Tandy 3 Voice Sound - SN76489 ISA Soundcard Project

[matze79]

All PC-Speaker issues are fixed now and now its also short circuit safe.

[carlostex]

Great job, very nice to see this progress.

[JonSmith]

Thumbs up! Can't wait!

[carlostex]

I'm interested in a couple of PCB's, if you plan to make them available.

[keropi]

matze79 are these changes documented so I can replicate them?

[matze79]

more or less

i send you a PM keropi.

Carlostex, we working out the bugs, i'm sure it will be avaible soon on serdaco

[ITzTravelInTime]

I hope you post some pcb files or something like that, i'd like to play with the disgn a little bit (just to match the holes and the headphone jack position to use the metal bracket i use for the adlib clone) and also because i'd like to build one from scratch, what a bout availability in the future? i'd like to use it with my upcoming pc xt build

[root42]

more or less

i send you a PM keropi.

Carlostex, we working out the bugs, i'm sure it will be avaible soon on serdaco

I also still have one of your early prototype boards. Any chance I can upgrade it as well?

[mil]

I am also interested in a couple of PCB's.

[matze79]

Just have a little patience until ~ spring 2019!

[matze79]

still some small adjustments needed, current progress :

[Scali]

Looks great! I love the volume wheel!

[root42]

God we need someone with a tool for making custom brackets. But yeah, looks lovely!

[keropi]

yep - it looks very nice !

[matze79]

God we need someone with a tool for making custom brackets. But yeah, looks lovely!

ah i already have a solution for that into mind

[root42]

Then also make some for the snark barker!!

[matze79]

looks lovley but has EMV problems.. so needs redesign i cut few things on the pcb and wired the gnd and vcc directly to power supply and so on..
still noise inside the signal.

my two testing boards on perfboard did work fine.. so it must have todo with the pcb design..

[root42]

That is something that eludes me completely. How does one go about reducing noise on the PCB level? I remember one video by Dave from EEVblog where he simply added two layers to an already two layer board, simply by adding one pure GND and VCC plane, iirc. That supposedly reduced emissions as well. Not sure about the physics behind that.

[matze79]

this way parasitic capacitance is eliminated i think.

[Tiido]

Planes increase parasitic capacitance, which (un)intentionally helps to round off the signal edges slightly which will reduce emissions. Their main positive effect comes from reduction of loop area on return currents etc., the noise can couple straight into the plane rather than through other stuff elsewhere, so less has to radiate outwards or into other stuff.