I soldered a K8042 symmetric power supply and combined it with a Velleman 3018 transformer (18V). This supposed to give a DC output between +/- 15V and +/- 18V DC. However, there is 27 VDC at the output and the 121 ohm resistors smoke … 
. Specs of K8042 say that output is adjustable between 1,2 and 24 VDC, so the 27 VDC is too high and may explain the smoking.
Someone any idea what the reason for the 27 VDC could be ? or how it can be solved ?
Most likely an assembly problem. Make sure both regulators are not swapped. Check direction of diodes.
If you can post links to HI-RES and SHARP pics of your assembly, we can take a look.
Below some photos. Hope you find something.
Component placement looks OK.
A couple of solderings look suspicious and might need re-work.
Check burned resistors, replace if necessary.
Also, replace both regulators.
If you wish, you can return the kit for inspection/repair.
Just unsoldered the 2 120R resistors and the voltage regulators.
The resistors still give 120R (actually 122R) when measured, but I’ll replace them anyway by new ones.
Will also buy some new voltage regulators and keep you informed.
Actually, initially I mounted the voltage regulators in swapped position, but as I got a too high output, I detected this and put them in the correct place (already before posting my message). As the switching to the correct position did not change the output measurement, I thought the problem would be elsewhere.
However as you suggest to change the Voltage regulators. Could they be damaged by the initial swapped mounting ? And afterwards when put in the right positions give the same output voltage ?
Most definately they are damaged due to swapping!
I replaced the 120R and both Voltage Regulators with new ones. Still 26.8 & 26,9 Volt on both outputs.
Any idea what I could still test ?
How does it work when I return the kit for inspection/repair ? Where should I bring or send it. Are there any cost associated ? How long does it +/- take ?
That is very strange…
Sorry, at this time we do not know why it does not work.
You can return your kit to your distributor or mail it to:
Velleman Projects Tech. Dept.
Legen Heirweg 33
9890 Gavere
Belgium
If repair is not performed under warranty conditions, a small fee is charged.
OK, thanks for your kind support.
Just to keep you informed of the happy end. Went with the module to my distributor. There we found (thanks AITEC) that the two potentiometers were damaged, probably because of the initial switched mounting of the voltage controllers. Bought two new ones and now everything works fine. 
Happy to read it works fine now.
Hello,
I reactivate this topic because I have the same problem ampi had. However, I didn’t swap the VRs so I don’t understand where it comes from.
Could an error when connecting the transformer cause this?
Thanks
No, normally the transformer has nothing to do with it.
Sorry, this forum does not allow picture uploads
If you can provide LINKS (e.g. by using a free online picture base) to HI-RES and SHARP pics of your assembly (both solder- and component side)
then we can take a look and provide some feedback.
Here are some pictures:
https://plus.google.com/u/0/photos?tab=wq#photos/109966848668698683943/albums/5751650453263672017
Franck
Sorry, the link does not seem to work…
Sorry, this one should work
https://plus.google.com/photos/109966848668698683943/albums/5751650453263672017
Sorry, but soldering looks rather poor.
Unfortunately, picture quality does not allow us to spot further problems, but it looks like a lot of joints need rework.
Check for solder bridges too.
Don’t mean to jump into the middle.
It looks like you may have VR1 and VR2 swapped
oh yeah I understood I swapped the VR. I really didn’t notice there was a difference.
I’ll replace the parts as ampi did
But your remark caught my attention. Are my soldering that poor? I maybe put too much…
http://i163.photobucket.com/albums/t290/valizatools/IMG_0848.jpg
AC voltage is RMS and when rectified will charge the caps to the peak of the wave and for 18v AC a 27v DC output is normal, if you want 24v DC use a 15v transformer.