Troubleshooting

[Appeelicious]

So when I boot up my ti-99/4a it has a slight buzzing in the background that gets louder when I depress a key. Is the chip that handles sound in any way related to keyboard pushes?

[Tursi]

It's interference from the 9901 switching during the keyboard scan, it's perfectly normal. I even emulate it in Classic99. 

 

 

[+arcadeshopper]

1 hour ago, Tursi said:

It's interference from the 9901 switching during the keyboard scan, it's perfectly normal. I even emulate it in Classic99. 

 

 

it seems to be louder on some consoles.. maybe capacitor issues?

 

[Tursi]

Maybe, but probably not. The inside of the TI console is a ridiculously noisy place - put an oscilloscope probe anywhere.

 

The sound chip has an analog input with a bunch of circuitry acting as an antenna, then a bunch of analog amplification circuitry running halfway across the console. It picks up noise from the VDP and the 9901 primarily, but there are other sources too. And we know that every console is slightly different under the hood

 

To be honest, we've heard very, very few stories of bad caps inside a TI console, and I'm not entirely sure the ones we heard were not just people being cautious. It's pretty amazing how well they've lasted.

 

Edited January 20, 2023 by Tursi

[+jedimatt42]

That aspect of hearing what is going on was a nostalgia point for me. I know my 4As fresh out of the box in the 80s did that too. 

[Tursi]

40 minutes ago, jedimatt42 said:

That aspect of hearing what is going on was a nostalgia point for me. I know my 4As fresh out of the box in the 80s did that too. 

That was how I could tell I had the RF tuning dialed in

 

[+OLD CS1]

After loading a BASIC program from tape, I would turn up the TV volume so I could hear when the computer was done processing the load.  Never really took that long, but it was long enough for me to go off somewhere else.