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Repair (almost) Ericsson MC 218 (Psion 5mx)

You can download gerber files in the file zone: files.bs0dd.net/gerbers/
When ordering, please remember to include Stiffener: Polyimide, thickness 0.20 mm.

Meet the Ericsson MC 218 PDA. Experts will rightly note that this is just a rebranded Psion 5mx with customized firmware.

Being a copy of 5mx, MC 218 inherits the sad disadvantage of its brother - unreliable screen flex. After 2 months from the moment of purchase, my MC 218 finally gave in (the 5mx PRO is still holding on) and the next time I opened the lid, the following picture appeared before me:

Yes, the PDA flex cable is out of order. The reason for this is quite logical. The original cable has two (apparently technological) holes, one of which is located right in the middle, between the tracks. Over time, a crack inevitably starts from this hole, which eventually reaches one of the nearest tracks and cuts it... and now the PDA is broken! But it must be admitted that such a mistake is inherent only to the 5mx model. The classic Series 5 has a different cable and there is no such treacherous hole in it.

Initially, I had the idea to simply lay a copper wire instead of the broken track, but my poor soldering skills ruined the second end of the cable, as you can see in the first photo.

This made me think about completely replacing the cable. Psion is, in fact, expensive. Very expensive! And the PDA itself and accessories for them cost a very impressive amount of money on Ebay, not to mention the parts. The only place where you can still find the flex is the British online store Psionex. The cable can be found here. However, at the sight of the price your eyes tend to fall out of their sockets, and your jaw - to drop. A small and rather simple flex is sold for... 60 euros! Given that this is not the original (probably custom-made), given the slightly modified circuitry and the absence of the "cursed" holes.

To understand, I bought the 5mx PRO and MC218 at a flea market for 50 euros (yes, it is VERY much lower than the market price, but it is a fact), so I didn't want to pay for the cable a price exceeding the device itself, and, perhaps, for the best.

While telling my friends about my situation, I was told a rather pleasant thing (By no means advertisement! I wasn't paid for this), the Chinese JLCPCB produce very small batches(5 pieces) of two-layer flex cables at a price of only $2 for these same 5 pieces! It is foolish to deny that this is many times more profitable than the cable from Psionex.

There was only a "minor" nuance left. To make a cable, you need its scheme in the form of a gerber file. I think it goes without saying that I don't know how to make schemes, it's not my profile at all. And this story would have ended nothing if someone hadn’t agreed to help me. Konstantin Kuzminov helped to make a scheme based on my photos and measurements, he didn't take any money for it, agreed for "invaluable experience".

In the end, two versions of the flex were drawn. A version close to the original, using only one layer and bending. And a "modernized" version, close to Psionex. For myself, I ordered the second version.

In addition, a cable for Nokia 9110 Communicator was also drawn. I was "lucky" to get two devices with faulty cables, the price of new ones on Ebay (about 11 euro per piece) is also not very pleasant.

You can download gerber files in the file zone: files.bs0dd.net/gerbers/
When ordering, please remember to include Stiffener: Polyimide, thickness 0.20 mm.

In the end, the cables were ordered. However, it turned out that the "promotion" with $2 only applies to one flex per order, the other one is already at the regular price, so they had to be split into two orders (yes, it works). Taking into account delivery to the EU, the production of each cable cost me $10 for a batch of 5 pieces.

The order was processed almost without any errors. The Chinese only asked what the total thickness of the cable and the stiffener for the side inserted into the connector should be (rather strange, since everything was already specified). Well, a total thickness of ~0.3 mm turned out to be enough. For 9110 they also asked why I ordered a two-layer cable, while I only had 1 layer. The answer is actually simple - $2 for some reason only applies to two-layer cables, for a single-layer order the full price is charged... a strange decision. That's why I had to leave the second layer empty.

Manufacturing and delivery took about 2 weeks. Having ordered the flexes in mid-September, I received them in early December. Here they are! Moreover, when ordering 5 cables, there were 7 of them. Apparently, they specifically provide spare ones in case of defects or I don't know. But all the better!

I tried the cable for the 9110 right away. It turned out to be a little longer than necessary, and it sticks out a little at the top of the communicator. But it looks like the flex turned out to be quite suitable for use. Victory, it turns out.

Unfortunately, the cable to the MC218/5mx needs to be soldered. My hands are "crooked", but life forces me to do it. It worked... scary, but it worked. The screen's functionality was completely restored!

The story could have ended there, but someone made a mistake. There was an mishap during assembly... I pressed the display too carelessly and the digitizer glass cracked! As a result, it also developed additional cracks.

Yes, the assembled PDA ended up being "almost" working. But the damage to the glass affected the operation of the sensor, now it determines the coordinates of touch rather poorly, and in the place of the crack it cannot work normally at all. It is unlikely that I will be able to find another digitizer in the near future (I need it specifically for MC218, since the glass has a different set of icons than the 5mx), so the PDA will probably go back to the shelf until better times (by the way, I use the 5mx PRO, as a more perfect model).

Overall, despite the contradictory result, I can say that the replacement of the cable itself was successful. Of course, I don't know how long it will last in theory. But I believe that taking into account the correction of the design flaw, it may turn out to be very reliable.

11 December 2024 year, 18:34:26 CET

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