MK 188 stoped working

Kits Timers and Clocks
1

Hi.
I have a MK188 that has been working fine for quite a while. Now it stopped working and lets all power through at all time; i.e. it is like I connected the batteries directly to the electric motor I have. The error arose as I connected and disconnected the power a couple of times and changed from a ~5 minute pause to a ~5 seconds pause. I don’t know if some component got burnt for some reason or what else it could be. The component VR1 gets suspiciously hot in a few seconds after connecting the power.

Any hints on how to solve this would be very welcome!
Thanks.

2

Does the IC get hot as well.
You should check T1 for shorts or test it with the diode function on your multi meter.

3

The IC does not get hot, only VR1. I will get back on T1 when I’ve managed to borrow a multi meter.

4

You could also try removing the IC and then check VR1 for getting hot.

5

Thanks for helping out!

I’ve tried removing the IC. That lead to a total shutdown; no power came through (so no heat in VR1). Also checked T1 with a multimeter. No connection detected between the different ends, and connection to the card itself is good.

6

Now, what conclusions should I draw from this?

7

Check if you measure +5V between pin 1 and pin 14 of the IC.
If this is the case, then the power supply looks OK.
Most likely, the controller is defective.
Please check with your Velleman distributor for a spare controller or return it to:

Velleman Projects Tech. Dept.
Legen Heirweg 33
9890 Gavere
Belgium

US residents: please call (817) 284 77 85

8

If I got the right pins I measure 3.94 V.
I can see if I can get a new controller. I can’t find the papers right now, so I could use a reminder which one is the controller.

9

Voltage is more or less OK.
The controller is the IC you have removed to measure this voltage.

10

I had to buy a the product a new to get spare parts, but replacing the IC sure did the job. now things are up and running again. Thanks for the help!

11

Glad to hear it’s working again