Let's start with the symptoms.
The major fault with the radio two:
1. Periodically, the screen light up all segments.
Over time, the problem progresses, the screen will light up constantly, and then it all turns into clicks and spontaneous on-off with an inscription on the AUX screen.
2. Off of the segments on the screen.
Over time, it lost more and more segments. Some, after heating the passenger compartment or a pair of fist blows on the dashboard screen starts to operate normally.
We will understand in turn with each of the problems:
The reason for periodic or constant glow of the screen
- the thermal breakdown of the zener diode D783 in the chain of supply 5 volts.
Reason subsequent clicks
- overheating of the linear regulator power audio processor IC712.
How does this happen.
Panasonic engineers incorrectly calculated the ballast resistor R789 zener diode, the zener flows the maximum allowable current, the zener diode is overheated and is its thermal breakdown. Zener diode ceases to give proper reference voltage to the transistor, the fully open and the radio power circuit falls into place 5 7-8 volts. It becomes noticeable in the first place on the screen (it lights). From the same voltage is fed to the radio a lot of things, including a power converter for the audio processor. From high voltage it starts to heat up more, heated up to a certain critical temperature, and it is activated thermal protection that it begins to turn off - include. At the same time we are beginning to hear the applause.
How to treat the problem.
First you need to remove the head unit from the car radio.
Then disassemble the head unit
In the photo marked problem areas \ details:
The picture control voltage written on them control everything renovated.
Change in the zener diode D783 BZX55C5V6 in a glass enclosure with the leads and solder it on these findings away from the transistor. Legs are marked with black top ring to the point, without rings to the bottom left. Trying to look at the original Zener SMD package is stupid idea.
If the screen is not lit continuously, the Zener still not completely burned, and breaks it only at a good warm up. In this case, when checking his multimeter it will look quite serviceable. I would like to change it, it is not necessary to wait for its final combustion.
To reduce the current through the zener change the R789 resistance to any nominal value 200-390 ohms in standard size 0805. I put 390 ohm usually. Just change standing next to a capacitor C784 100mkF * 10B. By heating it dries and loses half capacity. I change to a suitable size with a nominal value of 100mkF * 16B and preferably 105 degrees.
It turns out the following picture:
To change or not the transistor Q784 (2SD1758) here moot and everyone decides for himself the extent of their capabilities.
In principle, the current through the transistor goes to 1A area is half of its maximum, this will not burn it. But setting the transistor to a larger rated current decreases its heat.
If there is no transistor in a suitable housing, it is best not to fence garbage hung on wires from the transistors and leave everything as it is.
For it is desirable to use an air desoldering station.
I for repair sealed his place MJD44H11G transistor with a maximum current of 8A.
But then again, it is not necessarily.
Leave everything as it is, if there is the necessary equipment or the transistor and the city Frankensteins.
The scheme of power we have corrected, regulators have become less warm, but still they are significantly heated. We solve this problem, as elsewhere, - putting up radiators on all that hot.
I use the radiators on the memory chips cards:
They are excellent for our purposes.
Glue them to the thermally conductive adhesive.
I use a two Arctic the Alumina Adhesive , and can Alsil, but one component, in this check when buying whether it is not dried up. Thermal paste, or you can not
use superglue! Thermal Grease poorly kept, and superglue bad conductor of heat. Just do not use the Velcro that goes glued to some radiator factory. She also poorly kept falling off and with good heating. On the mound radiator can fall off and get something close. Only the hot melt!
Search glue and radiators should be in local shops of computer junk.
Clay heatsink on the transistor Q784 and standing next stabilizers IC701, IC712, IC401. Since stabilizers IC701 and IC401 around the little room, and they do not heat strong - I sawed in half and one heat sink glue them half, but at the IC712 necessarily a glue. IC712 most heated, due to its overheating occur and clicks.
The result is the following picture.
Now you can safely put the radio.
During assembly it is necessary not to forget to put a conventional thermal paste
on a large heatsink, which is set to the amplifier transistor 2 and the side of the head unit. At its factory forgot to apply!
Now we assemble everything in reverse order and enjoy operating the radio.
And now briefly to the masters:
Change in the zener diode D783 BZX55C5V6 or any other 5.6 volt 0.5 watt cathode upwards. Change the R789 resistance to any nominal value 200-390 Ohm in 0805.
If possible, change the transistor Q784 to something appropriate to the body with a large current (such as MJD44H11G), if there is no suitable housing - leave as is.
Change the capacitor C784 to the appropriate dimensions and parameters with a temperature of 105 degrees.
Be sure to stick to the hot melt adhesive heatsinks on Q784, IC701, IC712 and IC401. In Q784 and IC712 as possible bigger and taller.
When assembling the amplifier heatsink coat with thermal paste.
If you have not started having problems, but you want to prevent them in the future - change the resistance, seal the radiators on the transistor and stabilizers and the assembly promazhte where necessary, thermal paste and your tape recorder to work happily! It is better to prevent a problem than to treat it.
The reasons for the problems.
Blame fallen off most contact soldering matrix LCD screen to the motherboard. Usually extreme fall off contacts.
Perhaps the plant using fragile lead-free solder may not fully washed flux, perhaps, too lazy to bite off the long ends. But after some time under vibration load brazing destroyed.
To display diagnostics - through diagnostic mode light all segments of the screen (how to do this is described below). If any segments light up - then blame display.
How to treat the problem.
You can buy on the dismantling of the same screen, but the problem of the mass, and sooner or later will come and fur animal to the next screen.
To repair it is necessary to solder all the screen contacts with ordinary lead-containing solder.
In short - it:
1. Remove the triangle over the radio, unscrew the 2 screws beneath the screen.
2. Remove the speedometer up visor.
3. Take out the speedometer itself.
4. Take out the radio screen.
All this business is held by snap, otkovyrivat convenient special plastic spatula to remove the skin.
After removing the screen from the machine screen itself from black plastic and remove the white back cover closing costs. Everything is fixed as by snap.
Before soldering it is desirable to wash with soldering varnish solvent place, so soldering will be much easier.
After all welds are not in a hurry to collect. Connect the screen to the radio and check the result.
For ignition of the screen characters:
1. Turn on the radio.
2. When it is on, simultaneously press and hold the "1" and "6" buttons and holding them to press the power button. "DIAG" sign appears on the screen. If it is not lit up - turn the tape recorder and try again. Main synchronously press "1" and "6".
3. Press the "3" button is switched on and off all display segments.
4. To exit the diagnostic mode Hit the mute button radio.
When all segments lighted stir a finger contact tails. If nothing is lost - all soldered well, you can still collect and set back. If you are lost - propaivaem again.
Sorry for my language, my 1st language is GERMAN, 2nd Lithuanian, 3RD Russian, and 4th is ENGLISH