exxos's Atari, Amiga & retro forum

Howdy, got a TT that was supposed to have black screen problems, which it did on both powerup and in the middle of a disk format (Epson-340) after working for a while. Recapped the PS, then it worked for a little while and then back to black screen. Found some broken ceramics around the 1992 chip, replaced them as well as recapped the motherboard and it seems good but I have NO sound, not on the RCAs or the internal speaker. Found another broken ceramic C932 which looks to be part of the LAN circuit, so that should not be a sound issue. PS has good voltages and the 1992 chip has its 8.2v pin good, so a bit stumped at this point. I should note that when I received it, the roms has been replaced but put in upside down and the TT had nothing, replacing the now toasted roms with the original German it is working, replaced the German with US roms and still working but no sounds, nothing, no keyboard sound, just dead silent. Any ideas on where to go from here? Perhaps the upside down roms did some damage on the motherboard? Is there some way to test the audio circuit, I am guessing around the 1992 chip? Thanks!

I wonder if you can still purchase replacement DACs. There are two of them underneath the PSU. That's probably what I'd do.

Check if chips related to sound have 5V and clock.

CHeck the speaker first! My original one died.

Also, check the power supply. One of the first things to go when my old PSU was on the blink was the sound.

Wasn't there some odd jumper setting relating to sound on those machines ?

I would check the ym chip outputs show something on key presses to see if there is at least a source signal...

exxos wrote: 12 Dec 2020 14:42 Wasn't there some odd jumper setting relating to sound on those machines ?

I would check the ym chip outputs show something on key presses to see if there is at least a source signal...

Nope. There's a software configuration option controlled by the microwire interface to turn the speaker off, otherwise it's just like the STE.

You must turn on the "Bell" into the CPX to turn the Keyclick on ...

frank.lukas wrote: 12 Dec 2020 17:39 You must turn on the "Bell" into the CPX to turn the Keyclick on ...

Key "click" is on by default, as with all TOS versions.

stephen_usher wrote: 12 Dec 2020 17:49

frank.lukas wrote: 12 Dec 2020 17:39 You must turn on the "Bell" into the CPX to turn the Keyclick on ...

Key "click" is on by default, as with all TOS versions.

Interestingly, the keyclick icon was grayed out, turning it back on I still got no sound

The speaker connector on the mainboard has three pins but the speaker has two so it can be connect wrong ...