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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 10th Oct 2018, 8:45 pm   #21
ThePillenwerfer
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Default Re: 486 PC. Keyboard problem.

Tants can also fail of course.
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Old 10th Oct 2018, 8:53 pm   #22
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Default Re: 486 PC. Keyboard problem.

I wondered if the proprietary board is masking any area's of memory.... Is it worth trying to boot the motherboard with the bare minimum of boards plugged in?
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Old 10th Oct 2018, 8:58 pm   #23
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Default Re: 486 PC. Keyboard problem.

Would a 'PC diagnostic card' be any use for this? I have one for ISA/PCI slots.
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Old 10th Oct 2018, 9:22 pm   #24
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Default Re: 486 PC. Keyboard problem.

PC boot problems also make me think PSU.
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Old 10th Oct 2018, 9:52 pm   #25
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Default Re: 486 PC. Keyboard problem.

It certainly sounds like a motherboard fault. The BIOS will try to measure the amount of RAM during a full-length power-on self test, by determining the first location that can't be read back after writing to it. A loose connection on an expansion card or SIMM, or a dodgy decoupling capacitor, could certainly cause unreliability. Is the processor in a quick-release socket?

If the CNC machinery connects to the motherboard via expansion cards that plug into the old-fashioned 8- or 16-bit slots, then in the worst case it ought to be possible to replace the whole motherboard

Incidentally, my secondary school had in the CDT department a mini-CNC lathe controlled by a BBC Master 128. Very sophisticated for c.1987! It was most often used for making threaded inserts for lampholders.
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Old 10th Oct 2018, 11:02 pm   #26
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Default Re: 486 PC. Keyboard problem.

UPDATE.

I removed the PC from the control cabinet, placed it on the bench and reseated everything in sight.

I then connected mains, a VGA LCD monitor (the machine uses a CRT monitor) and a keyboard. Put an MS-DOS start up disk in the FD drive and switched on.

The PC complained about the FD, so I produced another one. Then PC then booted up correctly about 20 times. I thought I'd fixed it!

I put the PC back in the control cabinet and connected it to the CRT monitor and the mains supply inside the cabinet. The same keyboard was used throughout. Nothing else was connected to the PC, which actually controls the machine via a com port.

The PC booted up once and then went back to its old tricks. I powered it from a wall socket rather than from the supply in the cabinet and connected the LCD display instead of the CRT one. Still no joy.

There is no difference electrically between this and the bench set up.

Physically the PC was horizontal on the bench, but is vertical in the control cabinet. Also the PC case is screwed into the control cabinet, so I suppose something could be distorting.

I'll have it back on the bench tomorrow.
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Old 10th Oct 2018, 11:16 pm   #27
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Default Re: 486 PC. Keyboard problem.

Just for reference, I couldn't identify the PC or motherboard manufacturer. It uses a double sided riser board fitted with a VGA card, an FDC card and several com port cards.

Three com ports are used. One for an external serial printer, one for the machine's internal keypad and one to control the machine.
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Old 11th Oct 2018, 7:49 pm   #28
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Default Re: 486 PC. Keyboard problem.

The PC misbehaved on the bench just as it had in the cabinet. I think I've tracked the problem down to a combination of dodgy floppy disks and dodgy floppy disk drives, both of which are in short supply here following a mass clear out a few years ago. I finally found a combination which worked reliably.

I then reinstalled the PC in the control cabinet connecting it to the cabinet's mains supply and the CRT monitor. I must have rebooted it successfully about 50 times during the course of the day without one failure. I won't believe it's finally fixed until it's been running for a couple of weeks without failure though.

The application software loaded OK, but unfortunately the PC won't talk to the machine. Next thing to do is find a way of checking out the (serial) com ports.
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Old 11th Oct 2018, 9:09 pm   #29
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Default Re: 486 PC. Keyboard problem.

Assuming the serial printer works (tested on another pc?) then you could send text strings to it from MSDOS then plug it into the other ports to check them.

Without loading a terminal program, the MSDOS "mode" command will show which ports are present e.g.

mode

Status for device COM1:
-----------------------
Baud: 1200
Parity: None
Data Bits: 7
Stop Bits: 1
Timeout: OFF
XON/XOFF: OFF
CTS handshaking: OFF
DSR handshaking: OFF
DSR sensitivity: OFF
DTR circuit: ON
RTS circuit: ON

then to send a string to that port:-
echo 1234567890 > com1:
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Old 11th Oct 2018, 9:39 pm   #30
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Default Re: 486 PC. Keyboard problem.

Alas no serial printer, it's quite possible the machine never had one.

However I could run the hyperterminal program on another PC and send characters to it as you suggest.

The problem may be more fundamental than a com port problem though. The back up battery on the machine's control card has leaked dissolving the tracks to its com port. This is quite a common problem. Ironically the battery doesn't actually do anything in this application.

Fortunately I have a spare control card taken from another machine which was upgraded to use a USB port. Further testing will have to wait until next week though.
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Old 12th Oct 2018, 5:49 am   #31
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Default Re: 486 PC. Keyboard problem.

Does it use a dedicated, expansion bus card to talk to the CNC lathe, or is all tbe communicstion done by RS232?
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Old 12th Oct 2018, 7:11 am   #32
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Default Re: 486 PC. Keyboard problem.

All RS232.
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Old 13th Oct 2018, 11:32 am   #33
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Default Re: 486 PC. Keyboard problem.

Hi Graham,
are you using the original boot disk to start the pc?
Reason for querying is generally serial ports are configured by the CONFIG.SYS and AUTOEXEC,.BAT files during booting.

Additionally there might be dip switches or hard wired selections on the Controller Card (which you changed) involved. If so, are they the same on both original and replacement cards?

Regards - Mike
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Old Yesterday, 6:49 pm   #34
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Default Re: 486 PC. Keyboard problem.

Quote:
Originally Posted by buggies View Post
Assuming the serial printer works (tested on another pc?) then you could send text strings to it from MSDOS then plug it into the other ports to check them.

Without loading a terminal program, the MSDOS "mode" command will show which ports are present e.g.

mode

Status for device COM1:
-----------------------
Baud: 1200
Parity: None
Data Bits: 7
Stop Bits: 1
Timeout: OFF
XON/XOFF: OFF
CTS handshaking: OFF
DSR handshaking: OFF
DSR sensitivity: OFF
DTR circuit: ON
RTS circuit: ON

then to send a string to that port:-
echo 1234567890 > com1:
I had another play this afternoon. At this stage I just want to prove that the serial ports are working before I attempt to connect to the machine.

At start up the BIOS shows three com ports with addresses $3F8, $2F8 and $3E8.

Entering "mode" at the DOS prompt was a dismal failure, possibly due to the fact I can't find a way of pausing the display before it scrolls off the screen. I couldn't find a way of generating the pipe character | from the keyboard I was using.

Entering "mode com1/status" at the prompt returns "RETRY=NONE". Same for com2 and com3.

I configured com port 1 using "mode com1:9600,N,8,1,P. Did the same for com2 and com3. Got responses showing ports had been configured.

mode com1/status now returns "RETRY=B" Same for com2 and com3.

Entering "echo 1234567890 > com1" at the prompt returns "invalid device request writing com1". Same for com2 and com3.

I assume I have a hardware problem with the com ports?
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Old Yesterday, 7:27 pm   #35
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Default Re: 486 PC. Keyboard problem.

Quote:
Originally Posted by Station X View Post

I had another play this afternoon. At this stage I just want to prove that the serial ports are working before I attempt to connect to the machine.

At start up the BIOS shows three com ports with addresses $3F8, $2F8 and $3E8.

Entering "mode" at the DOS prompt was a dismal failure, possibly due to the fact I can't find a way of pausing the display before it scrolls off the screen. I couldn't find a way of generating the pipe character | from the keyboard I was using.

Entering "mode com1/status" at the prompt returns "RETRY=NONE". Same for com2 and com3.

I configured com port 1 using "mode com1:9600,N,8,1,P. Did the same for com2 and com3. Got responses showing ports had been configured.

mode com1/status now returns "RETRY=B" Same for com2 and com3.

Entering "echo 1234567890 > com1" at the prompt returns "invalid device request writing com1". Same for com2 and com3.

I assume I have a hardware problem with the com ports?
Mode > fred.txt to create a text file if there is an editor on the machine.

I have forgotten most of this stuff but a quick look at a web site reminds that the retry is just what to do on timeout - but I think you should have got more info returned than just that.

Probably copy config.sys com1: would give the same invalid device error as the echo command. Any possibility the ports need RTS-CTS linked or special drivers for the ISA card (hopefully not).

Google found a similar but unresolved fault here:-
http://www.verycomputer.com/12_2bd04c9fc271e788_1.htm
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Old Yesterday, 8:05 pm   #36
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Default Re: 486 PC. Keyboard problem.

A couple of questions please George.

If special ISA Card drivers are needed I assume they won't be on the DOS start up diss, but will need to be loaded as part of the application software?

Should the echo command actually show characters RECEIVED from the RS232 port? If so I can see the possible need for RTS/CTS linking.
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Old Yesterday, 9:31 pm   #37
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Default Re: 486 PC. Keyboard problem.

Quote:
Originally Posted by Station X View Post
A couple of questions please George.

If special ISA Card drivers are needed I assume they won't be on the DOS start up diss, but will need to be loaded as part of the application software?

Should the echo command actually show characters RECEIVED from the RS232 port? If so I can see the possible need for RTS/CTS linking.
No specific drivers provided on the DOS disk(s). I think DOS should manage to work the ports if they are recognised in the BIOS.
No, the echo command will not show anything locally so would need either scope or pair of parallel back-to-back LEDs + resistor on the TX pin on the D connector.
Procomm is a DOS comms program which is only about 140k so the exe file can be added to a floppy. The freeware version procomm230.zip can be found by scrolling down on this page:-
http://www.aspectscripting.com/support.shtml
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Old Yesterday, 9:42 pm   #38
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Default Re: 486 PC. Keyboard problem.

I booted another PC from the DOS start up disk and got similar responses to those I described in post #34.

Then I started the same PC in windows XP, pressed the Windows and R keys simultaneously to get a run prompt and entered "CMD" to get a DOS prompt.

Entering "mode" at this prompt returned the full parameters of the port.

So perhaps the "REPLY B" response is a red herring?
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Old Yesterday, 10:48 pm   #39
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Default Re: 486 PC. Keyboard problem.

I agree that the reply is most likely not important. There was a difference in some of the DOS commands between version 3.3 and 6.2 but I would need to do some digging tomorrow. Which version are you booting?
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Old Yesterday, 11:58 pm   #40
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Default Re: 486 PC. Keyboard problem.

Just to add: If you type a DOS command which generates more than a screen of output which promptly flies off up the screen out of sight, then appending /P to the end of the command will make it display each page with a pause. Press a key (possibly space, possibly just any key) to get it to move to the next page.

Example:

DIR /P will display the contents of the current directory page by page until all of the contents of the directory have been shown.

With the MODE command I think you can limit the amount of output from that by entering

MODE COM1:

In which case it will only generate information specific to that COM port.
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