3 Oct
2015
3 Oct
'15
1:21 a.m.
Hello everyone,
I'm working to troubleshoot a 286 laptop style computer. I've kind of
hit the end of my knowledge and wondering if anyone has any insight.
The computer in question I've never seen run. So I don't know normal
behavior. There were a few caps inside that were leaking electrolyte, I
cleaned it all up and replaced them. A few traces look a little bit
corroded but test fine.
First thing I'm thinking, is did the BIOS eproms loose a bit or two of
data from age? Bit rot? I did read off the two BIOS chips (high and low
pair I assume.) I can see text like Copyright Pheonix Technologies 1988,
but I can see that for instance the first character of the text Copyright
is wrong, it's a P in one file and 9A in the other.
Second thing I hooked up Oscope and cut on computer. It never does a
floppy seek. When I poke around the 27c256 EPROM I see constant activity
on all address lines, and all datalines. This includes the OE pin as well.
Would a normal runnng computer hit the BIOS that much?
Any thoughts appreciated!
--
Ethan O'Toole
3 Oct
3 Oct
12:40 p.m.
On Oct 2, 2015, at 10:21 PM, ethan at 757.org wrote:
Hello everyone,
I'm working to troubleshoot a 286 laptop style computer. I've kind of hit the
end of my knowledge and wondering if anyone has any insight.
The computer in question I've never seen run. So I don't know normal behavior.
There were a few caps inside that were leaking electrolyte, I cleaned it all up and
replaced them. A few traces look a little bit corroded but test fine.
First thing I'm thinking, is did the BIOS eproms loose a bit or two of data from
age? Bit rot? I did read off the two BIOS chips (high and low pair I assume.) I can see
text like Copyright Pheonix Technologies 1988, but I can see that for instance the first
character of the text Copyright is wrong, it's a P in one file and 9A in the other.
Second thing I hooked up Oscope and cut on computer. It never does a floppy seek. When I
poke around the 27c256 EPROM I see constant activity on all address lines, and all
datalines. This includes the OE pin as well. Would a normal runnng computer hit the BIOS
that much?
Any thoughts appreciated!
--
Ethan O'Toole
When you drop into BIOS, is anything actually set? Can you set the time, and get it to
stick?
I have a Twinhead 386sx/16 I bought new, the only thing I've used it for in the past
20 years is a serial terminal, and every time I go to boot it, I have to drop into BIOS,
and configure things, as the BIOS battery is long dead.
Zane
1:20 p.m.
On Oct 2, 2015, at 10:21 PM, ethan at 757.org wrote:
> Hello everyone,
> I'm working to troubleshoot a 286 laptop style computer. I've kind of
> hit the end of my knowledge and wondering if anyone has any insight.
> The computer in question I've never seen run. So I don't know normal
> behavior. There were a few caps inside that were leaking electrolyte, I
> cleaned it all up and replaced them. A few traces look a little bit
> corroded but test fine.
On Sat, 3 Oct 2015, Zane Healy wrote:
When you drop into BIOS, is anything actually set?
Can you set the
time, and get it to stick?
"WHEN"??!?
First question:
How far does the machine in question get in the start-up?
Does it get to the point of initializing video?
Do you get any POST codes?
(those are BEFORE you can "drop into BIOS", which I assume means goto the
"CMOS setup"
I have a Twinhead 386sx/16 I bought new, the only thing I've used it for in the past
20 years is a serial terminal, and every time I go to boot it, I have to drop into BIOS,
and configure things, as the BIOS battery is long dead.
Zane
--
Fred Cisin cisin at xenosoft.com
XenoSoft http://www.xenosoft.com
PO Box 1236 (510) 558-9366
Berkeley, CA 94701-1236
1:26 p.m.
> Hello everyone,
>
> I'm working to troubleshoot a 286 laptop style computer. I've kind of hit
the end
> of my knowledge and wondering if anyone has any insight.
Make/model? (Just in case anyone knows it and knows if it has any quirks).
>
> The computer in question I've never seen run. So I don't know normal
behavior.
> There were a few caps inside that were leaking electrolyte, I cleaned it all up and
> replaced them. A few traces look a little bit corroded but test fine.
>
> First thing I'm thinking, is did the BIOS eproms loose a bit or two of data
from
> age? Bit rot? I did read off the two BIOS chips (high and low pair I assume.) I can
> see text like Copyright Pheonix Technologies 1988, but I can see that for instance
> the first character of the text Copyright is wrong, it's a P in one file and 9A
in the
> other.
That would worry me. If one bit of the BIOS program (as opposed to copyright messages)
is wrong then the machine could well behave very oddly. Having found that I would want to
get a known-good dump of the BIOS into EPROMs.
That's an odd failure too. Most times true bit-rot turns 0's into 1's. Now
assuming that first
character should be 'C' (or 0x43), then in one case it becomes 'P' (0x50)
and in the other it
becomes 0x9A. In neither case is that simply setting bits that should be cleared. So
perhaps
not bit-rot but some other failure of the memory device.
>
> Second thing I hooked up Oscope and cut on computer. It never does a floppy seek.
> When I poke around the 27c256 EPROM I see constant activity on all address lines,
> and all datalines. This includes the OE pin as well. Would a normal runnng
computer
> hit the BIOS that much?
OE/ might be something as simple and MemRd/ (Memory Read). Is it bringing CS/ (chip
select)
low that often?
A machine of that vintage may or may not 'shadow' the BIOS ROM -- that is copy it
into RAM for
faster access. If it does, then it probably won't access the ROM once the copy is
complete (but is
it completing the copy -- and detecting it has gone through all the locations ?). If it
doesn't (which
is actually quite likely) then it will be running a program from ROM to set up I/O devices
and attempt
to read the boot disk. Which means much of the processor activity _will_ be reading the
BIOS ROM.
>
> Any thoughts appreciated!
When you drop into BIOS, is anything actually set?
Can you set the time, and get it to stick?
I have a Twinhead 386sx/16 I bought new, the only thing I've used it for in the past
20 years
is a serial terminal, and every time I go to boot it, I have to drop into BIOS, and
configure
things, as the BIOS battery is long dead.
Are you getting confused between the BIOS (the I/O drivers and bootstrap in EPROM) and the
BIOS parameter table (often called the 'BIOS' or 'CMOS' (as it is stored
in battery-backed
CMOS RAM) by the PC crowd)? I was under the impression that the OP's machine
didn't
produce any display (does it? If so, what?) and doesn't respond to the keyboard.
-tony
4:44 p.m.
Make/model? (Just in case anyone knows it and knows if
it has any
quirks).
Yamaha C1, one of these:
That would worry me. If one bit of the BIOS program
(as opposed to
copyright messages)
is wrong then the machine could well behave very oddly. Having found
that I would want toget a known-good dump of the BIOS into EPROMs.
It doesn't behave at all. The LCD backlight never comes on, and it always
thinks that it's in external video mode. There is a dip switch on the back
to set this between internal and external display, and it never switches
to internal. I don't have a CGA monitor, but I tried to cross wire a
Commodore 1084S over to it and nothing.
That's an odd failure too. Most times true bit-rot
turns 0's into 1's.
Now assuming that first character should be 'C' (or 0x43), then in one
case it becomes 'P' (0x50) and in the other it becomes 0x9A. In neither
case is that simply setting bits that should be cleared. So perhaps
not bit-rot but some other failure of the memory device.
Hmm yea I just looked. I pulled a chip and put it in the reader. The first
read looked similar, then it seems to be going downhill. The reader I have
supports the device directly (ATMEL 27C256), and it's a Needham EMP-100.
Just tried setting it to AMD and a few other brands but I don't think that
changes the read speed or power or anything.
OE/ might be something as simple and MemRd/ (Memory
Read). Is it
bringing CS/ (chip select)
low that often?
Yea the CS is staying active. Since it never really POSTS or brings up the
LCD backlight, it never does a floppy seek. I'm guessing the CPU is stuck
in an instruction loop or something, possibly because BIOS is damaged?
A machine of that vintage may or may not
'shadow' the BIOS ROM -- that
is copy it into RAM for faster access. If it does, then it probably
won't access the ROM once the copy is complete (but is
it completing the copy -- and detecting it has gone through all the
locations ?). If it doesn't (which
is actually quite likely) then it will be running a program from ROM to
set up I/O devices and attempt
to read the boot disk. Which means much of the processor activity _will_
be reading the BIOS ROM.
I'll look through the manual to see if it has an option to shadow ROM
BIOS. I remember that options on the later computers!
When you drop into BIOS, is anything actually set?
Can you set the time, and get it to stick?
Never gets this far unfortunately.
I have a Twinhead 386sx/16 I bought new, the only thing I've used it for in the past
20 years
is a serial terminal, and every time I go to boot it, I have to drop into BIOS, and
configure
things, as the BIOS battery is long dead.
Yup, I've seen that. This machine has a rechargable battery set of 3 coin
looking things in a nice pack that is separated from the motherboard and
everything. Great design. It's a strange laptop format computer that has
no battery option.
Are you getting confused between the BIOS (the I/O
drivers and bootstrap
in EPROM) and the
BIOS parameter table (often called the 'BIOS' or 'CMOS' (as it is stored
in battery-backed CMOS RAM) by the PC crowd)? I was under the impression
that the OP's machine didn't produce any display (does it? If so, what?)
and doesn't respond to the keyboard.
No display, the LCD actually never lights up. There is an option to switch
between external CGA or internal LCD, no matter what setting the dip
switch is set to it always says external display -- another hint that
something is very wrong.
Thanks for the replies!
I'm trying to find someone with a working machine and going to ask them to
run a bios dump utility. Not sure if it will work but short of finding a
working specimin it's my next hope.
There is a 3rd Eprom in the machine, it's not a bios and it won't be
readable by the bios dump util I found so another potential issue.
--
Ethan O'Toole
5:05 p.m.
On Sat, 3 Oct 2015, ethan at 757.org wrote:
Yamaha C1, one of these:
It doesn't behave at all. The LCD backlight never comes on, and it always
thinks that it's in external video mode. There is a dip switch on the back to
set this between internal and external display, and it never switches to
internal. I don't have a CGA monitor, but I tried to cross wire a Commodore
1084S over to it and nothing.
Using your oscilloscope, does the external video connector show anythings
resembling a video signal?
BTW, SOME after-market "CGA" connectors added a signal for composite
video, which would be relatively easy to interface to. Does your manual
have connector pinout?
Yea the CS is staying active. Since it never really
POSTS or brings up the
LCD backlight, it never does a floppy seek.
Do you have a floppy in the drive? Some "smart" systems won't try to seek
the floppy if they already figured out that there's no disk in it.
I'm guessing the CPU is stuck in
an instruction loop or something, possibly because BIOS is damaged?
That, unfortunately seems likely. On a 286 machine with internal/external
video, the BIOS is likely to be farily unique, unlike most desktops, where
many other BIOSs would work.
No display, the LCD actually never lights up. There is
an option to switch
between external CGA or internal LCD, no matter what setting the dip switch
is set to it always says external display -- another hint that something is
very wrong.
"SAYS external display"? how? by lighting an LED?
I'm trying to find someone with a working machine
and going to ask them to
run a bios dump utility. Not sure if it will work but short of finding a
working specimin it's my next hope.
If you can find a duplicate machine, that can confirm/solve bad BIOS.
--
Grumpy Ol' Fred cisin at xenosoft.com
6:20 p.m.
Using your oscilloscope, does the external video
connector show anythings
resembling a video signal?
BTW, SOME after-market "CGA" connectors added a signal for composite video,
which would be relatively easy to interface to. Does your manual have
connector pinout?
It does! I just looked in it. So there is a video pin (good news), bad
news is .. it's Herculeas! The old high resolution monochrome output.
Dip switch 1 switches between CGA external and internal, 2 turns on
herculeas mode. When it's in CGA mode it says that a pull up or down
resistor is applied and the video signal on that pin is disabled.
Do you have a floppy in the drive? Some
"smart" systems won't try to seek
the floppy if they already figured out that there's no disk in it.
I tried it with one, nothing. It has a hard drive and hard drive
controller as well (20MB, custom interface board.)
That, unfortunately seems likely. On a 286 machine
with internal/external
video, the BIOS is likely to be farily unique, unlike most desktops, where
many other BIOSs would work.
Yea. A while ago I traced back the dip switch to some IC which is likely
read during startup of the system by the bios, which in turn selects
internal or external display.
"SAYS external display"? how? by lighting
an LED?
Correct, LED shows if external display is selected.
If you can find a duplicate machine, that can
confirm/solve bad BIOS.
I might be able to get hold of the bios, but I'm worried about the 3rd
EPROM. It sits in the middle of a bunch of Yamaha branded chips. The BIOS
chips are in the middle of a Chips & Technologies 286 chipset group. The
people I find might be able to dump the BIOS via dos program but not that
3rd IC. But at least if I could split the one I could compare it.
Here are mainboard pics I took when doing the cap replacement:
http://imgur.com/a/CQHcy
I might recheck that mess near C113
And sharing is caring, here is floppy disk images of the software (more
rare than the computer rare) that goes with the computer (fairly rare in
working condition.) I'm going to scan all the documentation I have
eventually and add it. Looking at the docs the expansion connector might
be good enough to be ISA. Hmmm PC IDE for it!?!
https://users.757.org/~ethan/pics/geek/Software/Yamaha_C1_Laptop/
--
Ethan O'Toole
8:41 p.m.
On Sat, 3 Oct 2015, ethan at 757.org wrote:
I might be able to get hold of the bios, but I'm
worried about the 3rd
EPROM. It sits in the middle of a bunch of Yamaha branded chips. The
BIOS chips are in the middle of a Chips & Technologies 286 chipset
group. The people I find might be able to dump the BIOS via dos program
but not that 3rd IC. But at least if I could split the one I could
compare it.
Here are mainboard pics I took when doing the cap replacement:
http://imgur.com/a/CQHcy
I might recheck that mess near C113
Did you only replace those small green Nichicon parts? If so, I would
inspect/test the others as well. My experience with these type of early
mixed SMD/through-hole boards is that some companies tried to reflow them
with the small electrolytics already in place which would damage their
seals and cause them to leak as they aged. It doesn't seem to be specific
to any particular brand/series either as I've seen Nichicon, Nippon,
Panasonic, etc all affected by this.
If a new set of BIOS EPROMs doesn't fix it, it might be time to look into
an in circuit emulator for the 80286. PODs for LCC sockets do exist,
although they might be harder to find than a POD for the PLCC or PGA
versions.
4 Oct
4 Oct
12:10 a.m.
Did you only replace those small green Nichicon parts?
If so, I would
inspect/test the others as well. My experience with these type of early mixed
SMD/through-hole boards is that some companies tried to reflow them with the
small electrolytics already in place which would damage their seals and cause
them to leak as they aged. It doesn't seem to be specific to any particular
brand/series either as I've seen Nichicon, Nippon, Panasonic, etc all
affected by this.
I only replaced the one style that was leaking on the mainboard, there is
also a bunch of others I think that are smaller.
On the driver board that runs the LCD I recapped it as well. I'll go back
and look at the smaller caps. I put the oscope on the power lines and
didn't see crazy ripple, but I only used an analog 20mhz tektronix not the
crazy heavy old HP thing with the high frequency.
If a new set of BIOS EPROMs doesn't fix it, it
might be time to look into an
in circuit emulator for the 80286. PODs for LCC sockets do exist, although
they might be harder to find than a POD for the PLCC or PGA versions.
Hmmm that would be cool :-)
Hopefully it doesn't get to that though.
--
Ethan O'Toole
2:28 a.m.
might be able to get hold of the bios, but I'm
worried about the 3rd
Remember the BIOS might have been specifically modified for that
machine. Things like internal/external video selection are not going
to be in a generic desktop mchine BIOS
EPROM. It sits in the middle of a bunch of Yamaha
branded chips. The BIOS
That may well be the display character generator. In which case if it contains
_something_ you will get a display.
-tony
3 Oct
3 Oct
8:53 p.m.
On Sat, Oct 03, 2015, ethan at 757.org wrote:
I'm trying to find someone with a working machine
and going to ask them to
run a bios dump utility. Not sure if it will work but short of finding a
working specimin it's my next hope.
I assume you already know of Markus Kunn:
<https://markuskunn.wordpress.com/2013/08/25/yamaha-c1-the-kraftwerk-computer/>
--
Eric Christopherson
3214
days inactive
3215
days old
11 comments
6 participants
participants (6)
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ard＠p850ug1.demon.co.uk -
cisin＠xenosoft.com -
echristopherson＠gmail.com -
ethan＠757.org -
healyzh＠aracnet.com -
tothwolf＠concentric.net