Low Sound Level on a old Quasar YTS2623EK

Hello,

TV Model:
Quasar YTS2623EK

Problem:
Low Sound Level (half of normal)

Description:
TV enter the shop with a blow out resistor and diode related to the supply
of the Audio Amp.
We replace the parts and it was working, but the customer complain the sound
is too low now.

We check all parts related to audio, even replace the IC, same result.

We finally found that the volume is DC controlled via a AN15150114A. If we
push the DC manually the sound level is quite loud, but the controller chips
do not goes more than half level.

Sound raise from 0 to 30 on the on screen display, and stay equal from 30 to
60. We observe that the DC raise from 0 to 3 volts on the DC control pin of
the amplifier, while the on screen display raise from 0 to 30, but the DC
stay stable to 3Vdc from 30 to 60.

So do anyone know why the AN15150114A is unable to push higher than 3 Vdc?
Its a sort of PWM control going out of the chips, we can not find any speck
for that chips. We have no way to find one to check if the chip is OK. This
is an old unit.

Everything else is OK.

Bye
Jacques


--
Jacques St-Pierre
Président Directeur Général / Chief Executive Officer
MULTI-ÉLECTRONIQUE (MTE) INC.
www.multi-electronique.com
Tél. : (418) 724-5835

 

I would check the DC level output with a scope. Is it choppy or filtered?
Also, check if there is some capacitor in the circuit that has failed. The
capacitor could be breaking down and limiting the voltage to the audio
amplifier. Another good test would be to float the pin in question and see
if the voltage increases without a load on it.

Good luck.