exxos's Atari, Amiga & retro forum

It has a very strange multi-layered modification on the sound chip people haven't seen before. Does anyone know what that was for? Thx.

edit: updated the title to rev H as suggested by Atarian Computing.


^ Oddly on the top of the motherboard in the bottom right hand corner where it says REV_____ it has a very faint hand stamped 'B'. I don't know why that doesn't correspond with the PCB revision on the underside pictured above.

Nice pictures! TT revisions are a mess. Your's probably is a REV.H. I've seen many C302406-001 REV A boards with REV.H topside.

Interesting.. Pins all bent on the IO ports on the YM chip.. Wire goes to "DD enable" to the 1772 by the looks of it. I will take a guess its a factory fix ? Maybe you could take out the YM chip and see if there is any tracks visible ?

I'm certain that there are two revisions of REV.H. Let me show ya:

Here is the earlier revision from this forum:


And another early H.


Here is proof that C302406-001 REV A boards can be REV.H


Notice how the bottom left corner is green instead of metallic?


Let's look at another newer REV.H:


Now compare these pictures to yours.

So my conclusion so far is that if you were to turn the earlier REV.H around it would probably read C301763-001 REV D. I've never even seen a picture of a TT board with REV.D on the topside.

Very interesting. And yet none of them have that Yamaha chip mod. I would take it apart but it's kind of complicated, as it has got a PCB layer underneath it with an IC or two underneath.

My eyes are pretty tired after I tried to figure out what is that quite big light green resistor located at near PSU connector and c120 capacitator :shock: :lol: Is that 10ohm resistor? I'll soon try to bring life to TT that has some components missing and that resistor is one of them.

tjam wrote: 04 Dec 2019 02:54 My eyes are pretty tired after I tried to figure out what is that quite big light green resistor located at near PSU connector and c120 capacitator :shock: :lol: Is that 10ohm resistor? I'll soon try to bring life to TT that has some components missing and that resistor is one of them.

Yeah, you happened to run into one of the mysteries. It's marked as LD01 on the silkscreen. However, it does not appear in the schematic. I should know as I've painstakingly re-created it in KiCad.

It appears to be part of the TT ECL Video Subsystem. Components here get a letter "D" added after the regular designator. C becomes CD, R becomes RD, U becomes UD, etc. By that convention, LD01 would be L, which typically is a designator for a coil, inductor, bead, ferrite bead. It sure doesn't look like one. Also, there are no other "L" components on the whole board.

Based solely on looks, it could be a resistor or a capacitor. There are several smaller green resistor-looking caps on the board.

So, TL;DR is, no clue...

tjam wrote: 04 Dec 2019 02:54 My eyes are pretty tired after I tried to figure out what is that quite big light green resistor located at near PSU connector and c120 capacitator :shock: :lol: Is that 10ohm resistor? I'll soon try to bring life to TT that has some components missing and that resistor is one of them.

On my TT Rev.H it seems to be brown-black-black-gold.
But I can´t read what is written underneath.

Mine (REV.C - PGA model, C301763-001 REV A):

Atarian Computing wrote: 04 Dec 2019 16:20 Yeah, you happened to run into one of the mysteries. It's marked as LD01 on the silkscreen. However, it does not appear in the schematic. I should know as I've painstakingly re-created it in KiCad.

It appears to be part of the TT ECL Video Subsystem. Components here get a letter "D" added after the regular designator. C becomes CD, R becomes RD, U becomes UD, etc. By that convention, LD01 would be L, which typically is a designator for a coil, inductor, bead, ferrite bead. It sure doesn't look like one. Also, there are no other "L" components on the whole board.

Based solely on looks, it could be a resistor or a capacitor. There are several smaller green resistor-looking caps on the board.

So, TL;DR is, no clue...

Ah I see.. It surely looks odd, because it's quite big to be 10ohm resistor, but because of color coding I assumed it has to be resistor. I just figured out that axial caps and inductors also has color coding :stars: As far I can tell from pictures (I'm really not sure) it looks to have brown, black and black bands and 10% tolerance :lol: Probably it's not resistor because it's marked to be "L" component, but axial inductor :shrug: