TYPICAL FAULTS OF VARIOUS HOUSEHOLD APPLIANCES

1). Repair of the membrane keypad in microwave ovens.

I decided to share with society how to repair the membrane keyboard in microwave ovens.
Often in microwave ovens the following malfunction is observed, the furnace begins to "live its own life". Does not respond to keystrokes, spontaneously starts, and all this manifests chaotically and randomly, can recover and some time to work normally. The reason for this disgrace is that the insulation between the keyboard conductors deteriorates. It is not possible to check this with a multimeter, too low a test voltage, and for some reason the controller has enough. Often, the master decides that the processor is faulty, and completely in vain. The best solution is to replace the keyboard keyboard, if there is, if not, then you can restore the old one. The keyboard consists of two films, on which conductive paths and contact pads are placed, opposite each other. Between them is a mask, with slots in front of the pads, it is still very sticky and glues the film. To repair it is necessary to paste the keyboard, then the main thing is not to make sharp movements, and do not pull it evenly and too much. We remove the electronic unit. We take a table knife, with a round tip and gently pull the edge of the films so that you can grab the top with your fingers, and then the main thing is not to bend or jerk. The outgoing trail of conductors is not necessary to be unstuck or torn off, and it is more coastal with it. You need to shred so that the upper film separates, and the sticky mask and the lower film remain on the body. After several attempts it will turn out beautifully and accurately. Next, next to the body, put a book of suitable thickness, we turn it away, as it were, open, peeled off the film with contacts up (book for convenience). We take an adhesive tape and seal the entire surface of the film, except for pads, it is better to use a narrow 6-8 mm, it is more convenient to work. We return everything to our own place, we put the electronic unit in place, collect it and check it, and it all works. This way more than a dozen various microwave ovens have been restored, most of them Samsung (they are simply in use the most), DEU and Shivaki. All of the above does not apply to the GoldStar furnaces of models MA 651 and MA 851 in them they really die COP444, however it is successfully treated with "roasting" (in 50% of cases), but this is another story.

Vladimir

2). Polyspan ViewStation; SPU41-13-2 (Power supply from videoconference)

The power supply is not fully operational, there are no output voltages + 5V and + 12V. The clicks are heard, the LED is off. Diode D23 is defective P6KF180A. The resistor connected in series to the capacitor C23 is burned.

3). EIMO-450Afpal is a document camera.

When you turn on, you hear a soft snap. At the same time, the LEDs D809 (B & W) and D810 (Auto) flash simultaneously. The appliance does not turn on. When measuring the output voltage of the PSU (it should be + 12V), it can be established that in time with the cod, the output voltage rises from 0 to + 3.8V. Defective power supply - capacitor C9 is defective 4.7μF / 50V (lost capacity). It is easy to determine the thermal effect.

[email protected]

4). HUNTRON HTR1005B-1ES. Measuring device. Signal analyzer.

1) The displayed waveforms are not correct. After trying to measure a heavily charged capacitor, the device failed. The device does not have input voltage protection. Very often two resistors R5 (215 Ohm) and R6 (13 Ohm) burn.
2) When measuring parameters by switching input "A" and input "B", sometimes failures occur. The LEDs signaling the activated input are switched, but however only one input operates. This is due to a defective NE555 chip. Although at first I thought the contact of the switching relay would stick. But after the replacement of the relay, the malfunction was still evident. The NE555 chip is defective.
The device has a picture tube C327P31B. (Regenerator adapter No. 8013).

Maxim [email protected]

5). POWER SUPPLY.

An interesting malfunction of the computer power supply unit is the ATX. Almost like in a joke "does not execute the command NO SMOKE", that is, the smoke from it goes. Smoke comes from the capacitors of secondary rectifiers, after the unit is started from standby mode. All output voltages are overestimated by about 2 times. However, there was no voltage at the output contacts on the + 5V circuit. Stabilization of output voltages is carried out just by the analysis of this particular circuit, and for this reason the block went "peddling". And the defect turned out to be a factory fault - the inductor, at the very end of the 5V circuit, is simply inserted into the board, and not propyanjana: Good luck to all!

Korzhov Oleg [email protected]

6). AON to Z80 version 23.

The digital part works fine. The call to the station is not heard in the handset, although the conversation is normal. However, there is no feedback. The conversation part in this phone is assembled according to the phone scheme of TA-1158. The reason was in the broken transistor KT3102B (microphone amplifier).

7). Kettle - with automatic shutdown (of any company).

Frequent malfunction: the kettle shuts down prematurely and the water does not boil. Do not climb the switch! The fault is eliminated by simply removing the scale in the place where the foam contacts the heel of the attachment. This place should be completely descaled (can be removed mechanically). After this procedure, you need to fill in 0.5 liters of water, fill it with a bag of citric acid and, without closing the kettle, bring it to a boil (boil 5-10 minutes). If there was a lot of scale, then this procedure will have to be repeated several times. After such cleaning, the kettle looks like new and works perfectly.