyone got any bright ideas? Please?
 
Final update

Final update

OK, the problem with this camera is definitely affected by ambient temperature.

When cold, the shutter is entirely unreliable - no two releases seem to produce the same shutter speed. However, when warmed to body temperature everything works as it should.

Given that the battery is brand new and making good contact, this suggests two possible causes - something in the electronics is about to die, or the shutter is gummed up with old lubricant.

I have inspected the shutter, and it looks OK, but will give it a swizz with some ronsonol, just to make sure. If that does not work it has to be the electronics, in which case I have 2 choices - either I try to buy a replacement module, or this becomes a parts camera.

Anyone got a spare GSN/GTN module that works?
 
OK, this is an old thread. Here are some thoughts just in case it might help!

When the Electro 35 was designed, resistors and other components were quite sensitive to temperature changes, so they put a thermistor in the shutter circuit to compensate for it. Maybe the thermistance is dead, or the condenser or another part has become even more sensitive to temperature changes and is causing the problem.

I have an early Electro 35 GT with the ASA dial reading 12 to 500 ASA. Since I shoot mostly Tri-X in Diafine, I replaced the condenser (which was 3µF in my early model) and three resistors (which control the red and yellow lights and the flash speed) to convert it to 50-2000 ASA. That allows me to shoot at 1200 ASA and still have some headroom for exposure compensation.

The modified shutter is accurate in most conditions but I do have some problems with f/16 at lowest ASA and very low light. Sometimes it works, sometimes the squeal you hear at the end of the exposure turns into a fixed-pitch, continuous tone and it won't close by itself. I don't mind because long exposures at f/16 do not really need to be accurate... but your problem might be related : it seems that a low-light / small aperture combination will really push the circuit to the limits of what it can reliably handle. Maybe yours just has smaller safety margins due to aging components.

I'd still suggest replacing the condenser, just in case. You can find the electronics diagram in the repair manual and there's another version here: http://personal.inet.fi/koti/picnet/Y35G/
 
You DO know that pad has to be exactly the right thickness, don't you?

Edit: It has to be 2mm thick and has to be fairly solid rubber. I use red rubber washers to cut them. If it is even a little thicker/thinner than this, or too soft, it can cause a bewildering assortment of malfunctions. That is nearly always the first thing that needs to be checked on a GSN.
 
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