Just to be clear, it's not just beep & enter, it's:
memory power switch on the bottom must be on
cold reset (ctrl+break+reset)
enter
beep
enter
Since you are flying blind, you have to start with a cold reset to
ensure that you are starting out at the main menu, and the cursor is on
BASIC.
Carefully avoid accidentally pressing any keys at all except as
specified. For example, this all goes out the window if you touched an
arrow key or a letter after the reset.
Press enter, which gets you into BASIC.
Then type "beep" and press enter to execute a beep command.
But it doesn't prove anything if you didn't strictly and exactly follow
the steps from reset. You might have just typed beep into the menu or
into telcom or something for instance.
--
bkw
On 2/18/22 03:00, Gsvacances Free wrote:
Hi Brian,
I did try to type “beep” and enter but couldn’t hear anything so I
assume although the CPU seems active, the whole thing (CPU + RAM +
ROM) is not.
Today, I’ll check the reset line in various places and bus activity on
the memory PCB and keep the list updated.
Gilles
*From:* Brian White
*Sent:* Friday, February 18, 2022 12:43 AM
*To:* [email protected]
*Subject:* Re: [M100] Model 200 with LCD all black from power on
There is also the beep test, which tells you if the machine is running
and the problem is only the lcd, or if the machine is not running,
which means the lcd is probably fine.
Cold reset, then press enter, then type "beep" (without quotes), and
press enter.
If the cpu is running and the rom loaded and ram is working, then it
will beep. If you don't get a beep, then the cpu is probably not running.
bkw
On Thu, Feb 17, 2022, 3:47 PM Gsvacances Free <[email protected]> wrote:
Hi Brian !
Thanks for your reply.
I tried CTRL + BREAK (PAUSE) + RESET or POWER but although I hear
clicks in the speaker nothing else occurs and no change on the LCD
(= still black).
I’ll check the reset line in various places and bus activity on
the memory PCB tomorrow.
Gilles
*From:* Brian White
*Sent:* Thursday, February 17, 2022 7:02 PM
*To:* [email protected]
*Subject:* Re: [M100] Model 200 with LCD all black from power on
Did you ever actually do the cold reset 3-finger salute? I didn't
see you say that you did.
I don't remember what the keys are for 200 but it's in the manual
and probably on club100 and bitchin100 too.
ctrl + break + reset or something like that.
Mere power-cycle isn't good enough, you have to do that reset
hot-key once after any crash or full memory power loss etc. Then
after that you can use the power button normally.
bkw
On Thu, Feb 17, 2022, 9:35 AM Gsvacances Free <[email protected]>
wrote:
Thank you for your reply Jeff !
The reset switch seems to work as I hear a click in the
speaker but nothing changes on the LCD.
So I’ll check that the reset line is going wherever it needs to.
As for bus activity, I only checked at the CPU but not on
various RAM and ROM chips.
So will do it too and keep you updated !
Thanks again for your quick reply !
Gilles
*From:* [email protected]
*Sent:* Thursday, February 17, 2022 2:22 PM
*To:* [email protected]
*Subject:* Re: [M100] Model 200 with LCD all black from power on
It sounds like you are on the right track. The first three
things I check: PCR - Power, Clock, Reset. It seems you have
already checked the first two. If the reset circuit is not
working the machine will not start up in a known state and
many strange things can happen.
The next few checks: BADS - Bus, Address Decoding, chip
Selects. You have already checked for bus activity but double
check that you are getting all the bus signals to all the main
chips. I had a PC-8201 recently where I checked bus activity
at the RAM which was fine, but there was a broken trace to the
ROM. If I had checked in both places at first it would have
saved me much time. If any off the address decoding/chip
selects are wrong/missing all manner of strangeness will occur.
The black screen at power up is the classic symptom of the
computer not booting up. When powered up the LCD drivers will
turn on every pixel. During the boot process the computer will
reset the LCDE drivers which turns all the pixels off. Being
stuck in this not booting state can be anything from bad RAM,
ROM, address decoding chips, etc.
Jeff Birt
*From:* M100 <[email protected]> *On Behalf Of
*Gsvacances Free
*Sent:* Thursday, February 17, 2022 6:31 AM
*To:* [email protected]
*Subject:* [M100] Model 200 with LCD all black from power on
Hi everyone,
Gilles here (male name in France).
I have a model 200 which shows an all black LCD screen.
I replaced the battery and fully charged it, no change.
I checked the voltage at the battery when the model 200 is
unplugged and it’s about 3.4-3.5v.
I can hear a click noise in the speaker when I switch the 200
on and also when I press the reset button.
But, appart from that, nothing seems to occur.
I checked the CPU clock and it is fine.
I also checked the buses and nothing seems stuck.
Power supply for all the chips seems to be correct.
On the LCD connector, I also have some AC voltages of various
frequencies.
On very rare occasions (2-3 times not in a raw), the M200 LCD
screen is greyish and the contrast pot adjustment seems to work.
But when the M200 is black from the start, the contrast pot
does nothing.
I disconnected and reconnected both the keyboard and the LCD
flex cables without any change and the symptoms.
I don’t see any traces of corrosion nor breakage on the PCBs.
There is no option ROM inserted in the memory board and if I
put the switch on the OFF position, the LCD screen does
nothing and I also hear no click noise in the speaker.
If I switch it ON, the LCD goes black again.
I’ve read the mails related to the same symptoms and used them
to check things here and there but, well, no joy !
I have a multimeter and an oscilloscope but don’t know what
else I could check.
Any suggestions ?
Thanks in advance for your help !
Gilles
--
bkw
