Maybe you didn't supplied all required voltages to radio ,previously cpu output had 5 volts ,now don't .Or cpu is thinking it don't need to turn on radio . Try to measure resistance from cpu output to gnd ,in two scenarios , when radio is unpowered and when you supplying radio 12 volts .If cpu holds low level on its output ,you will have 43.6k from output to gnd when unpowered and about 20-300 ohms to gnd when cpu has its 5 volts .
Power seems to be how I've previously hooked it up.
Jeez you're clever...
Resistance To chassis
unpowered 44.7k
powered 19.5
Going to have to remove my home made transistor aren't I?
Out of interest...
The start botton gets 33.1mV
When I push it gets 41mV
The DVD eject button gets 5.3v and goes to 3mV when pushed but I think that was like that earlier.
Jeez you're clever...
Resistance To chassis
unpowered 44.7k
powered 19.5
Going to have to remove my home made transistor aren't I?
Out of interest...
The start botton gets 33.1mV
When I push it gets 41mV
The DVD eject button gets 5.3v and goes to 3mV when pushed but I think that was like that earlier.
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19.5 kiloohms or ohms to gnd when powered ?
Start button i guees is connected to LC chip on front panel ? Maybe it has key scanning ,so low voltage can mean nothing ,there may be short pulses with 5v level ,and long pause , so voltmetter measures average value. Oscilloscope would help to digging deeper.
Short pulses or digital signals sometimes can't be distinguished from dc low value voltage with simple multimeter .
DVD eject button seems to be connected somehow different than start button ,or start button simply has no voltage .As we remember ,we still have no 5 volts from Q701 pnp transistor ,going to front panel.
Start button i guees is connected to LC chip on front panel ? Maybe it has key scanning ,so low voltage can mean nothing ,there may be short pulses with 5v level ,and long pause , so voltmetter measures average value. Oscilloscope would help to digging deeper.
Short pulses or digital signals sometimes can't be distinguished from dc low value voltage with simple multimeter .
DVD eject button seems to be connected somehow different than start button ,or start button simply has no voltage .As we remember ,we still have no 5 volts from Q701 pnp transistor ,going to front panel.
19.5 ohms. not kohms
Yes start button is connected.to the lc on the front panel.
Yes DVD is getting power from another line in the mainboard/front panel connector.
I did try and do continuity through the cpu on the pin that was giving the 5 volts because I had traced the power source back to that voltage divider previosly... Maybe I killed it.
Yes start button is connected.to the lc on the front panel.
Yes DVD is getting power from another line in the mainboard/front panel connector.
I did try and do continuity through the cpu on the pin that was giving the 5 volts because I had traced the power source back to that voltage divider previosly... Maybe I killed it.
Question now is why cpu no longer trying to turn on radio. Maybe some trace broken ,or you turned radio off and need to somehow try turn it on .Is there no reset button with hole for a needle ?
Previous problem was the power switch Q702 Q701 not working as should ,at least as i understanded voltages .But now no command to turn on from cpu .Also as i remember, you have tested to turn on q701,with 1k resistor from its base(pin1) to gnd ,and 5v was there on Collector output to front panel .
Previous problem was the power switch Q702 Q701 not working as should ,at least as i understanded voltages .But now no command to turn on from cpu .Also as i remember, you have tested to turn on q701,with 1k resistor from its base(pin1) to gnd ,and 5v was there on Collector output to front panel .
You mentioned DVD eject button ,which goes somewhere else and has 5 volts.Maybe processor now is in sleep state,but can accept a disk.
Can you connect a cd module in place ,and try to put a disk ,will it respond ? Can't remember exactly ,how other radios responds to disk inserting when in off state .You saying 12 volts to radio going the same way as earlier ,can you verify this ? Try to measure 12v on power amplifiers supply pins ,mostly there is a big electrolytic capacitor near amplifier chip ,you can measure voltage on it . Car radios have 2 or more power supply wires ,on only one voltage must be present always to keep radio stations memory and settings ,but radio will never turn on without other voltages ,because simply components like amplifier or display will get no supply voltages .
But BA4900 ic has a single 12v input ,so there is a some question to - pin7 of BA4900 goes to constant +12v or to IGN / ACC 12v input pin on power connector ? If it goes to constant , try to leave 12v only on constant 12v input ,leave other power inputs unpowered for some time, and then supply them again ,but dont remove power on const 12v, simulating ignition key in car .Maybe that will wake up cpu.
Do you have power switch ,can be rated few amperes,and can wire it to disconnecting 12v to other power supply pin .I mean you supplying 12volts from power supply to more than one pin on connector , and the same is done in the car .
Can you connect a cd module in place ,and try to put a disk ,will it respond ? Can't remember exactly ,how other radios responds to disk inserting when in off state .You saying 12 volts to radio going the same way as earlier ,can you verify this ? Try to measure 12v on power amplifiers supply pins ,mostly there is a big electrolytic capacitor near amplifier chip ,you can measure voltage on it . Car radios have 2 or more power supply wires ,on only one voltage must be present always to keep radio stations memory and settings ,but radio will never turn on without other voltages ,because simply components like amplifier or display will get no supply voltages .
But BA4900 ic has a single 12v input ,so there is a some question to - pin7 of BA4900 goes to constant +12v or to IGN / ACC 12v input pin on power connector ? If it goes to constant , try to leave 12v only on constant 12v input ,leave other power inputs unpowered for some time, and then supply them again ,but dont remove power on const 12v, simulating ignition key in car .Maybe that will wake up cpu.
Do you have power switch ,can be rated few amperes,and can wire it to disconnecting 12v to other power supply pin .I mean you supplying 12volts from power supply to more than one pin on connector , and the same is done in the car .
11.92v going to two pins on the power connector. (on page 1 of this thread pin 3 and pin 4) and Ground connected to pin7 of the power connector
Also pin7 (VCC - 12v) of power amp BA4900 ic has 11.92v Pin 5(VDD output) is 5.91v
It wouldn't take a CD in. Good thought though wish I had of thought of that one.
Just shorted my power supply trying to re-connect the ignition power after having it disconnected for a few mins. So may have to fix that if it doesn't come back on after a small rest.
Also pin7 (VCC - 12v) of power amp BA4900 ic has 11.92v Pin 5(VDD output) is 5.91v
It wouldn't take a CD in. Good thought though wish I had of thought of that one.
Just shorted my power supply trying to re-connect the ignition power after having it disconnected for a few mins. So may have to fix that if it doesn't come back on after a small rest.
Power supply back up.
Removed pin4 the ignition power for a bit then readded and it didn't wake up the power form the cpu.
Tried with power only going to pin3 (vcc) it did not wake up CPU power. 5v on collector pad where 2622(q702) use to be.
Tried with power only going to pin4 (ignition) (disconnected pin3) it did not wake up CPU power. only had 0.599v on collector pad where 2622(q702) use to be.
Removed pin4 the ignition power for a bit then readded and it didn't wake up the power form the cpu.
Tried with power only going to pin3 (vcc) it did not wake up CPU power. 5v on collector pad where 2622(q702) use to be.
Tried with power only going to pin4 (ignition) (disconnected pin3) it did not wake up CPU power. only had 0.599v on collector pad where 2622(q702) use to be.
BA4900 is not power amp , its power supply regulator ic .
I mean audio power amplifier ,which outputs goes to speakers connector pins. That must be big ic on big heatsink on the back.
Some components are connected from switched 12 volts (ign / acc),so if amplifier has 12v ,we can assume they have supply too .Also some amplifier ic's have diagnostic protection output pin ,which goes to cpu input ,and can block radio operating .In example if you shorted speakers wires ,and ic detects that and not burns,but prevents turn-on.
Also i have seen power amp ic shorted its supply pins ,and main trace burned out ,gnd or vcc , so somewhere on the board instaed of gnd potential i've had some voltage .
I mean audio power amplifier ,which outputs goes to speakers connector pins. That must be big ic on big heatsink on the back.
Some components are connected from switched 12 volts (ign / acc),so if amplifier has 12v ,we can assume they have supply too .Also some amplifier ic's have diagnostic protection output pin ,which goes to cpu input ,and can block radio operating .In example if you shorted speakers wires ,and ic detects that and not burns,but prevents turn-on.
Also i have seen power amp ic shorted its supply pins ,and main trace burned out ,gnd or vcc , so somewhere on the board instaed of gnd potential i've had some voltage .
Oh I see sorry...
Just when I think we are coming to the end we hit a new area and the interest sparks up again
There is one pin on the AMP ic with voltage
The cap is reading 11.92v (incorrect in the pic - missed the 9 out)
It has a low ESR reading onboard of about 0.06 for a 2200mf 16v
There is 11.92v going through that coil
There is a diode that is connected to the 12v input trace in the opposite direction that I would have thought, so guessing some kind of feedback?
It reads 0.33v in both directions.
I've been caught out a lot with diodes reading differently when in circuit and zenner diodes having readings both ways. So not sure about this one.
Just when I think we are coming to the end we hit a new area and the interest sparks up again
There is one pin on the AMP ic with voltage
The cap is reading 11.92v (incorrect in the pic - missed the 9 out)
It has a low ESR reading onboard of about 0.06 for a 2200mf 16v
There is 11.92v going through that coil
There is a diode that is connected to the 12v input trace in the opposite direction that I would have thought, so guessing some kind of feedback?
It reads 0.33v in both directions.
I've been caught out a lot with diodes reading differently when in circuit and zenner diodes having readings both ways. So not sure about this one.
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This diode blows fuse ,shorts power supply ,if somehow 12 volts gets in wrong polarity ,plus to ground.But it should not have similar readings in both directions.I think diode is ok ,just capacitor charging and because of this you have incorrect readings .Diodes in circuit can measure wrong ,need to desolder if unsure ,or use dmm ,supplying only up to 1 volts in diode mode ,and less than 0,5v in resistor mode,also watch for readings ,if they are not constant ,maybe capacitor is charging somewhere .Amplifier ic numbers not visible ? Not worth to look at datasheet for presence of diagnostic output pin .From photo i can count 25 pins ,and as i remember ,some ic's have this output pin ,in example tda7385 .I'm just trying to somehow help you ,find something what is not as it should be .
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