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kl99

Ti-99/4a console not working anymore

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Hi!

 

During working on my BoCC game my shiny new console suddenly hang up.

Never happened before because I didn't use it that much yet.

 

I switched it off and on (Power on switch).

But since that it simply won't give me the famous title screen anymore.

 

) Power LED lights up

) It is showing black screen

) Is is making a deep noise (in a loop)

 

It's a Texas Instruments Black/Silver PAL Version.

Serial: R057005 40 83 ROI

Assembled in Italy

 

When I try another PAL console with the same power cable and video cable, everything is working.

So it can't be the power adapter.

 

I originally had a nanoPEB device connected to the console.

Once I figured out, the machine doesn't like to boot at all, I disconnected it.

 

No Cartridge is (was) placed in the slot.

When I insert a cartridge, the reset (pin1) seems to get triggered, but then I get a black screen and the noise again.

 

A few weeks ago I saw a very good checklist what to check in such a situation. But since I am reading a few hours each day about Ti-99, I simply can't remember where this checklist was. Maybe some user group newsletter in the whtech archives.

 

Can anyone give me an advice what could be wrong?

What should I check?

 

Many thanks, Klaus

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Hi!

 

During working on my BoCC game my shiny new console suddenly hang up.

Never happened before because I didn't use it that much yet.

 

I switched it off and on (Power on switch).

But since that it simply won't give me the famous title screen anymore.

 

) Power LED lights up

) It is showing black screen

) Is is making a deep noise (in a loop)

 

It's a Texas Instruments Black/Silver PAL Version.

Serial: R057005 40 83 ROI

Assembled in Italy

 

When I try another PAL console with the same power cable and video cable, everything is working.

So it can't be the power adapter.

 

I originally had a nanoPEB device connected to the console.

Once I figured out, the machine doesn't like to boot at all, I disconnected it.

 

No Cartridge is (was) placed in the slot.

When I insert a cartridge, the reset (pin1) seems to get triggered, but then I get a black screen and the noise again.

 

A few weeks ago I saw a very good checklist what to check in such a situation. But since I am reading a few hours each day about Ti-99, I simply can't remember where this checklist was. Maybe some user group newsletter in the whtech archives.

 

Can anyone give me an advice what could be wrong?

What should I check?

 

Many thanks, Klaus

 

I had a console that used to do this, and the problem was actually the power switch on the front. If it does not move across to the right then it seems that some circuits do not get powered up. Make sure the power switch does not have a problem.

 

If it is not this, then I would suspect the Scratchpad RAM chip has failed, and therefore the 9900 processor cannot initialise and boot the console.

 

Mark

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The first thing I would try is "reseating" any chips in a socket. The system GROMs are socketed, as well as the sound chip and VDP. Common problems with the 99/4A seems to be one or more of the DRAMs going bad (VDP RAM). Since there are 8 of these chips, and since the console relies on them 100%, a failure of any one of them will cause the console to stop working.

 

If reseating chips does not help, and you don't have the skills (electronics, soldering, etc.) or equipment to test the video subsystem, send me the console and I'll fix it.

 

I doubt the SRAM is bad, I think the symptoms would be different. Plus, the SRAM is a little more robust than the DRAM - but this is totally speculation without having access to the console.

 

If you have more than 1 console you can do some basic swapping of things like the power supply, GROMs, sound chip, and VDP to make sure it is not one of those parts causing the problem.

 

Matthew

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Thanks a lot to you for your replies.

 

I have disassembled the consoles.

It isn't the power switch, and is isn't the power board of the console. It must be something on the mainboard.

When using the mainboard from the other console the setup is working...

 

Nothing seemed loosened on the board, I pressed on all sockets with my finger.

 

With reseating all sockets you mean, take them completely out and insert them again, right?

Like here? http://www.pixcontroller.com/Products/RemovePIC.pdf

 

I can try that this weekend.

 

Wow, fixing at your place is such a nice offer, can't believe how wonderful our community is.

I still hope to be able to at least detect the source of the problem.

 

Thanks Mark and Matthew,

 

Klaus

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Thanks a lot to you for your replies.

 

I have disassembled the consoles.

It isn't the power switch, and is isn't the power board of the console. It must be something on the mainboard.

When using the mainboard from the other console the setup is working...

 

Nothing seemed loosened on the board, I pressed on all sockets with my finger.

 

With reseating all sockets you mean, take them completely out and insert them again, right?

Like here? http://www.pixcontroller.com/Products/RemovePIC.pdf

 

I can try that this weekend.

 

Wow, fixing at your place is such a nice offer, can't believe how wonderful our community is.

I still hope to be able to at least detect the source of the problem.

 

Thanks Mark and Matthew,

 

Klaus

 

 

If you still have the console apart.....

 

Take the grom connector (cart connector) out and try starting the computer. If it boots then you need to clean the connector. Pretty simple fix if it works and more common than most suspect.... Good luck.

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Hi again!

 

I have tried reseating the VDP, the Sound Chip and the GROMs for now. Still not working. :(

As these pins on the chips are really likely to break, I have some fear of damaging the 2nd console, If I do more experimenting.

 

In one week there is a retro-faire in Vienna., I hope to find TI-99 stuff there, maybe even a console.

 

Since I am about to start a local TI club for Austria, there will be hopefully some way to fix this console locally some day, without shipping to America back and forth.

 

Matthew, I still highly appreciate your offer and I am a big fan of your VideoCard Replacement Project.

 

br, Klaus

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Klaus,

 

Ah, I didn't realize you were out of the U.S. That does make it most expensive, unfortunately. You have a few options to troubleshoot at this point:

 

1. Wait until I get the F18A done (making a circuit board for the FPGA is proving more complicated than I thought it would be.)

 

2. Get an FPGA development board and you can beta test the F18A.

 

3. Desolder all the DRAMs and put sockets in their places. Then get a known good DRAM and start a systematic replacement of each one until the console works, or appears to get better. Keep in mind that more than one chips may have failed. The best way to do this is to get eight known good DRAM chips, then replace one of them with a chip from the set that you pulled from the problematic board. This should let you isolate the bad DRAMs.

 

4. Remove the DRAM chips and test them with a device that can do DRAM testing. My EPROM programmer can test certain RAM and logic chips, I think it includes DRAM.

 

If the DRAMs prove to all be good, now you are into *real* computer board troubleshooting. Now you have to start tracing signals, testing logic chips and buffers, etc. For this kind of work you really need an O-scope at the very least, and preferably a logic analyzer.

 

Matthew

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