Complete Re-Cap of a TI99/4a

[Alleged-Geek]

Hi all,

 

Just thought I would share with you my latest YouTube clip, a complete re-cap of my TI99/4a.

This clip is start to finish with absolutely nothing left out, I replace all the electrolytic capacitors in both the Power Supply and Motherboard PCB’s. I also demonstrate what happens when you miss connect an electrolytic capacitor… exploding stuff!

 

I hope that some of you will find this useful.

 

 

 

In my next clip in the series, I am planning to install a FlashRom 99as well as share my design of a joystick adapter to allow play with standard Atari type sticks.

 

Best regards,

 

Steve

 

 

[matthew180]

9 hours ago, Alleged-Geek said:

... a joystick adapter to allow play with standard Atari type sticks.

http://www.mainbyte.com/ti99/hardware/cables/joystick.html

 

There are also some compact commercial Y-adapters that were available BITD.

 

Mainbyte has a good list of typical mods, including the alpha-lock joystick fix, which is totally worth doing if you are poking around inside the console with a soldering iron.

[Alleged-Geek]

Thank you Matthew, everyone here has been so friendly!

 

I will have to take a proper look through that site, it looks fantastic.

 

I have already designed and manufactured a prototype PCB using a simillar schematic and will pop the gerber files and bill of materials on to my github when I complete the mod.

 

I will see what I can do with the alpha-lock mod as far as I can see it involves cutting a trace on the keyboard PCB which is something I am a wee bit reluctant to do as I like to keep my collection to as close to stock as possible. I do have a couple of ideas though  

 

Thanks again,

 

Best regards,

 

Steve

[humeur]

I would never understand why to change things without having measured before their condition.
Would it occur to you to change tires on a car when they are good, Or change new batteries with new ones.

 

JL

[SkyPilot]

26 minutes ago, humeur said:

I would never understand why to change things without having measured before their condition.
Would it occur to you to change tires on a car when they are good, Or change new batteries with new ones.

 

JL

Many business replace all light bulbs after a percentage burn out to save time, labor and aggravation.  When one capacitor fails, changing them all may prevent having to open it up again in the future. 

[+arcadeshopper]

if you look in the FAQ it has both the schematic for the joystick adapter as well as two assembled ones available ..both in my store if you need, also i have blank pcb's for jedimatt's board

 

[Alleged-Geek]

1 hour ago, humeur said:

I would never understand why to change things without having measured before their condition.
Would it occur to you to change tires on a car when they are good, Or change new batteries with new ones.

 

JL

Hi there,

 

thank you for taking the time to message. Everyone is entitled to their opinion on this but I have been in the electronic business for over 30 years and electrolytic capacitors do dry out  with age (and these were over 40 years old)  when they do fail they can cause a whole lot of damage.

 

To properly test the capacitors they have to be de-soldered from the PCB and as I had most of the capacitors in stock and the others were relativley cheap, I thought that it would be a good idea to replace them anyway.

 

I did test the old capcitors after de-soldering them and although most of them were in quite good condition, I did find 2 which were an accident waiting to happen.

 

Best regards,

 

Steve

[Alleged-Geek]

1 hour ago, arcadeshopper said:

if you look in the FAQ it has both the schematic for the joystick adapter as well as two assembled ones available ..both in my store if you need, also i have blank pcb's for jedimatt's board

 

Hi there,

 

thank you very much, I have just had a quick look at your amazing site; it is packed with some really good information!

 

it's pity you are based over the pond!

 

Best regards,

 

Steve

[humeur]

hello

 

Change without even measuring esr, why not change the TTLs which also take age.
I know that every time I say the needlessness of doing it without at least a measure it displeases it has become a fashion.

 

The death of a capacitor is defined as a change in capacitance, dissipation factor or leakage current beyond a given threshold. This threshold varies depending on the capacitor manufacturer. It is not a sudden and violent death, such as an explosion due to overheating or a manufacturing defect (inflated capacitor for example). The service life has no relation to the probability of this type of failure.

 

If we follow this logic Drams are to be changed as a preventive measure because their capacitor over time is destroyed and on ti it is often.

 

 

https://www.astuces-pratiques.fr/electronique/duree-de-vie-des-condensateurs-chimiques

 

Best regards,

Edited July 13, 2022 by humeur
change

[humeur]

1 hour ago, SkyPilot said:

Many business replace all light bulbs after a percentage burn out to save time, labor and aggravation.  When one capacitor fails, changing them all may prevent having to open it up again in the future. 

hello

 

So a question about Yours do you change a lot and often really dead.
I'm not talking about a company, which is another area than ours with our old computers

 

Best regard

 

JL

[SkyPilot]

4 minutes ago, humeur said:

hello

 

So a question about Yours do you change a lot and often really dead.
I'm not talking about a company, which is another area than ours with our old computers

 

Best regard

 

JL

 

You bet I do!  If I replace one electrolytic capacitor, I replace them all.  Why bother to do a half-assed job?  They sell capacitor kits for that very reason. 

 

[82-T/A]

22 hours ago, Alleged-Geek said:

Hi all,

 

Just thought I would share with you my latest YouTube clip, a complete re-cap of my TI99/4a.

 

This clip is start to finish with absolutely nothing left out, I replace all the electrolytic capacitors in both the Power Supply and Motherboard PCB’s. I also demonstrate what happens when you miss connect an electrolytic capacitor… exploding stuff!

 

I hope that some of you will find this useful.

 

 

 

In my next clip in the series, I am planning to install a FlashRom 99as well as share my design of a joystick adapter to allow play with standard Atari type sticks.

 

 

Best regards,

 

Steve

 

 

This is very cool, and I have saved it to watch later tonight. A quick question if you don't mind me asking. Are you classically trained as an Electrical Engineer, or is this something you just took up as a hobby? I'm a pretty competent guy, and I've re-wired a house, re-wired a car, and can do the usual stuff with a computer. I've even fiddled with a breadboard for my Arduino One. But I've never gotten to the point where I've tried to replace things. I do think I swapped out a chip once (desoldering the leads, etc.) but I can't even remember what that was for. To be honest, I still don't even understand why an LED only works when the positive goes one way, versus the other (unlike an incandescent bulb where positive and negative can be reversed and it still heats the coil. I guess maybe it has something to do with it being an LE(D) ... Digital Input Output Device? is that what DIOD stands for?

 

Anyway, been thinking of getting into this... but debating if I would do better just getting an Associates in Electronics, or if I should try to go for a Masters in EE or some nonsense. I'm in my mid-40s now, and keep going back to school to learn and get degrees for various things, and I'm kind of wearing myself out.

[SkyPilot]

40 minutes ago, humeur said:

hello

 

Change without even measuring esr, why not change the TTLs which also take age.
I know that every time I say the needlessness of doing it without at least a measure it displeases it has become a fashion.

 

The death of a capacitor is defined as a change in capacitance, dissipation factor or leakage current beyond a given threshold. This threshold varies depending on the capacitor manufacturer. It is not a sudden and violent death, such as an explosion due to overheating or a manufacturing defect (inflated capacitor for example). The service life has no relation to the probability of this type of failure.

 

If we follow this logic Drams are to be changed as a preventive measure because their capacitor over time is destroyed and on ti it is often.

 

 

https://www.astuces-pratiques.fr/electronique/duree-de-vie-des-condensateurs-chimiques

 

Best regards,

 

I'm quoting your changed edited post.  Apples and Oranges, now it seems an argument is what you want, not biting.  Do whatever you want.

[Alleged-Geek]

10 minutes ago, 82-T/A said:

 

 

This is very cool, and I have saved it to watch later tonight. A quick question if you don't mind me asking. Are you classically trained as an Electrical Engineer, or is this something you just took up as a hobby? I'm a pretty competent guy, and I've re-wired a house, re-wired a car, and can do the usual stuff with a computer. I've even fiddled with a breadboard for my Arduino One. But I've never gotten to the point where I've tried to replace things. I do think I swapped out a chip once (desoldering the leads, etc.) but I can't even remember what that was for. To be honest, I still don't even understand why an LED only works when the positive goes one way, versus the other (unlike an incandescent bulb where positive and negative can be reversed and it still heats the coil. I guess maybe it has something to do with it being an LE(D) ... Digital Input Output Device? is that what DIOD stands for?

 

Anyway, been thinking of getting into this... but debating if I would do better just getting an Associates in Electronics, or if I should try to go for a Masters in EE or some nonsense. I'm in my mid-40s now, and keep going back to school to learn and get degrees for various things, and I'm kind of wearing myself out.

Thank you for your kind words.

 

I started my career in college then did an apprenticeship in electrical and electronic engineering but my job has changed considerably over the years and I now teach practical electrical and electronic engineering skills to undergraduate students. I am unsure about the American Education System; is an Associates in Electronics similar to our degree where takes 4 - 5 years whereas a Masters typically take a year? Obviously you will learn more with the longer course but a masters shoud cover all the basics.

 

as for a diode it only conducts electricity in one direction therefore an LED (Light Emitting Diode) will only light up if the current is going in the correct direction.

 

hope that kinda helps.

 

Best regards,

 

Steve

 

[82-T/A]

1 hour ago, Alleged-Geek said:

Thank you for your kind words.

 

I started my career in college then did an apprenticeship in electrical and electronic engineering but my job has changed considerably over the years and I now teach practical electrical and electronic engineering skills to undergraduate students. I am unsure about the American Education System; is an Associates in Electronics similar to our degree where takes 4 - 5 years whereas a Masters typically take a year? Obviously you will learn more with the longer course but a masters shoud cover all the basics.

 

as for a diode it only conducts electricity in one direction therefore an LED (Light Emitting Diode) will only light up if the current is going in the correct direction.

 

hope that kinda helps.

 

Best regards,

 

Steve

 

Thanks Steve... I appreciate the response. Yeah, I'm trying to learn the basics really.

 

In our college system, it basically works like this:

 

Associates Degree (first 2 years)

Bachelors Degree (next 2 years)

Masters Degree (Yet another 2 years)

Doctorate Degree (Yet another 2-4 years)

 

Some people get an Associates degree, most just get a bachelors, and then some go on to get a Masters, and then some go on to get a doctorate.

 

As long as you've achieved the prerequisite level, you can then go on and get as many degrees as you want that are one above, or any level below what you've already accomplished.

 

 

The problem with getting a Masters is that it *generally* presumes you would already have a background in a particular field. I have a few degrees, but nothing related to electrical engineering, so I would not be able to get a Masters in EE with the background I have now. Some fields, like law, they'll let you get a Masters without a prior Juris Doctorate. But kind of why I thought about getting an Associates because they teach the fundamentals, "hands on" rather than just more theory and such.

 

[matthew180]

13 hours ago, Alleged-Geek said:

I will see what I can do with the alpha-lock mod as far as I can see it involves cutting a trace on the keyboard PCB which is something I am a wee bit reluctant to do as I like to keep my collection to as close to stock as possible. I do have a couple of ideas though  

There were several suppliers of keyboards used in the 99/4A, and some of them use wire-jumpers on the non-solder side (single-sided PCB, jumpers used when traces needed to cross).  In my 99/4A, the keyboard conveniently had a wire jumper exactly where the diode needs to go, so no need to cut a trace; just replaced the wire jumper with a diode.

 

I understand wanting to keep things stock, etc., but the 99/4A has a lot of design flaws, uh, I mean "decisions", and the alpha-lock position interfering with the joystick *up* direction is one change that most people would prefer to not keep stock.  It is up to you though, just remember to put the alpha-lock in the up position any time you want to use the joysticks.

 

[+arcadeshopper]

1 hour ago, matthew180 said:

There were several suppliers of keyboards used in the 99/4A, and some of them use wire-jumpers on the non-solder side (single-sided PCB, jumpers used when traces needed to cross).  In my 99/4A, the keyboard conveniently had a wire jumper exactly where the diode needs to go, so no need to cut a trace; just replaced the wire jumper with a diode.

 

I understand wanting to keep things stock, etc., but the 99/4A has a lot of design flaws, uh, I mean "decisions", and the alpha-lock position interfering with the joystick *up* direction is one change that most people would prefer to not keep stock.  It is up to you though, just remember to put the alpha-lock in the up position any time you want to use the joysticks.

 

I put one on the ribbon cable that goes between the keyboard and the motherboard..