Fixing the 7-segment LED of Sony sound system

[debojitacharjee]

I have one Sony 5.1 sound system but its 7-segment LED display is not working properly because the numbers (volume level) are not showing up completely and all the segments don't light up. Sometimes, the whole display shows nothing at all.

I need to know whether the LED driver IC (PTC 6955) is gone?

I would also like to know what the bus lines (CL, CE, DO, DI, SBY... ACF) are on the board for?

What is the connector with the labels RES, P4, VSS, PA0, and VDD for?

There is another chip HT48F50E, and could that be damaged?

The model number of the sound system is SA-WID7.

I have attached the snapshots of the chip and PCB.

 

[rjenkinsgb]

The fault could be dry joints or bad connections, the controller IC or the LED module itself - or various other causes.

I'd expect the pin labels to be;
SBY = Standby

DI = Data In
DO = Data Out
CE = Chip Enable
CL = Clock

Those four look like an SPI link, while the SCL/SCA are common labels for an I2C link.

No idea on TUN or ACF

The HT48 is a Holtek microcontroller; the small connector is likely a programming or debug port for that?

 

[debojitacharjee]

The fault could be dry joints or bad connections, the controller IC or the LED module itself - or various other causes.

I'd expect the pin labels to be;
SBY = Standby

DI = Data In
DO = Data Out
CE = Chip Enable
CL = Clock

Those four look like an SPI link, while the SCL/SCA are common labels for an I2C link.

No idea on TUN or ACF

The HT48 is a Holtek microcontroller; the small connector is likely a programming or debug port for that?

I tried clean the PCB using alcohol but the problem didn't go away. I guess the LED driver IC (6955) is damaged. If there is any dry or bad connections then the problem would be permanent. But the LED display changes randomly and sometimes most of t he segments don't work, and sometimes no display at all. Do you think changing the IC will resolve that because the microcontroller can't be damaged, otherwise the system won't work with the inputs from the remote control.

 

[Les Jones]

If the volume control is a rotary encoder (Rather than a potentiometer.) it could be dirty/ damaged contacts in the rotary encoder causing the problem. I think that is more likely than a faulty IC.

Les.

 

[Nigel Goodwin]

If the volume control is a rotary encoder (Rather than a potentiometer.) it could be dirty/ damaged contacts in the rotary encoder causing the problem. I think that is more likely than a faulty IC.

Les.

While that is an EXTREMELY common problem, it would cause the volume to go up and down, not the display to have missing segments.