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5150 - keyboard issues

luckybob

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Recently got a 5150 from Craigslist for a good price. -VIDEO-

Long story short, I decided to work on the keyboard first. No point in anything else unless you can type. I was hoping to just re-attach the space bar and it would work fine afterwards. Sadly that did not correct the issue. The system is acting as if there is a key being held down constantly. I had to completely tear down the keyboard to properly reconnect the space bar. Which went fine. The foam inside is acceptable in condition. The problem remains.

I felt I would pick the brains of the people here before I sank money into something that might not work.

1 - keyboard acts like a key is stuck down. The system will boot into dos/basic and constantly beep until it crashes.
2 - Using just the PCB, the errors remain.
3 - I currently do not have another keyboard compatible with the 5150.
4 - There are no visible issues with the electronics.

This would explain why the previous owner scrawled BAD over the top of the keyboard. (which I removed) I don't want to lead the witness here, but after some internet searching I've come to the conclusion there is an issue with the electronics.

Any advice on how to proceed?

Side note: I'm going to work on building a XT-PS2 adapter just to get things working. (8051 based - its what I have)
 

Stone

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Since not all keyboards are created equal it would really help if you told us whether this is a true IBM Model F (buckling spring, OEM) or some other type.

Sorry, but I'm NOT going to watch a one hour video to 'maybe' find the answer. :)

If you want a Model F for a PC (5150) I have an extra.
 

luckybob

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It is a true 88 key IBM. And there are links in the video description to "fast forward" to relevant parts.

My main goal is to fix the one I have. If that provides unfruitful, then I will happily take you up on your offer. Thank you.
 

luckybob

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Whatever you want to call this:

IBM_Model_F_XT.png
 

modem7

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Recently got a 5150 from Craigslist for a good price.
As you have discovered:

* The power-on self test of the 5150 does not display progress of the RAM test.
* You have to be patient with these things - some timeouts (such as for the 1701 error) can be quite long.

The system is acting as if there is a key being held down constantly.

Looking at the video, you saw a "301" error when the keyboard was disconnected from the motherboard, and no 301 when it was connected. So, per [here], that means that the keyboard responded to the interrogation by the 5150's POST.
But you did not see a byte preceding the 301 (e.g. "22 301"), so as far as the keyboard is concerned, there is no stuck key.

The following is an example of what is observed for stuck key/s:

On my 5150, if I continuously hold down the G key whist I power up the 5150, I observe:

* cursor appears 5 seconds after power-on; then
* 15 seconds later, a "22 301" error is displayed per [
here]; then
* a beeping from the speaker; then
* when BASIC eventually starts, the beeping stops, and under BASIC's 'ok' prompt, I see lower case G's continually being displayed one after the other.

If I then repeat the operation, but this time holding down both the R and T keys, I observe:

* cursor appears 5 seconds after power-on; then
* 15 seconds later, a "13 301" error is displayed per [
here]; then
* a beeping from the speaker; then
* when BASIC eventually starts, the beeping stops, and under BASIC's 'ok' prompt, I see one lower case R followed by lower case T's continually being displayed one after the other.


Any advice on how to proceed?
Proceed to obtain a functional PC_XT-class keyboard so that you can prove that the supplied keyboard is faulty.

Out of curiosity, it would be interesting to see what you observed if you simulated a stuck key by holding a key down.
 

luckybob

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83. Excuse me for not having counted.


@modem7

Ill put the keyboad back together tonight after work and update.
 

luckybob

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Hehehehe... Man, I guess I got doubly lucky. One looooong hour filled with mis-information.

Again I need to apologize for not being born with the innate knowledge of every system out there. I guess I should just be happy you were magnanimous enough to grace us plebs with your divine presence. Should you continue to mingle with the rabble, I would be open to LEARNING what misinformation I presented.
 

Trixter

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Stone assumes everyone who posts is very familiar with the system they are asking help for; please don't let his attitude spoil your fun.

modem7 has given excellent advice, and I concur that the keyboard is likely at fault, but you need another keyboard to verify that. Assuming you are still talking to Stone, I would purchase his known good working keyboard he is offering, or one from somewhere else, so that you can proceed through process of elimination.

The fact that your system boots to ROM BASIC is an excellent sign that the overall system unit is in good health. If you paid $100 or less for your haul, you did good.
 

luckybob

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As a retired internet troll, I'm honestly not bothered in the slightest. ^.^

I'm on a fixed income, and I blew February's budget on this machine. I did get it for $100 though. I'm quite happy, as I was also able to confirm my 5153 monitor to be working.

As for the keyboard. It is no longer responsive at all. I don't get a keyboard error either. Holding a key down does nothing. I'll probably sell it for parts on ebay to pay for a new one. Shame, as it's in good condition as I took the time to wash it down properly. If I was a betting man, I would guess there was a problem with the metal can chip on the board. According to a schematic, it's doing the sensing of the key presses. I did pull out my multimeter, and all chips are getting 5v. I don't own a scope to troubleshoot further.

I saw in my internet searches, someone made a converter for ps/2 to 5150 using a 8051 chip. I happen to have the parts so in the next few days I might give that a try.
 

SpidersWeb

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I've had with a few other Model F's - where either a key "foot" isn't sitting right or the PCB itself has something partially conductive on it (by PCB, I mean the area where each key touches the PCB). I've had this cause stuck keys, DOS crashes etc before - but running with the keys removed (just using my finger on the PCB) it'd work correctly.

Good luck with the 8051!
 

KC9UDX

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I would hold off selling that keyboard until you build your adaptor. If the adaptor doesn't work, your keyboard isn't necessarily dead.
 

luckybob

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I've had with a few other Model F's - where either a key "foot" isn't sitting right or the PCB itself has something partially conductive on it (by PCB, I mean the area where each key touches the PCB). I've had this cause stuck keys, DOS crashes etc before - but running with the keys removed (just using my finger on the PCB) it'd work correctly.

Good luck with the 8051!

I did that too! Before I put it back together (for the 2nd time), I tried just about everything I could. When I first started this thread I could use my fingers to "press keys" Only the enter key ever really worked reliably. I even cleaned all EIGHTY THREE flappers, but no avail.

@KC9UDX

I agree. I also wish I had a 2nd machine so I can definitely rule out the keyboard and not a problem with the motherboard. I have TEN 5 pin din style keyboards at my disposal, and none are compatible.
 

Chuck(G)

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The converter that some use here employs a single 8-pin PIC12F629 MCU. You wouldn't even need a PCB to build it--there are only a couple of passives involved--not even a crystal.
 

Stone

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Stone assumes everyone who posts is very familiar with the system they are asking help for...
Hardly...

88 ╪ 83

When you have the item in question in your possession it isn't very difficult to accurately assess its visible features.

Posting inaccurate information when seeking to acquire help from others is akin to sending those who are attempting to help you down a rabbit hole.

If counting the keys is too mundane a task in your search for assistance from those who are quite willing to offer their time to you then you're asking a bit too much, IMO.

A wild goose chase is something I never liked and still don't.
 

nestor

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Also take a look at the keyboard female connector on the motherboard, maybe it is dirty or it has bad solder joints. Move the keyboard plug with the computer powered on while pressing some keys and check if the behaviour changes.
 
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