Yashica Electro 35 misbehaving from f8 ->f16

Jonno85uk · Dec 6, 2021

That's good news.

As an update for my issue. I didn't test for a voltage drop but instead hooked up an external power-supply with more than enough current capacity. No change.

With my spare Electro GT i've been working on making a replacement circuit board using an msp430. I've put it on the backburner for now as life has got in the way, but once i've proved the design with the GT i'll make a board for the GTN.

Bob Palmieri · Dec 6, 2021

Well now - we do seem like a dedicated lot here, you more impressively than I!

I'll be eagerly following your progress in this quest.

However, I will admit that the idea of adding manual shutter speed control as an option has tempted me. The finder in these things is quite friendly to glasses wearers. Shutter speed indicator for auto use, however, I'll leave to more dedicated souls.

gone · Dec 6, 2021

Bob Palmieri said:
DeOxit

Thanks for the tip on the DeOxit. That's something that should be on my shelf. I once had a can of something similar, but it was more for electrical contacts in automotive/motorcycles.

Bob Palmieri · Dec 6, 2021

momus said:
Thanks for the tip on the DeOxit. That's something that should be on my shelf. I once had a can of something similar, but it was more for electrical contacts in automotive/motorcycles.

"Tech In a Can," as we say...

River Mantis · Sep 3, 2023

Nicholas Lindan said:
The schematic above makes little sense in the details but I suppose provides a sort of overview.

I'm a bit confused though - do the resistor values on the camera with the problem match the schematic?

I would suspect that if it isn't a contact problem then a transistor may have lost gain. That's not that uncommon in mid-60's plastic packaged transistors.

Any markings on the transistors? It is possible that one or more were gain selected - as evidenced by the presence of a thermistor to try and hold the gain steady over temperature.

The usual 'universal' replacements are the 2N3904 (for NPN, arrow pointing out) and 2N3906 (for PNP, arrow pointing in (TR-2)). If it were my camera, and the circuits were similar, I'd try replacing TR-1 with a 2N3904 and see what happens.

Can you provide pictures of the electronics control board - both sides?

But I would still suspect contacts. Try springing the wipers up a wee bit. You could measure the voltage at the wiper return wire as the aperture changes. If the schematic is half-way correct it should be steadily increasing as you go towards f16. The camera needs to be on and the shutter button part-way depressed (i.e. 'red' or 'yellow' position) (again trusting the schematic somewhat).

It's rather unusual circuit. T2 is controlled by current and it's loaded onto a thermistor so it's working as a linearised and temperature stabilised amplifier, but what's the purpose of it? The working principle of the circuit is just a comparator.

Yashica Electro 35 misbehaving from f8 ->f16

Jonno85uk

Bob Palmieri

gone

Bob Palmieri

River Mantis

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