I just returned from dead very nice CD/MP3 player. After hooking it up, I noticed that it is not giving +12V output to power antenna/amps, but there is special pin in harness for that. Opened it again and... this pin is not connected to anything 
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I found where I can splice to +8V internally (which can be on/off from headunit). I need chematic probably based on FET, or PNP of bulletproof relay (actually, simple relay will work fine, just don't have one that clicks on 8V) to make that +12V output switchable by +8 low power source. That output should sirvive accidental connection with +12 and ground... Thank you!!!
.I found where I can splice to +8V internally (which can be on/off from headunit). I need chematic probably based on FET, or PNP of bulletproof relay (actually, simple relay will work fine, just don't have one that clicks on 8V) to make that +12V output switchable by +8 low power source. That output should sirvive accidental connection with +12 and ground... Thank you!!!
This should work. The 4148 can be replaced by virtually any diode. It's not necessary but it protects the input circuit in case the FET shorts. If you want added protection of the drive circuit, insert a 1k ohm resistor in series with the diode.
The 8v will drive the FET on. The FET will ground the relay coil.
The 8v will drive the FET on. The FET will ground the relay coil.
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