Electronics > Repair

Vintage chip Programmer : " Micropross ROM 3000U "

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Hello people,

I am trying to diversify my collection of old stuff. I decided that having 40/45 old scopes was nice, but opening my mind to other types of TE would bring diversity and spice in my collection.
So since I like the early days of programmable chips, EPROMs, PROMs, GAL/PAL etc.... I thought it would be fitting to get a vintage / period programmer to go with these chips, if an opportunity arose.
Such an opportunity just arose the other day, on my local ad site Leboncoin.fr.  A big ass programmer for only 20 Euros + as much for shipping... it's a boat anchor.

Was very filthy, gave it a good clean last night and took it apart, played with it.

- It's branded " Micropross " ... made in France here, says the plaque at the back.

- Model " ROM 3000U "

- Made in early 1987 from the date codes I could find on chips. Some chips are dated 1984....

- It's got a removable programming fixture. The one that came with my unit as you can see is a 40 pin DIL ZIF socket.

- The black rectangle above the fixture is a piece of ESD foam, nice touch. Somehow the foam is still presentable up close, and not 100% turned to dust. As long as I don't touch it, it's fine...

- It's got two serial ports at the back , DB25, for I/Os.

- Has a floppy drive  ! Makes it look expensive !  >:D

It's got a built-in computer and tries to boot from the floppy at power up (it was supplied with a disk labeled "System Disk", albeit written in French) , so could technically be stand alone I guess... but it can't because there is no user interface on this thing at all. Well there is a buzzer and a PowerON LED, but other than that.... no display or keypad to speak of, at all.
The floppy looks like it's a backup copy, not the original, as you can see the label looks nice/computer generated, but it's applied on some generic Verbatim floppy. I tried to read the floppy on my vintage MS-DOS computer, but it says the disk is not formatted, or at least not formatted for a PC...
which I guess makes sense ? I mean the computer in this programmer is very low power, MIPS and ROM size wise, so I guess it can make sense that the designers came with a custom formatting and file format, bare bone, that would require very low CPU grunt and code size.
So I think I could do some more work... maybe I could try to do a binary dump of the disk and see if I can see "patterns" in it, hell maybe decode some ASCII text in there ! That would be fun.

So I guess it definitely requires to be connected via serial port to some desktop computer running some software, in order to operate.
I can't find any information about this programmer on Google, never mind software, so it's basically a brick, a big door stop, a boat anchor.
Still, it was so cheap and cute that I bought it anyway just to play with it and tear it down, and the joy of owning it. So that's what I did. I am not disappointed at all in this regard, I very much am happy I bought it. Result below with pics to be spread over multiple message for clarity.

I am writing this thread to document this thing. Given how hard it is to find any info on it, it makes it exotic/rare so worth being exposed I thought, especially since it's quite a substantial piece of gear...

Also I am hoping that people who actually know about this thing, might give me some info about it. Any info is better than none at all....
My hope is that it's not French, but rather Canadian. I mean French stuff is confidential and low volume, there is rarely any information about them, never mind a comprehensive service or user manual or anything really. If it were Canadian, hence more North American, I might caress the hope that like most high-end gear from that part of the world in the '80's, like Tek or HP.. there is decent documentation about it somewhere... somewhere.... but where ?

Thread could also be used to append stuff if I ever try go further with this thing. Like say try to repair the cosmetic damage, do some reverse engineering, or ever find some piece of info about it. I could put everything here, it would then be a one stop shop for other people as well, should anyone on this planet happen to have another one of these...


Anyway, now I will post all the pics, sorted by category / theme, with some text to explain what's going on.

First round of pics for this introductory post, let's start with the exterior pics here, and cosmetic damage.
So as I said it's big, really big, and really heavy as well.
Back panel is a still plate. Rest of the enclosure is two halves top and bottom. Very thick, chunky plastic, which I suspect might be reinforced with fiber glass or something. Surface finish is grainy/textured.
At the back we have as I said not much but two DB25 serial port, and a cooling fan, equipped with an air filter luckily, which probably explains why the inside of this thing is kinda spot less, lovely.
It was very dirty and dusty when I got it. Spent 30 minutes cleaning it and rubbing the top with a wet scotch brite pad to remove most of the minor scratches and marks.

Damage :

1)  Now looks much better only the very deep scratches are left, and there is one that's huge, very deep and very long... I would rather qualify it as a gouge, or even a trench  :palm: it's so deep the it dug into the core of the material, which as yuo can see is brown, which makes the gouge visible from a mile away  :(

2) At the front there is a "grill" that runs all along the edge. Most of it is fake, except where it is not : near the left corner it's an actual grill, provides an exhaust port, the PSU is right behind it. Two "bars" of the grill have been broken/missing. By sheer luck one of them actually ended up inside the device and I stumbled upon it when I tore down the thing. The piece is intact so I could potentially super glue it back into place. I would still be missing the other/second bar, but it looks much better with one missing bar than it does with two.. so better than nothing me think.

3) Seller did pack it properly so it got damaged during transport : the front lower right corner got a big hit, it cracked, starting from the bottom/hidden area, but then propagating towards the front and top of the case, going through the floppy drive bezel then ending up in the bottom left corner of the fixture area. There, the crack ended and led to a chunck of the case being  broken, ejected... but I don't have this missing piece sadly. So again one can see the brown material exposed, looks crap. The crack could be super glued I guess. The missing material I do'nt know... either I could fill it with epoxy or something, then paint it, trying to mix a custom colour to match the existing finish as best I can. The texture/grain would be lost but it would still be much improved.
Other possibility is to steal a small chunck of plastic from an inconspicuous area at the bottom of the case, and use that to craft a replacement piece that would fill the hole. This would require good skills to shape the piece just right, but would have the advantage of providing the same colour and surface texture as original.

Details of the main 3 damages : gouge on top, broken grill at the front left, big crack at the front right.

Now cracking the thing open !!  >:D

Very nice construction inside. Thick black anodized aluminium plates, to begin with.
The floppy drive is secured to two angles using... overkill gorgeous stainless steel BTR screws, lovely.
On the left we have the power supply, which looks like an off the shelf industrial grade module. Only the black aluminium cover looks custom.

On the right, the heart of the system, that big black box...  which hosts 5 boards stacked horizontally. The back plane connecting them all together is therefore vertically mounted. that one is visible, it's the one you can see on the pic. Said board also supports a buzzer, and the output cable coming from the power supply connects straight to it.

Pic of the system disk as well.

Now the power supply.

All the outputs are available on the edge of the board which is kinda exposed. The terminals are labeled, to some degree.

so we have +/- 5V with sense wires, and +/- Vdc ... "Vdc", it's all it says ! I measured them and it's +/12V.

All rails are good and low ripple, so the PSU is fine and the filter caps in this thing are somehow still good !  :-+

I then popped the cover to see what it looked like inside.

It's a switching supply, 100 watts it says on the read panel.
Primary has two switching transistors, topology looks similar to the primary of the supply in my old Tektronix 22XX series scopes of the same era : no controller IC, but a discrete / home made oscillator. Primary of the transformer has a middle tap going to the supply, then the two transistors switch one half of the primary winding, in turn.

The supply with the most grunt is of course the +5V rail, to feed the bucket load of current hungry TTL chips you expect to find in such a device of this era.
This rail appears to be the "master" rail, regulated by the primary. On the secondary you din no regulation for it : just a beefy double diode mounted on a heat sink to full wave rectify the secondary winding from the transformer, then filter caps and that's all. I measured it at about 5.15V (under load/normal operation). As usual in those days they pump up the 5V TTL rail to make sure it can deliver in action...

The other 3 rails, "secondary" ones shall we say, do have their own dedicated regulation on the secondary side.

The +/- 12 V rails are done with a 7812 and 7912 in za TO3 package. The -5V supply looks like is done with an LM337 in a TO220 package.

Now the stack of 5 boards constituting the heart of the system, inside that big black box.

Removed the top plate so I could have a better look. removed two plates on either side, that secure the locking tabs at the back of the boards, just in case the boards decided to unplug themselves...

Then I could pull the boards one to have a look. Here it is.

Board #1  (starting from the top)

It's the CPU board. It runs with an 8 bit CPU, a 6502, running at 8MHz if I believe the crystal that's located..... two miles away, at the very opposite side of the board !  :palm:

The EPROM for the code next to the CPU is D27128A, so only 16KB. Not much...
There is another EPROM on that board, but far away from the CPU so I don't think it contains code... maybe some lookup table that's part of the glue logic, who knows.

Board #2

This one is the floppy drive controller. The left half of the board contains all the chip that make up the controller, and the right half is an array of RAM chips dedicated to the operation of the controller.

Board #3

This board is I would say the "master" I/O board. It is connected to the two remaining board below it, via a couple ribbon cables as you can see.
It also carries the connector for the extra mega super wide huge ribbon cable that goes to the programming fixture / ZIF socket.

The left half of this master IO board (c), has mostly some diverse analogy stuff:

- A local voltage regulator, LM317 in TO220 package.
- Op-amps : x2 LM358
- Comparators : x2 LM339
- x3  AD558 = 8 bit DAC
- The obligatory, lone discrete transistor... a 2N2222A of course, what else !  ;D

The right half on the other hand has a clear structure / pattern to it. Definitely pure I/O stuff.
It has some TTL chips, lots of ULN series chips so must be Darlington arrays I guess.
Lots of diodes as well, and lots of LM339 comparators.

Board #4

Two more I/O sections similar to the one described above.

Board #5

This board, the last one, is analog. Looks like it's sole purpose is to generate various programming voltages.
All along the top edge of the board, we have a series of x5 LM317 voltage regulators mounted on the individual heat sinks, with nearby, a cluster of x5 multi-turn trimmer pots, with a dab of glue on their screw.

The third of the board near the bottom / back plane, is filled with TTL chips, I guess to interface with the backplane/ CPU board.

Then in the remaining space on the board, middle left and bottom right, we have two spots of analog stuff :

a local voltage regulator LM337, some op-amps again, LF351 and LF358, some ULN interface chips again, and a LF398 op-amp no, looked thatone up and it's something completely different : a sample and hold chip ! So I guess these programming voltages are not just "open-loop"... they must actually be monitoring what's going on as well, to be 100% sure !  :-+


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