Has anyone followed this channel to fix a TI 99?

[AtariNostalgia]

I find that he is quite knowledgeable and I'm trying to follow his footsteps where applicable to my broken machine. I was just wondering If anyone else has any experience with this channel?

 

 

[+arcadeshopper]

I find that he is quite knowledgeable and I'm trying to follow his footsteps where applicable to my broken machine. I was just wondering If anyone else has any experience with this channel?
 
 

His methods and techniques are sound but we can only hope that as he gains more experience with the platform he doesn't spend so much time trying things that aren't the issues.

Sent from my LM-V600 using Tapatalk

[InfiniteTape]

42 minutes ago, arcadeshopper said:

His methods and techniques are sound but we can only hope that as he gains more experience with the platform he doesn't spend so much time trying things that aren't the issues.

I enjoy watching his videos, but I definitely find my self yelling at the screen for him to stop and look up documentation rather than guessing. That's especially true when he's outside his comfort zone of C64 or Apple II.

 

That said, at least he's willing to branch out. 8-Bit Guy seems to go out of his way to exclude TI from his content.

[+OLD CS1]

2 hours ago, InfiniteTape said:

I definitely find my self yelling at the screen for him to stop and look up documentation rather than guessing.

This.

2 hours ago, InfiniteTape said:

8-Bit Guy seems to go out of his way to exclude TI from his content.

Not a difficult task when your focus is other platforms.

[AtariNostalgia]

The thing is, this specific TI99 I'm working on, exhibits the same type of errors as the video does thus far. I'm only using a multimeter, I don't have an oscilloscope. I'm worried If I skip to his 4th video, I might miss out on something important, but don't want to follow the video for hours If he is just testing useless things. From the errors so far in the video, what do you think is wrong with this TI, in this case mine, so I can take a short cut? Coincidentally, mine is also a beige unit, non QI.

[+arcadeshopper]

The thing is, this specific TI99 I'm working on, exhibits the same type of errors as the video does thus far. I'm only using a multimeter, I don't have an oscilloscope. I'm worried If I skip to his 4th video, I might miss out on something important, but don't want to follow the video for hours If he is just testing useless things. From the errors so far in the video, what do you think is wrong with this TI, in this case mine, so I can take a short cut? Coincidentally, mine is also a beige unit, non QI.

His problem the whole time was the damaged CPU which requires desoldering the whole thing and replacing it

Sent from my LM-V600 using Tapatalk

[AtariNostalgia]

7 minutes ago, arcadeshopper said:

His problem the whole time was the damaged CPU which requires desoldering the whole thing and replacing it

Thanks for the reply. I have a couple on order from China, they still haven't arrived, and I hope they aren't fakes when they get here. My order also contains a few 74LS04's

[AwkwardPotato]

Worth noting that the black screen & cacophony symptoms can be caused by the failure of almost anything, so it's a good idea to check the SRAM/ROM especially, and also the 'LS373/244/245 multiplexer setup and VDP if you haven't already, before going to the trouble of replacing the CPU.

 

Edit: And to answer the original question, his troubleshooting methods are great, but frustrating at the same time, given how many years' worth of documentation are on AtariAge and elsewhere. You should be fine working without an oscilloscope.

Edited July 17, 2021 by AwkwardPotato

[+OLD CS1]

13 hours ago, AwkwardPotato said:

You should be fine working without an oscilloscope.

Yeah, but no one earns nerd cred working like that.

[Airshack]

15 hours ago, InfiniteTape said:

8-Bit Guy seems to go out of his way to exclude TI from his content.

   Agree. Disappointing as he’s a Texan from the DFW area as well. Seemed completely disinterested in the 99/4 story as he documented “Texas Tech History” which was a four-part series featuring a few seconds of TI-99/4A mention and ONE MINUTE of conversation about Texas Instruments place in that history. Everything in one minute?

   He spent maybe five seconds mentioning the TI-99/4A. Just enough time to show a still photo of his trophy 99/4 he never powers on.

 

   David’s programs are usually excellent otherwise.
 

 

[AtariNostalgia]

10 hours ago, AwkwardPotato said:

Worth noting that the black screen & cacophony symptoms can be caused by the failure of almost anything, so it's a good idea to check the SRAM/ROM especially, and also the 'LS373/244/245 multiplexer setup and VDP if you haven't already, before going to the trouble of replacing the CPU.

You haven't left anything else out have you? ?

At this rate, I might as well just keep it for parts instead of ordering everything.

[matthew180]

I agree with most of what has already been said here, especially the "yelling at my screen" part.

 

I started watching the channel and was particularly interested to see how he would go about fixing the 99/4A.  I had to stop part way through.  Most of the problems he was having are known issues and such, and these days the *FIRST STEP* to fixing any retro computer should be to find the main group for that platform and see what is already known.  Using an emulator to reproduce symptoms is also a great way to isolate common failures (especially in VRAM).

 

I also tried to find some contact information for the guy, to see if he really wanted to exchange ideas about fixing his 99/4A.  Alas, I could find no contact info or otherwise, short of posting a comment on the video (not happening).  I suspect he is more concerned with maximizing the exposure of his videos than actually fixing the system or participation in a community around the various systems he works on.  Not that such a thing is bad, to each their own.  But people watching the video for help in trying to fix their own 99/4A, they will probably end up making things worse.

 

There is a great troubleshooting guide that was created by the TI technicians who had to fix consoles back in the day.  Check the documents thread here in the forum.  Some common failures are the DRAM ICs used to make the 16K of VRAM.  Also, the white "bus bars" on the motherboard are known to break at the solder joints and can cause all kinds of strange failures.  The ROMs tend not to fail, or cause total death, and neither to the GROMs (they seem pretty resilient).  I have seen the 9900 CPU fail, but only because someone was trying to hack a reset-mod into the system.  NOTE: The VDP runs very hot and NEEDS a heat-sink.  So if you are running the system with the top shield off, make sure you have a heat-sink on the 9918A VDP.

 

Using just a multi-meter can make things a little harder, but not impossible.  A logic-probe would help for testing bus signals though.  With some patience and letting the symptoms guide you, for sure you could get the system fixed.  Also take advantage of the forum here and all the help people are willing to give.