Solved Sega system C (Columns) no sound at all

[Georgian2]

Hello,

Here I have this problem with an C board. There is no hum nor any sound comming out of the TDA1518 Audioamplifier. There is sound going in to pin 13 and 2 but nothing at all on the output. The Mute pin (pin11) is at 11.5V, amplifier has 12.5V. If I pull the mute pin low, while doing it there is a very low hum on the speaker. I have no ideea what is wrong here. Original was TDA1518Q, I replace it with two TDA1518BQ and an TDA1510 and no difference at all. There is continuity between the amplifier pins and speaker.

What could be wrong here? There are no schematics for this board. The audio section appears to work just fine since I can hear the sound with an external amplifier. when I tap in to pin 13.

 

[Ace`]

I have a system c board with this exact problem, still haven't figured out what the issue is. I was tempted to bodge in one of those small amp boards just so it would work but it just got thrown in the 'for another day' pile in the end.

 

[Georgian2]

I have a system c board with this exact problem, still haven't figured out what the issue is. I was tempted to bodge in one of those small amp boards just so it would work but it just got thrown in the 'for another day' pile in the end.

It is a wierd issue indeed.

 

[Ace`]

I remember I even tried lifting pins on the amp to isolate them from the rest of the board, the amp isn't happy about something. Unless there's some of those small filters in the output that are also used on the sega saturn? they're starting to fail now and cause all sorts of issues on the saturn. I cannot remember if it has those filters though as it's been a while.

 

[Georgian2]

I remember I even tried lifting pins on the amp to isolate them from the rest of the board, the amp isn't happy about something. Unless there's some of those small filters in the output that are also used on the sega saturn? they're starting to fail now and cause all sorts of issues on the saturn. I cannot remember if it has those filters though as it's been a while.

I got it, buddy!
Since the C64 is the only part that is not on the input side, I checked it and it measured as an 280Ohm resitor using an component tester. New 220uF cap in and sound is great!
This took me quite a while now )

https://www.radiomuseum.org/tubes/tube_tda1518.html The cap on pin 12.

 

[Ace`]

Nice, I recapped mine so it's not going to be that easy for me. Glad you got yours going though.

 

[Georgian2]

@Ace` are you looking to sell your board? Even without sound is ok.

 

[Ace`]

I might trade it, but I cannot really get to it at this moment in time.