Psion II LZ Repair

 

Psion_Organiser2_System_2

I thought I would post this sooner than later, as this is something I’m presently working on.

For those who might not be familiar, the Psion II was an early form of pocket organiser produced and sold by the British firm Psion. During its lifespan the organiser went through several versions. Beginning with the CM, a very basic unit with just 8kb of memory and ending with the top end LZ64, which has a 20 column 4 row display as well as whopping 64kb ram.

As part of an ongoing series of pocket computer reviews I’m writing, I have covered several models of the Psion II. Sadly the LZ64 suffers from a persistent and quite irritating whistle, which I believe comes from aging capacitor.

Today I removed all but two of the nine electrolytic caps inside my LZ in a bid to rid my unit of the blasted whistling. Here you will find some info on the capacitors I removed and their location on the PCB. If you own an LZ or LZ64, this information should be useful. As always the same rules apply, you repair your own gear at your own risk. If you set your shirt sleeve on fire, pour hot coffee on the cat or fall out with the postman, you can’t blame me! I’m simply providing this information as is. Hopefully it will result in a silent LZ, except for the for the odd beep and click of course!

insideorg

Fig.1 A single screw holds the top PCB in place

After you’ve removed the screws and popped open your Organiser, you’ll find the motherboard screwed to the front half of the case. Laying the device face down, unscrew the top board which is held in place by a single screw (see fig1).

The main logic board is still connected to the keyboard via a ribbon cable just behind the pins for the ROM slots. This cable is pretty stiff and will take some gentle persuasion so as to bend the logic board up enough to remove the screws holding the keyboard PCB to the front case.

Once you have the boards removed turn them over so you can view the logical board the right way up. Remember to handle the two PCB’s with care, after all they are 30 years old and tend to be delicate.

insidepsion

You should now see something similar to fig.2. Note the already exposed pins below the cluster of caps, this is because one of the 25v 10uF capacitors has already been removed from the board.

Using an already warm soldering iron, I removed each cap, recording their values as I went along.

Of the seven radial electrolytic caps, the LZ has;

5x 25v 10uF
1x 50v 1.0uF
1x 6.3v 100uF

For now I’m leaving the two large axial caps in situ, as I want to try the LX with radial caps replaced but the axial caps remaining. If the whistling persists this might indicate which caps are the culprit.

Until the new caps arrive there isn’t much more I can do, so I shall leave you with this pretty diagram, which shows the values and orientation of each cap.

-Keep on geeking!

cap_layout

 


Palmtop and Palm PCs Part One

hp200lx

image courtesy of http://www.200lx.net

Whether you owned one or lusted after them on the shelves at Tandy or Dixons, during the late 80s and throughout the 90s, the personal assistant (or PDA) reigned supreme to anyone after a portable computer but not wanting spend the hefty price tag of much larger, more powerful laptops. Covering the history of these devices would cover more than a fair few articles alone and is a little beyond the scope of what we are going to do today.

Last year I was lent a Hewlett Packard 200LX by my friend Darren, who thought I might get a kick out of using this tiny DOS compatible palmtop. As it happens, he was right. Playing around with the 200LX has been interesting to say the least, even leading to the purchase of a Psion 3a for my own personal use.

The HP boasts a chiclet keyboard similar to those found on calculators and industrial equipment and features many of the same functions found on modern keyboards today, such as functions keys and a numerical keypad for quick data entry.

While using the HP, I have to admit I’ve held something of a love/hate relationship for the keyboard. In the beginning I struggled to type on it with any proficiency, often mashing the keys with my apparently podgy fingers. Only by the second week did things begin to change and suddenly I found myself typing with relative ease. I’d still occasionally catch the wrong key but overall I could turn out text at an acceptable pace. I wouldn’t say the 200LX is the best device for writing, blogging or any decent jaunt of typing for that matter. As a note taker it isn’t half bad, but to be honest there are better options available, but we’ll get in to that later.

The QWERTY keypad takes up roughly a third of the physical width of the device with a numerical pad occupying the remainder. What you’re left with feels awkward and slightly squashed to use. I can’t help thinking this might have been avoided had the designers simply used a full size keyboard, assigning the number pad down the right side, accessible via an FN key, a feature that was not unheard of in the late 80s and which is still used by laptop manufacturers today.

HP200LX_SG70200118

image courtesy of www. keesvandersanden.nl

Setting aside my issues with the keyboard, the 200LX is actually a very capable portable PC or as it was known back then, IBM compatible. Written in gold above the screen is reads “Palmtop PC-2MB RAM”, that isn’t a gimmick or HP trying to use some fancy words to make the 200LX sound better than it is. The 200LX is as much a PC as any IBM XT, running DOS 5.0 on an 80186 compatible HP Hornet CPU. You can run a variety of DOS programs ranging from early DOS versions of Microsoft Word & Wordstar, extending even to a few old CGA games. Just don’t go expecting Wolfenstein or Doom, as I honestly struggled to get much more thank Zork to work for me. Sadly the display on the 200LX doesn’t lend itself well to fast moving graphics, ultimately suffering with motion sickness inducing screen blur. That being said, it doesn’t mean you can’t have some fun with the tiny computer, just so long as you work towards the machines strengths and not its weaknesses.

It’s due to DOS support that the 200LX, as well as the 95LX and 100LX are still popular today. Should you happen to own industrial equipment such as a CNC machines that uses DOS specific software to input data. A HP Palmtop might offer a compact, inexpensive means of communicating with your machines without the need of a bulky desktop computer or laptop. In addition both the 100LX & 200LX are capable of reading from compact flash adapters through their PCMCIA ports, making it easy to transfer files to and from the device without need of the data cable.

The 200LX also comes equipped with an IR port, offering the latest in 90s wireless data transfer. By today’s standards the baud rate is lacklustre and you’ll be hard pressed to find much to interface it with. There were some compact infra red printers manufactured back in the day, which I believe will link up to the 200LX.

Overall the 200LX has some good points about it, which include

-Decent Display
-Long Battery Life on 2xAA batteries
-Built in DOS 5.0
-PCMCIA port
-Rugged design

Software

The 200LX comes packed with an impressive list of built-in applications;

  • Appointment Book
  • Application Manager
  • Database
  • Filer
  • HP Financial Calculator
  • Lotus 1-2-3 release 2.4
  • Memo Editor
  • Notetaker
  • Pocket Quicken
  • Phone Book
  • World Time and Stopwatch

All of which does not include any software you can choose to load from compact flash. Aside from all the available DOS software you can run, there is also a library of HP specific titles to install. Once loaded in to the memory of the 200LX, there it will remain until such time as it is deleted or the device is reset. Access to a limitless DOS library obviously has its advantages, which makes the Palmtop such an appeal device.

Taking all that in to account you could be forgiven for overlooking some of the devices other failings. Were you looking to buy one today, the 200LX still retains a relatively high asking price as a bit of collectable retro kit, valued anywhere between £50-£140.

Personally I’d find it hard to justify paying more than £60 for one of these devices, as great as they are, there are better examples of pocket sized computing. In fact while I was writing this article I discovered they addressed my issues with the keyboard in a later model, doing pretty much what I had suggested. Other companies such as Atari, Amstrad, Psion, Sharp had devices which rivalled the HP Palmtop PC. While some were less compact than others, each took a stab at offering portable computer for users on the go. Only a few however offered you an IBM compatible computer that fit in your inside coat pocket, fewer still did it as well as HP had with the 95LX and later models.

Stay tuned for the next part of the article, when I take a look at another pocket portable, the Psion Series 3.

Keep on geeking