How to replace a triac in a washing machine?

Replacing a triac in a washing machine is quite simple, any person who knows how to use a soldering iron can handle this task. The main difficulty is to determine which semiconductor on the board is damaged and select an element that is completely similar to the faulty one. These two problems are not so easy for an ordinary person to solve. Let's figure out how to properly perform diagnostics and find suitable components.

Let's make sure the element is faulty

First of all, you will need to access the washing machine control board. To diagnose semiconductor elements, you will need a special device - a multimeter. To partially disassemble the machine, one screwdriver is enough. The algorithm of actions will be as follows:

• Turn off the power to the machine,
• Turn off the tap that supplies water,
• Remove the top cover of the case by unscrewing 2 bolts,
• Remove the powder receptacle,
• Unscrew the bolts holding the control panel,
• Take a photo of the connection diagram of the instrument panel to the board to avoid making mistakes during subsequent assembly,
• Reset the contacts and remove the instrument panel.

However, the method with desoldering semiconductors is more complicated, you will have to perform additional manipulations with radio components on the control board. Therefore, beginners prefer to check the simistors directly on the spot, without disconnecting them from the module.

To check the semiconductor for breakdown, you need to put the multimeter probes to the power contacts of the triac (the left and middle "legs"). The tester screen may display either 0 (indicates a faulty element) or one (meaning the part is fully functional). Some devices display the letters OL instead of 1, they also indicate sufficient resistance.

At the second stage of diagnostics, one of the multimeter probes must be moved to the control output. In this case, the voltage drop should be from 100 to 200, small differences are acceptable.

Next, check whether the semiconductor junction opens. To do this, hold the multimeter probes on the power terminals and quickly touch the control contact. The readings on the tester screen should change immediately. This adjustment will indicate that the triac is working properly.

When the tested semiconductor gives correct results at all stages of diagnostics, it means that the problem is not in this element of the circuit. You will have to test other triacs. If the failure is confirmed, it is necessary to replace the part.

How to select a replacement part?

Having decided to replace a semiconductor, it is important to take a responsible approach to the selection of components. When buying a new triac, you should pay attention to the isolation of the element, its peak rating and opening current. But how can you find out the characteristics of a part removed from the control board of a washing machine?

Therefore, the first thing to do after desoldering and diagnosing the triac is to rewrite its marking on paper. For example, if the original semiconductor has the inscription BTB 15-700BAK, then it contains the following information:

• BT – semiconductor element series,
• B – means that the thyristor body is not insulated (at the same time, index “A” indicates that the semiconductor is isolated),
• 15 – peak current of the triac (in this example, 15 Amperes),
• 700 – peak voltage (in our case it is 700 Volts),
• VAK is a combination indicating the opening current of the thyristor, in this example it is 50 mA. The designation СВ will indicate an opening current of 10 mA.

The last letters of the marking are of great importance. If the control board had a thyristor with an opening current of 50 mA, and the purchased element is characterized by only ten mA, then the machine will not work at full capacity, but only at 10-20% of the possible potential.

It is also worth paying attention to the index indicating whether the simistor is isolated or not. For example, the semiconductor with the characteristic "B" considered in the example can be replaced with an analog with the index "A".

If your control board had an isolated simistor, for example, BTA 15-700BAK, then you should buy a semiconductor with the index "A" for replacement. If you install a new element without insulation, the control module may well short-circuit. Therefore, it is better not to risk it.