TDK S-60 low volume on one side

[AlenZGB]

I try to fix low volume on one side. I tough it could be LM4752T, but after replacement
still, low volume on one side. I change few wierd caps but still nothing.
Any help with that?

Sorry for posting links, dont know why but upoad wont work.
Green connector is the problem. always low volume, hardly to hear when i turn to max.
With blue, thats the caps i replace, and i replace LM4752T also.

EDIT:

sorry for messy soldering, didnt clean it run out of alcohol.

 

[bertus]

Hello,

When you reduce the size of the pictures to about 300 kB, the uploads will work.

Bertus

 

[davenn]

Green connector is the problem. always low volume, hardly to hear when i turn to max.
With blue, thats the caps i replace, and i replace LM4752T also.

I assume the 2 connectors circled in green go to the speakers ?
if not where to ?

I also assume the 2 smaller connectors on the right side (each 3 pin) are audio input from another stage ?

 

[AlenZGB]

I assume the 2 connectors circled in green go to the speakers ?
if not where to ?

I also assume the 2 smaller connectors on the right side (each 3 pin) are audio input from another stage ?

i took picture of other side. 2pin connector that has black and white wire is the one that originally goes to that green circled connector, and it goes to 3.5mm jack and on speaker.

Those 2 connectors are from the lets say control panel, turn the volume up and down and 3.5 input jack from PC or any other source of music. One is 3 pin and the other one is 2 pin.

 

[Tha fios agaibh]

I would Check the diodes and then swap ic502 with ic504 which are likely opamps.

If problem follows to opposite side you know it's bad.

 

[Harald Kapp]

Also make sure it is niot the speaker itself that causes the issue. Swap speakers to check this

 

[AlenZGB]

I would Check the diodes and then swap ic502 with ic504 which are likely opamps.

If problem follows to opposite side you know it's bad.

IC502 i did change with new one.
IC 502 and IC 504 are not interchangable, one has 7 pins and other has 5 pins.
As far as i check on the web, the one i change (LM4752T) is for the speakers, and other one(LM1875T) is just for sub.
Maybe im wrong. Correct me if i do

Also make sure it is niot the speaker itself that causes the issue. Swap speakers to check this

I did swap speakers, i did even swap the connectors that goes from board to 3.5 mm jack.
no luck.

 

[Tha fios agaibh]

"Not interchangeable"

Sorry, only saw 4 leads at first.
Looks like the lm1875 is for the sub and the lm4752 is the amp ic.
Compare input signals feed with similar input sources (left/right) on pins 2 and 6.(Voltage with respect to ground)

If similar, you should have similar outputs on pins 1(left) and 7(right)

 

[AlenZGB]

"Not interchangeable"

Sorry, only saw 4 leads at first.
Looks like the lm1875 is for the sub and the lm4752 is the amp ic.
Compare input signals feed with similar input sources (left/right) on pins 2 and 6.(Voltage with respect to ground)

If similar, you should have similar outputs on pins 1(left) and 7(right)

I measure, voltages on both sides are identical,
INA and INB is around 4.6V (pin 2 and 6),OUTA and OUTB is around 11.4V (pin 1 and 7).

And one thing i noticed, maybe its normal, not sure. OPAMP that is for speakers left and right is cold.
and other one for sub is around 50C, even if sub is not connected. it has big heatsing but i need to remove it to measure.

According to measurement it should work on both sides. Im kinda confused now more then before.

 

[Tha fios agaibh]

Are you using AC scale on your meter?
Also check the caps next to your green circled connector.
50c does sound rather warm but its an independent output which should be unrelated to L R amp section.
You could try using an audio probe (Google search circuit) or just use a speaker with a .01uf cap in series to check output pins, but to trace the audio path before lm4752 it will need to be amplified.

Solder joints look a bit scary around the lm4752.
Also, have you checked the small signal diodes?

 

[AlenZGB]

Are you using AC scale on your meter?
Also check the caps next to your green circled connector.
50c does sound rather warm but its an independent output which should be unrelated to L R amp section.
You could try using an audio probe (Google search circuit) or just use a speaker with a .01uf cap in series to check output pins, but to trace the audio path before lm4752 it will need to be amplified.

Solder joints look a bit scary around the lm4752.
Also, have you checked the small signal diodes?

I use DC scale.
I did put put 1000uF 50V instead of old one that was 1000uF 16V and i did get around 90% sound volume.
Dont know it thats cuz of the difference in voltage.

Thanks for pointers.
Love to learn something new. Honestly didnt cross my mind to measure voltage on LM4752, i did only do resistance
measurement and continuity test.
soldering dont look so scary off the picture. Just wierd cuz i didnt clean it. was just for testing only.
ill clean all as it should be. it will be less scary for sure.

 

[Mrgscott]

Any luck with this? I have what sounds like the same issue. Same speaker, same problem, the right output (black/white cable) not working at all.