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What is a "Printer Port LED" (for a Toshiba T3200SX)?

charnitz

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I am troubleshooting a Toshiba T3200SX that turns on, but shows nothing on screen and doesn't make any beeps or show disk activity except an initial flash of the disk activity and key lamps. In the maintenance manual, I found mention of a "Printer Port LED" that can be plugged into the parallel port and apparently will display POST codes as it tries to boot up. Has anyone heard of a such a thing?

Failing to acquire a printer port LED, I have a logging, four-channel oscilloscope. Is there any documentation on the parallel port pinout for this purpose that I could use that to determine what code would have been sent to the printer port LED using the oscilloscope?
 
See old discussion here.

Thank you for the thread. It was long, but I read it in full and learned some things.

See [here] also.

Thank you for the link. I saw in the thread that Chuck(G) referenced that you provided a diagram of the original:

http://minuszerodegrees.net/temp/3/ppl862rrghf.jpg

And I saw your reference in the Toshiba T1000 Manual 2-12 where it says: "Read the final LED status as a hexadecimal value from left to right."


I realized that I could use my multimeter to do the same thing as an LED, one data pin at a time (using the multimeter probes to go from each data pin to ground pin 25). This is what I got reading the data pins in the physical order they appear on the parallel port oriented with pin 1 (strobe) at upper right:

data pin 8 ->0010 1001<- data pin 1

I also saw this once:

0000 1101

If data pin 1 is the least significant bit, then I read these as 29h and 0Dh respectively. Am I reading the bit order right?

In the T3200SX manual these correspond to:

29h: PIT interrupt check
0Dh: PIT Channel 2 test and initialization

It seems like both codes indicating the programmable interval timer, even though it could be a coincidence, strongly implicates the PIT. This unit was just shipped through the winter storms of late for two weeks and was working before it shipped. Would it make sense for a PIT problem to develop in that time?
 
Well, perhaps this floating module might have something to do with it? :shock:

floating-mod.jpg

I notice that if I have the bit order backwards, the initial error code is:

1001 0100

Which would correspond to this POST message:

94h: 1st 64KB memory error

Which is a Halt error. That could make sense based on this floating module.

I can't explain the other error code I saw, as that in the other bit order would be:

1011 0000

And there is no entry in the manual for a B0h error code.
 
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