Tip & How-To about Televison & Video

Working with Switch mode Power supplies.

To help in identifying common problems in SMPS circuits.


There was a time when we had only transformers fitted on all the appliances which was sturdy and could stand up to rigourous voltage conditions. The disadvantges was the growing cost of copper & lamination metal, the weight and the universal voltage condition.
The switch mode power supply came in to replace all the devices with an added advantage od space, cost and range of voltage but brought in higher failures when there was a voltage error.
So I am listing few tips to look into a SMPS failure and possible safeguards.
First of all in a SMPS failure if a fuse has blown the chances are there is a fault in the circuit and very rarely the fuse can be replaced unless the component is sorted out.
So check from the power supply the possible major components to suspect.:
1. Fuse
2. The surge protector -- usually a varistor ( metal oxide)
3. Rectifiers- in bridge circuit.
4. Chopping oscillators- Intergrated circuit.
5.Chopping drivers-- MOSFETS ( now incorporating a single IC for OSC and drive )
6. SM ferrite transformer.
7. Main filter capacitor ( will be seen as leak or short)
8.Discrete reverse feedback diodes, capacitors or fusible resistors .
9.Optocoupler which is the feedback trigger.
10.Short in the secondary circuit can switch off power by current limiting.

These are the most possible components that one must check on in case of a SMPS failure.
To prevent a SMPS failure it is important that there are no transcient surges in the line supply, So have a good tight connection. If isolation transformers are used for costly sets it will be ideal to check many failures.
Try not to leave the sets always connected to mains except if it is necessary to set the clock functions or timer functions.

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1 Answer

what is a smps on a samsung tv?


SMPS(Switching Mode Power Supply) is a device which converts commercial power into high-efficient/high quality power necessary for all sorts of electrical appliances, with using the switching of a semiconductor component and the power conversion function of a transformer.
It consists of electronic components such as a semiconductor component, a transformer, an electrolytic condenser, a passive component, an injection molded part/apparatus, etc.

Sep 06, 2014 | Televison & Video

4 Answers

Sony KV-32FS12 32" TV


This condition be directed us toward pin modulator transistor Q504 which may shorted. Parts necessary to fix this unit may be D501, D504 and Q504.
Check this site if you need the schematic diagram: //http://www.eserviceinfo.com/downloadsm/19977/SONY_KV32FS16.html
Good Luck.

Jan 28, 2008 | Sony FD Trinitron WEGA KV-32FS120 32" TV

1 Answer

GE electrical house breakers keep tripping. Any problems or recalls


You may have overload that power circuit with too many appliances.
Check the load of each of the appliances on that power circuit, add them together and check to see that it does not exceed the rating of the circuit breaker.
OR
You have an overload or short/fault on an appliance on the power circuit that is protected by that circuit breaker.
To identify the faulty appliance, disconnect all the appliances on that circuit and then connect each appliance one at a time to see when the circuit breaker trips out. When that happens you have identified the faulty appliance.

Jan 21, 2012 | GE Hammering

1 Answer

my one year old microwave just stopped working. The light is on, but nothing else.


Sorry to read about your problem, I hope this helps you out.

here are some issues, but you still maybe under warranty.
  1. Blown fuse in HV transformer primary circuit or HV fuse (if used).
  2. Bad connections (particularly to magnetron filament).
  3. Open thermal protector or thermal fuse.
  4. Open HV capacitor, HV diode, HV transformer, or magnetron filament.
  5. Shorted HV diode, HV capacitor (will blow a fuse), or magnetron.
  6. Damaged protective VDR from filament to chassis (not commonly used).
  7. Defective HV relay (not commonly used).
Microwaves must be serviced by technicians due to the inherent dangers involved in repairing these appliances. Internal capacitors can retain a lethal electrical charge even though the unit is completely unplugged. A microwave radiation leakage test must be performed on the unit following any internal component repair.

I tried to help you. Please help me and Rate/Vote on my response. We take the time to answer your question's. take the time to rate us.Thanks and good luck

4 Thumbs - Very Helpful
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Jan 05, 2011 | Goldstar MV-1501 Microwave Oven

2 Answers

micro wont heat. fix or replace? what could be the prob?


Sorry to read about your problem, I hope this helps you out.

Here are some problems you can have
  1. Blown fuse in HV transformer primary circuit or HV fuse (if used).
  2. Bad connections (particularly to magnetron filament).
  3. Open thermal protector or thermal fuse.
  4. Open HV capacitor, HV diode, HV transformer, or magnetron filament.
  5. Shorted HV diode, HV capacitor (will blow a fuse), or magnetron.
  6. Damaged protective VDR from filament to chassis (not commonly used).
  7. Defective HV relay (not commonly used).
Microwaves must be serviced by technicians due to the inherent dangers involved in repairing these appliances. Internal capacitors can retain a lethal electrical charge even though the unit is completely unplugged. A microwave radiation leakage test must be performed on the unit following any internal component repair.

I tried to help you. Please help me and Rate/Vote on my response. We take the time to answer your question's. take the time to rate us.Thanks and good luck

4 Thumbs - Very Helpful
3 Thumbs - Helpful

Jan 05, 2011 | Kenmore 63792 Microwave Oven

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