Sunday, October 24, 2010

Repairing a Mickey Mouse Lamp

My daughter has a nice Mickey Mouse lamp.
We bought it years ago and it worked nicely for many years, until "somebody" connected it to an X10 Lamp module.
After few times, the lamp stopped to work completely.
In this article I'm documenting the repairing process.

The lamp

lamp1.jpg
Here the lamp.  Mickey is pulling the cord every time the big red button is pressed, while some sentences are spoken, turning the lamp on and off.

The circuit

Inside the base of the lamp, are present four PCBs.
  • Main control module
  • lamp activation module
  • pushbutton support
  • main power support
Here a schematic block of the lamp, obtained looking the circuit :
disneylamp2.png 
The LAMP control module feeds the transformer via a main fuse, and it  receives from the Main control module the command to activate the bulb.
Here a picture of the inside :



On the left lower corner, it is located the main control module, just below the transformer.
On the righ side, the LAMP control module.

Main control module

The main control module circuit, is the main PCB of the lamp.
The main controller module performs these functions :

  • it power supply the circuits
  • it controls the bulb  via the LAMP control module
  • it controls a motor for some motion effects
  • it generates sounds/voices when the lamp is activated/deactivated
  • it handles the main on/off pushbutton

LAMP control module

The bulb  control module (called LAMP in the block schematic) feeds the transformer that power the main control module via a fuse, and it receives via photocoupler the comand to turn on/off the bulb.

Here a schematic of the LAMP module :
 


Open the lamp

It is quite easy to open the lamp.
On the base there are 4 adhesive pads. Under each pad there is a hole containing a screw that connect the base with the main body of the lamp.
After the screws are removed, the bottom of the base is coming out.
The PCBs and the transformer are screwed to the upper part of the base.
The only annoying thing is that all the wires are soldered to the PCBs, no connectors. 
 bottom1.jpg bottom2.jpg
 bottom3.jpg lamp2.jpg

The problem

The lamp was totally dead.
Measurement made on the LAMP  control module didn't show up any problem.

The diagnosis

Since all the functions of the lamp, motion, voice and lamp, were dead, as the first thing I checked out the  power supply.
Hooking a voltmeter to the transformer secondary (blue wires) showed up 0 volts.
Then I disconnected the transformer secondary from the main control boards and did again the tests.
Still 0 V.
So it seemed the transformer was gone.
To be sure of that, I disconnected also the primary of the transformer (cutting out the red wires) and removed it from the base.
The primary resistance of the transformer was infinite, the secondary one 0.6 Ohms.
So the primary of the transformer was broken, thus no power to the entire circuit.
I then hooked up a DC power supply to the main board control, when the secondary  of the transformer was connected.
Around 7V the circuit started to work.  Pushing the ON/OFF button the character spoke and moved as usual.
However connecting the main power (110V) to the lamp, the lamp remained OFF
Possible reasons :

  • a) also the circuit that control the bulb had problems (SCR dead or some diodes broken)

    OR
  • b) the LAMP control module needed to be driven with a signal in sync with the AC line
    Since I used a DC power supply to test the main control board, I didn't have any AC signal

    OR
  • c) the bulb was broken
The last one was correct.
The bulb was broken.

The  repair

Since all the functionalities of the lamp were present when powered with the DC power supply, in order to repair the lamp, the transformer had to be substituted.
In order to do so, I had to figure out  what transformer to use.
The original transformer was labeled "HUNG KAI 4104".
A search  with google showed only a Chinese company who produce it (Hung Kai Electric Co) and that the model 4104  belonged in the category of transformers below 15W, with max. voltage of 42V.
Clearly the original transformer was  NOT sending out 42V, a main line capacitor on the main control board  was a 16V max electrolitic.
Since the main circuit board was working with 7V DC, my first guess was that the transformer had to be a 6V one.
I found on Jameco a 6.3 V transformer, 1.2 A , with dimensions "close" to the original one. 
Approx 6.3 V AC, once filtered  become around 8V DC

Here the "fix".
The transformer is little bit bigger than the original one, so it is attached upside down, with  some high heat hot glue on the top and a velcro support (not in the picture) on the base to avoid movements (safety must be always the first concern when repairing electric appliances).
It is also possible to see the rewiring (yellow and white wires) connected to the original wires (red and blue).
The small gray wire is the one in parallel to the original pushbutton, connected to a jack.
This is used to command the lamp with an X10 Universal module  (see below).
The unused wires on the transformer, were cut and insulated and glued to prevent short circuits.



The improvement

Since the lamp was open, I decided to add a jack to "bring out" the push button ON/OFF function.
In this way it is now possible to control the lamp with a remote push button or connect the lamp to a X10 Universal Module .

1 comment:

  1. Hi there! glad to drop by your page and found these very interesting and informative stuff. Thanks for sharing, keep it up!


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