About a year ago I had to repair the microwave oven brand Bork models MB IIEI 2623 S1, failed due to the significant surge in outlet. The fault was entirely normal - failed transformer the power control unit. Replace half an hour, an hour of work. But the main the problem was no need for me to repair the transformer in sale. Had little to alter the scheme. The work was facilitated by the fact that the transformer was struck by the pattern of the windings showing the values of their AC voltage. However, their output current is not specified.
In Fig.1 provides a diagram of the transformer with rectifiers power. It fully saved the factory numbering details.
As you can see - it is very simple and does not contain in its composition voltage stabilizers. Apparently, the voltage under load on top the rectifier circuit is about 5 V, and the lower - order 20...22 V. Judging by the diameter of the wires of the secondary winding of the transformer output current pyativoltovom the rectifier is unlikely to exceed 0.5...0.6 A, and the second - 0.1 A. In the further work all these assumptions were fully confirmed.
The scheme of the new power unit shown in Fig.2.
Its Foundation is still widely used by many radio Amateurs in his work is quite "ancient" output transformer vertical TCE-110-LM. Conclusion 5 of this transformer is not used. Due to the different number of windings compared to the burned-out had to change diagram rectifiers and input the voltage to 5 V. the efficiency of the unit somewhat deteriorated, but the reliability has improved dramatically. The numbering again entered details on the scheme starts with 10. All other details are taken from the old block.
Before use, remove the strip of paper between the halves the transformer core, forming a non-magnetic gap. After the obligatory check on the performance in the idle state, the transformer is not should be warmed completely, it is useful to impregnate the core some varnish for metals. These measures are further fully relieve him from the unpleasant buzzing and will greatly reduce the load current. Not getting the varnish on the windings the transformer, which can cause damage to wire insulation due to their dissolve in it. And this may cause a short circuit in the windings. If instead of varnish to use varnish, the transformer can be fully impregnate her. It absolutely will not damage the windings. But the drying may take approximately on the week. If the summer is to put varnish impregnated transformer in the sun, the drying time somewhat reduced.
DA1 chip is mounted on the radiator with the cooling surface area of not less than 120 cm2. Chips instead of CRRA you can use the import ML7805A, L7805CV or any similar on the output voltage of 5 V. the Diodes VD10 VD13... you can use silicon or germanium. They must be able to withstand average a direct current of at least 0.5 A and a reverse voltage of 40 V. the Capacitor C10 can apply any compact with the capacity and voltage of not less than specified in the diagram (Fig.2).
Instead transformer TCE-110-LM it is also possible to TCE-110-L-2. The numbering of the conclusions they have completely the same. Before installing it is desirable to disassemble the core of the transformer and collect the P - and W-shaped plates overlap. Preferably the core of the transformer after testings to impregnate any lacquer for metals.
With proper details accurately assembled circuit establishing absolutely not will require. Problems with placing a fairly large power transformer and other parts does not occur. Inside the housing of the microwave oven free space more than enough.
Literature
Author: M. Ryjenkov, Republic of Buryatia, Barguzinsky district, village of Suvo