Exposing the hidden secrets of a transistor .

[@terryblackman6217]

Ps. This was for optical sound.

[@terryblackman6217]

You took me right back to when I was a child. My father was into movie projectors, 9-5 and 16mm. He used to scrape transistors and use them to replace the old photo cells. And they worked well.

[@andytipping70]

brought back memories - before you spoke i saw the transister in the tester and shouted out OC71 at the wife lol. Made me think of the ladybird book - where they showed building a radio , holding components onto a piece of wood with brass screwcups. Im certain that involved OC71's too

[@gpo746]

Yes it did, OC71 and an OC45 , that was the first radio I ever built . Had trouble getting the Jackson 500pf tuning cap so never worked properly with a substitute.....roll on years later with ebay and I found the Jackson tuning cap and rebuilt it for fun. I have a stock of various OC types , occasionally used them when rebuilding a radio . I still have my ladybird book , I bought it decades ago at a church jumble for 5p

[@MichaelBeeny]

@@gpo746 I can hear the hiss from those OC71s all the way here in New Zealand. lol

[@BigA1]

From memory, when I broke the glass to (I think) an OC71, the filling substance was more like a grease - probably a silicone grease. Not that I tried it, but I remember reading how some people mounted the transistor in their spin dryer and centrifuged the grease to one end - thereby optimising the transistor for optical work.

[@MichaelBeeny]

As a kid the OC71 could be used to detect modulated voice from a lamp connected in series with secondary of an output transformer. Range was quite small, about 3-4, feet, but magic to a youth just playing with electronics. I seem to recall OCP71s were outside of my pocket money at around 25 shillings. An OC71 was around 2 shillings. The OC71 was mostly used as a preamp or pre driver. A very noisy one if I recall. Often used to drive a pair of OC72s in push pull in really low-cost transistor portable radios. With just about 200mW output on a good set of batteries.

[@kendom33]

Gosh Michael. I remember the OC44 ! Youre right about the blue putty.

[@truthreigns7]

Very interesting and educational Mr. Michael.

[@andymouse]

This was one of many experiences I had as a kid many years ago that started my love of electronics ! I scraped the black paint of an OC71, and it did indeed respond to light, much to the delight of a little boy ! but for the life in me can't remember if it had putty in it. However over the years I have seen one with the blue putty in it so the jury's still out on that ! I hope someday to learn the definitive proof about the story but people of our era are getting fewer gradually ! OMG ! That box of transistors is incredible have you had them for years ? Priceless. Never seen the OCP71 before today so Thank you ! Thanks for making this video as this little transistor story has never been demonstrated this well (perfect) on youtube before I don't think. So jealous of those transistors !! also made me think of another early one and that's the AC128 that featured in a "Ladybird book of electronics" I had as a kid. There you made a real 'breadboard' using a piece of wood and brass screws and cups to connect stuff up !!....cheers.

[@donny121able]

My only criticism is that you don't do enough videos. But understandable, time is valuable. Thanks for all your uploads. My favourite KZbin channel by far.

[@donny121able]

I remember in School we cut the top off the transistor to use as a light sensor, and a way to set an alarm if smoke passed. My love for electronics grew from there.

[@angelosanagnostou5550]

Interesting bit of information. Thanks Michael.

[@wisher21uk]

Wow that’s fascinating Michael, what a brilliant bit of information thank you so much 😊

[@richarddunkling2807]

In the early 1970's, where necessary to get an item of refurbished military equipment to pass its noise specification permission had been granted to repaint chipped transistor cases. Around about that time I also became aware of the AF117 internal S/C issue while struggling to repair a portable radio.

[@proluxelectronics7419]

I vaguely remember projects in everyday electronics called for a scrubbed OC71,

[@mrnmrn1]

Some hobbyists under the influence of the constant parts shortages on the other side of the iron curtain were desparate enough that when they couldn't source a glass encapsulated transistor, they cut open a metal canned one. It worked, but exposing the die to the moisture in the air made them unstable, especially germanium ones. It was somewhat more reliable if they sealed back the package with clear epoxy. Am I seeing right that the dedicated phototransistor is not filled with silicone grease? It would make it even more sensitive to light. The regular transistor is filled with silicone grease to thermally couple the die to the glass case, but since phototransistors are very low power, it is not needed there.

[@Linkvagen]

Really interesting. Heard about this, but despite my great curiosity, never seen or tested it. Very interesting to see.

[@mistermikeanson]

I remember doing that many many many years ago!!

[@Lyndalewinder]

When I saw the video title I thought at first it might be about Tin Whiskers in the likes of AF116 transistors 🙂

[@glennlove461]

so you think you're Russell Ohl

[@andytipping70]

was a bit more curious than i should have been as to why you have a pink phone case lol

[@JulieSkinner-f5j]

Hi Michael, would you consider turning off AI generated sound on your videos, I download your videos to watch when I have time and keep for reference lately your videos are coming with German commentary. It is very hard to follow content for english speaking persons like myself..Regards Julie.