Our pizza oven broken yesterday. Well, it broke last time we used it, but we didn’t realize before yesterday night (when we had the pizzas already prepared). I started to repair the oven directly yesterday night (it’s quite simple and cheap to do actually), and as our guests were quite interested in the process I figured I post the description here.
Oven description: it’s a very cheap “Gala Pizza Pronto” oven with a stone bed. It’s genious for making pizzas yourself; the pizzas turn out to be much like a “real” pizza (and not either dry or overly soft like in a normal oven, and they have a proper bottom).
German disclaimer: Hier geht es um die Reparatur von einem Pizzaofen. Ich beschreibe die Reparatur auf Englisch. Wenn es aber Fragen geben sollte, bin ich natürlich gerne Bereit diese auch auf Deutsch zu beantworten!
French disclaimer: Ici une description comment reparer un four pizza. La description en bas est en englais. Néanmoins, je veux bien repondre à tout les question qui s’est pose en Français!
Open the casing
Most suppliers use special screws for safety (to keep people like us from messing with the interiour). While we’re at it: DISCONNECT THE POWER CORD before opening the casing. If you don’t, well, that would maybe be a Darwin award, but I felt anyways obliged to put this warning here. In my case, the oven had tri-wing screws (see picture).
For repair work, two things are really important to have:
- a multimeter (I assume that you know how to use one, if not check for a guide on the internet, e.g., at Sparkfun
- a bitset with may different types (see picture, mine cost 10 bucks and has like 8 different bit types)
Try to trace the circuit of your oven. The circuit of the cheap ovens (like mine) is very simple: it consists of a temperature regulator (marked “poti” in the drawing), the 2 heating elements and a thermal fuse. See high-tech drawing above. Pizza goes between the two heating elements (I forgot to draw that).
Follow all the cables and check if they are not broken, disconnected or similar (simple) problems. Check that you have connectivity between the wall plug and the ovens interior, somebody might have broken the cord (i.e., by tripping over it).
All ok? I thought so. Next step!
Check the heating elements
Next, we verify that the heating elements didn’t burn-out. Heating elements are super simple: they have a certain (small) resistance and can sustain high currents without burning. This means you can apply some voltage to them and they heat up. Thus, we can check them: if they have a infinite or zero resistance, they are broken. In that case you can trash the oven (unless you manage to find a replacement of course). If they work, they should show a small resistance as shown in the picture (26 Ohms sound about right).
Check the fuse
If the heating elements are ok, it’s time to check the fuse. It’s usually attached close to the inner casing of the oven, and hidden in a layer of non-conductive heat-resitant tubing. The picture shows what it looks like. Test the fuse, if there’s no conductivity it’s broken.
Replace the fuse
To replace the fuse, read the model number of the fuse. In my case, it said:
These are quite common, I’ve found this part at the local electronics store for 2 bucks. Replace the fuse and voila, your oven should work again!
A note on replacing the fuse: as you can’t solder or use anything with plastic, the connections in such an oven are usually crimped. If you can’t manage to open the existing crimp-connector or have the part available, you can replace it with the metal part from a screw terminal (see picture). Just remember to strip off the plastic!