49 replies to this topic

[Xmsteel]

Tursi, on Mon Aug 8, 2011 1:11 AM, said:

Xmsteel, on Sun Aug 7, 2011 6:19 PM, said:

zylon, on Sat Aug 6, 2011 4:07 PM, said:

$5

The cord is too short and the hookups arent right

Um.... that's a strange note. Can we get a look at your machine and the connector you are working with? There's only one style of 99/4A keyboard cable on all the machines that have ever passed through my hands, including the QI 2.2 models.

Perhaps we are diagnosing the wrong issue here!

I believe I posted a picture of the setup in my first post...

[Tursi]

Xmsteel, on Mon Aug 8, 2011 1:49 PM, said:

Tursi, on Mon Aug 8, 2011 1:11 AM, said:

Um.... that's a strange note. Can we get a look at your machine and the connector you are working with? There's only one style of 99/4A keyboard cable on all the machines that have ever passed through my hands, including the QI 2.2 models.

Perhaps we are diagnosing the wrong issue here!

I believe I posted a picture of the setup in my first post...

I suggest you take another look - that shows the side of the keyboard, not the cable or the pin header on your motherboard.

From that picture, though, it looks like the same standard keyboard as usual, meaning the keyboard in post 17 should be fine.

[Xmsteel]

Tursi, on Mon Aug 8, 2011 4:01 PM, said:

Xmsteel, on Mon Aug 8, 2011 1:49 PM, said:

Tursi, on Mon Aug 8, 2011 1:11 AM, said:

Um.... that's a strange note. Can we get a look at your machine and the connector you are working with? There's only one style of 99/4A keyboard cable on all the machines that have ever passed through my hands, including the QI 2.2 models.

Perhaps we are diagnosing the wrong issue here!

I believe I posted a picture of the setup in my first post...

I suggest you take another look - that shows the side of the keyboard, not the cable or the pin header on your motherboard.

From that picture, though, it looks like the same standard keyboard as usual, meaning the keyboard in post 17 should be fine.

Correct, but look at the difference in post 17 and mine. Mine is in a big fat casing and it is just a plain board. Would it even fit right?

Also, If you REALLY want to see the cord I can take another picture, but the one on my keyboard is longer and I can tell just by looking. Even mine is a tight squeeze.

[Tursi]

I've taken dozens of these machines apart.. the difference in cable length is negligable. It's always a tight fit, length wise. It's designed to fold in tight and not have much, if any, slack.

His is a different style than yours, but there were quite a few different style keyboards. If you look at where the PCB is compared to the mounting holes on yours, you'll see they are about the same. (#17 surprises me a little by having a clip on the cable, I've never seen that before ).

I'd give it a better than 99% chance that keyboard will work fine in your machine. Except for the box of NOS keyboards I have, I've never seen the exact same keyboard in two different TI-99/4A consoles.

if you're worried, get the beige one from TexIn Treasures (or wait for me to get home )

[Xmsteel]

Well, if #17's will work I guess I'll get it... I looked on ebay and no one would sell them for cheap and they weren't even tested or known if they work.

If worse comes to worse I can wait for you to get home...
How much are you asking?

---
ALSO: Are you SURE it is the keyboard it self? I will be upset if I buy a keyboard for a machine that has a bad board or something....

[InsaneMultitasker]

If you have a continuity tester / meter you should be able to use this schematic to test a few keys. I find it quite improbable the keyboard is bad unless you broke all row and/or column wires in the keyboard cable.

http://www.mainbyte....d/keyboard.html

[Tursi]

Xmsteel, on Tue Aug 9, 2011 10:21 PM, said:

ALSO: Are you SURE it is the keyboard it self? I will be upset if I buy a keyboard for a machine that has a bad board or something....

Cost of shipping for mine.

But no, like InsaneMultitasker I'd be surprised if it's the keyboard that's bad. It's just the only thing that you can really try. Another console is a better bet, honestly.

[Xmsteel]

I don't have a tester.... and no keys work, I pressed them all to try to get passed the "Press Any Key To Continue"

I received the computer this way, so I don't know whats wrong.
Supposedly it worked fine when it was last used, but it hadn't been started up in a while.

What could it be if not the keyboard?

[Xmsteel]

*Bump...

Has been 4 days with no response. Still wondering about above post.

[Willsy]

I would say it's the 9901 chip.

You really need a multi-meter. You could try examining the solder joints round the male keyboard connector on the motherboard. If you have a soldering iron, melt them and re-make them, in case the 5V or 0V lines have gone open-circuit.

Otherwise, it would be impossible for the *entire* keyboard to not work, since the keyboard is actually a number of seperate circuits IIRC. It's a purely mechanical device, with no electronics on it. So the fact that no keys works at all would tend to imply that

a) The keyboard is not getting a power supply
b) The 9901 is faulty

If it were the 9901, one would expect the whole machine to just lock solid, and not even boot, but the 9901 has to be a suspect in this particular fault.

You can buy two 9901's for $18 plus shipping here: eBay Auction -- Item Number: 220824044636

Mark

[Xmsteel]

Willsy, on Sun Aug 14, 2011 3:34 AM, said:

I would say it's the 9901 chip.

You really need a multi-meter. You could try examining the solder joints round the male keyboard connector on the motherboard. If you have a soldering iron, melt them and re-make them, in case the 5V or 0V lines have gone open-circuit.

Otherwise, it would be impossible for the *entire* keyboard to not work, since the keyboard is actually a number of seperate circuits IIRC. It's a purely mechanical device, with no electronics on it. So the fact that no keys works at all would tend to imply that

a) The keyboard is not getting a power supply
b) The 9901 is faulty

If it were the 9901, one would expect the whole machine to just lock solid, and not even boot, but the 9901 has to be a suspect in this particular fault.

You can buy two 9901's for $18 plus shipping here: eBay Auction -- Item Number: 220824044636

Mark

Thanks for the response.

I've started taking apart the TI-99/4a, but I have run into a problem. I can't get the main board out. I have the power board and keyboard off, and I have unscrewed everything to the main board, but it just wont come out of the casing.

It appears to be stuck in the middle (the two sides pop up and pull up fine)... I don't want to break it...


EDIT: It also appears that 2 capacitors are missing on the power board. Titled W4 and W2.


EDIT 2: Here are pictures of the keyboard cord and the prongs on the board it connects to (if it helps)...

Edited by Xmsteel, Sun Aug 14, 2011 3:00 PM.

[Tursi]

Yep, that's a standard keyboard. I see why you were concerned about the ribbon cable. As far as I know, despite the difference in length, all TI keyboards should still work (they are attached in different places, IIRC).

Mark, there's no +5v or ground lines on the TI keyboard. It's a pure switch matrix, roughly half the pins drive columns, and the other half read rows (roughly because it's not even). http://nouspikel.gro...ts.htm#Keyboard

This is why it's really unlikely that it's the keyboard which is bad if /no/ keys at all work. That means either at least half the wires are broken, the keyboard is not connected, or the 9901 is bad.

The problem with the 9901 being bad is that it's not a socketted part. Replacing it is a rather advanced soldering job.

There is a screw on the center of the main board, towards the rear of the case. Depending on where your clips may have slid, it may be obscured? (shouldn't be, but check). Other than that, just be gentle. Sometimes the cartridge port catches a bit and needs to be worked loose, but you'd feel the tension over there if that were the case.

 pic1.jpg   228.47K   17 downloads
 pic2.jpg   176.83K   18 downloads
(this second picture by Mainbyte, as I didn't have an unmodified motherboard pic )

I wouldn't worry about the power board, there were a lot of those too, and not all components were populated on all of them. You are clearly getting working power.

[Xmsteel]

The cartridge port doesn't seem to be an issue. I can clearly see it coming out, but for some reason dead on in the center its like its as stiff as can be.
I'll check all screws again though. (I'll take a pic if I'm having issues).

Also, I was afraid of that. I was praying that it was a socket (My Mac Classic has a chip that looks similar and is a socket).

UPDATE: Yep, that little screw was the one. Unscrewed it and the board came out easy as pie.
I took a picture of the power board/supply to show the capacitors (I think) are missing/broken, as well as the board with the 9901.


^ Specifically "W4" and "W2" (Which are kitty-corner from each other.

9901 to the right of the socket with the blue sticky stuff on top.

Edited by Xmsteel, Sun Aug 14, 2011 9:04 PM.

[Tursi]

Ah, I should have paid attention to the letters you said, the 'Wx' are wire jumpers. They are likely cut on that one for a reason, I can't check to see if mine looks the same. Again, if you get the master title page, your power supply is fine. The console needs all the voltages to run at all.

The one with the heat-sink compound is the 9918A video chip. It's a good idea to replace the compound with new heat sink compound if it's gone hard or is dirty - the 9918 /does/ actually need the heat sink or it will die. (Fastest I've seen was less than 24 hrs.)

It still seems strange to me, though, I've never heard yet of a console dying this way. I posted the pinout to the keyboard earlier -- what if you power it up and just try shorting the keyboard connector pins (from one column to any row - don't short row-to-row or column-to-column).. you should be able to get it to advance.

[Xmsteel]

I do have the heatsink for it, it just came off because I didn't know it was attached to the metal shield. I don't think that has anything to do with the problem(s).

How would I go about "shorting" the pins? Do I just do 1?

[sometimes99er]

Tursi, on Sun Aug 14, 2011 11:43 PM, said:

It's a good idea to replace the compound with new heat sink compound if it's gone hard or is dirty - the 9918 /does/ actually need the heat sink or it will die. (Fastest I've seen was less than 24 hrs.)

I've had new graphics cards stop operation (safe guard), because of bad or missing compound, so yes, I think it's important !

My old XP had the cooler (dedicated) much larger than the graphic card itself.

[Tursi]

Xmsteel, on Mon Aug 15, 2011 1:03 AM, said:

I do have the heatsink for it, it just came off because I didn't know it was attached to the metal shield. I don't think that has anything to do with the problem(s).

How would I go about "shorting" the pins? Do I just do 1?

The heat sink is not attached to the VDP in any way (in most machines), don't worry, you did no wrong there. It always comes off with the shield. Just make sure there is enough grease still on it when you put it back together, and make sure you include the clip on that side of the shield to hold it down.

It's safe to run it for brief periods without the heat sink, I've never had problems with periods of 10-15 minutes.

If you aren't sure what I mean by shorting the pins I'm a bit wary to describe the process, as there is a change to induce damage if there wasn't any before (if you short row-to-row or column-to-column). But, maybe you have nothing to lose at this point. Basically, just get a wire, expose a little bit on each end of it. Hold one end to one of the column pins (use the pinout linked above), and tap the other end of it to one of the row pins. The TI should respond and leave the master title page, at least. Try several combinations and see if any work.

Of course I'm talking about the pins on the keyboard connector, not any of the ICs.

In honesty the machine is pretty tough and a brief short even to the wrong pins probably won't hurt it, but you can never say for sure, so consider it experimental and potentially slightly risky.

Edited by Tursi, Mon Aug 15, 2011 5:35 PM.

[Xmsteel]

Tursi, on Mon Aug 15, 2011 5:34 PM, said:

Xmsteel, on Mon Aug 15, 2011 1:03 AM, said:

I do have the heatsink for it, it just came off because I didn't know it was attached to the metal shield. I don't think that has anything to do with the problem(s).

How would I go about "shorting" the pins? Do I just do 1?

The heat sink is not attached to the VDP in any way (in most machines), don't worry, you did no wrong there. It always comes off with the shield. Just make sure there is enough grease still on it when you put it back together, and make sure you include the clip on that side of the shield to hold it down.

It's safe to run it for brief periods without the heat sink, I've never had problems with periods of 10-15 minutes.

If you aren't sure what I mean by shorting the pins I'm a bit wary to describe the process, as there is a change to induce damage if there wasn't any before (if you short row-to-row or column-to-column). But, maybe you have nothing to lose at this point. Basically, just get a wire, expose a little bit on each end of it. Hold one end to one of the column pins (use the pinout linked above), and tap the other end of it to one of the row pins. The TI should respond and leave the master title page, at least. Try several combinations and see if any work.

Of course I'm talking about the pins on the keyboard connector, not any of the ICs.

In honesty the machine is pretty tough and a brief short even to the wrong pins probably won't hurt it, but you can never say for sure, so consider it experimental and potentially slightly risky.

I only have one column of pins. You are talking about the ones on the board right? That I took a picture of? You mean touch one pin to another? Or???

[Tursi]

Yes, look at the link I posted above to the pinout of that row of pins. Half of the pins are dedicated to rows on the keyboard, and half to columns. It creates a little matrix that lets the computer work out which key is pressed. But the connector is a single row.

http://nouspikel.gro...ts.htm#Keyboard

[Xmsteel]

Tursi, on Tue Aug 16, 2011 3:18 AM, said:

Yes, look at the link I posted above to the pinout of that row of pins. Half of the pins are dedicated to rows on the keyboard, and half to columns. It creates a little matrix that lets the computer work out which key is pressed. But the connector is a single row.

http://nouspikel.gro...ts.htm#Keyboard

IT WORKED! I'm excited even though I'm not sure what that means!

I did Pin 9 to 11, and got passed, then when it shows the list I did 7 to 8 and got to the TI Basic screen!

Is this a good thing or not? And what does it mean? But yes, It worked!

[marc.hull]

Xmsteel, on Tue Aug 16, 2011 4:18 PM, said:

Tursi, on Tue Aug 16, 2011 3:18 AM, said:

Yes, look at the link I posted above to the pinout of that row of pins. Half of the pins are dedicated to rows on the keyboard, and half to columns. It creates a little matrix that lets the computer work out which key is pressed. But the connector is a single row.

http://nouspikel.gro...ts.htm#Keyboard

IT WORKED! I'm excited even though I'm not sure what that means!

I did Pin 9 to 11, and got passed, then when it shows the list I did 7 to 8 and got to the TI Basic screen!

Is this a good thing or not? And what does it mean? But yes, It worked!

It means buy a new keyboard and fix your computer all ready...

[Tursi]

I'd agree with Marc

[Xmsteel]

Tursi, on Tue Aug 16, 2011 10:02 PM, said:

I'd agree with Marc

So Its just the keyboard that is the problem? Not the 9901?

If so thats great news

Now I just need to find someone here that is willing to sell me one... Ebay has some for insane prices..

[zylon]

Told you there'd be help in here.

[Xmsteel]

zylon, on Sat Aug 20, 2011 5:05 PM, said:

Told you there'd be help in here.

Thank you for the referral