I scored a cheap 29 LX from a truck driver at work. He claimed radio was working and lit up fine, then he heard a sizzle and radio shut down. Then he smelled the magic smoke.
OK.... can't loose for $10, even worth that in parts I thought. All protection diodes good yet no voltage to PCB. Nothing "looks" burnt. Next, time to ohm out the power wires from chassis jack to main board. BINGO.... the tiny black ground wire they use in these now has an open. Closer inspection shows insulation puffed up and a tiny speck of bare wire sticking out. Actually looked like a small solder blob!
Replaced that puny wire with 16ga, added 6A10 diode across chassis jack and for good measure replaced filter cap. Also replaced all the protection diodes cuz they cheap and I have plenty.
Radio powers up! Woot Woot! Oh... bummer... no display back lighting..... Display does work along with all functions. Just no lighting. And yes, I went into menu and turned up brightness all the way... got zilch. I strip it down, remove LCD and do some comparisons against a working unit to find I seem to have a short to ground in the LED+ wire coming out of the back lighting driver/high voltage box that is mounted on the chassis.
Does anybody have any experience/thoughts with this box??? Mostly surface mount.. looks like a small xformer, some resistors, caps, diodes and maybe an inductor. Nothing visually burnt. I even see a 6 pin IC...
I guess it be time for a PC based microscope and try to find some parts info and schematic/parts list. But I hear even that can be a challenge.... Help me Obi One... you're my only hope!
OK.... can't loose for $10, even worth that in parts I thought. All protection diodes good yet no voltage to PCB. Nothing "looks" burnt. Next, time to ohm out the power wires from chassis jack to main board. BINGO.... the tiny black ground wire they use in these now has an open. Closer inspection shows insulation puffed up and a tiny speck of bare wire sticking out. Actually looked like a small solder blob!
Replaced that puny wire with 16ga, added 6A10 diode across chassis jack and for good measure replaced filter cap. Also replaced all the protection diodes cuz they cheap and I have plenty.
Radio powers up! Woot Woot! Oh... bummer... no display back lighting..... Display does work along with all functions. Just no lighting. And yes, I went into menu and turned up brightness all the way... got zilch. I strip it down, remove LCD and do some comparisons against a working unit to find I seem to have a short to ground in the LED+ wire coming out of the back lighting driver/high voltage box that is mounted on the chassis.
Does anybody have any experience/thoughts with this box??? Mostly surface mount.. looks like a small xformer, some resistors, caps, diodes and maybe an inductor. Nothing visually burnt. I even see a 6 pin IC...
I guess it be time for a PC based microscope and try to find some parts info and schematic/parts list. But I hear even that can be a challenge.... Help me Obi One... you're my only hope!
