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old car stereo LCD backlight

die.nard

Jun 28, 2023
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Hi!

I want to put a period-correct car stereo into my car.


uc


I got this Sony XR-C33R in a local scrapyard, and after some cleaning I tested it. Everything works, cassette deck included, but the display backlight is dead, which makes impossible to read anything under the sun.

Here some photos of the board:

FRONT:
uc



uc


uc


uc


REAR:
uc


uc


uc


uc


I'm not very familiar with printed circuits, I've just done some small repairs on analogic things before, so please forgive me if I ask you something nonsense.

My questions are two:

1) where should I look for backlight LEDs? The display looks like a single piece that can't be disassembled

2) all the buttons seems to have both green and amber microleds. Is it possible to "hardware switch" from green to amber light?

Thank you so much!
 

Delta Prime

Jul 29, 2020
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I'm not very familiar with printed circuits, I've just done some small repairs on analogic things before, so please forgive me if I ask you something nonsense
You are officially forgiven!
You're lucky, I speak fluent nonsense.
I have no time right now but for others you're going to like this!!!
 

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  • sony_xr-c33r.pdf
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kellys_eye

Jun 25, 2010
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You have to remove the LCD 'module' to access the back lights. They are standard (if not micro-miniature) filament lamps. Finding replacements won't be easy but the opportunity to change them to LEDs (a colour of your choosing too) has to make it worthwhile.

IIRC such LCDs have the lamps right up against the glass, under the metal shield.
 

Bluejets

Oct 5, 2014
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where should I look for backlight LEDs? The display looks like a single piece that can't be disassembled
The latter would be normal manufacturing process being from auto which is subject to an amount of vibration.
The LED itself could be as many are in LCD displays, located at one end of the readout.
Leds such as this rarely fail and it may be connection problems given the number of vias visible on the board and the age of the device.

Perhaps time to think along lines of replacing the head section with something like this............

https://www.ebay.com.au/itm/193515230629
 

Delta Prime

Jul 29, 2020
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Yes Amber and green LEDs as shown in the schematic along with the pilot lights .You must be an intermediate soldering iron aficionado. Along with proficiency with an multimeter with very thin needle like probes.
All the information is here in the schematic. I'd be happy to accommodate (Guide) you in your Period Correct Car Radio endeavors.
Regards.. Delta Prime.

Screenshot_20230628_161650.jpg
 
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Delta Prime

Jul 29, 2020
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If you're unfamiliar with reading schematics that is okay you may be able to correlate the component designations the White print called solder mask on the PCB the correlation between the schematic components identification and the actual location of these components on the PCB itself. And yes we can make all Amber LEDs illuminate.I could trace out the components on the
schematic that correlates with the associated photos component
location of interest. If you'd like.
 

kellys_eye

Jun 25, 2010
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The LED colour is 'set' during manufacture - the schematic shows the optional colour(s) and the resistors that must be fitted to make them work but there is no real opportunity to alter the colour unless you want to replace all the LEDs and change the fitted resistor values.
 

Delta Prime

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but there is no real opportunity to alter the colour unless you want to replace all the LEDs and change the fitted resistor values
This is partially correct the opportunity is definitely real.
You are fortunate that the opportunity presents itself but this is all dependent on your skill set.
If you embark on this journey you be able to change the color of the LEDs to any hue you wish. In fact with the simple addition he or she will be able to choose any color LEDs even multiple colors with the switch of a button to set the mood when putting in your favorite music mix tape.
-Regards... "DP" ;)
 
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kellys_eye

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Rather than 'make work' and discuss the change of colour it would be prudent to fix the initial issue of backlight loss and go from there. It's often easy to talk/consider changing the colour but quite difficult for the uninitiated and you are likely to not even notice or consider the manufacturers choice after a while.

As long as it works....... leave it alone (or, in electronic parlance - if it ain't fixed, don't break it)
 

Delta Prime

Jul 29, 2020
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As long as it works....... leave it alone (or, in electronic parlance - if it ain't fixed, don't break it)
Sound advice.
Ain't... Ain't a word so don't say ain't.
-Regards Delta Prime
 
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kellys_eye

Jun 25, 2010
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Ain't... Ain't a word so don't say ain't. You've just been DP'd

From Cambridge English Dictionary.......

ain't
not standard
UK

short form of am not, is not, are not, has not, or have not:
He ain't going.
"Can I have a cigarette?" "I ain't got none left."

--------------------------

You've just been buuuuurned..........
 
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Delta Prime

Jul 29, 2020
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Sound advice.
Ain't... Ain't a word so don't say ain't.
-Regards Delta Prime
I'm fireproof. And quotes can easily be edited by those of us who are unscrupulous.
Example.
From Cambridge English Dictionary.......

ain't
not standard the way you put it good sir.
UK

short form of am not competent, is not relevant, are not as wise as you are, has not got a shoulder to cry on, or have not the grit to say I'm sorry:
He ain't going to fall for my shenanigans.
"Can I have a cigarette?" "I ain't got none left."

--------------------------

You've just been buuuuurned..........
 

die.nard

Jun 28, 2023
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I have no time right now but for others you're going to like this!!!
Thank you! This will be gold as soon as I'll be able to understand it hahaha

Leds such as this rarely fail and it may be connection problems given the number of vias visible on the board and the age of the device.
You must be an intermediate soldering iron aficionado.
One thing at a time. Before dismantling the metal shild that protect the LCD, I want to check all connections and components in the circuit of back lights.

Looking at p.31 of the pdf, IC901, from pin 62, 63, 64, start a circuit that goes to LCD things, I think. In the following photo, what are PL901, 902 (A)? Am I looking in the right direction? Also CE, DATA e CLK (B)... are related to back light?

If I'm following the right path I suppose I have to check (visually) pin 62/63/64 connections, trace integrity and (with a multimeter) R954 R955 R956 resistances (I've found them all on the board), right?
Immagine.jpg

Thank you so much!
 

kellys_eye

Jun 25, 2010
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I'm fireproof. And quotes can easily be edited by those of us who are unscrupulous.
Any editing I do is for spelling and/or clarification, nothing else.

Although the word may be 'non standard' it is in general use and that the Cambridge Dictionary includes it gives it some legitimacy. But this really isn't a place to discuss language. If you find the word objectionable then please feel free to ignore it.
 

Bluejets

Oct 5, 2014
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"I ain't got none left."
Bit off topic I know but.....Ooops....double negative...so you DO have some left then...???

As for the radio, same as I said before but you might try gving all the selector switches a good drink of contact cleaner of your choice.(I use CRC or WD40)
A radio this age is bound to have dodgy contacts somewhere and electronics are usually fairly reliable.
 
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Delta Prime

Jul 29, 2020
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Without applying power to your unit, conduct the following tests.
With digital multimeter put it on the lowest setting ohms resistance do not use continuity no beeping.
While in resistance setting touch your test leads together make a note of the resistance of your test leads. Check the connector blue line and arrows that's your ground pins 2, 4 ,and 15. You should see a resistance on your meter at any two points you check a little higher than your previously noted resistance of your test leads if not then that ground line is open meaning there's a disconnect.
Still do not apply power check pin 13 to the pilot light PL 901. See if there's continuity meaning there is a resistance a little higher than the noted resistance of the test leads at those two points.The red arrow pointing towards b+ by the blue arrow that points to pin 15 was a mistake disregard that red arrow pointing down. sorry for confusing you.
Those ugly green arrows corresponds to the backlight pilot light see the numbers how they correlate with each other.


Screenshot_20230629_171341_1688084950392.png
 
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Delta Prime

Jul 29, 2020
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Looking at p.31 of the pdf, IC901, from pin 62, 63, 64, start a circuit that goes to LCD things, I think. In the following photo, what are PL901, 902 (A)? Am I looking in the right direction? Also CE, DATA e CLK (B)... are related to back light?
(B)No those are related to the display characters to set your clock .
(A) PL is short for Pilot Light. The ugly green arrows shows the relationship
 

Delta Prime

Jul 29, 2020
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PL 901 PL 902 there is no polarity meaning no positive no negative. It's just a little wire inside that glows to put it simply. Also since they are in series with each other.One after another I believe they may be 6 volt pilot lights cuz the voltage will add 6 volts + 6 volts =12 volt when you put them in series. one may still be good because if one is bad or the filament is broken there's no longer a closed path to the power source it is now open.so be careful when you desolder them. the LED the other hand
Are different story we'll get to those later.
 
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Delta Prime

Jul 29, 2020
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they may be 6 volt pilot lights cuz the voltage will add 6 volts + 6 volts =12 volt
To clarify the schematic as you'll see it shows B+ that's shorthand for battery positive. B+(Battery positive) commonly pronounced B plus = 12Volts.
GND is shorthand for(Ground) or B- (Battery negative) commonly pronounced B minus. B minus = 0Volts. So we will be on the same page we'll be referring the voltages as stated in the schematics B+ and GND . B plus and Ground.
 
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