In the pursuit of authenticity, germanium diodes are being ordered, examined and used.
I already have some 1N60 from a Chinese eBay seller, just in cases I needed to do some fine signal detection (and to change from the Schottky)
Their forward drop tensions (in mV): 284, 281, 283, 281, 279, 280, 278, 282, 279, 280, 281.... pretty good.
What about the reverse leakage ? Voltages are measured across a 10K Ohm resistor when 9.82V is applied to the diode and resistor : 100µV/10K=10nA (my DMM can't resolve more and the readings decrease quickly)
But the "look" of the 1N60 makes it too close to a vulgar 1N4148... Why make a special circuit if it doesn't look special ? So I got myself a little lot of Д9Б (pronounce D9B because it's russian) and their larger glass package lets you see the spring-y point-contact structure. Awesome :-)
I measured the following forward drop voltages (in mV) : 278 286 271 288 255 264... It's less consistent, more scattered, I should expect from 0.2 to 0.3V of drop (this depends of course on the current).
What about the reverse leakage ? Across the 10K resistor I read (in mV): 23, 30, 28, 53, 34, 50, 29, 24, 36, 34... So I have to expect up to 0.5µA of leakage (at 9V). That's 2 orders of magnitude leakier than the 1N60 but still way less than a Germanium transistor...
But wait, the pursuit does not stop there. On the Internet, there is a smal (monetary) line between funky and spooky. I got some crazy looking OA7 diodes and the untrained eye wouldn't know what this 2-legged thing is. "Is this an antique capacitor ?" Awesome ;-)
I got 10pc OA7 (yet). Don't they look cute ? Like they are sleeping in a very wide bed...
I measured the whole lot's characteristics:
|n°||drop (mV)||Leakage (µA)|
The drop is lower than the others. This is balanced by a higher leakage, up to 5× the D9B. This is yet a, probably, a better detection diode.
I have once found Philips-made diodes with ultra-low forward-drop voltage for analog detection purposes but they are too modern ;-)
I also found in my archive 40 tiny bead-like diodes. They are pretty and quite unique so they might be used as well, despite being Silicon-based ;-)
More diodes should arrive (D311, more OA7, maybe OA9) and they will be tested as well but there is something else I have to do !
I had bought the first Ge transistors lots because I want(ed) to use them as double diodes... There would be less wiring to do when I want to reset 2 flip-flops with the same signal. So let's see if this works.
I got some МП13Б (MP13B) :
|n°||Vf1 (mV)||Vf2 (mV)|
(I didn't care about collector/emitter order but they can be guessed by whichever is higher by 10mV)
and МП26А (MP26A):
|n°||Vf1 (mV)||Vf2 (mV)|
The values are pretty consistent and even lower than the above diodes !
Now it has to be seen if the leakage and the transistor effect will wreak havoc in the circuits...
LEDs are diodes, right ? Alexander just used some for his NAND logic gate. Well I got some AL102BM as well, for function AND aesthetic :-)
The package came with a little datasheet :
It's not very bright but that was the intention, I was looking at the glow of. the first, low-efficieny LEDs. I'm not sure if it's the BM or БМ version, so I can't be sure it's limited to 10mA, if my guesses are good. Well there isn't much light anyway at 10mA or 20mA and it's intended only as small indicator.
This is the best I could do :
Let's hope it's enough ! If I limit the current to 10mA per LED, the display alone will draw 60mA...
Just for the sake of it, I tried to capture the glow of the LED crystal, at very low voltage (otherwise the camera's sensor is flooded and bleeds) :
Can you see the little square ? :-)