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Repair an NTSC TI99/4a with limited equipment?


Atari2600PAL

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  • 4 weeks later...

Have received my F18A from @arcadeshopper today and am excited to fit it

 

But I was wondering if anyone could give me any tips/do's/don'ts I should look out for before I start please?

 

Having looked at various articles/faq/etc. I'm not 100% sure how best to approach this with regards to where/how to run the ribbon cable (I was intending to cut the case to attach the VGA connector in some way along with a 3.5mm socket for sound out on the back, but not sure if I should just run the ribbon able outside and rig up something external)

 

Do I leave half/all the shielding off? Do I cut a slot in the shielding to run the cable out? or is there a way to run the flat ribbon with this mk1 version out of the shielding without cutting a slot please?

 

Any ideas/suggestions would be greatly appreciated please

 

Many thanks

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I rather stupidly extracted the VDP before cleaning the thermal grease off so not 100% sure which way it was orientated in the socket (I think I know but not 100% sure)

 

Could anyone confirm I have the F18A / Socket orientation correct before I fit it in the socket please?

 

image.thumb.jpeg.d3e204180d396f38b4a81edf92d26c67.jpeg

 

Many thanks!

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Found some images on-line that confirmed it's the correct way around, so went ahead and re-assembled 

 

Have just run the ribbon cable out the back of the console for now, and picking up audio from the original composite lead connection

 

Wow. What an amazing picture improvement.

 

(The only slight issue is an effect similar to a slight moving heat haze, most noticeable on the cyan boot and basic screens, but I assume that's my old screen and can live with that for the vastly better image. Will try a newer monitor sometime, in the meantime I want to try out the 80 column mode)

 

Well worth the upgrade!

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25 minutes ago, Duewester said:

Congratulations on your repair outcome.

Just tried Force Command 80 column mode and the “issue” is too noticeable for me to use 80 col mode with this screen

 

Will use it for just the crisper display it gives and avoid 80 col until I can test on another screen

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3 hours ago, Atari2600PAL said:

Found some images on-line that confirmed it's the correct way around, so went ahead and re-assembled 

 

Have just run the ribbon cable out the back of the console for now, and picking up audio from the original composite lead connection

 

Wow. What an amazing picture improvement.

 

(The only slight issue is an effect similar to a slight moving heat haze, most noticeable on the cyan boot and basic screens, but I assume that's my old screen and can live with that for the vastly better image. Will try a newer monitor sometime, in the meantime I want to try out the 80 column mode)

 

Well worth the upgrade!

that smells like interference..  verify the monitor is grounded to the same ground as your system.. (ie plugged into the same strip/etc) also may be filter caps on the monitor going south 

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4 minutes ago, arcadeshopper said:

that smells like interference..  verify the monitor is grounded to the same ground as your system.. (ie plugged into the same strip/etc) also may be filter caps on the monitor going south 

I did try plugging them into a strip earlier, next to each other, with everything else off and it was the same

 

will get my modern monitor out of storage, hopefully tomorrow, and see what that looks like to compare

 

Thanks

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6 hours ago, Atari2600PAL said:

I rather stupidly extracted the VDP before cleaning the thermal grease off so not 100% sure which way it was orientated in the socket (I think I know but not 100% sure)

 

Could anyone confirm I have the F18A / Socket orientation correct before I fit it in the socket please?

 

Sorry for the late reply, but I see you found the correct orientation.  Also, in the photo you posted there is a white arrow on your socket that indicates pin-1.

 

7 hours ago, Atari2600PAL said:

Any ideas/suggestions would be greatly appreciated please

 

Case mods are left as an exercise for the owner, but there are a lot of posts here in the forum where people show their various physical case-mods, including their F18A installs, etc..

 

The main suggestion I always make is: *DO NOT* leave the ribbon cable hanging out of the back of the system!  This was more a problem with the original F18A since its VGA cable was more robust and would easily rip the F18A out of the socket.

 

The MK1 video ribbon cable is designed for internal use and will not hold up to dangling out the back of the system.  You can get longer or shorter versions of the 22-pin FPC ribbon cable if you need one that is a different length to accommodate your install.

 

At the very least cut a notch out of the back (lower half of the case) and screw the VGA connector to the case (I included extra-long VGA header screws for exactly this situation).  This is what I did for my F18A minimal hacky 99/4A install.  See attached photo.  Should work out similar for the MK1.

 

The MK1 ribbon can be bent/creased, but only once or twice, so make sure it is how you want it before committing to any folds.  Also, do be careful around the flip-lock connectors on the boards, they are not designed for any kind of strain relief, and the cable should not pull-on, or exit, the connector at any angle.

 

4 hours ago, Atari2600PAL said:

The only slight issue is an effect similar to a slight moving heat haze

 

The F18A image is pretty solid and stable.  I suspect you will have better results with the newer monitor you are going to try.

 

4 hours ago, Atari2600PAL said:

Wow. What an amazing picture improvement.

...

Well worth the upgrade!

 

Thanks, I'm glad you like it.

 

f18a_994a.jpg

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7 hours ago, matthew180 said:

The main suggestion I always make is: *DO NOT* leave the ribbon cable hanging out of the back of the system!  This was more a problem with the original F18A since its VGA cable was more robust and would easily rip the F18A out of the socket.

Uh... oops...

 

20230801_205505.thumb.JPG.0746741d4abf5e546e8eb8db5e54ecfc.JPG

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9 hours ago, matthew180 said:

At the very least cut a notch out of the back (lower half of the case) and screw the VGA connector to the case (I included extra-long VGA header screws for exactly this situation).  This is what I did for my F18A minimal hacky 99/4A install.  See attached photo.  Should work out similar for the MK1.

Thanks for the info @matthew180

 

Will take a look at cutting the notch. But putting it in the lower case means leaving the shields off permanently? Is this ok please?

 

Is the grounding issue a VGA only thing? I have other machines attached to the same screen (ZX Spectrum / RF, C64 / S-video, Atari 2600 / Scart composite) and they don't show any sign of a similar effect

 

Many thanks

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As I WAS concerned about damaging the ribbon before I try another screen I've mounted the VGA port on the back (removed the component side shield)

 

Tried changing the ribbon while I was at it, just in case it had an issue, but haze problem still remains. Will try another screen later.

 

A bit wobbly but best I could do with a Stanley knife and not much else (most of my tools like my Dremel are in storage). But not my main console so didn't mind butchering it a bit. At least it's secure now.

 

image.jpeg.100646682d1f474e8ab614b52aa66555.jpeg

 

 

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Just tried my spare TV (that I replaced with a small one to make room on my rack for the PEB) and it looks great on that

 

I guess I'm going to have to rearrange my systems on the rack as I don't fancy trying to do a repair on the small screen TV, for now at least

 

Many thanks all

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8 hours ago, Atari2600PAL said:

But putting it in the lower case means leaving the shields off permanently? Is this ok please?

 

Keeping the shields on or off is mostly personal preference.  I suspect TI had to do that BITD to pass FCC tests, since the 99/4A is a very noisy computer.  I don't know if interference among electronic devices is still today what it was in decades past?  If you want the shields in place, you will probably need to notch those as well, and put some electrical tape (or similar) around the cut-edges to prevent them from damaging the cable (and your fingers), etc..

 

I did an ADAM computer mod once where I opened a hole in the RF shield:

 

https://forums.atariage.com/topic/202406-f18a-adam-adpater-and-case-mod/

 

Unfortunately there is no "one good way" to mod a case for a connector that did not originally exist on the device, and each person's opinion of "acceptable" is going to be different for everyone.  Ruggers Customs has done one of the best mods I have seen:

 

https://forums.atariage.com/topic/315250-ti-994a-show-your-modded-systems-here/?do=findComment&comment=4749951

 

8 hours ago, Atari2600PAL said:

Is the grounding issue a VGA only thing? I have other machines attached to the same screen (ZX Spectrum / RF, C64 / S-video, Atari 2600 / Scart composite) and they don't show any sign of a similar effect

 

I don't think your problem is a grounding issue; there are plenty of ground conductors in the FPC (ribbon) cable between the MK1 and the monitor.  RF interference... perhaps, but again I'm doubtful.  Noise would mess up the picture in random ways, and what you describe is a crawling effect.  That would indicate a sync problem, i.e. the monitor is not syncing to the incoming horizontal and vertical sync pulses correctly.

 

The other systems you mentioned are connected to the monitor's composite or s-video interfaces, and they have different timing and video signaling.  You should try another computer with the monitor that outputs native VGA to see if the results are similar to the MK1 picture.

 

I have a monitor that remembers the sync timing for its interfaces (DVI and VGA), and when I plug a different VGA source into the monitor, it has a built-in menu "auto sync" option that re-calibrates / syncs the monitor to the incoming video signal.  You might check your monitor's menu to see if  it has anything similar.

 

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Thanks for all the info @matthew180, much appreciated 

 

Both monitors are actually Sony TV’s with very limited options in the menu. (My modern monitor was a non-starter, I realised, as it wouldn’t work with the other devices. I do have an OSSC etc. but not very impressed with it so far so it’s still in its box)

 

The output on the larger Sony TV is pretty amazing, the F18a is a great upgrade

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2 hours ago, matthew180 said:

Keeping the shields on or off is mostly personal preference.  I suspect TI had to do that BITD to pass FCC tests, since the 99/4A is a very noisy computer.  I don't know if interference among electronic devices is still today what it was in decades past?

I would love to have a way to measure the RF output and interference in the VCF room.

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  • 1 month later...

glad i own aown a ti99 4/A just recently along with it’s original power adaptor and with some nintendo and atari games for it among other ones😆

however i got issues with it’s keyboard since texas instruments used a cheap ass mailor membrane for most of it’s ti99 systems in it’s keyboards,wich don’t age well,i had to desperately and rappidly hit key 2 to get a game bootup,some keys do work but most of them don’t or hardly respond once i press them,now if only i could find a replacement keyboard for it wich uses switches instead (like many later models of the ti99 did), i could replace that old keyboard with it once i do know exactly what am doing,

becides am astonished that i can’t find most pictures of the original ti99/4 ,even on youtube those ones who owns the original model of the ti99/4,just barelly shows them,i know both models do look similar but i just would like to see the ti 99/4 from every corner,am curious about it’s tv out plug and adaptor,also i heard that early models of the ti99 uses dc adaptors while larer models uses ac adaptors,but it makes me wonder,are both plugs the same? If so,then not only could this cause confusion but also destruction of those ti99 systems if you don’t pay attention,am astonished that finding proper imagines and videos of the ti99/4 just became more sparse then it should be.

Yeah i know the ti99 4/A did sold a 150 times better then the original one from 1979 but still,,,,

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4 hours ago, johannesmutlu said:

glad i own aown a ti99 4/A just recently along with it’s original power adaptor and with some nintendo and atari games for it among other ones😆

however i got issues with it’s keyboard since texas instruments used a cheap ass mailor membrane for most of it’s ti99 systems in it’s keyboards,wich don’t age well,i had to desperately and rappidly hit key 2 to get a game bootup,some keys do work but most of them don’t or hardly respond once i press them,now if only i could find a replacement keyboard for it wich uses switches instead (like many later models of the ti99 did), i could replace that old keyboard with it once i do know exactly what am doing,

becides am astonished that i can’t find most pictures of the original ti99/4 ,even on youtube those ones who owns the original model of the ti99/4,just barelly shows them,i know both models do look similar but i just would like to see the ti 99/4 from every corner,am curious about it’s tv out plug and adaptor,also i heard that early models of the ti99 uses dc adaptors while larer models uses ac adaptors,but it makes me wonder,are both plugs the same? If so,then not only could this cause confusion but also destruction of those ti99 systems if you don’t pay attention,am astonished that finding proper imagines and videos of the ti99/4 just became more sparse then it should be.

Yeah i know the ti99 4/A did sold a 150 times better then the original one from 1979 but still,,,,

A couple of useful data points for you:

 

1. The membrane keyboards (Mitsumi built them for TI) were the last keyboards TI used. About 80% of all machines ever made used mechanical switches (almost all black keyboards (there are a minimal number of black Mitsumi keyboards out there) and about half of the beige keyboards use some type of mechanical switch (Stackpole or Alps, for the most part)). The Mitsumi keyboards are identifiable by two means: they have a beige/brown circuit card and they have REALLY sharp cornered keytops. None of the other keyboard types match this (they have green circuit cards and the corners of the keytops are rounded). Just look online for a TI keyboard that matches the characteristics of one of the keyboards that isn't from Mitsumi and switch it out with yours (very easy to do, although the connecting cables can be brittle) or follow some of the tutorials online to restore the membrane on your existing keyboard (difficult and may damage the membrane beyond repair if unsuccessful).

 

2. The 99/4 did not have a TV out adapter that was any different from the one on the 99/4A. The original Dimension 4 prototypes DID have TV out without the need for an external modulator, but that design did not pass the necessary emissions testing to go into production. I know of exactly 2 and 1/2 examples of any members of the Dimension 4 family in the wild--one is in a museum and the other 1 and 1/2 are in my possession. There is an extensive set of pictures (inside and out) that I posted in this thread. The Zip file should give you plenty of data.

 

3. 99/4 power adapters can be weird. The earliest US releases use the same power outputs as the ones in a 99/4A (approximately 16V AC and 8V AC). The majority of the ones released in Europe are the same, but there is a small class of easily-identifiable exceptions: any 99/4 with a volume slide switch where the Solid State Software badge would normally be uses an external power supply with a DC output. Those machines get all of their DC voltages from the power supply AND one of the pins at the power input is really fat compared to the other pins to make it hard to plug the wrong power supply into the machine. These exceptions were only made in the last month or so of 1979 and the first couple of months of 1980. The volume slide switch controlled a speaker under the grille behind the cartridge port, needed when the monitors they were using didn't have built-in sound capability.

 

4. Somewhere between 80,000 and 100,000 99/4s were sold.

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11 hours ago, Ksarul said:

A couple of useful data points for you:

 

1. The membrane keyboards (Mitsumi built them for TI) were the last keyboards TI used. About 80% of all machines ever made used mechanical switches (almost all black keyboards (there are a minimal number of black Mitsumi keyboards out there) and about half of the beige keyboards use some type of mechanical switch (Stackpole or Alps, for the most part)). The Mitsumi keyboards are identifiable by two means: they have a beige/brown circuit card and they have REALLY sharp cornered keytops. None of the other keyboard types match this (they have green circuit cards and the corners of the keytops are rounded). Just look online for a TI keyboard that matches the characteristics of one of the keyboards that isn't from Mitsumi and switch it out with yours (very easy to do, although the connecting cables can be brittle) or follow some of the tutorials online to restore the membrane on your existing keyboard (difficult and may damage the membrane beyond repair if unsuccessful).

 

2. The 99/4 did not have a TV out adapter that was any different from the one on the 99/4A. The original Dimension 4 prototypes DID have TV out without the need for an external modulator, but that design did not pass the necessary emissions testing to go into production. I know of exactly 2 and 1/2 examples of any members of the Dimension 4 family in the wild--one is in a museum and the other 1 and 1/2 are in my possession. There is an extensive set of pictures (inside and out) that I posted in this thread. The Zip file should give you plenty of data.

 

3. 99/4 power adapters can be weird. The earliest US releases use the same power outputs as the ones in a 99/4A (approximately 16V AC and 8V AC). The majority of the ones released in Europe are the same, but there is a small class of easily-identifiable exceptions: any 99/4 with a volume slide switch where the Solid State Software badge would normally be uses an external power supply with a DC output. Those machines get all of their DC voltages from the power supply AND one of the pins at the power input is really fat compared to the other pins to make it hard to plug the wrong power supply into the machine. These exceptions were only made in the last month or so of 1979 and the first couple of months of 1980. The volume slide switch controlled a speaker under the grille behind the cartridge port, needed when the monitors they were using didn't have built-in sound capability.

 

4. Somewhere between 80,000 and 100,000 99/4s were sold.

Thanks for mentioning this👍

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