Acorn electron ULA socket repair.


Ok apologies in advance for no photo's on this page but this repair was done a long time back before I even created this website. So the next time I encounter this, I will update this page.

Does your electron suffer from crashes/white screens when warmed up?

Does it fail to start on switch-on?

Does it start then garbled text/graphics appear on the screen?

If any of the above are present it could be one of the following;

Either a bad solder joint on the internal PSU board where the mains lead attatches, caused by wear and tear.

or;

As I have found on 3 occasions the ULA socket (IC 1) is to blame. The ULA socket is the achilles heel of the Acorn electron. Hence the reason that if you examine a few electrons, the method of securing this large IC to its socket changes many times over its production run, with the last incarnation on Iss.6 boards being soldered directly to the mainboard and not socketed.

What happens with the socketed ULA's is one of two things, either there is not enough pressure being exerted "downwards" on top of the chip to make good contact with the pins underneath, or, as I found out on one example, a broken pin in the ULA socket.

The first case (downward pressure) is easy to diagnose, tho bare in mind that I done this at my own risk and do not take any responcibility for injury to any person who takes it upon themselves to repeat this operation.

With the electron switched ON and the top cover folded forward with keyboard connector still attatched, I used finger pressure on top of the ULA to see if it would change the state of the machine, more often than not if the machine was not running, I could apply pressure, re-insert the power cord and it would fire up fine, until I released the pressure.

My fix for this case is simple, unclip the ULA securing bar/clip. Remove and clean the "fingers" of the socket with some alcohol based fluid, then the contacts on the underside of the ULA. Next cut a square of paper (not card) just smaller than the top size of the ULA. Re-insert the ULA, place the paper on top of the chip then re-attatch the securing clip/heatsink. This may sound like a bodge, but the paper (1 leaf) being enough to press the ULA down a couple of thou. more into the socket and make good contact.

If this doesnt fix the problem then it could be more serious, and by that I mean a possible broken pin in the actual socket, not for the feint hearted. First disconnect the electron from the mains and remove the top cover and disconnect the keyboard ribbon. Next, unclip the securing clip/heatsink on the ULA. Be careful not to slip with any tools used and damage anything else.

With the top clip/heatsink removed, withdrawl the ULA from the socket and put it somewhere safe and Static Free after cleaning its contacts with some alcohol cleaner.

Next take something small and pointed, a pin will do, and to each pin in turn in the socket exert a "slight" downward pressure. You should feel resistance pushing back it the pins are good. Or as I found, one pin felt fery soft and it was found to be fractured and hence not putting enough "upward" pressure on the ULA to make contact.

Now the tricky part, remove the broken pin "part" from the socket without loosing it!! Then with a needle file you must file away the plastic socket around the broken pin to reveal enough of the good metal to effect a repair.

Try not to cut into or damage pins on either side. An idea of the proceedure I am trying to convey here can be found in another article on this site regards pin repair on a Watford Electronics 12 ROM board.

When enough of the good pin is exposed you now have to place the broken part of the pin up against the good. Making sure the end that presses on the ULA is at the same height as the other pins in the socket.

This can be achieved by placing small strips of paper under the pin to raise it in line with the rest. Now, hehehe Using a soldering Iron with a pointed tip, join the two parts of the pin together without soldering to any other pin. The part your trying to re-attatch will definatly move during this operation, but dont add more solder, just re-heat and with a pin or tweesers prod the pin into position.

Finally replace the ULA and clip, re-assemble the electron and switch on. If it works then job well done.

This repair "will" sound crazy, but I have done it and it did work.

Alot of patience is required for this, but it saved another Acorn from the scrap bin.


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