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TI-99/4a Modification Weekend.

mitsumi keyboard repair keyboard Reset Button Mod Tursis internal 32k mod

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#1 Sinphaltimus OFFLINE  

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Posted Fri Sep 23, 2016 3:00 PM

So far, I've repaired another Mitsumi keyboard. I have to say, it would not work until I completely separated the entire membrane from the board (pix and videos takes). It was a success.

I've completed Shift838's reset button mod.

 

I'm a little more than halfway through Tursi's internal 32k 2 chip mod. 2 chips and a gazillion freaking solder points with wires.  Certainly well beyond my skill level but I'm doing the best I can with what I have. Hope it works by the time I'm done. May not be tonight, maybe tomorrow. But everything is fully documented with pics and videos. so we'll see how well those came out also.

Just starting this long thread to keep it all neat and tidy.and in one place. I'll be creating pdfs as well. 

 

For now, I'll be posting random pics here once in a while.

https://www.facebook...206716095292992

 



#2 Shift838 OFFLINE  

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Posted Fri Sep 23, 2016 3:13 PM

pictures look like they are coming along nicely.

 

patience is the key.  Well and a steady hand!



#3 Sinphaltimus OFFLINE  

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Posted Fri Sep 23, 2016 4:44 PM

I quit. Waybeyond my level of expertise. What happened was I broke a pin off the memry chip and I was way in deep. Only option was to undo that chip and start there again. Instead, I decided to undo it all. Good thing I did too. 

I ruined the TI. It no longer works. It would have sucked to get it all together and find that out. I am a bit frustrated and upset so I'm gonna take a nive long break for the rest of the evening. tomorrow I will double and triple check all my clean up to ensure nothing it shorting, otherwise, it's been a bummer. At least I know my limitations. I reall don't think I have the right tools for this kind of soldering. Finer tips would have been great, and a heat sync I could use here. I have one but not for this application.

Sp I'll end up getting another TI that I will put the reset switch in and speed mod and I'll end up picking up a side slot 32k when they are ready.



#4 arcadeshopper OFFLINE  

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Posted Fri Sep 23, 2016 8:02 PM

there's a pcboard that makes that mod a lot easier

 

Greg



#5 Sinphaltimus OFFLINE  

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Posted Sat Sep 24, 2016 2:18 AM

Too late now. I killed a console. Not going to risk that again.

#6 Sinphaltimus OFFLINE  

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Posted Sat Sep 24, 2016 3:15 AM

In doing this particular mod, I'm doing some wishful thinking in assuming I may only have damaged one of three chips or as many as all 3.

74LS138...$0.65 Jameco
74LS245...$0.65 Jameco

and/or the 9900

Sucks I don't have a bulk order to place. I'm willing to shell out for the top 2.

I understand that if I had r have a short on anyone of or all of these chips, other chips or components may also have been damaged.

What I get is a black screen and non-stop tone. 

So I'm not done with this console yet. It would be so cool to kill it then bring it back to life. 



#7 mizapf OFFLINE  

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Posted Sat Sep 24, 2016 5:40 AM

It would be so cool to kill it then bring it back to life. 

 

You think about black candles, occult symbols on the wall, and a beheaded chicken? :-D



#8 Ksarul OFFLINE  

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Posted Sat Sep 24, 2016 10:23 AM

On 9900 chips, there is a seller on eBay that sells the AMI variant (TI's authorized second source for the chips) in groups of four for $10 plus shipping. The part number for these is S9900P.



#9 Tursi OFFLINE  

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Posted Sat Sep 24, 2016 11:07 PM

Well... what do you think you did wrong? The console is pretty resilient! Is it just some spilled solder or something along those lines? A little solder braid will let you suck that up!

As for the broken pin, yeah, you can really only count on bending an IC pin once, back and forth will break it. But it just takes patience and practice.

Can you post a high res picture of the area you think may be damaged?

#10 Sinphaltimus OFFLINE  

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Posted Sun Sep 25, 2016 2:34 AM

The board itself looks clean. I'm not in front of the instructions now but the most difficult part for me was soldering to the chip above and to the left of the 9900 if the print on the 9900 is right side up.

I know I was cooking that thing trying to during, unaided and resolder.

WTF are those long white things? Totally in my way and a nightmare. When I get home from work later I will post hi res macros of every location I touched.

#11 Tursi OFFLINE  

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Posted Sun Sep 25, 2016 4:42 PM

I'm not sure what the long white things are... I know we talked about them in the forums before, but I forget. However, they are important and can be damaged - if you bent them you may have broken one of the tabs.

(Are they jumpers? Resistor packs? Alien communication crystals? Are they on the schematic? ;) )

#12 Sinphaltimus OFFLINE  

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Posted Sun Sep 25, 2016 4:53 PM

Well... what do you think you did wrong? The console is pretty resilient! Is it just some spilled solder or something along those lines? A little solder braid will let you suck that up!

As for the broken pin, yeah, you can really only count on bending an IC pin once, back and forth will break it. But it just takes patience and practice.

Can you post a high res picture of the area you think may be damaged?

 

 

I think I found the issue:

I'll have to clean it up a bit more to confirm. I think I broke some traces on the board.

Here are 3 photos of the area in question.

Attached File  20160925_165657.jpg   429.25KB   3 downloads
Attached File  20160925_165830.jpg   713.61KB   3 downloads
Attached File  20160925_165906.jpg   599.53KB   3 downloads

 

 

And then there's this thing that was realy really really really really annoying. I carefully bent it so i don't think I damaged it that way but I also hit is a few times with the soldering iron. So there's that.
 

Attached File  20160925_165357.jpg   377.82KB   3 downloads

Attached File  20160925_165413.jpg   428.54KB   3 downloads

Attached File  20160925_165445.jpg   461.46KB   3 downloads

Attached File  20160925_165510.jpg   406.07KB   3 downloads

Attached File  20160925_165537.jpg   456.06KB   4 downloads

Too tired to do anything tonight but tomorrow after work I'll clean up that board a bit more and see how badly it's damaged.


I'm far from done with this. It wouldn't be the first time I've damaged a mainboard and consequently repaired it. I used to desolder and resolder some Amiga chip sockets back in the day when my eyeballs worked better and my hands were steadier. So I'm going to ride this board as far as I can within reason, which means, until it works again. 

And then I will try the ram mod again with better wires pre-tinned as per some private suggests.

:)


Edited by Sinphaltimus, Sun Sep 25, 2016 4:58 PM.


#13 Tursi OFFLINE  

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Posted Sun Sep 25, 2016 5:44 PM

I see... yes. You might try to pick up a cooler soldering iron, too... how many watts is the one you are using rated for? Things look really burned. You usually don't want more than 15w. Radio Shack (or equivalent) will sell a crappy one (which will work) for about $15. What's on the chip in the second picture? Is that glue? (No need to glue the chips down!)

https://www.amazon.c...c/dp/B00IKMC2N8

Pre-tinning will save you tons of grief... pre-tin the wires and pre-tin the pins you are going to attach to, then it should only take a second or two to join the wire to the pin. Also make sure to keep the solder tip clean - if there is an excess of solder on the tip you'll more easily get bridges. A little copper sponge works great for that.

https://www.amazon.c...e/dp/B009IN1P9U

When you're piggy-backing the smaller chips, before you bend the pins out, rock it on the desk a bit to nudge the pins inward, so that it grips the chip underneath tightly. (THEN bend out the required pins). For these ones, do not pre-tin, since otherwise you'll get a loose connection when the solder melts.

Good luck! Definitely good that you keep trying. :)

#14 --- Ω --- OFFLINE  

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Posted Sun Sep 25, 2016 5:53 PM

Pre-tinning will save you tons of grief... pre-tin the wires and pre-tin the pins you are going to attach to, then it should only take a second or two to join the wire to the pin. Also make sure to keep the solder tip clean - if there is an excess of solder on the tip you'll more easily get bridges. A little copper sponge works great for that.
 

 

Yeah, no 45W irons with screwdriver tips!   :lol:

 

Yes, ALWAYS pre-tin, but also use a little flux on the wire AND the piece you are connecting it to... just a tad on a wooden (non-conducting) toothpick will work fine.



#15 Shift838 OFFLINE  

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Posted Sun Sep 25, 2016 8:29 PM

i use one that you can adjust the temperature with a very fine point.  It's made by Madell.



#16 Ksarul OFFLINE  

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Posted Sun Sep 25, 2016 8:42 PM

I use a Pace soldering station with a pencil tip and set to 632 degrees Farenheit. You definitely want to go the low-wattage pencil route for soldering.

 

On the evil white things--they are rails to carry voltages around the board. Break one of the connections and you lose power to part of your board. They are relatively fragile too. . .I'm not sure if all of them are power off the top of my head, so some of them may also be there to jump ground signals from one area on the board to another.



#17 --- Ω --- OFFLINE  

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Posted Sun Sep 25, 2016 8:51 PM

The one I use (pictured below) has been great for what I've use it for.  << THIS EBAY LINK >> has an almost exact model for about $10.00 less than what I paid.  Mine, like this one only displays the temp in Celsius though.   It also comes with a spare heating element at numerous tips.

 

gallery_35324_1027_1193434.jpg



#18 Lee Stewart OFFLINE  

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Posted Sun Sep 25, 2016 9:42 PM

...

On the evil white things--they are rails to carry voltages around the board. Break one of the connections and you lose power to part of your board. They are relatively fragile too. . .I'm not sure if all of them are power off the top of my head, so some of them may also be there to jump ground signals from one area on the board to another.

 

Was not there a suggestion that their shape might have been used for managing the flow of hot air?



#19 Sinphaltimus OFFLINE  

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Posted Mon Sep 26, 2016 3:40 AM

 
Was not there a suggestion that their shape might have been used for managing the flow of hot air?



Wow! That's exactly what I thought they were for. A case with no fans those white things really resemble something related to air flow. This is one if those tubes I wish I said something about it first. Lol.

#20 Sinphaltimus OFFLINE  

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Posted Mon Sep 26, 2016 3:50 AM

I don't have fancy soldering stuff.

I use a jensen 47b723 and a radio shack brand that has no labels, it was a cheap one back in the day. I should probably purchase more varied tips for these.

I use 60 tin 40 lead solder.Kester, Rakhi Shack and Archer brands (I've had spools of this stuff for years).

I list ny Cooper sponge.

So yeah, probably due for some parts and tips. I have to keep it under 25 bux and can't purchase for another 2 weeks.

I think it's time to start putting things on ebay to raise funds.

And for this weekend coming up....(clipped from facebook status)

"So last weekend I completed a keyboard repair and reset button mod however I botched the internal ram mod and in the process damaged the mainboard. That's a repair project for another time.

However, this weekend is going to be a lot of smaller priests to complete.

I'll start off by adding male header pins to my GoTek floppy emulators, then I'll add lcd and third button modifications to both, then I'll program one for use with the ti.

Then, it's time to modify both my Amiga 500 case and my TI-99/4 PEB. For the Amiga I'll need to cut jokes for the lcd and the third button.

Same for the peb. However the peb has more work. Because of ny atx psu mod on the orb, I need to install heat probes with monitor on each of the voltage regulars in the expansion cards. Displays to be mounted on the peb (more hole cutting). Then I have to extend dine internal power cables, install the GoTek along side a 3.5"floppy, add the reset button to my ti but mount the button on the PEB next to the GoTek third button.

I also want the peb reset button to be removable at the console for transport. With the option to add a button in the fly via external connection for use without the peb (male header pins)

So it's shaping up to be another computer modification weekend.

My goals are to make these computers as modern as possible (within budget) so I can put them back in to production.

The TI is my learning system. I am going to use it to learn Assembly Language.

The Amiga is awaiting a Vampire II board witch is an upgrade that will make the old Amiga add fat and as powerful at what it does as a modern PC is at what it does. Then I'll be back to r making music art and animation on it retro style fir video games.

Eventually I'd like to develop for the Amiga, much in the same capacity I'm developing for the TI currently.

Ask while improving my developing skills on the pc.

I'm not doing it alone. I've got a subset brilliant support network and community with the TI. Software engineers, hardware engineers and the balance if years and years of experience.

In the Amiga side, well, you wouldn't believe how alive the Amiga community really is. And if your observant enough, you can find the talent to ask for help.

So that's that."


Edited by Sinphaltimus, Mon Sep 26, 2016 4:15 AM.


#21 Sinphaltimus OFFLINE  

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Posted Tue Sep 27, 2016 6:53 AM

I snagged this after making an offer 5 bux less than asking.

$29 shipped.

http://r.ebay.com/gxSMCw

Edited by Sinphaltimus, Tue Sep 27, 2016 6:53 AM.


#22 Sinphaltimus OFFLINE  

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Posted Fri Sep 30, 2016 5:37 PM

This weekend was very productive and successful thus far - Installed male header pins on GoTek for programming, completed LCD display and third button mod, and added a bonus modification of LEDS.

>>Here<< is the photo trail on Facebook and in the comments. I set it to public, no FB account required. 

I will put together a write up eventually, just documenting the steps I took specific to my needs but anyone can do it.

turning in for the night, will get back to it tomorrow where I plan to mount everything in the peb AND install the temperature probes for my PEB cards due to the ATX mod I completed some weekends ago.

https://www.facebook...207081953159210

 


Edited by Sinphaltimus, Fri Sep 30, 2016 5:37 PM.


#23 Sinphaltimus OFFLINE  

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Posted Sat Oct 1, 2016 2:24 PM

My favorite image so far...


Attached File  TIwipe.jpg   336.69KB   1 downloads



#24 Sinphaltimus OFFLINE  

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Posted Fri Oct 7, 2016 7:54 PM

Button battery holders expected to here Tuesday - left - Supra Ram 512k+rtc trapdoor expansion for Amiga 500 and on the right a mini memory module I'm going to need for my first baby steps in to assembly.

 

14572312_10207131435596240_8450436054148



#25 aftyde OFFLINE  

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Posted Sat Oct 8, 2016 11:51 AM

This weekend I accomplished a number of small projects.  One was the installation of a decent fan in my PEB - amazing, no more jet engine.  Scraped, cleaned, and relabeled all the cards in the PEB.  Lastly, I installed the MG ROM's into my Corcomp DSDD controller and popped that in to see how well it'll work with the Lotharek drives - jury is still out on that one... :)


Edited by aftyde, Sat Oct 8, 2016 11:51 AM.






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