QBZJ@CORNELLA.BITNET.UUCP (07/15/86)
The otherday Rick Flashman cited the president of Batteries Included
as having said that the blitter upgrade to the 1040 would be accomplished
by removing the 68000 from its socket, plugging the blitter board into the
socket and then remounting the 68000 on the new card. Are there any
hardware differences between the 520 and 1040 that would prevent yu
from cutting the pins off the 68000, soldering on a socket, buying
a new 68000 (what are they... $20?) and installing the blitter board. My
understanding was that the footprints were very similar. The only problem
with this upgrade path might be a lack of sace within the case of the 520
or possibly the power supply. It wouldn't be much fun to do, but it sure
sounds easier than the memory upgrade. It sure would be nice to get the
blitter on a 520st. Anyone have any useful technical information to add to
this?
peter lorrainejhs@disunix.UUCP.UUCP (07/16/86)
Shudder, horrors! You don't want to CUT THE PINS OFF the 68000, just unsolder them carefully, remove it, and solder in the socket in its place. Removing an IC is not a picnic, but it can be done successfully with the right equipment. One needs a low-wattage soldering iron such as an Ungar, designed for PC board soldering. Also a "Solder Sucker" or "Solda-Pullt" or some such device which acts as a micro vacuum cleaner to suck the solder out of each PC board hole into which a pin of the IC to be removed is inserted and soldered. You heat each "pad" as the area around the hold is called, and often it paradoxically helps to add fresh solder, mostly for the effect of the fresh flux. If the exhortation "strike while the iron is hot" ever applied, it does here. While the solder is freshly melted, and helped along by the fresh solder flux, apply and activate the vacuum device and slurp out all the solder you can get. Remove the heat as quickly as possible. If it didn't work, let it cool a bit before trying again. Another method that can be used is a "solder wick". This is a tiny strip of woven copper wire which has lots of surface area for its size. Melt the solder and touch it to the pad and it will soak up an amazing amount of solder by capillary action. I have found that solder wick works best for final removal of solder, after getting the bulk of it with a vacuum device. Yet another trick that is often useful is to clean off your soldering iron and apply heat with it from BELOW the board, with the soldering tip offering a downhill path for solder to flow away on. This seems to work best for removing excess solder from the pad if it is NOT TOUCHING the IC pin. The final trick that sometimes helps is heating and blowing through the hole, either just with your lips or with some kind of tube or -- best of all -- compressed air gun. The problem with this is that it causes little blobs of solder to fly all over the place -- that's why the vacuum approach is better if it works. When you have cleaned out all the solder you can, you can usually start prying the IC out gently. Sometimes a few pins will still be sticking to the board with a light coat of solder. You may need to re-heat these, or you may be able to free some of them with tweezers or an Exacto knife. At this point, you are on your own, but you will probably be able to work out a solution. Heating a pin and prying the IC usually gains you more ground each time than you realize until the IC finally pops out easily. My advice to anyone attempting to remove an IC for the first time, especially a big one like the 68000, is to follow the Golden Rule: "Never Force Anything" -- following this will probably enable you to get the 68000 out intact and in a reasonable amount of time. Also, be sure you have the right equipment --a rule which will save you a lot of grief not only in this situation but many others involving electronic equipment as well. Don't attempt to do such a task until you have the right equipment (solder sucker and solder wick and low-wattage iron and fresh roll of Ersin 60/40 solder and tweezers etc.) Don't apply heat too freely. Do all of this and you will probably do OK. -John Sangster jhs@mitre-bedford.arpa
I6191008@DBSTU1.BITNET.UUCP (07/17/86)
In-Reply-To: Your message of 16 Jul 1986 1201-Edt (Wednesday). >Shudder, horrors] You don't want to CUT THE PINS OFF the 68000, just >unsolder them carefully, remove it, and solder in the socket in its plae. John, I WANT to! Your discription about removing a 64 pin IC was quite well, but... I did that several times, mostly with success. But I also screwed up a pcb by fighting to long with it. Especialy when you've got very small pin wholes on double sided pcb's it happens that you can't suck out the solder properly. The pcb is very expensive, the price of the CPU is 30$ or less. For the unexperienced it might be less dangerous just to cut the pins and solder them out one by one. Even for this method you need something to suck the wholes free. And what do you do with your unsoldered CPU? You can't clean the pins properly, so they wont fit well in the socket. By the way, the blitter chip wont need new software? It just uses the traps? When will it be available? And finally, I know there are special clip-on sockets, where there is no need to remove the CPU. And why don't you solder the Blitter chip directly on the CPU? Johann Zuschlag (I6191008@DBSTU1.BITNET)
collinge@uvicctr.UUCP (07/20/86)
In article <8607161601.AA21826@mitre-bedford.ARPA> jhs@disunix.UUCP.UUCP writes: >Shudder, horrors! You don't want to CUT THE PINS OFF the 68000, just >unsolder them carefully, remove it, and solder in the socket in its place. > ... >Another method that can be used is a "solder wick". The worry is that you damage your board. But solder wick works astonishingly well and very quickly, minimizing heat. I have found that, having done the solder wick thing and the pin is not quite clear, a GENTLE wiggle on the pin will almost invariably free it. Yes, the wick gets THAT MUCH solder. If not another treatment from the other side of the board usually does it. Doug. -- Doug Collinge School of Music, University of Victoria, PO Box 1700, Victoria, B.C., Canada, V8W 2Y2 decvax!nrl-css!uvicctr!collinge decvax!uw-beaver!uvicctr!collinge ubc-vision!uvicctr!collinge