Soldering is a skill that improves with practice. You don't have to use real components to practice with. Just use some thin scrap wire (telephone cable, cat5 or similar network cable etc) and solder to some strip board.MatGubbins wrote:not to be too chunkily soldered.
Using too much solder on a joint is a common mistake. Use the fine solder (60/40 22SWG / 0.7mm). Tin both the pin and the stripped end of the wire before trying to make a joint. What do I mean by this "tin"? It means heat up the pin or wire with the tip of the soldering iron and then apply a little solder to the point where the tip is in contact with the pin or wire, so that a small amount of solder flows over the pin or wire, but without becoming a blob. Then cut the stripped part of the wire to length. You should now be able to make a nice neat solder joint. Remember, the tip has to be in contact with both the pin and the wire, and this is the point where you feed a little more solder in.
A properly made solder joint is far better electrically than a spring clip, but yes you could do it that way.MatGubbins wrote:- Am I right in thinking that you could avoid soldering to the bent pins at all by just snipping them off the intermediate IC socket and using test probes to connect to the pins on the EEPROM? You'd still have to solder to the switch and the test probes themselves, but even for me that bit wasn't particularly hard.
The information is in the thread, even if it does not stand out. The thing is, as far as the CPU is concerned, sideways ROM (ROM/PROM/EPROM/EEPROM/E2PROM/Flash) and sideways RAM is all the same when it comes to the address used to access it. So what goes for one, is the same for the others (note though that this only applies for the sockets on the main board, as various third party suppliers came up with some different arrangements with sideways RAM).MatGubbins wrote:- I couldn't see any information/recommendation in the thread on which ROM socket to install the EEPROM in or which ROM banks it would appear as. Now having re-read this I see sydney's post on Mar 24 2014 covers this (although it superficially looks like it's relevant to a sideways RAM upgrade only).
If properly clipped in, they should not come off under normal use. I am presuming that you handle your Acorn gear with care and don't do the 1 to 3 inch drop test...MatGubbins wrote:- I tend to move my Acorn machines around a fair bit due to lack of a proper home; what are the realistic risks if one or more of the flying leads are floating around loose when the machine is turned on? My gut feeling is this is pretty safe, as the test clips I'm using are spring loaded and I think the tip would safely retract if this happened, so they wouldn't short anything out at random.
There is a good reason for using a resistor. Given that this modification is aimed at people who may not be hardware experts, it will limit the current and therefore resulting damage if the switch was wired up wrong. We do not want a high current +5V supply directly connected to RnW!MatGubbins wrote:- (I'm sure this is really really naive, please go easy on me!) Why is the 10K resistor needed on the connection to 5V? I'm looking at the BBC B circuit diagram and all sorts of pins just seem to be connected to 5V with no resistor at all. I *did* use one, but due to a quirk in how I ordered my parts I have 5 EEPROMS, 5 switches, 2 IC sockets and only one 10K resistor, so I'm wondering if I can get away without it if I want to build another one. I also find myself wondering if I could do away with the switch and just have a flying lead from EEPROM pin 27 which I connect to +5V in normal operation and to IC14 pin 1 when I want to reprogram; having to take the lid off to reprogram would be a minor hardship.
Also, this modification can be used (in theory) for other EEPROM/Flash chips, and the requirements may vary between different makes/types, so including a resistor reduces the chance of damage if the wire is connected to the wrong pin.