So first, I want to thank Brian who sent me these microfiches from HP. They are from 1984.
Brian used to work for HP. He was an HP engineer and he was working in RF, and send me a whole
bunch of parts too. And in some of those fiches there's something really precious,
which is the cross-reference for components. So, when you have HP components - like these
are from my HP 98035 clock, these are the dead circuits we replaced in the last episodes.
But they don't have regular numbers. At least this one has, it has a Mostek marking. But
usually you only get the HP number. In this case 1818-0469, or in this one it's Motorola, but
you have no idea what it is: it's in 1820-1592. And there have been cross-references published,
mostly by HP actually, but they are incomplete. And one times out of three there's a part that
you can't find any reference to, and that's really a problem. And you might have spied
my stash of HP components here. And same thing, they would be categorized using their HP number.
So everything has this four digits dash four digits number to it, even the spring has it. So,
basically, this thing happens to be, hopefully, the Rosetta stone for all the HP parts up to 1984.
Plus look what I got: I got a whole bunch of parts. Same thing, I have to find out what those
are. Brian was an RF engineer, so here you see the little transistors, like the one that were used my
RF amplifier I tried to repair recently. And you know, it turned out the amplifier
worked. But if it hadn't, I didn't have the spare parts. Now I do! Thank you Brian.
So task number 1 is to read, or better, scan the microfiches.
There are old microfiches reader aplenty on eBay, but not particularly cheap, nor did I want
to encumber myself with a bulky reader that give pretty poor images actually. There are
good quality ones that can scan a fiche, but these are both huge in size and in price.
So instead, I cobbled one together, out of an Andonstar 207 microscope that they had
sent me for free. So, Andonstar sends them pretty liberally to YouTubers with no strings attached,
in the hope that they will use them in their videos, which is actually what I am just doing.
So thank you very much Andonstar.
However, I am well endowed with real microscopes, and the Andonstar is microscope potato vision
compared to the real thing - obviously it’s a lot cheaper. So I normally work with the
real microscope, and when it’s time to take a photo for a video at limited resolution,
I turn to the Andonstar. That’s how I took the failed quartz crystal pictures in a
previous episode for example. You can even have fun making pretty die pictures, if you
are not too picky about the amount of noise and pixelation - this is obviously made to a price.
But back to our microfiches here. So my first impulse was to put something white underneath,
and then put the microfiche on. And as you can tell, at first it doesn't look that good.
But that's because you have the reflections from the direct lights that are in the microscope
head. So if you turn that down, and all of a sudden it is much better.
So that quick experiment showed that I had enough resolution - although just
barely - and the correct magnification and field of view to not only view,
but also take a readable picture of the microfiche.
So it was now just a matter of getting nice uniform back illumination, and this old LCD
screen from a SONY DVD player, which has the worse resolution ever - it was like 230 times 480 -
it was easy to take apart. The LCD screen came out nicely, it was just glued on the periphery.
So now, if I just can figure how to light up that puppy, I am golden.
And you can tell this is a Cold Cathode Fluorescent Light - CCFL. So that's before they
had LEDs. So it's a few hundred Volts on here. It's like one of the fluorescent tubes: you have
first to strike it at 600 volts, and then once the discharge has started, you have to regulate
it to 300. And that's what this little circuit does. But there are five leads out of there that
went into the rest of the board, so what do they do? But I could get the number of the chips and
I got a hit off that chip. It's a Microsemi and it's, sure enough, a CCFL controller.
And they even had a schematic, which is not exactly what this is, but you can tell how this
is supposed to be hooked up. It's supposed to control a bunch of high power transistors that
go into a transformer, and go into your light. And then you see that exactly on the [board].
Right here is the controller. Here is probably an array of power transistors,
and here is the transformer, and then it goes to the light. So I pretty quickly found that
the ground here was over on the two first wires. And then I looked for the chip
power and it was somewhere else. It was the orange one. So here you have the two grounds
and the chip voltage. There is one pin that was hooked up to the brightness control pin. And then
the last one was the red pin, and this went to the high power transistor. So I
figured out this must be the voltage of the inverters. They must have been able to
power the power transistors at a different voltage than the chip itself. So what I did,
is that I tied those three together to plus five Volt and I tied those two to the ground.
And I also checked that the enable pin - this was always enabled. Because sometimes there is
a disable to blank the screen, but that was actually done with the brightness on this.
So give it five Volt. Almost worked. Huh, it goes into protection mode. So when it does like this,
it means it's trying to strike the tube, and then into it went into some kind of protection.
Okay, I just gave it 5.2 Volts instead of 5 Volts. So my guess is that probably, you want
to get the CCFL voltage of the power transistor section a little bit more voltage than the chip,
that's why they were separate. But we'll be happy with our 5.2 Volts.
So I needed just one more thing so the film would stay flat for getting a good focus across it, and
I just took the front glass of two picture frames, and off we go. Microfiche scanner on the cheap.
Okay, so now I think it's a pretty convincing microfiche reader, and scanner - because of
course you can take a picture of all that. And look, there is even an inversion setting on this,
so I could make it black on white for OCR. And so you notice, it's a little bit yellowish, but not
to worry. Going the wrong way. The minus makes it brighter, go figure. There we go, all right!
And we can start to explore our part numbers.
For example, let's try to look up those three parts. This is a transistor from Brian's
collection, and it was not in the currently published equivalence tables. This is the quartz
- the broken quartz. We actually know what it is, but I couldn't find any reference on the web. So
maybe we will find more details about this. And this is the ROM. It has a MOSTEK number on it,
but I couldn't find any reference on it. So let's see if we can find a little bit more about it.
First the transistor. I didn't have to go very far to find it, it was on page four. Right here.
Oh there it is, right there. And this is why I realized the cross-reference
tables were incomplete: because they don't all have equivalents. But I would have enough data,
if I find this one in the circuit, to replace it with something equivalent.
So let's try the quartz now. And it was a little further, on fiche 19. 0412 right there, at the
bottom. Oh, and in this case it is completely blank. There is no information on it whatsoever.
Totally, totally blank except it's one megahertz. So no dice on that one.
Let's try to do this one. We found out from the schematics that it was something
similar to a 2716, but not exactly a 2716. And that one was on fiche 22.
It should be over here between 0448 and 0477, and it's not. But the thing is that,
those are all mask ROMs, and they are all the same chip. Completely the same chip.
So there is no difference between all of those numbers, except the program that's written on it,
the mask that they are going to use. So they are all AMD AM9216BDC. And here it is, this is the
AMD 9216. A 2k by 8 [bit] read-only memory. Indeed it's a mask ROM. And if you look at the selection
pins, they can be ordered - and I suppose you change the mask for that - in either logic:
in either positive select or negative select. So this is why ours add a reverse select on it.
And off I went and started to look up all the new old parts I got from Brian,
with many of them not being on the published cross reference lists, in particular the juicy ones,
like the early J-FETs or dual matched transistors. I was able to identify a 100% of them.
There were some really neat ones, many of these older Fairchild metal can op-amps,
and this gated sense amplifier which will come in handy for core memory work.
And even a vacuum tube - this is actually a microwave triode, good for up to 425W of pulsed
power at 5 GHz, new in the box. They managed to put a cathode, an anode and a grid in a
super small pencil shaped tube, with the grid connection being the large disk in the middle.
I’m not sure if we’ll ever make this one work again,
but it sure would be fun and with Electroboom levels of high voltage…
Anyhow, thank you to viewers, subscribers and patrons for contributing such treasures to the
channel, and to Andonstar for sending me the microscope with turned unexpectedly useful.
Link in the doodly doo. See you in the next episode!