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WesleyNL

LCA90177 a JVC TV Audio Board

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Posted · Original PosterOP

hey guys i disambled a old plasma tv and came across this audio board, now i have a  question who is this tech tha can tell me where audio input is,

 

 

audio 1.jpg

audio 2.jpg

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i would guess those connectors at the bottom of the board (on the first picture) cause i would assume SR and SL is stereo left and right, but dont take my word for it, i have basically no experience im just going by deduction

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Posted · Original PosterOP

i forgot to mention that,

those empty conectors are indeed speaker output, left/right and middle connector is left and right bass

 

i have the speakers here, it is like a sound bar that i took appart from the tv

speakers.png

 

the thing is i try to find out if i can ge sound out of this board,

but it have those hard wired connectors on the left side and a 3 pin in the middle,

i tried to power it up, but no sound when i connect a 3.5" to that 3 pin conector,

i don't hope this amp is like a car amp and use a remote to turn on,

since it have no leds or anything i don't know if it actualy turns on eitherso i am hoping to find someone that can help me with this

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It would help if you say the exact TV brand and model number ... i suppose it's JVC but what's the model.

 

The reason is because we may have a service manual or some schematics for that model of TV or for that series of TVs and those service manuals may include schematics for the audio board, or may include descriptions of connectors.

 

Anyway, yeah, that's an audio board... the big chip in the center on heatsink is the amplifier chip, IC6621 , and if you unscrew those screws and clean the thermal paste, you may see the model of the amplifier chip and then you can get the datasheet for it and from there maybe you can follow the pinout and discover the inputs and maximum voltage supported and so on.  (that TH labeled chip on heatsink is thermistor, if it gets too hot it acts like a fuse and shuts down the board to protect the amplifier chip)

 

SL , SR , CB  are kinda obvious, the outputs ... speaker left, speaker right, center/bass

The C connector is probably the input ... all those blue capacitors are for decoupling and various things, and on the bottom in that area is that JRC chip IC6521 is some preamplifier / opamp etc

 

There may be enable/standby pin in a header ... when connected to ground or some voltage (3.3v , 5v) the amplifier is enabled. 

 

there may be some other pin in the header, which may need a pwm signal or some voltage within a range (ex .. 0.5v ... 3.3v = 0%..100% volume or a resistor must be set between two pins in the header to set the volume.

 

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ebay page said this board is in jvc vm-42wx84  so found service manual for that one https://www.manualslib.com/manual/1335797/Jvc-Pd-42wx84sj.html

 

see page 90 (2-49)

kinda bad luck ... that jrc chip is configured through i2c or spi so probably need some arduino and set of commands to enable and configure it

 

image.png.d5addf8fc516c08283cc51b539d27758.png

 

 

image.png.983eaa803d7e3dc5e66cf210114d74f6.png

image.png.c0d05040147b8fa6a6bd230815bab17b.png

 

image.png.47ed40207a7556a24ec61b7767032bd8.png

 

image.png.40c9d824dd4e70eccea324b2b0414c7b.png

 

so A and B are power ... A is 12v , B is ... if the chip is ta8270ha like datasheet says, probably 12..16v

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Posted · Original PosterOP
10 hours ago, mariushm said:

It would help if you say the exact TV brand and model number ... i suppose it's JVC but what's the model.

 

The reason is because we may have a service manual or some schematics for that model of TV or for that series of TVs and those service manuals may include schematics for the audio board, or may include descriptions of connectors.

 

Anyway, yeah, that's an audio board... the big chip in the center on heatsink is the amplifier chip, IC6621 , and if you unscrew those screws and clean the thermal paste, you may see the model of the amplifier chip and then you can get the datasheet for it and from there maybe you can follow the pinout and discover the inputs and maximum voltage supported and so on.  (that TH labeled chip on heatsink is thermistor, if it gets too hot it acts like a fuse and shuts down the board to protect the amplifier chip)

 

SL , SR , CB  are kinda obvious, the outputs ... speaker left, speaker right, center/bass

The C connector is probably the input ... all those blue capacitors are for decoupling and various things, and on the bottom in that area is that JRC chip IC6521 is some preamplifier / opamp etc

 

There may be enable/standby pin in a header ... when connected to ground or some voltage (3.3v , 5v) the amplifier is enabled. 

 

there may be some other pin in the header, which may need a pwm signal or some voltage within a range (ex .. 0.5v ... 3.3v = 0%..100% volume or a resistor must be set between two pins in the header to set the volume.

 

This was that tv that stopped working

 

Also the amp is visible i k ow that the chip on heatsink is the amp , its a ta8270h

20200518_172336.jpg

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Posted · Original PosterOP
10 hours ago, mariushm said:

ebay page said this board is in jvc vm-42wx84  so found service manual for that one https://www.manualslib.com/manual/1335797/Jvc-Pd-42wx84sj.html

 

see page 90 (2-49)

kinda bad luck ... that jrc chip is configured through i2c or spi so probably need some arduino and set of commands to enable and configure it

 

image.png.d5addf8fc516c08283cc51b539d27758.png

 

 

image.png.983eaa803d7e3dc5e66cf210114d74f6.png

image.png.c0d05040147b8fa6a6bd230815bab17b.png

 

image.png.47ed40207a7556a24ec61b7767032bd8.png

 

image.png.40c9d824dd4e70eccea324b2b0414c7b.png

 

so A and B are power ... A is 12v , B is ... if the chip is ta8270ha like datasheet says, probably 12..16v

So it need 2x 12v

 

B is 12v says on the psu 

 

So a is 12v to ? I need to connect those 2 together to power it up

 

  arduino ,well i have a teensy witch i use for argb but i am not pro in config it

 

As you can see where the amp was connected to ,the large2 pin conn on bottom right side of front

20200519_193435.jpg

 

20200519_193439.jpg

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Posted · Original PosterOP

Guess i just remove the amp transistor and use that,

 

sadly i wont be enjoy the probaly balanced  audio of the board

 

There some youtubes how to use  and connect these transistor amps

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You could probably work around that NRJ chip (which must be configured to work)

Connect your stereo input directly on two inputs of the chip, and find the enable  / standby / mute pins of the amplifier chip and see how they turn on/off - usually by tying them to ground through a resistor, or connecting to some voltage above some threshold.

 

I didn't have time yesterday to go in detail because it was almost 2 AM and I had to wake up at 6:30 AM to go to work... but I can spare a few minutes now

 

Looking at the datasheet .. there's standby, out , mute pins ... see datasheet page 2,3 and onwards

 

image.png.eff7417a38f3b965bf1f26ec69556dff.png

 

So put more than 3v on pin 4  ( usually 5v is common, but this chip seems to accept 12v as well) and the chip powers on and amplifies what's on its inputs and puts the amplified signal on output.

So maybe you could cut the trace going to this pin , and solder your own wire to the pin ... and you can have a on/off switch to turn on the amplifier.

 

image.png.99467f5255cc3454719d60b1f149ae0f.png

 

image.png.e57d68ccadb8ac77e3b73586fb073008.png

 

Resistor should be 4.7 kOhm - 10 kOhm , capacitor is ceramic 1 uF (very common) ... connect both to ground (negative of power supply) to mute the amplifier temporarily)

 

Your audio channel inputs are pins 11, 12, 14,15 (with a 0.22uF or something around that value) in series with the input for decoupling purposes. The negative of each input goes to pre-gnd if I'm not mistaken, pin 13 :

 

image.png.c4963f9baf25b553eb1b23dcf1253b4d.png

 

 

 

So yeah you could try it out ... power on both connectors to 12v , and you have a 4 channel amplifier.

Keep in mind that this is low power, it's not that great... with 12v input, datasheet says around 15w (maybe 20w with 16v input) with 4 ohm speakers on all drives if you want to keep distortion below 1% :

 

image.png.8fb9a8634ededf50b1d4038a9a119043.png

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Posted · Original PosterOP
On 5/20/2020 at 6:08 PM, mariushm said:

You could probably work around that NRJ chip (which must be configured to work)

Connect your stereo input directly on two inputs of the chip, and find the enable  / standby / mute pins of the amplifier chip and see how they turn on/off - usually by tying them to ground through a resistor, or connecting to some voltage above some threshold.

 

I didn't have time yesterday to go in detail because it was almost 2 AM and I had to wake up at 6:30 AM to go to work... but I can spare a few minutes now

 

Looking at the datasheet .. there's standby, out , mute pins ... see datasheet page 2,3 and onwards

 

image.png.eff7417a38f3b965bf1f26ec69556dff.png

 

So put more than 3v on pin 4  ( usually 5v is common, but this chip seems to accept 12v as well) and the chip powers on and amplifies what's on its inputs and puts the amplified signal on output.

So maybe you could cut the trace going to this pin , and solder your own wire to the pin ... and you can have a on/off switch to turn on the amplifier.

 

image.png.99467f5255cc3454719d60b1f149ae0f.png

 

image.png.e57d68ccadb8ac77e3b73586fb073008.png

 

Resistor should be 4.7 kOhm - 10 kOhm , capacitor is ceramic 1 uF (very common) ... connect both to ground (negative of power supply) to mute the amplifier temporarily)

 

Your audio channel inputs are pins 11, 12, 14,15 (with a 0.22uF or something around that value) in series with the input for decoupling purposes. The negative of each input goes to pre-gnd if I'm not mistaken, pin 13 :

 

image.png.c4963f9baf25b553eb1b23dcf1253b4d.png

 

 

 

So yeah you could try it out ... power on both connectors to 12v , and you have a 4 channel amplifier.

Keep in mind that this is low power, it's not that great... with 12v input, datasheet says around 15w (maybe 20w with 16v input) with 4 ohm speakers on all drives if you want to keep distortion below 1% :

 

image.png.8fb9a8634ededf50b1d4038a9a119043.png

i tried out powering on by using both power lines connected to the adapter of 12v4a but nothing happends , no audio still

 

so something is still turned off i guess

 

by chip you mean the ta8270h?

kind of lost what you explained

 

cut the trace, and put a switch between that trace ?

isn't that the same as put a switch on pin 4 without cutting the trace?

 

i have to connect Conector A and B together to same adapter ,

connect the grount of adapter to the mute pin 4 if i understand correctly ?

 

and i know 12v aint enough to full power the amp , but i use a adapter of 12v 4ah


the speakers

CB or well LF Bass are 15w 8ohm each

SR/SL are 10w 8ohm each

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