1n34a or 1n4148 diode for OM1n and canon Ftb?

[Neofito]

I am about to modify this two cameras, according to many readings but specially this one http://olympus.dementix.org/Hardware/PDFs/OM1DiodeVer2_1C.pdf I see recomended a 1n34a but also a couple of times the 1n4148, so I wonder if someone has experience with the modification in these two cameras (that I think behave quite similar) regarding the load and accuracy of the light meter.

Or if you have better experience with another diode with the porpuse of using silver oxide batteries.

Thanks.

 

[koraks]

I see recomended a 1n34a but also a couple of times the 1n4148

The 1n34 is a germanium diode - which is a rare beast these days, although I'm sure they can still be had (maybe not this exact type, but something similar). Germanium diodes have a voltage drop of ca. 0.3V, while a normal silicon diode like the 1n4148 (and many, many other types including the 1n400x series) have a forward voltage of roughly 0.7V. Apparently in the conditions in this particular application, the forward drop of the 1n34 even works out as less than the nominal 0.3V:

I'd try a simple Schottky diode instead. There's plenty to choose from; any small signal type should get you close. A regular silicon diode is a poor choice in this application; this includes the 1n4148.

And welcome to Photrio

PS: there are all manner of adapters to tackle this problem; if you root around the forum a bit, you'll find some (recent) threads on this topic. Might be easier than modifying the camera.

 

[Jonathan-sv]

I am about to modify this two cameras, according to many readings but specially this one http://olympus.dementix.org/Hardware/PDFs/OM1DiodeVer2_1C.pdf I see recomended a 1n34a but also a couple of times the 1n4148, so I wonder if someone has experience with the modification in these two cameras (that I think behave quite similar) regarding the load and accuracy of the light meter.

Or if you have better experience with another diode with the porpuse of using silver oxide batteries.

Thanks.

Following the information at

https://www.butkus.org/chinon/batt-adapt-us.pdf

I used a BAT43 diode to reduce the voltage of a single silver oxide battery to something close what the mercury cell gives. I made an adapter for a Leica MR-4 meter that sits on top of an early M series camera (M2, M3).

I think the choice of which diode to use is a function of the current draw of the meter, but it has been a while since I looked at the info in the batt-adapt-us.pdf.

I wired the diode directly in the shell of an old battery so I made no changes to the meter at all. I haven't tried it in any other meter or camera. I have a bunch of the diodes sitting around somewhere since they wouldn't sell me just one. I have plans to make a couple more adapters but they are just that--plans.

After a brief look at the doc you referred to it sounds like that person made a lot of current measurements so his recommendations are probably OK. But I personally like the idea of putting the diode in the adapter so you can try different ones without opening up the camera or meter each time.

Jonathan

 

[ic-racer]

If opening the camera, you might consider a micro voltage regulator.

 

[Neofito]

The 1n34 is a germanium diode - which is a rare beast these days, although I'm sure they can still be had (maybe not this exact type, but something similar). Germanium diodes have a voltage drop of ca. 0.3V, while a normal silicon diode like the 1n4148 (and many, many other types including the 1n400x series) have a forward voltage of roughly 0.7V. Apparently in the conditions in this particular application, the forward drop of the 1n34 even works out as less than the nominal 0.3V:
View attachment 345659

I'd try a simple Schottky diode instead. There's plenty to choose from; any small signal type should get you close. A regular silicon diode is a poor choice in this application; this includes the 1n4148.

And welcome to Photrio

PS: there are all manner of adapters to tackle this problem; if you root around the forum a bit, you'll find some (recent) threads on this topic. Might be easier than modifying the camera.

How do I know which Schottky diode will drope the voltage as much as i need? The 1n34 is quite aboundant on europe-ebay and still affordable.
I know there is this M9 adaptor, but is 40€ with shipping...

And it looks like a very interesting forum! glad i found it on google.

Following the information at

https://www.butkus.org/chinon/batt-adapt-us.pdf

I used a BAT43 diode to reduce the voltage of a single silver oxide battery to something close what the mercury cell gives. I made an adapter for a Leica MR-4 meter that sits on top of an early M series camera (M2, M3).

I think the choice of which diode to use is a function of the current draw of the meter, but it has been a while since I looked at the info in the batt-adapt-us.pdf.

I wired the diode directly in the shell of an old battery so I made no changes to the meter at all. I haven't tried it in any other meter or camera. I have a bunch of the diodes sitting around somewhere since they wouldn't sell me just one. I have plans to make a couple more adapters but they are just that--plans.

After a brief look at the doc you referred to it sounds like that person made a lot of current measurements so his recommendations are probably OK. But I personally like the idea of putting the diode in the adapter so you can try different ones without opening up the camera or meter each time.

Jonathan

could you post a picture of your adaptor? I have a simple metal adaptor to use with silver batteries that perhaps I can fit the diode there. I see the adapter on the pdf, perhaps I give it a try and if i dont succed then go for the modifitacion. But if you can post a picture of your adapter maybe helps me a bit.

If opening the camera, you might consider a micro voltage regulator.

mmm, that actually sounds better since i could even use a normal alkaline battery, any reference or model to consider?

 

[eli griggs]

How do I know which Schottky diode will drope the voltage as much as i need? The 1n34 is quite aboundant on europe-ebay and still affordable.
I know there is this M9 adaptor, but is 40€ with shipping...

And it looks like a very interesting forum! glad i found it on google.

could you post a picture of your adaptor? I have a simple metal adaptor to use with silver batteries that perhaps I can fit the diode there. I see the adapter on the pdf, perhaps I give it a try and if i dont succed then go for the modifitacion. But if you can post a picture of your adapter maybe helps me a bit.


mmm, that actually sounds better since i could even use a normal alkaline battery, any reference or model to consider?

Use an actual silver cell for a power source, as recommended, as at the least, it'll last longer than the alkaline.

 

[reddesert]

The Schottky diode insertion isn't an exact science because it depends on the current draw of the camera circuit. Most cameras using button batteries draw only a small current when the meter is in operation, and the voltage drop is a function of this current. For example here's the datasheet for a BAT54 diode: https://www.vishay.com/docs/85508/bat54.pdf
See Figure 1. At a current of 0.1 mA, the diode drops 0.2 V, at 10 mA it drops 0.3 V. For a 1N4148 silicon diode, the respective voltage drops are 0.5 V and 0.8 V, which is too much. Light meter circuits of this era are relatively crude instruments, so there are likely several different Schottky diodes that will get you in the right area, just read the datasheets for the forward voltage drop.

 

[Jonathan-sv]

How do I know which Schottky diode will drope the voltage as much as i need? The 1n34 is quite aboundant on europe-ebay and still affordable.
I know there is this M9 adaptor, but is 40€ with shipping...

And it looks like a very interesting forum! glad i found it on google.

could you post a picture of your adaptor? I have a simple metal adaptor to use with silver batteries that perhaps I can fit the diode there. I see the adapter on the pdf, perhaps I give it a try and if i dont succed then go for the modifitacion. But if you can post a picture of your adapter maybe helps me a bit.


mmm, that actually sounds better since i could even use a normal alkaline battery, any reference or model to consider?

Hello,
I will post a picture of my adapter when I get home, but it looks like a sloppier version of the one in the pdf I referred to. I noticed that the cameras you want to try it in (the Olympus and the Canon) are on his list of cameras where it worked. I don't think the kits referred to in the pdf are available any more but the parts are all available if one searches.

Are you in the EU? I might have a spare BAT43 Schottky diode sitting around (I think I had to buy several) and I could send it to you in a letter. Might also be some of the copper foil sitting around. Apparently it is sold here for keeping snails out of garden planters and such. The shell of the adapter I made is from an alkaline battery. I'm not sure if the metal adapters sold have enough space for the diode. Of course, if you want to wire the BAT43 right inside the camera that doesn't matter.

Way back when there was AM radio, I used a 1n34 diode in a crystal radio. You wanted to have a germanium diode because the forward voltage drop was smaller, and silicon diodes, with a higher voltage drop, didn't work.

Jonathan

 

[ic-racer]

I got this a while back and have yet to use it as I use zinc batteries which don’t need a voltage conversion.

Mercury Battery Replacement Voltage Regulator

Old photographic equipment and portable electronics relied on mercury (mercuric oxide) coin cell batteries that are no longer available. Can a modern voltage regulator emulate a replacement from a silver-oxide cell?

www.robotroom.com

 

[Jonathan-sv]

Hello,
I will post a picture of my adapter when I get home, but it looks like a sloppier version of the one in the pdf I referred to. I noticed that the cameras you want to try it in (the Olympus and the Canon) are on his list of cameras where it worked. I don't think the kits referred to in the pdf are available any more but the parts are all available if one searches.

Are you in the EU? I might have a spare BAT43 Schottky diode sitting around (I think I had to buy several) and I could send it to you in a letter. Might also be some of the copper foil sitting around. Apparently it is sold here for keeping snails out of garden planters and such. The shell of the adapter I made is from an alkaline battery. I'm not sure if the metal adapters sold have enough space for the diode. Of course, if you want to wire the BAT43 right inside the camera that doesn't matter.

Way back when there was AM radio, I used a 1n34 diode in a crystal radio. You wanted to have a germanium diode because the forward voltage drop was smaller, and silicon diodes, with a higher voltage drop, didn't work.

Jonathan

Here are pictures of the adapter I made, following the instructions in that pdf file. Not real attractive but it works. The copper contact on the bottom of the adapter doesn't have to be round, as long as it makes contact with the silver-oxide battery. I had problems with the silver-oxide batter making contact within the MR-4 meter so I put tape around the outside for insulation. I think the biggest headache making these is opening up the alkaline battery, though you want a steady hand to do the soldering.

 

[Neofito]

Hello,
I will post a picture of my adapter when I get home, but it looks like a sloppier version of the one in the pdf I referred to. I noticed that the cameras you want to try it in (the Olympus and the Canon) are on his list of cameras where it worked. I don't think the kits referred to in the pdf are available any more but the parts are all available if one searches.

Are you in the EU? I might have a spare BAT43 Schottky diode sitting around (I think I had to buy several) and I could send it to you in a letter. Might also be some of the copper foil sitting around. Apparently it is sold here for keeping snails out of garden planters and such. The shell of the adapter I made is from an alkaline battery. I'm not sure if the metal adapters sold have enough space for the diode. Of course, if you want to wire the BAT43 right inside the camera that doesn't matter.

Way back when there was AM radio, I used a 1n34 diode in a crystal radio. You wanted to have a germanium diode because the forward voltage drop was smaller, and silicon diodes, with a higher voltage drop, didn't work.

Jonathan

Yes, I live en europe, but dont worry, BAT43 are quite cheap

I got this a while back and have yet to use it as I use zinc batteries which don’t need a voltage conversion.

Mercury Battery Replacement Voltage Regulator

Old photographic equipment and portable electronics relied on mercury (mercuric oxide) coin cell batteries that are no longer available. Can a modern voltage regulator emulate a replacement from a silver-oxide cell?

www.robotroom.com

That can probably fit on the om1 backplate, not so sure about the Ftb.

Here are pictures of the adapter I made, following the instructions in that pdf file. Not real attractive but it works. The copper contact on the bottom of the adapter doesn't have to be round, as long as it makes contact with the silver-oxide battery. I had problems with the silver-oxide batter making contact within the MR-4 meter so I put tape around the outside for insulation. I think the biggest headache making these is opening up the alkaline battery, though you want a steady hand to do the soldering.

I think I will give it a try, looks quite a challenge to do something so small. If it doesnt works, I can always solder the diodde to the camera as I planed and call it a day... Is probably easier to just add the diode to the camera, even if you have to do it to every camera. So far I only plan to need it in two, although I may buy more cameras in the future (well, we all know that for sure I will buy more cameras in the future, ahahah).

 

[AZSkip]

There is a camera repair vendor that recommends an ECG109 diode. Do the BAT 43 and the ECG109 achieve the same result?

 

[Neofito]

There is a camera repair vendor that recommends an ECG109 diode. Do the BAT 43 and the ECG109 achieve the same result?

ECG109 I see is a germanium diode and discontinued, which could explain why is so expensive on ebay... I wonder if it was discontinued for a better sustitute.

 

[Neofito]

http://www.qrp.gr/ultimatextalset/index.htm here I found an interesting table with different diodes and the voltage they drop with some given currents. What I think I still didnt read is how much load creates the lightmeter of cameras such as Ftb or OM1.

Any ideas?

 

[reddesert]

This information of forward voltage drop vs current draw is literally plotted for you on every diode's datasheet - just google "BAT43 diode datasheet" or whatever diode type you are interested in. It's true that the current draw of any given lightmeter is not easy to know unless you measure it yourself, also that the current drawn probably depends on the light level since CdS photocells are variable resistors.

Thus, trying to come up with the exactly correct diode is a quest for precision that you can't really expect to attain, and it probably doesn't matter since these old lightmeter circuits are pretty crude. I would just try a Schottky diode with a small drop that is easy to get, such as BAT42, BAT43, 1N5817, 1N5818, etc.

 

[Buzz-01]

I use an 1N6263 and an SR44 battery in my OM-1 and that seems pretty accurate throughout the EV range when compared to my digital SLR's meter.

 

[Nicholas Lindan]

There is a camera repair vendor that recommends an ECG109 diode. Do the BAT 43 and the ECG109 achieve the same result?

"ECG" parts were sold by Sylvania in the ~1960s as 'universal' parts for servicing TV sets and radios (in those ancient days when such things could be serviced). These parts were not characterized for voltage drop over current and temperature ranges. What you got was whatever some manufacturer made too many of. The 'radio store' that sold the parts had a book that had substitutions - for an 1n34a use an ECGxxx and such like. ECG parts are probably the last things you should use.

1nxxx parts are well documented with specifications conforming to JEDEC (https://en.wikipedia.org/wiki/JEDEC) standards. A 1n34a made by Texas Instruments would have the same specifications as one made by Motorola as one made by... and they could all be interchanged even in very critical circuits (famous last words).

Europe uses a different system called Pro Electron / EECA, which is where the BAT numbers come from. Japan has the JIS standard. What is needed is a standard standard - make sense of all the standards floating around.

1n34a diodes were a 'popcorn' part produced in the millions (billions?), and there are still lots of surplus diodes available. The diodes were manufactured in a hermetically sealed glass housing and should be good for a very long time.

Germanium diodes, like the 1n34a, have been superseded by schottky diodes. The 1n4148 is the new (if ~50 years old is "new") popcorn diode (Digikey has 811,518 of them in stock should you ever want one) but it is a silicon device with twice the voltage drop of a germanium or schottky diode.

 

[Neofito]

This information of forward voltage drop vs current draw is literally plotted for you on every diode's datasheet - just google "BAT43 diode datasheet" or whatever diode type you are interested in. It's true that the current draw of any given lightmeter is not easy to know unless you measure it yourself, also that the current drawn probably depends on the light level since CdS photocells are variable resistors.

Thus, trying to come up with the exactly correct diode is a quest for precision that you can't really expect to attain, and it probably doesn't matter since these old lightmeter circuits are pretty crude. I would just try a Schottky diode with a small drop that is easy to get, such as BAT42, BAT43, 1N5817, 1N5818, etc.

yes, I am probably overthinking a bit, ahahahah, I will just take a shot with the information we have already here on this thread. Anyway I hope is also helpfull in tefutu

I use an 1N6263 and an SR44 battery in my OM-1 and that seems pretty accurate throughout the EV range when compared to my digital SLR's meter.

"ECG" parts were sold by Sylvania in the ~1960s as 'universal' parts for servicing TV sets and radios (in those ancient days when such things could be serviced). These parts were not characterized for voltage drop over current and temperature ranges. What you got was whatever some manufacturer made too many of. The 'radio store' that sold the parts had a book that had substitutions - for an 1n34a use an ECGxxx and such like. ECG parts are probably the last things you should use.

1nxxx parts are well documented with specifications conforming to JEDEC (https://en.wikipedia.org/wiki/JEDEC) standards. A 1n34a made by Texas Instruments would have the same specifications as one made by Motorola as one made by... and they could all be interchanged even in very critical circuits (famous last words).

Europe uses a different system called Pro Electron / EECA, which is where the BAT numbers come from. Japan has the JIS standard. What is needed is a standard standard - make sense of all the standards floating around.

1n34a diodes were a 'popcorn' part produced in the millions (billions?), and there are still lots of surplus diodes available. The diodes were manufactured in a hermetically sealed glass housing and should be good for a very long time.

Germanium diodes, like the 1n34a, have been superseded by schottky diodes. The 1n4148 is the new (if ~50 years old is "new") popcorn diode (Digikey has 811,518 of them in stock should you ever want one) but it is a silicon device with twice the voltage drop of a germanium or schottky diode.

wow, thank you for the information and explanation, very interesting! I'm glad I've opened this topic, I'm actually learning quite few things about diodes.