Ti99/4a + 32kb rom + FinalGrom99 = Lot of Blue screens (hardware failure?)?

[wietze]

Hi there guys,

 

Im a new user of the TI99/4a hardware, and just this week I finally received my FinalGrom99 and 32kb memory expansion part.

I have downloaded a few cartridges together with some homebrew games and gave them a spin.

Unfortunately, many of my attempts of loading a game failed. More often than not, I end up having a blue screen, and sometimes some sound or music is playing.

For example, Sabre Wulf and Ms Pacman do not run. For example Moon Patrol only loads some of the graphics (like the top part of the car, and the pits load).

Some other games do work. The behaviour of which games work and which do not is completely consistent. But so far, it feels like a lot of stuff is not working.

 

Since Im a complete noob with regards to the system, can anyone point me out to any common pitfalls, or ways to determine what Im doing wrong? Is this behaviour related to a hardware faillure?

 

I hope that you guys can shed some knowledge

 

Regards,

Wietze

 

Edited December 6, 2020 by wietze

[arcadeshopper]

Hi there guys,
 
Im a new user of the TI99/4a hardware, and just this week I finally received my FinalGrom99 and 32kb memory expansion part.
I have downloaded a few cartridges together with some homebrew games and gave them a spin.

Unfortunately, many of my attempts of loading a game failed. More often than not, I end up having a blue screen, and sometimes some sound or music is playing.
For example, Sabre Wulf and Ms Pacman do not run. For example Moon Patrol only loads some of the graphics (like the top part of the car, and the pits load).
Some other games do work. The behaviour of which games work and which do not is completely consistent. But so far, it feels like a lot of stuff is not working.
 
Since Im a complete noob with regards to the system, can anyone point me out to any common pitfalls, or ways to determine what Im doing wrong? Is this behaviour related to a hardware faillure?
 
I hope that you guys can shed some knowledge
 
Regards,
Wietze
 

First off do you have a Qi console?

Have you cleaned your cartridge port?

Start simple just the console and the finalgrom99.

Where did you get your cartridge images from?



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[wietze]

My console is a TI99/4a, that has the silver/metallic casing.

I got the cartridge images from various threads/packages from Atariage posts.

 

I assumed the ports to be clean enough, but I will give both the cartridge and the sidecart another clean.

[arcadeshopper]

My console is a TI99/4a, that has the silver/metallic casing.
I got the cartridge images from various threads/packages from Atariage posts.
 
I assumed the ports to be clean enough, but I will give both the cartridge and the sidecart another clean.

Try the zip on ftp.whtech.com under cartridges and FinalGrom99.

The random files that you're downloading from the for maybe for the final Grom or the flash ROM and may or may not require 32k if you have the 32k plugged into the console on the side port directly you shouldn't need an external power supply but if you have it plugged in to the speech synthesizer then you definitely need an external power supply

Console color is irrelevant the way you tell is via the different side port parts look in the pinned FAQ for more information

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[jrhodes]

You may as well give a good inspection to the sideport connector pins too.

My TI was a bit flaky getting the speech synth to work, turned to be dirty contacts on the TI's sideport.

Cleaned it up, everything works great now.

[arcadeshopper]

Best to start with just the console then add peripherals after getting it working at the base level

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[wietze]

I have opened the machine up. Im fairly sure that it is a non-qi version, thus a TI-99/4a; I have a sideport without any metal surrounding it.

I cleaned the sideport with alcohol, and I removed the `sponge' from the cartridge port, and gave it a clean as well.

The behaviour however remains the same.

 

See the link for an example of `Moon Patrol' (which is downloaded from https://ftp.whtech.com/Cartridges/FinalGROM99/ ):

http://frummel.org/~weedz/tmp/VID_20201206_212532893.mp4 (dont mind the colours, they are there, but my phone dont capture them well).

 

Are there diagnostic tools or programs one can recommend to run?

 

Kind regards

Edited December 6, 2020 by wietze
Made model number explicit.

[wietze]

I may have found some anomalies while running a ram test, but the program tells me that there are no errors found.

 

While running ram test/checkerboard: I noticed some off pixels:

And while running the address input test I got some off characters on the left (and a few flicking pixels on the right part of the screen in the drawn chars).

 

I am not sure if this means anything, or if its all good.

 

Testing a few games (from the downloaded url above):

- Alpine works

- Flappy Bird works

- Jet Set Willy works

- Sabre Wulf gives me a blue screen, but plays music, and mashing some buttons, starts the game and draws main character and some other sprites.

- Jet Pac gives me the cyan background color and a hanging buzzing sound

- Road Hunter works

- Miner 2049er works

- Lasso works

- Pacman gives solid blue screen, and does nothing, similar to moon patrol, but if I then press 1, the game starts; and it draws the players

- Ms Pacman does the same, if I mash some buttons the game starts and plays (draws player and ghosts).

 

 

Perhaps this helps explaining the situation? Could it be VDP related?

 

So perhaps its just the specific games? I have no idea.

Edited December 6, 2020 by wietze

[arcadeshopper]

VDP or VDP RAM issues it looks like

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[wietze]

How would I be able to determine whats up?

[GDMike]

There's some utube videos on ram troubleshooting for ti-99/4A.

 

Edited December 6, 2020 by GDMike

[Asmusr]

It appears that graphics mode is working but bitmap mode is not, which indicates a bad VDP. If it was the VDP RAM it would be visible already on the start screen.

[wietze]

50 minutes ago, Asmusr said:

It appears that graphics mode is working but bitmap mode is not, which indicates a bad VDP. If it was the VDP RAM it would be visible already on the start screen.

Awesome, I will have a look which VDP chip is in the machine, and see if I can source a new one.

 

[JB]

59 minutes ago, wietze said:

Awesome, I will have a look which VDP chip is in the machine, and see if I can source a new one.

 

TMS9918A, unless you're using a PAL console for some reason.

 

[wietze]

Just opened her up, and it seems to have a TMS9929NL vdp chip.

I currently connect the machine to the display using a `Texas Instruments TV PAL Encoder PHA 2030'. 

 

Could the use of a PAL vdp chip cause the abovementioned graphical behaviour with some programs? 

(Edit: some thread in this forum suggests that all cartridges encountered are PAL/NTSC compatible; so I assume answer is `no').

 

 

 

Edited December 7, 2020 by wietze

[+mizapf]

The only difference between PAL and NTSC is the refresh rate (50 Hz vs. 60 Hz) which is not compensated in the games that I know of (which means some games are significantly slower on PAL consoles). The higher lines count (NTSC has 525 lines vs. PAL with 625 lines) is not relevant and results just in a wider border; the logical geometry (resolution of the VDP) is the same.

[arcadeshopper]

Could be your display not supporting the output of the system..

 

The information that it was pal and you were using an adapter and what kind of display you have would have been nice to know up front would have made our suggestions a lot easier to make

 

The output of the pal signal is not quite component for modern displays

 

Ymmv

 

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[wietze]

41 minutes ago, arcadeshopper said:

Could be your display not supporting the output of the system..

 

The information that it was pal and you were using an adapter and what kind of display you have would have been nice to know up front would have made our suggestions a lot easier to make

 

The output of the pal signal is not quite component for modern displays

 

Ymmv

 

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Good call. Apologies for not thinking of this to provide this information. To make up for it; let me elaborate on the setup:

- TI-99/4A with TMS9929NL chip, outputting PAL

- Connected through the 6 pin din cable using Texas Instruments TV PAL Encoder PHA 2030, which outputs: Component and Audio leads

- Component input is connected to the RetroTink 2X

- Retrotink output goes into HDMI in of my TV

 

How does the remark of Asmusr hold up, regarding different screen modes?

[+mizapf]

Oh, this is not the PAL HF modulator? I did not know there is component output PAL encoder.

[wietze]

from above comments I have 2 things to try so far:

 

- replace Texas Instruments TV PAL Encoder PHA 2030 with direct cable connection to retrotink; I will have so see where I can acquire one

- replace the VDP chip (has been ordered)

[arcadeshopper]

My money is on the retro tink is not interpreting the signals correctly

There is a diagram in the FAQ for making a cable

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[wietze]

17 minutes ago, arcadeshopper said:

My money is on the retro tink is not interpreting the signals correctly

There is a diagram in the FAQ for making a cable

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Good point, so to rule out the Retrotink I removed the Retrotink from the chain. And thus doing:

- TI99/4A <> Texas Instruments TV PAL Encoder PHA 2030 <> TV Component input

 

But this results in the same behaviour; which means the Retrotink is not the cause.

The fact remains that the sprites of for example pacman and sabre wulf still show, but the playfield is not drawn. This is probably the same behaviour as happens with Moon Patrol.

Considering the display of these `faulty' screens is still crystal clear, and the other working games are crystal clear as well, it seems not to be the cable or the PAL Encoder at fault. Could it be that a part of the VDP chip is broken/bugged, like Asmusr suggested?

[arcadeshopper]

Like I said I think my money is on the ti signaling is not the same as your display is expecting that's why it's so clear but wrong

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[wietze]

Asmusr pointed me out in PM that I have a TMS9929NL chip, which is lacking the `A'. Which in turn implies it does not have support for the bitmap mode.

I hope that I can just replace the TMS9929NL chip with a TMS9929ANL chip then!

[arcadeshopper]

That may be it!

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