Psion Revo/Diamond Mako Disassembly & Battery Replacement


My Revo has been an excellent workhorse ever since my Series 5 met with an unfortunate accident in 2002. More recently I've experimented with moving towards something flashier including....

a Sony Clie UX50 (which I hated);
a Series 5mx (which I lost faith in after the screen ribbon broke);
a Nokia 9500 (which I also hated);
an XDA IIs (which I liked but it met with an unfortunate accident one bonfire night);
an XDA Exec (which I liked but it was too bulky for use as a phone);
a Blackberry 7230 (which is excellent for e-mail but limited as a PDA);
a Qtek 9100 (which is excellent all round... but...)

... a recent project has found me needing to store and read a lot of information on the move which requires a larger screen and keyboard than the Qtek offers, so I blew the dust off my Revo Plus and went back to using it.

Now, the batteries in it are still pretty good but it doesn't hold the charge it once did. Fortunately, replacement of the batteries is fairly simple if you have the right tools and half an hour to burn.

The usual disclaimer:
Unless you're a dab-hand with a screwdriver, don't attempt any of this. This page is just a guide - you follow these instructions at your own risk. Read through all steps before starting. If you have valuable data on your Revo then be sure to take a backup before you begin as following these steps will factory reset your unit.

These instructions cover battery replacement and further disassembly. Psion sure knew how to put together a good case though and this is an awkward machine to work on. There's not a millimetre to spare inside the case and disassembly is tricky as well as risky as fiddly jobs like this can end in tears.

Apologies for the focus in some of these pictures - I'm having some bother with the macro function on my digital camera (maybe I should pull that apart next..??)

1. Prise off the Psion nameplate. Careful use of a scalpel avoided damage to my nameplate but if you're using a heftier tool or have stronger glue holding your plate on then it may be dented or deformed during removal. Jake Palermo made the comment on the pdastreet forums that "The only thing I might add is to use dental floss to remove the nameplate. That can stop untoward bending of the badge." - thanks Jake!

2. Under the nameplate are two pins which sit in retaining slots and hold the screen casing on to the silver case top. Prise each pin up and push it towards the centre to release the case top.

3. Lift up the case top to expose (A) the battery pack, (B) the battery connector and (C) the IRDA/power connector circuit board.

4. You should be able to remove the battery bay from the main body of the Revo by unhooking the left side. This should give you the clearance you need to lever out the battery pack. Be careful to avoid twisting the ribbon on the right side of the unit.

5. Prise out the battery pack so that the rear of the battery bay is visible. On the right side is a spring. Unhook the spring from the top (i.e. from the silver case top).

6. On the left side there may also be a spring (however my model didn't have one). Remove this spring if fitted. There is also a pin holding the silver case top onto the graphite case bottom. Lever the pin out by pulling it in the direction of the arrow (below).

7. Use a small flat blade screwdriver to unclip the silver case top from the graphite case bottom starting at the left edge where the pin was removed. The right edge is held on by a spike so when the clips are released, push the silver case top towards the right to clear it of the spike.

8. Undo the screw that is holding the IrDA/power/battery connector board in place. The entire battery pack and circuit board can now be removed.


9. There may be some glue on the battery connector. It should break off easily allowing the battery pack to be disconnected and removed.


10. Carefully remove the plastic that encases the two batteries. Once removed you will find two NiMH 700mAh 'AAA' batteries along with a strip of circuit ribbon that the Psion uses as a temperature sensor. To replace the batteries you will need to have the equivalent size, type and capacity (although if you find a larger capacity battery, it should still work and provide longer running times). Replacement batteries will need to have solder tags so that you can solder the battery connector to them.


11. Desolder the battery connector from the old batteries and dispose of them accordingly (not in your household waste - your local authority waste disposal facility should have the means to dispose of and recycle old batteries). Solder together your new batteries with the positive end of one battery connecting to the negative end of the other. Solder the connector onto your new batteries with the red wire soldered to the positive end and the black to the negative end.


12. Encase the batteries to help keep them together and keep the moisture out. Heat shrink or tape will do and in this example I have used some Duck Tape. When encasing them, ensure the temperature sensor is held against the battery and, because of the limited space inside the Revo, keep the battery pack as slender and short as possible or refitting it may prove problematic.


13. Plug the new batteries into the circuit board. Use a small amount of glue to hold the connector in place. Don't use a strong glue such as Super Glue in case you want to change the batteries again in the future. A hot melt glue gun or silicon sealer is ideal for maintaining the connection and can be peeled off with a little force once dried.


14. Carefully refit the battery pack and circuit board. This is fiddly as there isn't much room for manoeuvre. Don't force any components and, if necessary, try rotating the new battery pack if any bulges are causing problems with fitting. Once back in place, push the case top back onto the screen and fit the pins back in place. If your battery pack isn't fitted properly then the Revo may have problems opening or closing so check for correct operation. Finally, glue the name plate back into place - but not with Super Glue in case you need to disassemble again in the future. Light application from a hot melt glue gun should do the job.

15. Reassembly is the reversal of disassembly. Just beware of the microswitch on the rear (arrowed in photo below). This turns the Revo on/off when the case is opened/closed and is easily broken if too much force is applied when refitting the battery bay back on.

Charge the new batteries for several hours before using (you may want to supervise charging to ensure there are no problems).

Replacement batteries can be purchased easily although you will need solder tag versions which means you can't just get some from Tesco. On the high street you should be able to get them from Maplin, on the Internet you can get them from Maplin or CPC. I have provided links below to these retailers - just check in with their homepages and search for 'aaa nimh'. At the time of writing CPC are the cheapest at £1.40 per unit including VAT (excluding delivery).

CPC Homepage
Maplin Homepage

Half an hour and just a few quid can breathe new life into that old Revo workhorse!


Further disassembly.

For those who may be interested, the remainder of these instructions cover disassembly of the unit to access the screen and motherboard. I took an interest in this as I wanted to see if I could fit a backlight into a Revo. I have read that the software to activate a backlight exists in the Revo (Fn + Space is supposed to be the activation key sequence as on the Series 5). I've also read that the Psion engineers left the wiring in place for a backlight, the just didn't include the lights themselves to save on cost and space. It is the quest to find this fabled wiring which drove me to risk all and pull this Revo apart further! To cut a long story short, fitting a backlight hasn't been possible. See the last picture for something interesting though....

Now, before I continue, let me just say this ain't for the faint hearted. After this surgery my poor Revo had suffered dents and scratches to the case (partly because I didn't have a guide such as this to work off so I had to figure it out as I went along). I also managed to break the microswitch that detects if the case is open or closed so I no longer have the functionality to automatically switch on or off by opening or closing the case.

There is also a real danger that you may cause terminal damage to your unit if following these instructions. Prising out the screen from the case with too much force will shatter it. A slip of your screwdriver across the motherboard will kill it. Consider yourself warned....


1. Pull out the pins of the screen hinge on either side of the keyboard. The screen and keyboard can then separate - but be careful not to put too much stress or twisting on those ribbon cables!

2. Prise up one corner of the keyboard and gently peel it off.

3. With the keyboard removed, lever out the PCB from the front of the unit.....


4. ... and flip the PCB over to expose the motherboard components. The speaker remains attached to the base of the case.

5. If you want to work on the screen, disconnect the ribbon from the motherboard by carefully flipping up the connector restraint and pulling the ribbon from the socket. With the restraint lifted the ribbon should require no force to insert or remove it. If you cannot remove the ribbon, ensure the restraint is correctly removed and do not force!

6. CAREFULLY start prising the screen unit from its surround. Start unclipping from the bottom and then move up the sides. Do not apply too much pressure or you may crack your screen. The rear of the screen is encased in metal and should not be damaged by gentle prising with a screwdriver.

7. Lift the screen unit from the casing.

8. A photo showing the rear of the Revo with the screen casing removed.

9. Once removed and flipped over, the metal casing can be taken off the back of the screen by first prising out the indented sections. The ribbon cable prevents complete removal of the casing.

10. This photo shows the range of movement you get from the screen's rear metal plate. Because the ribbon cable feeds through it, access is tight. I have removed the black tape covering the strip of PCB where the red arrow is pointing in this picture.

11. Could these two points hiding under that black tape be the fabled backlight connectors?? They're labelled EL+ and EL- but, at least on the model I hacked apart, they didn't seem to be the answer. I put a voltmeter across them but could get no reading, AC or DC, either with the unit on or with the unit on and the Fn + Space key sequence.

So near and yet so far huh?? I welcome comments from anyone who can shed light on how this can be done and I'd be happy to publish the instructions here. Unfortunately I don't have the technical know-how to take it further than this at the moment but if I ever crack it, I'll share the info here!

Update 20/02/07...

I have received the following link from Tony Hammond which gives further instructions on the Revo backlight. It looks like it would be more complicated than I hoped and as my Revo has gone to Silicon Heaven since originally writing this article, I don't think I will get any further with it....

Backlight link


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