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[TI99/4a] Looking for some recommendations

Kehvarl

Member
Joined
May 15, 2022
Messages
29
Location
Phoenix, AZ
I've just added a Ti99/4a (or rather 2 of them) to my collection. While I'm excited to get it running and enjoy them, I prefer to be cautious with 40 year old hardware.

I've dismantled, cleaned, and re-assembled one of the machines. There was very little dust, no rust, no capacitor goo on the boards, and the heat sinks on both the VDP and u601 seem to both be firmly held down by their thermal paste. I also don't see any heat damage or bulging capacitors on the internal power supply.

Once I test the transformers and build a new composite video cable, I'll be ready for a first power-on and some testing.

What I'd like are some recommendations on upgrades, and also other things I should watch for when testing these machines.
 

mnbvcxz

Experienced Member
Joined
Jun 15, 2011
Messages
283
Location
Portsmouth, England
Popular add-ons include nanopeb which gives 32k ram, serial port and emulates 3 400kb disks on an SD card, also there is the FG99 which allows you to load most if not all cartridges from an SD card, then there is the TIPI which connects an Raspberry-PI to your TI I am not familiar with this device but it seems very good.
 

VeryVon

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Staff member
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Oct 21, 2021
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the Land of the Cheesesteak
Good idea giving them a good once-over before power-on. Very wise.

These things are pretty bulletproof so there's a good chance they'll still work out of the box. I've had a half-dozen or so and never had an issue with a power supply pcb. As for the motherboard, sometimes you'll get the screaming black screen of death (probably a bad ram) or video is a bit jumbled up (bad vdp ram.) The cpu's go bad sometimes as well.

Some links:
  1. Critical tech reference & upgrades / mods : nouspikel
  2. arcadeshopper has some TI-99 stuff. To my knowledge nanopeb is no longer produced, but you can still get tipi
  3. AtariAge resources page (everything else...)
p.s. for theory of operation IMHO the "Bunyard Manual" is the holy grail.
 

Kehvarl

Member
Joined
May 15, 2022
Messages
29
Location
Phoenix, AZ
Thank you both for the recommendations.

It looks like FG99 relies on a CPLD that's a little difficult to source at the moment. I'll start watching ebay for that.
I'll also look into a nanopeb or 32k ram expansion and tipi, though it sounds like a tipi gives me more features.

Also, thank you for the technical references, these are fantastically helpful.
 

Kehvarl

Member
Joined
May 15, 2022
Messages
29
Location
Phoenix, AZ
It looks like Arcadeshopper is out of stock on Tipi+32 modules and FinalGROMs. I'll keep an eye out for those.

In the meantime, I assembled the proper video cable, fired up the machine, and it ran beautifully for about 5 minutes at which point the entire 2,W,S,X columns of keys went out. I'm hoping I didn't damage the keyboard cable when I did my earlier checkup.
 

geoffm3

Veteran Member
Joined
Oct 9, 2009
Messages
1,262
Location
Huntsville, AL
I am trying to fix my TI 99/4A console myself. I have a PEB and the disk controller doesn't work in it. I also have a FinalGROM99 cartridge, and with that and the Speech Synthesizer plugged in (or the PEB) a couple of games have problems. I replaced a few components in the console itself because with the PEB and the FinalGROM plugged in together, the console was unable to access the DSR memory space on the PEB cards so at initialization it wouldn't recognize that I had any expansions. That issues is fixed and I still have the other two issues. I think my disk controller issue is because I can't access the upper DSR memory at >5000 and above. Strangely though, accesses to any of the 32kB expansion memory work.
 

jbdigriz

Member
Joined
Feb 18, 2007
Messages
36
Good idea giving them a good once-over before power-on. Very wise.

These things are pretty bulletproof so there's a good chance they'll still work out of the box. I've had a half-dozen or so and never had an issue with a power supply pcb. As for the motherboard, sometimes you'll get the screaming black screen of death (probably a bad ram) or video is a bit jumbled up (bad vdp ram.) The cpu's go bad sometimes as well.

Some links:
  1. Critical tech reference & upgrades / mods : nouspikel
  2. arcadeshopper has some TI-99 stuff. To my knowledge nanopeb is no longer produced, but you can still get tipi
  3. AtariAge resources page (everything else...)
p.s. for theory of operation IMHO the "Bunyard Manual" is the holy grail.
I would add https://ftp.whtech.com to this list as well. Monster TI-99 archive.
 

ldkraemer

Veteran Member
Joined
Mar 14, 2013
Messages
2,252
Location
Chaffee, MO
I've been reading about the TI-99/4A's having either Stackpole or Hi-TEK Key Plungers
that slit down the sides and cause the key caps to stick down, causing repeats.

One solution is a collar that holds the cracked plunger together while letting the key cap
go into the plunger.

REF:

Lots of postings on various forums for DEC, HP, TI, Atari, and other computers with cracked
Key Plungers. Some solutions on ThingIVerse, and sites selling the laser cut collars that
keep the plungers from spreading and sticking.


Larry
 

VeryVon

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the Land of the Cheesesteak
I am trying to fix my TI 99/4A console myself. I have a PEB and the disk controller doesn't work in it. I also have a FinalGROM99 cartridge, and with that and the Speech Synthesizer plugged in (or the PEB) a couple of games have problems. I replaced a few components in the console itself because with the PEB and the FinalGROM plugged in together, the console was unable to access the DSR memory space on the PEB cards so at initialization it wouldn't recognize that I had any expansions. That issues is fixed and I still have the other two issues. I think my disk controller issue is because I can't access the upper DSR memory at >5000 and above. Strangely though, accesses to any of the 32kB expansion memory work.
Curious, how are you testing the DSR memory, with a mini-memory module? Also, is your gut feeling this is an issue with the console / PEB or both? I assume you've already thoroughly cleaned the edge connector & socket contacts, reseated all the cards. Might want to check this thread as well: let's chase some (PEB) ghosts
 

geoffm3

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Oct 9, 2009
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Huntsville, AL
Curious, how are you testing the DSR memory, with a mini-memory module? Also, is your gut feeling this is an issue with the console / PEB or both? I assume you've already thoroughly cleaned the edge connector & socket contacts, reseated all the cards. Might want to check this thread as well: let's chase some (PEB) ghosts

VeryVon: I'm using mini memory with the FinalGROM99 cartridge. Yeah, I've done all the usualy plugging and unplugging, checking power supplies out, etc. I'll check out your link though, thanks. Adding to the strangeness of the problem, the external RAM expansion memory in the PEB seems to pass every test, and the address decoding for the various pages of that memory all work... which should include wiggling the bits necessary to read the DSR ROM at >5000+, but no dice there. I suppose the PAL on the FDC could be bad or the ROM, but everything else on that seems to check out.

My gut feeling is that there's a problem is in the console. I did have to replace a chip in the console to make DSR access worth with the FinalGROM cartridge, as it wouldn't recognize the FDC controller was there until I did (but did with a real cart or no cart installed). I suppose it's also possible that the FinalGROM is doing something goofy on the bus.
 

geoffm3

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Huntsville, AL
Access to the disk controller via DSR (say, using a real Disk Manager 2, or TI BASIC 'OLD DSK1.<file>') locks up the system, I am suspecting that this is due to some of the code from the >4000-4ffff space jumping or running into the >5000-5FFFF space and executing junk.
 

geoffm3

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Huntsville, AL
My next course of action will be to use the TI RS232 expansion card to check into the >5000-5FFF space, as I should be able to wiggle some of the PIO connector pins accessing memory in that space.
 

geoffm3

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Huntsville, AL
Followup: I had an issue with the Final GROM 99 cartridge itself that I validated against a second borrowed console from a workmate. The behavior with it was the same, several games wouldn't play properly. There's a guy over in Atariage that made a new cpld image and avr image that was intended for the later beige QI consoles that fixed those issues for me, which is interesting since these are both black and silver models.

The disk controller issues still persist. I did verify that access to the >5000-5FFF space works with the RS-232/PIO card, so now I'm down to just the disk controller high ROM access being the issue I think.
 

fdiskitup

Experienced Member
Joined
Mar 2, 2022
Messages
84
Location
Chicagoland, USA
It looks like Arcadeshopper is out of stock on Tipi+32 modules and FinalGROMs. I'll keep an eye out for those.

In the meantime, I assembled the proper video cable, fired up the machine, and it ran beautifully for about 5 minutes at which point the entire 2,W,S,X columns of keys went out. I'm hoping I didn't damage the keyboard cable when I did my earlier checkup.
Keyboards on the TI99 seem to be the main failure. My top row 6-9 stopped working. But cold air can spray made it start working again !
it turned out to be cracked solder joints on the keyboard pcb.

Final grom99 and atari joystick converter are nice. Dont bother with the TI joysticks, i did :(
 
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