en-AU.vtt

WEBVTT
Kind: captions
Language: en

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English (AU) (Spoken) [Manually Transcribed Captions]
github.com/WizardTim/WizardTim-captions

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So I'm in the need of some TO-3 transistors 
like this one here although this one here is  

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a genuine HP spare from Motorola, it's some 
sort of BJT transistor this one's from 1988  

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so I don't particularly want to use this one but 
this is what a TO-3 transistor looks like if you  

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haven't seen one before it's a three pin device 
although one of the pins is actually the case  

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but I need a few TO-3 transistors 
for a project it's just a constant  

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current dummy load so I don't really want 
to spend very much on the transistors for  

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it but I’d like to use TO-3 transistors 
as something cool and unusual as using  

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TO-220 transistors does get a bit boring after 
a while although TO-220 is quite a nice package  

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so I’ve heard that the 2N3055 is a rather common 
TO-3 transistor so searching it up on Digi-Key we find  

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a few results here we have one, oh, unit price 
call and unit price AU$65 no thank you although  

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they do have some more and uh AU$107 no thanks
other than there so in stock and also exclude  

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marketplace items because I do not trust this 
Rochester Electronics I swear they mislead people  

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on how many they have in stock I’ve seen them 
with millions in stock which is not feasible but  

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searching for that we've got two left 
one for AU$107 which no chance and the other  

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from ON-Semi for AU$9.73 and they 
actually have stock although that's still way too  

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much if I was doing an actual proper project this 
is what I would buy but as just something for fun  

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um yeah no thank you so of course when you can't 
find something for a reasonable price on Digi-Key  

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of course down to eBay and here we have an eBay 
listing for those same transistors and we get  

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10 for the low low price of AU$4.84 although 
plus AU$2.64 shipping which is much better than  

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nine dollars and something for just one but how 
reputable are these especially when buying from  

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eBay which doesn't really support per listing 
feedback unlike AliExpress where you tend to  

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get a lot more feedback per listing and per 
seller so these look pretty suspicious although  

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I think it will be rather interesting to see 
what actually shows up so I’ve bought them  

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and this is what showed up here and oh 
boy yeah these look very very uh genuine

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let's have a closer look at one of them

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yeah so this marking looks a bit 
suspicious although it does say ST 2N3055  

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and a whole bunch of other manufacturing 
codes which seem to be the same on all of them

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although interestingly comparing it to 
the genuine HP part we can see that the  

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thickness of the metal and the size and 
shape of the can is actually correct so  

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maybe there is a chance for this 
one although if you've been paying  

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especially close attention you may have noticed 
there's something a little bit off about the top  

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it almost looks like someone has painted over the 
previous marking and put a new one on yeah that's  

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very confidence inspiring now in this case it's 
pretty obvious the paint doesn't match very well  

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although here's a trick many people when making 
paints they only really anticipate that people are  

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going to look at them under normal light so they 
don't really think about matching the paint for  

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UV light so looking at this under UV light we can 
see yes there's a massive difference between where  

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it's been painted yeah and this one's actually 
rather good they uh managed to get it on only  

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the top although here's one where they were a bit 
too generous with the paint and it's uh leaked  

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down the side so let's see maybe there's 
something underneath this paint not quite  

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sure why they'd paint over it and not just rub the 
previous marking off so maybe it's laser engraved  

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so spraying it with some isopropanol alcohol and 
wiping it we can see it comes off pretty easy

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so then I just submerged 
it in some more isopropanol  

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and then gave it a bit of a rub 
more and the paint quickly came off

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although unfortunately we can see underneath it 
isn't laser engraved it presumably was just ink  

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stamped so I’m not quite sure why they'd bother to 
paint over the entire thing instead of just taking  

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it off with solvent but sure whatever it must be 
cheaper somehow I don't really understand how low  

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paint's somewhat expensive especially metallic-ish 
paint although one thing I quickly realized was  

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that you don't actually have to submerge this 
in alcohol to remove the paint the paint can  

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just be scraped off with a plastic tool like this 
ruler here so I’m rather interested to see what's  

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actually inside this so I took a pair of side 
cutters to it and just started cutting it open  

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I could have used the Dremel but I didn't really 
want to get filings of metal all over this thing  

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because I think it might be interesting to have 
a look at it working without the case on and now  

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that we've got a little hole we can see that yes 
there is actually a die in here and it's a lot  

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bigger than I was expecting I was expecting some 
tiny little two by two millimetre die that's out  

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of say a 2N222 transistor that they've stuck in 
here but no it is actually a reasonably large die  

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so this may actually be a genuine part.

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So cutting it into it more just 
to take the entire lid off.

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And if you do go doing this please be careful 
because the metal ends up being quite sharp.

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and now that we've got it all off we can see that 
the die is actually mounted on this little piece  

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of metal here which presumably increases the 
junction-to-case thermal coefficient  

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so they definitely haven't cheaped out on that 
aspect so I’m wondering if this is actually a  

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genuine part that's actually a different 
transistor that they've just relabelled 2N3055  

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because that's a very commonly searched transistor 
and people will maybe pay more for that so I’m not  

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quite sure what's really going on here because 
this transistor looks like it would do the job  

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there's nothing really wrong with the size of 
the die or the construction of the metal case  

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the wire bonding is a bit dodgy but I mean that's 
sort of to be expected in these sort of low cost  

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electronics but I mean it would still work the 
wire bond here that's broken though that that  

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was because of me so yes rather interesting to see 
what's inside one of these cheap eBay transistors

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So I hope you at least learnt something 
maybe out of this I’ll just leave you with  

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this thermal image though that I thought was 
pretty cool of it operating without the case on  

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and as always thanks for watching