Aucbvax.1616
fa.info-micro
utzoo!duke!decvax!ucbvax!CSTACY@MIT-AI
Thu Jun 11 02:35:19 1981
INFO-MICRO Digest V3 #48
INFO-MICRO AM Digest Thursday, 11 June 1981 Volume 3 : Issue 48
Todays's Topics:
Desoldering Chips,
Modems - DC Hayes & 212 Speed Selecting & Autodialers,
Memory - 16K Hybrids & ExpandoRam modifications
----------------------------------------------------------------------
Date: 6/10/81 2350 EDT
From: CSTACY at AI
Subject: Desoldering chips
Here are the responses to DAN's query about ways to desolder many
chips from a pc board without damaging them. Thanks to all who
replied, and to DAN@ML.
Except for the fumes (use of open area and fan highly recommended),
torching ICs works very well. It is not bad on the chips; apparently
they tend to be far more sensitive to length of overheating than to
temperature, and they get heated for a far shorter time than with
irons since the torch makes it possible to melt all the pads at once.
Fumes ar STEP
FARTHER OUT.
See you on the ski slopes of Encaladeus,
Ken Haase
------------------------------
Date: 1 Jun 1981 10:59:16-EDT
From: cjh at CCA-UNIX (Chip Hitchcock)
Subject: mining on Io
As an acquaintance of the person who deduced Io's structure and
dynamics (and got a couple of publications in SCIENCE for it) I would
agree with all of REDFORD's points about the untenantability of Io.
HOWEVER, the end of the msg again forgets ?'s point that we can't
expect continuous linear advances over the course of history. In
particular, he makes a false analogy with mining in Colorado. After
all<ESM>, Colorado today is practically civilized (with the exception
of Coors)---they're even going to hold a World SF convention there
this summer!<LSM> I would argue that there are a couple of believable
analogies between \\1880's// Colorado and Io-as-it-could-be: both are
a substantial amount of travel time removed from what is called
c high heat is offset by the fact that it only takes about 5
seconds to unsolder a chip. The best idea to avoid fumes is to do
the whole process outside. At worst, you need a relatively sturdy
table with a vice on it. Also be careful to avoid splattering
yourself with hot solder. Unfortunately, I have seen the boards
you want to unsolder, and it doesnt look like you'll have room to
get the vice grips around the chips. You might consider getting 7
or 8 of those spring loaded clips designed to be used with the
H-bars, and unsolder an entire row of chips at once. Dave tried
the H-bar, and it was a total lose. It has slits that are supposed
to fit over the pins, but the pins didnt tend to be straight
enough to fit into the slits. Another idea might be to cut apart
the board and uses the busses that are already there (eg soldering
wire to the PC card at appropriate places).
Good luck
Bill W
-- WESTFW at WHARTON
Having removed many a socket and chip myself, and learning alot in
the process, may I recommend solder wick. I have never tried
torching, but as you point out, this is rather destructive. I
have tried and lost when using the H-brander and associated
extraction tools, it could have been because of the low
(Rat-Shack) quality or perhaps low tip temperature. In any case,
I have found solder wick the most relibable method, when it HAS to
come off.
-- NEAL at MIT-MC
ONE METHOD I'VE SEEN WORK VERY WELL IS TO FIND A CONTAINER LARGE
ENOUGH TO HOLD THE PC BOARD IN FLAT. HEAT UP PEANUT OIL IN IT,
PLACE THE BOARD IN FOR AROUND 10-15SECS AND THEN TAKE IT OUT AND
SMACK IT ON A TABLE. ALL THE IC'S WILL FALL OUT AND SINCE THERE
HASN'T REALLY BEEN ANY TEMPERATURE DIFFERENCE ON THE PINS OF THE
IC, IT WILL WORK JUST FINE. IN FACT THIS METHOD CLEANS THE BOARD
OF ALL ITS PARTS. THE ONLY THINGS THAT DON'T SURVIVE ARE SWITCHES
AND SOCKETS AND OTHER PLASTICS.
-- JEFFH at MIT-MC
A technique used by the MIT Electronic Research Society (MITERS) is to
use something that heats up a surface to the melting point of the
solder and set the board down and lift out the chips. I don't know
where MITERS got this thing, but it doesn't have to have much thermal
capacity only thermal conductivity to work. This means it doesn't
have to be a massive amount of metal to heat up (although the one at
MITERS does).
-- MAP at MIT-AI
------------------------------
Date: 3 May 1981 02:25-EDT
From: Barry A. Dobyns <BADOB AT MIT-AI>
Re: DC Hays modem query
Does anyone know if there is any difference between the 1977 DC Hayes
modem board and the current one that i should be aware of. I have
been offered one for about $150 and i am very tempted at that price.
-thanks
--barry
------------------------------
Date: 21 May 1981 17:34:33-PDT
From: ihnss!karn@berkeley
Re: 212's and speed select
I just went through the hassles with automatic speed selection on our
212's, and have our '70's DH/DM-11's selecting the originate speed on
cu and uucp calls.
In order to control the originate speed from the interface, you must
have the 212L1A (earlier models don't have it) and set the internal
switch to allow speed selection via connector pin 23 (instead of the
HS button).
I had to jumper pin 14, Secondary Transmit Data, to pin 23 inside the
modem so the unix driver could control the line through the DM-11.
I don't make use yet of the ANSWER mode speed indication from the
modem (remember, the originating 212 always controls the speed mode).
The 212 manual shows this as being on pin 12, which just happens to be
conveniently available as secondary receive data in the DM-11. I
don't see any conflict in these two signals; they are distinct and on
separate lines.
Another point: You'll have to modify the conn.c routine in uucp to set
the mode BEFORE the call is placed, as the 212 requires the originate
mode to be set before going into data mode.
Hope this helps.
Phil
------------------------------
Date: 6 May 1981 01:41:29-PDT
From: sdcsvax!dbw at Berkeley
Re: auto-dialers
I am interested in purchasing an auto-dialer but I am not sure where
to start. As usual cost is an issue but I am looking for good quality
as well. Is there some mechanism for obtaining this information, or
if not does anyone out there have any suggestions? If it makes any
difference, this will be going on a 16 bit uprocessor.
dbw
------------------------------
Date: 6 May 1981 1850-PDT
From: Geoffrey C Mulligan (at The Pentagon) <GEOFFM AT RAND-AI>
Vadic has just announced a new OEM board. It is vadic 300 baud
auto-originate and auto-answer modem. I don't remember right off hand
the Vadic number of the board. It has connections for the new modular
plugs. There are also a couple of s-100 based auto-dialer modems
available.
geoff
------------------------------
Date: 3 May 1981 (Sunday) 0439-EDT
From: WESTFW at WHARTON-10 (William Westfield)
Re: 16K * 8 hybird Ram chip ?
Does anyone make a hybird chip containing 8 4116 type chips to
yield a 16K * 8 ram ? I know Harris semiconductor has a hybird with
16 4K*1 CMOS static chips on it, yielding 8K*8 on a 40pin DIP,
but it would be nice to have the 16K*8 if you're willing to put up
with dynamicism (?).
Bill W
------------------------------
Date: 05/27/81 03:35:47
From: W8SDZ at MIT-MC
Re: Modifications for ExpandoRam I and II
Postal-Address: Chuck Weingart, 2152 W Iowa, Chicago IL 60622
EXPANDORAM I WITH Z80 4MHZ
Here's how to use an Expandoram I board in a 4Mhz Z80
system:
1. You need 200ns rams
2. Change R1 to 150 ohm, R2 to 2.7K ohms, R3 to 4.7K ohms
3. If you have an early board, lift pins 9 and 11 on U19
out of the socket. Follow directions if you have a
late board with a Z80.
4. Break the connection to U25 pin 5. Connect U25 p5 to
U13 pin 3.
If you have only 250ns chips, fiddle with the values of R2 and
R3, and make sure the CPU has an M1 wait state enabled. R3
controls the length of the refresh cycle, and in a 4Mhz system
with an M1 wait, you have about 700 ns to do the refresh.
Without the M1 wait, you only have 450 ns or so, so R3 must be
reduced. Do whatever works. Feedback I have gotten has
indicated the resistor values are OK for 250ns, sometimes.
EXPANDORAM II FIXES
These are the fixes to SD Sales Expandoram II for CPUs
such as Cromemco, Vector Graphics, etc.
1. X U11p4. J U11p4 to U10p3
2. X U10p4. J U10p4 to U10p10
3. Rmv C15, R7, CR2, C12.
4. x U18p6. J U6p13 to U6p1
5. X U22p13. J U22p13 to U22p7
6. X U18p11. J U18p11 to S100 pin 75
7. Take CR2 (step 3) connect across R5 - cathode to C3.
8. Replace C3 w/ 270pf. X U6p10. J U6p10 to U6p2
9. X U6p12. J U6p12 to U16p15
10. X U22p4. J U6p11 to U22p5 or 10
11. X U11 p14. J U11p14 to U21p6
12. X U11p15. J U11p15 to U20p1
13. Ground + side of C14 if REV A board. (they forgot to)
Abbreviations: X = "break connection to" J = "connect
Jumper between" Rmv = Remove.
These changes are my own! They have been given to SD sales, and my
reply was "Oh, we'll look at them." They are now being given out as
their own changes. Most of the changes are for timing problems, one
change is to use PRESET instead of a power on clear for resetting the
board, and two bugs are fixed: the notorious lock-up if anything funny
happens (like a wait state), and the M1 wait generator enabled whether
the board is enabled or not. I use all of these modifications in my
system. I put on the changes suggested by SD Sales, and there is no
conflict with mine, but their changes dont affect anything, and I took
theirs off again.
EXPANDORAM II BANKING
Here is how to change the banking port address on the SD
sales Expandoram II to 40H:
1. If you havent modified the board (above)
break the connections to U18 pins 3 & 4. Connect
U6 p15 to U6 p1. This frees up an inverter, and fixes
a bug at the same time.
2. Break the connections to U19 pin 3 and connect a jumper
around the breaks, because the signal doesnt stop at U19.
3. Connect a jumper between U18 pin 4 and U19 pin 3. Connect
a jumper between U18 pin 3 and U23 pin 16.
4. Replace U23 with a 74LS240. The banking port will be at
40H. It is not exactly compatible with Cromemco, however.
because the latter has eight bits and eight banks, and
any board can be in multiple banks. The Expandoram can
be in only one bank at a time, and uses only three bits
on the port to specify that. You may wish to alter which
bank port bits are latched.
If you want, do not replace U23, and the address will
be at 0BFH.
------------------------------
End of INFO-MICRO Digest
************************
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