"HiFi" CD radio clock: Z-778PM3Ui

[najrao]

This rather good looking product was made by "SEM industries, Hong Kong". Not even a user manual is forthcoming, even after an imploring mail.

As received, it is dead: needed replacing a zener and two bipolars to get up all of the several power rails. Not to mention a few resistors, capacitors and links which were victims of "snot" corrosion.

I have pictured only the display and buttons board. Because exactly these do not show any signs of life. The mother board and the radio board are separate.
The display is driven by a Samsung S3P8245 chip. The data sheet and app note shows the LCD pins directly connected to the chip pins; except nos. 48,49 and 50 which are to connect to external caps for voltage doubling or tripling, as the LCD supply. In this unit, 48-50 are led out to the main board thru 1k resistors, and cannot play a part of the LCD supply.

More importantly, none of the LCD pins are left out, all are connected up to pins 51- 80, and to nothing else. So, I do not know what this LCD supply means or where it applies. Yes, I am ignorant and unfamiliar.

Each of the LCD pins has a stepped waveform on it, average 1.3V dc. All the same.

I have checked that the S3P8245 is active, both the 8.0MHz and 32.768kHz oscillators are working (I replaced the 8M crystal).

Neither the display nor any of the buttons show any signs of life.

Repairing this some how will bring cheer to an aging relative, who needs such badly.

I hesitated a lot before asking help from my eev friends. Kindly help.

[PA0PBZ]

3 things maybe worth checking

 - the darkened pcb just above the display driver, it looks like something got hot under the LCD
 - some liquid spots just above the center of the pcb?
 - something that looks like there was a short just above and left of where the 2 wires exit at the right bottom

[najrao]

Thanks, PAOPBZ.
Yes, that was where a transistor had cooked and shorted. I have replaced it. Also, cleaned out the area with IPA. The brown patch is not conductive.
The 'liquid' marks are actually just the projecting edges of a small daughter board, which only carries two LED's for display illumination (which works).
Bottom corner are just two wires leading to a momentary push button to turn on/off some of the dc supplies; it works too. I have not cleaned properly after reattaching the wires (had broken off).