Category Archives: Retro Tech

RML380Z

 

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Like a lot of people who were at school during the 1970/80 period, the first microcomputer I used was an RML380Z. It wasn’t the first computer I ever used, that was a DEC System 20 (IIRC), but this shiny black box was the first machine that I could sit at and get its full attention.

 

I have been wanting to get a 380Z for a number of years but the silly prices on ebay have made that impossible until now. A chance meeting with a fellow computer collector led to me getting the example you see in the photo.

As you can see, it’s not in the prime of life, it’s covered in stickers and there is no keyboard. When it’s powered on I get a screen full of rubbish but it’s mine and I’m delighted.

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Exterior

The case is a 19” type made from pressed steel and aluminium. It has a handle on each side. The front is dominated by the two full height floppy disk drives (8” drives were available IIRC), the Logo and the power switch/reset button combination.

It was possible to lock the machine off, on or locked. Off and on are self-explanitory and “Lock” disabled the reset button. Perhaps thought useful for public installations.

At the back there is a host of connections.

Keyboard. This uses a 15 way D-type socket. The keyboard uses a parallel interface down which the ASCII encoded characters are sent. There is a micro-controller on the keyboard PCB that looks after scanning and translating the key-presses.

Cassette. This uses the DIN socket typical of the time.

TV. The usual TV antenna socket. My unit doesn’t have a modulator and so this doesn’t work.

Monitor. A composite video output. Rather unusually the 380Z uses a SO259 socket much used on amateur radio equipment. This is a high quality connector and is still an expensive item. I don’t know of any other manufacturer of micros using this.

Serial port. A standard issue RS-232 port.

Another D25. I’m not sure about this one. When time permits I’ll go in and have another look.

 

There are plenty of other cut-outs covered by blanking plates so expansion was not a problem.

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Inside the case.

 

The photo above shows my machine with the lid off. The back of the machine is at the bottom of the photo, the front at the top.

As you can see, there is plenty going on.

Power Supply.

To the left you can see the power supply. Unlike later machines, this is not a self contained, switch-mode unit. Instead it is a linear supply made from a collection of components fixed to the nearest piece of case or folded aluminium. Working on it is quite tricky as a fair amount of the machine needs to be taken apart to get the the components. It’s not something that you can take out and hold in your hand.

Card cage.

Like the PSU this term is a bit of a misnomer as the cards stand between pairs of guide rails individually screwed to the bottom of the case. There is plenty of room here. As you can see, I have five cards and there is room for four more.

Floppy disk drives.

On the far right of the case is a pair of 5.25” floppy disk drives. I havent taken these out to check the model numbers but early machines had DSSD drives giving about 84kb per side. Unusually, each side was addressed independently and so A: and B: were different sides of the same drive.

The cards.

I you can see, I have five cards in my machine.

VDU80.

6529f6d02e0556c5885a5f2c392016f7Next to the power supply is the video card. This supports 80 columns and gives composite video out. I noted the high quality connector on the back of the case. There is just a pair of twisted wires running from the connector on the card to the SO-259 on the case. Not the highest quality solution.

CPU.

2813ff65f9d8f5ffb48290dbf2e581e4The CPU card contains the Z80 processor so typical of business machines of the age. It has 32kb RAM in 4116 DRAM chips (the Z80 looks after refresh) and three TMS-2716 2kb EPROMs. It’s unfortunate that they used the TMS 2716 EPROM as these are very hard to get hold of now and tricky to read as they require several power supplies. The “ordinary” 2716s only need 5v and so became far more popular.

32kb RAM card.

 

1c04cc10496f433a822af21e5ad8d5d5Another collection of 4116s gives another 32kb RAM, maxing out the Z80’s address space.

Floppy disk controller.

391d2f4079ff9d7e668fadedabdbd119This really needs a better photo 🙂

Bus terminator card.

fd828ca323c3dfd912897b754c38e4c4Just a collection of resistors and test points really.

380Z – Hmmm

The 380Z seems to be my system of the month and is causing me head scratching. It’s becoming one of those puzzles where you have to slide pieces around but you can’t because something is always blocking them.

 

Memory

I have tried moving the DRAMs on the CPU card around by one socket. I’m not sure that this made any tangiable difference. The screen rubbish doesn’t have as many ‘C’s and ‘0’s in it but left long enough it changes anyway. Did it allways do that? Not sure.

I would really like to read the EPROMS but they’re TMS2716s and they are different to the run of the mill 2716s and so the EPROM programmer I was kindly lent by a friend won’t ready them without an adapter, which we don’t have.

 

Defying logic.

I have borrowed a logic analyser in an attempt to see what’s going on on the bus. As I mentioned before, in a previous post, the bus terminator card has a row of holes and each signal is brought out to one of them. I have soldered some header pins so I can pop the wires of the logic probe on to key sognals and see what’s going on.

The short answer is nothing. nada, nilque. The long answer is that the logic analyser isn’t playing ball. If I use the ‘scope I can see a clock, memory requests, M1 bipping up and down, activity on the data bus, _RD_ is low and the first eight or so lines on the address bus are wibbling as expected. It’s frustrating the analyser won’t work as that would be a great help.

 

More 380Z work.

The 380Z has got as far as displaying rubbish on the screen but no further. It’s quite a predicatable kind of rubbish from a sub-set of characters. Curious.

I have tried running with just the processor, VDU and the passive card that I think is for bus termination. The symptoms are the same. I started removing the chips on the CPU board one by one, using IPA to clean the pins and putting them back. After I had done about a third I just went for lifting the chips, squirting and reseating them.

I did get some different results but I had inadvertently missed a pin on one of the EPROMS. When I put it back where it belonged the machine went back to it’s old behaviour.

It was suggested to me that the EPROMS could have lost their memories by now as their expected life was around ten years so I will try and read them and verift them against some ROM images I have found through the 380Z group on Yahoo.

 

The bus terminator card has a row of holes for (I think) test pins, on every signal. I’m going to solder right angled header pins into these holes to get easy access to them and start probing about.

I also plan to shift the DRAM chips around by 1 socket and see if the fault changes.

Work on the 380Z

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I’ve been having a look at the RML308Z recently. One of the capacitors in the power supply went pop when I first powered it on. This is not unusual for machines of this age and it’s a good idea to inspect the caps before powering on a new machine. I decided to chance it and POP.

It turns out to be a tantalum on the 12v and a visual inspection wouldn’t have shown anything.

It’s very easy to open the case and look at the boards, even to take them out but to get to the PSU is a right pain. There isn’t a PSU in the usual sense. There is a portion of the machine that takes mains electricity and passes it through a collection of seperate bits, all bolted to different parts of the case.

Anything beyond a board swap is a bit tricky.

 

Anyway. I haven’t got a suitable replacement cap so I snipped of the remains of the old one and re-assembled. A look at the circuit diagram show this is for taking out the ripple and so isn’t vital – I don’t think.

I’ve now powered it on again and it’s nearly working…

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Toshiba T3100

6fd47f77257fcea0341953d444ca31ceThis is a bit of a mundane machine to me really. An AT class portable from Toshiba.

Not a laptop by some peoples rules as it needs a mains lead and cannot run from batteries.

I quite like the glow of the orange mono gas plasma display. Was this a dead end technology? Not sure… Isn’t this the same basic thing as the plasma TVs?

 

Wang Laptop

6b435e55d1efa322d29e755628f7b57eThis is a really unusual one.

Wang released their forray into the laptop market in 1985 and to be honest, it doesn’t seem to have made much of an impact. Just looking around for information on the ‘net doesn’t yield much and that must be saying something.

 

Technically it’s an x86 class machine with 640kb of RAM, and a mono LCD.

 

The unit is quite large, a goodly sized lap is needed here but for the period it’s quite good. Compaq’s sewing machine sized portable is not too far in the past and IBM’s PCAT is still in view.

The screen serves as the keyboard cover and opening it reveals a ful sized keyboard with nice keys full travel. It also reveals a thernal printer.

1de2a76c1adf95a3835bc0a7f62bcb6cInternally there is a hard disk drive but no floppy. An external drive is provided. I suppose that the logic was that you only plug in the floppy when you need it, the rest of the time you will be working from the hard disk.

Another unusual feature of this machine is the the external floppies (both 3.5″ and 5.25″ were available) are linked using SCSI. That’s very unusual. As this is before the advent of USB, SCSI was a sensible choice for removable devices as the connectors were tough and it could haul the distance without problems. Still and expensive and unusual choice. The first IBM PC floppy card could take two external drives and there just use the normal floppy bus.

Power is provided by a weighty external PSU and this “T”‘ off to power the floppy.

 

Retrochallenge 2013 – July 31. He shoots…

c6fcf7c869428cc478bd4e24cd345e56I have decided to enter Retrochallenge 2013. A spledid competition that runs throughout July every year.

Accoring to the website…

In a nutshell, the RetroChallenge is a loosely disorganised gathering of RetroComputing enthusiasts who collectively do stuff with old computers for a month.

And I have decided to use this as a dig in the ribs to try and get the Liberator going.

I’m not sure how I’ll do this blogging lark but I have a go while it’s fun 🙂

 


He Shoots… He misses…

So as Retrochallenge draws to a close for another year the Liberator is still not running.

One the plus side I have learned quite a bit about this interesting little machine. I have foubnd another one in the wild (well in Wales) and I have a certain admiration for its designers who gave the I/O board has its own processor to look after it. They gave it S5/8 ports instead of RS232. That should have been a great move. Sadly no one else followed.

It has memory cartridges, a bit like the USB memory sticks we take for granted and stacked RAM which usually looks like a dog’s breakfast but in this case uses eligant sockets.

This really is a nice machine. It just doesn’t work…

 


 

July 28 2013. Time is running out.

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Things have not been going quite as swimmingly as I had hoped. Replcing the flexi cable between the two boards did not bring the beeps back as I had thought and so I’ve been sniffing around but really I’m just getting the lie of the land.

This is what I think… There are two main boards (I’m not counting the keyboard PCB. It’s not fair the passive components I know but that’s just the way I am). There is the lower board pictured above (ironically). It has a microcontroller with a piggybacked EPROM, two S5/8 ports, the keyboard connector the LCD and other bits and bobs. I’m calling this the I/O board.

The upper board has the CPU, the piggy back RAM and the main ROM. I’m calling this the CPU board.

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The two boards are connected via the flexy PCB you’ve read about earlier.

The I/O board has the battery connector and so the CPU board is not a lot of use without its flexy umbilical. I’m not sure how far I should be able to get just playing with the I/O board. My guess is not very far as you don’t want the I/O board doing much more than initialising its peripheral controllers without the main CPU’s say-so.

This backs up what I’ve found. Without the CPU board the I/O doesn’t seems to do much. The problem is that it doesn’t do much with it either.

I do get a slight click from the piezo beeper when I connect a battery but that’s about it.

Hmmm. ‘scope time…

 

 


 

July 25 2013. Silent (not) running.

I mentioned in my last post that I’d had a problem with the flexi and made contac with another Liberator owner. Well it turns out that said Liberator owner, Peter, had an almost identical cable in his spares box and sent it over. Retro computing has some of the most generous people.

tonight I’ve carefully modded it to make it fit but I’m still not getting the old beep :-(. I seem to be getting 5V on the logic board but no signs of life.

time is running out but the saga continues.

 


 

July 21 2013. It’s all gone Pete Tong.

Things have not been going to plan just lately. It started very well. The new batteries were giving me a reassuring Beep. I opened up the case to get some more photos and to look for clues.

The problems started when I unplugged a flexi-pcb type ribbon connector or more correctly plugged it back in. There was a neasty cracking sound and more no more beeping.

I have clearly cracked the ribbon.

More bad-ish things in that my Mac Mini has decided that it doesn’t want to run in this hot weather and so I can’t get to my photos etc.

More of my computing time hace been spent getting another machine up and running. Ironic really that I am surrounded by machines but most are too retro to use for email, web editing, photos etc. (Yes I know you can connect a Spectrum to the ‘net but come on… Seriously)

I now have an old Dell rackmount server as my PC running Ubuntu 🙂

A bit of good news came in the form of an email from another Liberator owner, Peter, from Wales who has leapfrogged my efforts with some wonderful information an old school cunning. He is really on the ball with this and leaving me in the dust but a very welcome contact.

When I can I will sort out another cable and be back on the trail.

 


July 16 2013. More batteries.

I’ve found a set of batteries 🙂 Woo Hoo.

I’ve soldered them onto the PCB and fitted them into the batter pack. I’m back with the Beep now.

More investigation to follow.


July 10. 2013. Batteries.

The Liberator has a removable battery pack that was filled with four very fluffy batteries. I disposed of these very quickly, cleaned the board and tried to see what was what. An interesting feature is that the battery pack contains its own charging circuit so the 9V DC power supply plugs into the battery. I haven;t come across any other portable computer that does it this was. All of the others have the DC socket as part of the laptop. That’s curious.

These days you can’t get NiCd batteries any more and so I’ve been thinking of what to do.

I’ve taken the PCB layout of the charger board that’s in the battery pack and drawn what I think is the circuit diagram.

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The key component here is the LM317, a voltage/current regulator, which appears to be rigged to limit current. A freind at work suggested that if it’s in that state I could replace the NiCds with NiMHis. Their life wouldn’t be great but they would work.

I’m not sure what to do yet…

 

Cambridge Z88

03c5e984b174a7d79b66712afd665797The Z88 was launched in September 1987 and is, in my opinion about the pinacle of Sinclair design. It’s a compact, portable computer on the go.

Is has a Z80 processor, popular at the time. The decent size keyboard is reminicient of the Spectrum but a lot better. It doesn’t have much travel and stops abruptly but you could certainly type quickly and accurately for quite a while.

Above the keyboard is a small LCD that goes the whole width but is onlt about 2.5 CM high. There is no back light.

The integrated software is called “Pipedream” and has a word processor, spreadsheet and the other bits and pieces this class of machine from the UK sported at the time.

Despite its CMOS Z80, the Z88 could address a whopping 4MB of memory in 256 x 16k pages and EPROM and FLASH memory cartridges are available.

Sadly mine is on the blink at the moment, I suspect the keyboard as a reset has it skipping and dancing but the double shift key start and shutdown isn’t working.

 

Amstrad NC200

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The Amstrad NC200 is small portable computer released by Amstrad in 1993. It follows on the heels of its older brothers the NC100 and NC150. It has the same A4 footprint as its predecessors. Unlike the NC1000 It has a hinged lid that covers the keyboard and opens to reveal a backlit monochrome LCD screen the angle of which can be adjusted to a comfortable viewing position.

 

Outside.

 

The keyboard has five rows of full-sized keys but doesn’t have space for a number pad though it does have cursor keys. It also has five coloured keys. A Yellow function key. A green key marked “Calc”. Red labelled “Word”, blue, “Diary” and white, “Spread”. Holding Function and pressing one of the coloured keys will take you into the application written on the key, where you left off. This is very handy if, for example, you are using the word processor and need to do a quick calculation. Hit Function Green and you are in the calculator. Do the maths, hit Function Red and you are back in the document, where you left off. Groovy.

On the right hand side of the unit is a 720kb 3.5 inch floppy disk drive and a small slot marked “MEMORY CARD”. To the rear is a co-axial socket for DC power, a 25 pin parallel printer port and a 9 pin RS-232 port. The left hand side is blank. Underneath is a cover for the five C-cells. Another for a CR2032 battery that retains the RAM when you change the batteries. There is also a rectangual cover, secured by a screw, the purpose of which I haven’t established yet.

Getting started.

When you first power up the NC200 you are presented with a graphic menu. It shows the date and time and a picture of each option, word processor, spread sheet, games, calender, diary etc.

 

The word processor.

The word processor is quite a capable little thing for the period. It can search and replace, mark, copy and move blocks. Sadly there doesn’t appear to be an “undo” function as I’ve just found out to my cost. It does open a new line at the bottom of the document when you try to go down past the end of the document. what a nice touch. There is a spell checker, which doesn’t know the word Amstrad, but is easy to use. When you want to stop typing, just hit the “Stop” key and you are taken back to the word processing menu. You don’t need to save, it’s done it on the fly. That’s very nice.

 

Calculator

There is not much to say about the calculator really. It is graphical with an image of a roll of paper that shows a history of calculations as you would expect. One curious feature is that some keys on the main key area have numbers and operators printed on them. You must use these keys and not the number row at the top of the keyboard.

 

Spreadsheet.

I’ve not had much chance to get into this. It looks a bit quirky but considering that this is a Z80 machine with limited memory, any spreadsheet is an achievement.

 

Finally.

I’ve been typing this review on the NC200 and I must say I quite like it. The keyboard have full travel and a great feel. I find myself thinking that this thing is from the days before Windows took over. It is text based but it does a wonderful job of it. If you wanted a light portable word processor, with good battery life this was a great choice.

Amstrad NC100

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The Amstrad NC100 was released in 1992 by Amstrad as an all rounder for word processing, spreadsheets etc. The kind of run of the mill tasks most professional people wanted.

It is about the size of an A4 page with a good sized keyboard with a nice action. The screen is a small LCD that doesn’t have a backlight and if my unit didn’t have an intermittent fault it would be splendid!

The Wikipedia article is a good source of information here.