Time or future does not make obsolete components better.... it's worse....mrpi64 wrote:Sorry, if I didn't make it clear - it's an idea for the future, not for just now.
Thanks. I have tried a desoldering pump, but they don't work such a treat for me - there is always just a bit left. Of course, that's what the desoldering wick is for.MrEngman wrote:Hre's a few ideas for desoldering http://en.wikipedia.org/wiki/Desoldering
I have used a solder sucker often in the past to unsolder DIL devices without damaging them. Solder wick is also useful.
Almost every small chip that doesn't look important on that board is a logic device. There are quite a few Octal TX/RX buffers.klricks wrote:Time or future does not make obsolete components better.... it's worse....mrpi64 wrote:Sorry, if I didn't make it clear - it's an idea for the future, not for just now.
If there are any 74xxx series TTL or 4000 series CMOS chips then they may be useful for experiments or learning how digital logic works.
In my experience, trying to de-solder DIP chips with a single tip soldering iron is a lesson in futility especially in 4+ multi layer boards.
Hot air / vacuum de-soldering tools are quick and easy but rather expensive, though there is now a lot of cheap soldering equipment available out of China.
I have also used de-soldering alloy. This is a special solder alloy that is mixed with the solder at each pin. The alloy significantly lowers the melting point of the existing solder to where the solder will remain molten for several seconds giving enough time to pull the chip out. Works very well but is kind of expensive.
I have never seen a heat sink that would work on chip pins .... only for transistor leads and such. Most rework is aimed a replacing a faulty components on a board without damaging the pads. Not trying to salvage components for use elsewhere.
This chip is now made by Lattice semiconductor.drgeoff wrote:I'm not aware* that AT&T ever made FPGAs so if the chip really is a FPGA I'd surmise that the logo is on it because it is 'programmed' to perform some logic that AT&T required. Much less chance of it being part of a 'computer' than telco switching or transmission equipment.mrpi64 wrote:The AT&T chip is a "Field-Programmable Gate Array".
(I would expect some clues as to the original maker of the 'virgin' FPGA to be on the package.)
* does not mean they do/did not - I'm not aware of everything.
So what about the serial controller. Doesn't it have some sort of output so one of the connectors?mrpi64 wrote:Problem is, there is no serial port.
Don't even need the connector if you consult http://www.techfest.com/hardware/bus/multibus_sokos.htm for where on the board to solder leads for +12, +5, 0, -5 and -12 volt supplies.mjtessmer wrote:If there is a serial controller on the board, look for some MC1488's and MC1489's (TTL to RS232 level converters). You do not need a "multibus computer", just need a 86pin connector to provide power.
Well, if you wanted to build a homebrew computer, it would be fantastic - it has built in I2C, UART, DMA/MMU, Timer, e.t.c, so it drastically reduces the amount of circuitry required. It is also fully object code compatible with the 68000.Ravenous wrote:Looks pretty useless to me. Do you have any circuits for it?mrpi64 wrote:Also, eBay gem:
True, in the past when I needed to desolder large amounts of components from a multi-layer scrapboard I used a locking plierdrgeoff wrote:Unsoldering from single layer boards is much easier than from ones with plated through holes.
1. Techniques for removing a duff chip for replacement by another are not necessarily the same as those for removing a good chip for use again elsewhere.MrEngman wrote:I have used a solder sucker often in the past to unsolder DIL devices without damaging them.
I used to use the solder sucker to remove components to use again, not to junk them. e.g. PLDs that I wanted to change the programming of when they were solder directly into the board instead of fitted using a DIP socket.drgeoff wrote:1. Techniques for removing a duff chip for replacement by another are not necessarily the same as those for removing a good chip for use again elsewhere.MrEngman wrote:I have used a solder sucker often in the past to unsolder DIL devices without damaging them.
2. A solder sucker needs to be held at just the right distance from the joint. Too far away and it doesn't suck the molten solder. Too close and the recoil action when the piston is released causes the nozzle to strike the board potentially damaging the pad if that is a concern.
I was planning to use a matrix/eurocard board, and a DIN 41612 connector backplane to connect all of them together, like this. Does the board layout matter? I know that it can become a mess without some sensible layout.Ravenous wrote:Let me correct myself (I was being far too harsh with "Useless")
Before buying this you should defintely have a look and see exactly what's involved in building a working system. Including the tricky stuff like board layout and soldering.
Although there's probably all of the knowledge required from some of the experts on this forum, adding up all of the bits you'll need it might get much more expensive for a one-off build.
Anyway I think the right datasheet is here (I've only skimmed it very briefly):
http://pdf1.alldatasheet.com/datasheet- ... CCA84.html
I don't think that anyone will trust me with a gas torch but I think a soldering iron and some desoldering braid will do the job OK for now.mahjongg wrote:True, in the past when I needed to desolder large amounts of components from a multi-layer scrapboard I used a locking plierdrgeoff wrote:Unsoldering from single layer boards is much easier than from ones with plated through holes.
clamped (softly) on the component: Then placed the board upside down with the locking plier hanging from the component, then heating the back of board from the top, locally with a handheld burner
until the plier with the component fell out of the board.
Do not tighten the locking plier too much or the component, made soft by the heat, will be bent and become useless.
For smaller SMT components like SO-16 IC's I simply knocked them off the board after heating from the back with the same burner.
This method normally was the best and most efficient way to get the most components off the board undamaged.
I used this methods to desolder dozens of 74HCxx series DIP IC's from scrap boards.
Well, I don't really want to replicate a Pi - things like USB are a bit too modern for what I want. I want a pure old-school computer. There is serial on the board, But I can use that for ther peripherals for the board, as the 68070 has build-in UART. I want to use a terminal emulator (using the Pi's built-in UART, possibly) for terminal emulation (what else?), and the floppy disk controller & SCSI controller will let me to usedrgeoff wrote:The board is probably rather less powerful in compute terms than a RPi but consumes several times as much power. It does have some more specialised I/0 but lacks the simplicity and universality of USB (and ethernet?).
Each to his own, but in my eyes neither the intact board nor the parts that can be salvaged are really worth the trouble!