[chbot] Multi colour lamp

Richard Jones richard.jones.1952 at gmail.com
Sun Feb 7 04:19:54 GMT 2021

The Multi colour lamp module in our spa stopped working, it looks like
quite an interesting design. Link to photos:
I thought I would share the issue, just in case anyone has some good advice
for fixing, otherwise I can try to buy a new one as a last resort. The
module looks like a drop in replacement for a 12V 6W halogen bulb, and it
displays different sequences of colours which may gently fade from one
colour to another. Different sequences are selected by turning the lamp
supply on and off. A casual examination reveals an input bridge rectifier
and reservoir capacitor. The 8 leg device is a PIC 12F629 which has 5V
applied between pins 1 and 8. There are 3 driver transistors (bipolar or
FET?) which drive 3 of 9 LEDs red, green or blue. When I connect 5V via a
1k resistor to each driver transistor 3 LEDs of one colour will light.
There is no apparent water damage. So it looks as though the PIC is not
running. The assembly has a thin conformal coating that is easily pierced
for measurements.

There is a 5 pin connector that looks as though it takes the standard PIC
programming signals. But I have never got around to designing and
programming with PICs. The construction is a mix of through hole and
surface mount devices and looks easy enough to rework. This PIC needs a 12V
flash programmer, and is generally programmed in assembly language. So it
looks to me as though the learn in and tools required for replacing this
~$2 SMD are just not worth the time. Shame.

Thoughts anyone?

Richard Jones
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