I’m sure I posted this message here but for some reason it seems to have disappeared. I apologize if it appears twice.
I’ve been using the K8038 for months. It was working fine. One day I heard a pop while the dimmer was set on its lowest light setting.
When I checked the board the trace between R8, T2 and D2 was completely burn off. Also, the trace between C2 (+) and the push button terminal nearest C2 was burnt.
I repaired these traces but the dimmer no longer works. Upon checking various aspects of the circuit (power supply, triac operation, LED function) they all seem to work. The PIC though appears to have been damaged as it pulls down the power supply when inserted into the socket.
Jumpers 1 and 3 are installed while jumper 2 is not. It’s operating in 110V mode with the 1uF capacitor installed in as C1. It was connected to a standard low voltage (12V) transformer connected to only one low voltage halogen bulb. Not a very big load.
I’m very experienced at building circuits and have designed and built circuits far more complex than this unit. I’ve checked the circuit and everything is installed correctly and there are no shorts. As mentioned, it was working just fine for months.
I need help with three things:
I would like to purchase a replacement PIC. Where (how) can I order one?
I’d like some advice on what caused this malfunction and what I can do to prevent future failures.
I can see from the catastrophic failure that the fuse is of little use. The PCB trace(s) acted as more of a fuse. My concern is that as this device is not isolated from the line voltage and the fuse failed to blow as a result of this failure is this device safe?
Thank you for the reply I have sent you the email.
I have checked ZD1 and it is working just fine but I will replace it as you suggest.
I do not think that this is the problem though. I think there is a problem in the firmware that doesn’t turn the triac on at the right time. I think this resulted in a high current driven by a DC offset frying the traces.
I’m concerned that the fuse didn’t blow. If the device fails again I will discontinue its use.
After some months of normal operation, my K8038 (operating on 230 V) also seemed to have produced some wrong output to the 12 V transformer which made the transformer buzz very hard. And then the K8038’s fuse blow.
Today I’ve replaced the fuse (nothing else), did a short check and reinstalled the K8038 in the exact same installation and the K8038 is working normal (again)…
What is causing this problem which seems to make the output going wrong from time to time ?
A defective lightbulb or a temporary bad contact. If the transformer does not see a load for a short while, it starts to behave completely different.
There are two lightbulbs connected not sharing their leads up to the transformer and both lightbulbs are working fine without the K8038 and before and after replacing the fuse, with the K8038.
So no defect lightbulb and very little chances to a temporary bad contact.
A spike or other pollution of the mains, which causes the dimmer to lose sync and fire the triac at the wrong time.
All other 9 K8024 (the “old” dimmer) dimmers never got this problem in already many years on the same mains. Why is it possible that a spike or other pollution of the mains can cause this problem in the K8038 ?
Spikes or other pollutions of the mains are very common and the K8038 should have been tested for this in the (Pioneer Erpe-Mere ?) lab before going in production (?), as far as I remember.
Another unknown reason.
How was this problem fixed for mister Meyer ?
How can you fix this problem with my K8038 ?
Does Velleman still has “old” stock of the K8024 available ?
Sorry, at this time we do not know what might be the cause of troubles.
Aparantly it happens on rare occasions, so it will not be an obvious problem and most likely it will be hard to find.
Anyway, maybe we can come up with an answer if we have a chance to examine your unit.
If desired, you can return it for inspection/repair.
The K8024 has been obsolete for a while and is no longer available.
Sorry, warranty does not include return shipping.
Of course, if the unit is fixed under warranty conditions, it is returned free of charge.
If you want to avoid shipping costs and you can afford to wait a little longer, you can return the unit to your Velleman distributor.
If you decide to return it yourself, please send it to:
Velleman Projects Repair Dept.
Legen Heirweg 33
9890 Gavere
Belgium
Make sure to include a detailed fault description.
thank you for your answer about a possible returning of the K8038.
I’m afraid that it will cost me more (time and money) than replacing the K8038 by a reliable dimmer.
[color=#0000FF]Did mains electricity “spikes and pulses” (electrical transients) testing by a accredited lab took place on the K8038 ?[/color]
Sorry, this would require us to dig in the archives (dimmer has been designed back in 2005). Time is limited, so we do not really have the means to follow up on such requests.