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5150 16k-64k Keyboard not working?

F

framer

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Nov 27, 2008
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Murrell's Inlet SC
Keyboard just quit working, it has been working.

I have three IBM F keyboards and none work with this unit.

Anyone have a starting point.

Thanks

framer
 
No 301 error shown.

Yes, real IBM 83 key keyboard

Boot to OS without issue but keyboard does not work.

Tried DOS 1.1 3.2 6.22 CPM 1.0

All boot but no keyboard input.

Thanks
 
I even tried the original Diagnostics disk 1502367 Loaded fine but because keyboard does not work I'm unable to run diagnostics on the system board.

I've also unplugged all cables and cards and reattached with no joy.

Bizarre this is...

framer
 
I found the maintenance manual 6280087 worked the MAP and on page 0300-4 019 checked the voltage shown for the pins on the keyboard connector. Pin 1 was suppose to have +2.0v to +5.5V I shows .1mV or 0 Manuals recommends I replace the system board. Well that's just great. Board only lasted 39 years. FYI all other pins checked OK on voltage.

framer
 
Fortunately, the keyboard "controller" on the 5150 is very, very simple--mostly just a shift register. (See the schematic) using commodity parts. Should be a simple repair. Also, check from broken traces around the motherboard DIN connector--sometimes these get wrenched loose and you lose continuity.
 
If you say "also no sound" and clock pin with no signal, that points to a 8284 (U11) clock generator failure (that generates peripheral clock PCLK signal) or maybe 8255 peripheral controller (U36) because both things depend on that. Maybe a broken trace or something shorting pin 2 of the 8284. That should always output a 2.385MHz clock, and goes to pin 9 of U26, is divided by two and goes to pin 9 of 8253 (U34) for the sound and pin 3 of U82 for the keyboard. I would check all that signals and components.
 
framer said:
I found the maintenance manual 6280087 worked the MAP and on page 0300-4 019 checked the voltage shown for the pins on the keyboard connector. Pin 1 was suppose to have +2.0v to +5.5V I shows .1mV or 0 Manuals recommends I replace the system board. Well that's just great. Board only lasted 39 years. FYI all other pins checked OK on voltage.
Click to expand...
Pin 1 is the CLOCK line. It normally sits at a HIGH level. The MAP indicates that the measurement is to be done with no keyboard attached, and I presume you obeyed that instruction.

On an IBM 5160, grounding the CLOCK line instructs the POST to go into a 'MANUFACTURING TEST' mode, a mode where no 301 test is done. Quickly looking at the source code for the IBM 5150's POST, I see similar. I think your POST is going into 'MANUFACTURING TEST' mode because the CLOCK line is LOW (or somehow grounded).
 
I was wrong in my previous POST. In the IBM 5160, grounding the DATA line, not the CLOCK line, is a method of getting the POST to go into MANUFACTURING TEST mode.

I brought out a known-good 5150 motherboard of type 16KB-64KB, one fitted with the final BIOS revision, revision 10/27/82. Keyboard attached. No 301 error. Booted to BASIC where my keystrokes registered on-screen. Powered off. I then removed the keyboard then I grounded the DATA line and then I powered the motherboard on. No expected 301 error and then I soon heard a never-ending series of beeps. Looking at the source code for the 10/27/82 BIOS, the behaviour appears to match the MANUFACTURING TEST mode (skip keyboard test, skip ..., run the POST in a loop).

Out of curiosity, I grounded the CLOCK line instead of the DATA line, and I observed the same behaviour.

I put in the 04/24/81 revision BIOS. Grounding the DATA line, I saw the cursor appear, no 301 error, and then after a long minute of a flashing cursor, the never-ending series of beeps started.

But there is beeping, and the POST appears to be running in a continuous loop. And I realised that your, "No 301 error shown", was not conditional, i.e. maybe you do see a 301 if the keyboard is removed. So the MANUFACTURING TEST mode hypothesis is gone.
 
With multiple symptoms, I sometimes just pick one symptom and run with that.
If the fix for that symptom fixes the other symptom/s, good.
If not, pick one of the remaining symptoms then run with that, etc.

framer said:
Pin 1 was suppose to have +2.0v to +5.5V I shows .1mV or 0
Click to expand...
With no keyboard attached, at POST end (a normally running POST), pin 1 of the DIN connector should be HIGH (pulled HIGH by RN1, with U80 not driving it LOW).
Working backwards in the circuitry, what do you measure on pins 11 and 13 of chip U80 ?
Both pins are expected to be HIGH.
 
inmbolmie said:
If you say "also no sound" and clock pin with no signal, that points to a 8284 (U11) clock generator failure (that generates peripheral clock PCLK signal) or maybe 8255 peripheral controller (U36) because both things depend on that. Maybe a broken trace or something shorting pin 2 of the 8284. That should always output a 2.385MHz clock, and goes to pin 9 of U26, is divided by two and goes to pin 9 of 8253 (U34) for the sound and pin 3 of U82 for the keyboard. I would check all that signals and components.
Click to expand...

This. If you have a scope check PCLK
 
WOW! I guess I got homework to do next week. I will check the above and get back when I've gotten into it. Family stuff this weekend, wife got plans...


Logic probe, multi-meter and this forum my only tools.

Thanks for the insight for this issue.

framer
 
Confession: Before I read all the replies, I'd given up and pulled all the chips from the board that might be used to fix other PC XT I have. After reading the replies I decided to try again. I re-installed the CPU, memory, ROM basic & Bios. Hook everything backup outside the case so I might do some probing; however, the computer booted right up and worked. I installed it back in the case and ran diagnostics several times perfectly.

So if something does work beat it with a hammer and try again:crazy:

I guessing a corroded bin must have caused the issue?

Thank all, for keeping me from giving up too early on this system.

framer
 
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