Hi all
I have an old car stereo (Volvo TD-603 1992) which I have refurbished by removing the cassette mechanism and replacing it with a bluetooth receiver. That all worked well, but that's not what I'm writing here about...
The stereo - which outputs 4 channels to an external amp - lost one of the channels - rear right (RR). I followed the traces to find that the RR channel had a broken trace near the output jack, going between that and a break-off PCB which has vol, bal and fader controls. I repaired this channel with some wire soldered in, but it's still doing some funny things:
May I ask these questions...
1 - The PCB has white traces printed on the top-side of it, and these appear to be actual working traces - is there such a thing as this? It's an early 1990s product. Are the traces carbon or something? One of them was scratched and broken, but there didn't seem to be a way to repair this trace, other than solder a lead onto the pins on the bottom-side which has more standard PCB traces and solder pads.
2 - Each of the four channels has a trace going from this vol/bal/tone/fader board, carrying the audio signal to the output jack connector. This trace was broken on the RR channel. But when I was measuring continuity on these traces, I found that the three channels which still worked all had around 30 ohms between the vol/bal/tone board and the output jack - yet there doesn't appear to be any components or resistors there which would add this 30ohms - the only thing I can think of is that these white traces have more resistance than standard copper.
3 - Is this 30ohm deliberate? And will it change the audio signal considerably for the RR channel which (due to the repair) has 0 ohm in the same place where the other channels have 30 ohms? Or should I put in a 30 ohm resistor to bring the RR channel into line with the others?
The funny things it is doing is: sometimes it sounds like it's mixing left and right channels together - there is a sort of phasing sound. I am wondering if the output channels having different resistances could be making it go slightly haywire? Just a thought.
Many thanks for looking at this, and any thoughts gratefully received.
I have an old car stereo (Volvo TD-603 1992) which I have refurbished by removing the cassette mechanism and replacing it with a bluetooth receiver. That all worked well, but that's not what I'm writing here about...
The stereo - which outputs 4 channels to an external amp - lost one of the channels - rear right (RR). I followed the traces to find that the RR channel had a broken trace near the output jack, going between that and a break-off PCB which has vol, bal and fader controls. I repaired this channel with some wire soldered in, but it's still doing some funny things:
May I ask these questions...
1 - The PCB has white traces printed on the top-side of it, and these appear to be actual working traces - is there such a thing as this? It's an early 1990s product. Are the traces carbon or something? One of them was scratched and broken, but there didn't seem to be a way to repair this trace, other than solder a lead onto the pins on the bottom-side which has more standard PCB traces and solder pads.
2 - Each of the four channels has a trace going from this vol/bal/tone/fader board, carrying the audio signal to the output jack connector. This trace was broken on the RR channel. But when I was measuring continuity on these traces, I found that the three channels which still worked all had around 30 ohms between the vol/bal/tone board and the output jack - yet there doesn't appear to be any components or resistors there which would add this 30ohms - the only thing I can think of is that these white traces have more resistance than standard copper.
3 - Is this 30ohm deliberate? And will it change the audio signal considerably for the RR channel which (due to the repair) has 0 ohm in the same place where the other channels have 30 ohms? Or should I put in a 30 ohm resistor to bring the RR channel into line with the others?
The funny things it is doing is: sometimes it sounds like it's mixing left and right channels together - there is a sort of phasing sound. I am wondering if the output channels having different resistances could be making it go slightly haywire? Just a thought.
Many thanks for looking at this, and any thoughts gratefully received.