Car Radio Repair: Can you explain this? I can't..
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- čas přidán 23. 10. 2020
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docs.google.com/forms/d/e/1FA... While taking a deep dive into this radio failure, I noticed an issue with the PCB ground.. What is going on here?!?
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I performed board level repairs on OEM automobile radios for 35 years and have seen this issue a number of times. That component is likely not a zener diode. It is just a standard diode with a current rating above the value of the external radio fuse. Its only purpose is to prevent reverse polarity entering the board which would cause catastrophic failure. Under normal main power the diode is reverse biased and does nothing. It only conducts when reverse polarity is applied to the vehicle. Under that circumstance only the radio fuse should fail and briefly the maximum reverse voltage getting into the board is limited to the forward bias voltage of the protection diode p/n junction, about .7v.
I have seen these diodes short mostly at car dealerships where the vehicles sit a lot and the batteries go dead. The cause of failure then is improper reverse application of a jumper pack to start the car. This error is only supposed to pop the radio fuse but at times the protection diode shorts as well. The good news is the board is usually still ok. Once the diode is removed, the radio should work. I would install a good diode though for the protection it provides.
For some reason this error never seems to affect the ECM.
@stephencolsten1736 I have 2019 RAM radio that has no power. Where do you suggest I look? Could you help with diagnostics?
Most likely that second ground you're testing to is has a diode somewhere in the circuit that isolates it only to that top left mounting point. The easiest thing to do if you're gonna get serious about fixing shorts is just use a thermal camera and inject voltage with a limited amount of current so you dont completely toast the board.
Really enjoy your vids .currently going to school for biomed
Excellent! Where are you going to school? Let me know if you have any questions.
Measure the resistance. If the resistance is above a certain threshold it won't beep and it could be hitting that threshold with one continuity check but not with the other.
Great video
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Hi. I contacted my radio wrongly. A smoke coming from the radio. It won’t turned on. I find a burned smd T4. But still no power. What should else I should look at. Thank you
Also, there is a accessory fuse or a radio fuse in the car fuseblock
Can it be a TVS diode ? A TVS diode is placed in parallel with the positive and negative.
Below the specific voltage, they are "open", and once they reach there treshold voltage, they begin to conduct to clamp down the voltage.
You can leave temporary the diode out, and supply a low voltage like 3a5V (and limit the current at your lab supply) , at the pads where the diode was soldered, and then look how much amp the board draws. If the diode was short, the voltage over the diode can't be very high, so i don't think that there is further damage to the board.
Yes it is. SM6A27
I need to wait until Monday to access my power supply. (I took my whole soldering setup into work)
@@BetterBiomedChannel the minimum breakdown voltage of a SM6A27 TVS diode is between 24 to 30V.
So it seems that you have got a huge surge to blowup that diode, and the diode has protected your radio.
Is this radio installed in a truck or camper with 2x 12V batteries ?
If not, it's best to check the battery voltage when the car is running, to see if the voltage is not abnormal high (more then 14,5V) due a bad voltageregulator on the alternator.
Another cause can be when you recently used jumper cables or a booster when the car battery was flat, that causes a surge when disconnecting.
This is a bit late but you should just swap the dmm leads...that's all..i think by replacing the zd would fix it..good to know..thanks.
Radio car integrated circuit board repair 📻📠📺☢️🎧
I'm sorry buddy, I can't understand the corners puzzle,,
I love such videos where a technician stuck as i.
ih excuse me i have an acustar car stereo af 1991 serial 21210824 it d'ont run me i have a schematic diagram ?
Sorry, the only way you'll probably get a schematic is contact the manufacturer directly. otherwise, if the stereo will not turn on, check for fuses or transistors near where the DC power enters the main circuit board / power supply.
@@BetterBiomedChannel Tanks a lot for the answer.
@@BetterBiomedChanneltanks a lot for answer a alreary ceck the fuse but it is good.
Thats a thermal disapation pad it uses solder vs thermal paste
Rockford amplifiers I've worked on you need to directly short and solder the FETs back to pcb pads.
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