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I've recently decided to turn an SC-811 from a scrapyard 1995 Volvo 850 into an in-home tape player. I re-worked the wiring harness and got a 13.5 power supply and generally, the unit is working great!
The issue I'm having is getting the backlights to work. From what I can work out, the pins "REOSTAT (+)" and "REOSTAT (-)" are involved in controlling the intensity of the backlights. I've tried ramping up a voltage between these pins and at 14 volts I noticed a very faint light... the PSU I was using only went up to 60 V and at that level, they were lit but still dim. I'd be amazed to learn that voltages greater than 14 are needed to get the lights to max brightness.
Does anyone know what type of signal is expected on the REOSTAT lines? Voltage? Current? Resistance? Nothing I've tried so far seems to work and I don't have the rest of the Volvo to test what these pins are outputting when the car is on.
On this diagram, 11 is labelled TEL, but on the PCB for my 811, these pins are labelled REOSTA(+) and REOSTAT(-) and respectively have a pink and black wire on the harness.
SC-811 Stereo Backlighting
