can i  replace the diode (RL-205) with (RL-207)
because i our area  RL205 is not available and  RL207 has 1000 peak reverse voltage while RL-205 has 600 peak reverse coltage…..
please replay me

R.mohammed ali

Hi Mohammed,

If the ampere is the same yes you can replace it.



Hi ! Jestine first of all I would like to thanks for which you was sending last this week I was test sony tv the problem of it’s on power supply board .The problem of it’s as follows :, fuse , resistor 470 k ohm and power regulator transistor c3550 blowed (birned) even though I have been got these problem I can’t repair becouse of power regulator transistor c3550 problem . the plame is I cant get it in the shop by it number, so can you tel me the equvalent of these transistor .

HI Teferi,

According to my databook the equivalent part numbers are BUW11A,BUW131A,2SC3152,2SC3376.



HI Maylis,

I need to know how to check ..diagnose a problem tv Mcu

Make sure it has supply voltage ad the crystal is good other than that you may need to know the output waveform with the help of digital scope. No output waveform means it has problem. If the programs has corrupted it could produce waveform too but those waveform are abnormal. You need a programmer to reprogram the MCU if the data has corrupted.

and what it function really is..

To execute function base on what the designer have program into it. Ex-In lcd /crt monitor one of the functions is to detect signal from the VGA cable so that it could produce a on signal to optoisolator ic to turn on the power supply.

nd what happen if it is not
working properly.

It could produce lots of weird symptom from  no display, display shut down, osd problem and many others in lcd/crt monitors.



Hi Justin, I pray that all is well with you. I have in my shop a 1400 bass guitar amplifier from Hartke Systems. The problem was that when you roll the volume pot, it sounded like rolling thunder. I figuren it was a bad pot, so I got one from the manufacture and replaced it, (a 4 lead one) Same problem. the problem seems to stop when I remove the effects sent and return input board (jacks) from the main board. This dosent make sence to me so. What now. Thanks Ed

Hi Ed,

Thanks. Yes in your case it seems to be doesn’t make sense. Could the new one be defective too (if a volume pot has been kept for a long time)? I suggest that you get the philip oil based spray on the volume pot and adjust it to make it smooth. if the problem still persist then there might be problem in the electronics circuit. you can trace from the volume pot to check if there is any bad components along the lines.



HI Lito,

good am sir thanks for the site for my review on my coming exams for Electronic Certified Technician…if you could give me too with review materials on Registered Master Electrician exams?….

Sorry I do not have those material.

another question sir, a fuse of 250v 20A 197degree centigrade because the available is 250v 10A 227 deg centigrade can  I replace with this one?…

You cannot replace with a 10 a 227deg fuse. The amp has to be near to the original value and the deg has to be lower and not higher than the original.

if I have 2 10A 250V …can we make 20A out of it?….thanks a lot sir..

Two fuses in parallel will increase the amp rating but its not a good practice.



Hi Jestine,

I have replaced the power IC but no help. By the way, I have recorded new video which should be clearer than before ( I have cleaned the surface of the picture tube ), I hope you could see the display noise now. Any other suggestion?


HI Boling,

Try run on your windows pc instead of the vga signal generator. use your scope to probe on the h/v signal output from the h/v oscillator ic to see if there is any interference. Noise in the equipment is one of the hardest to detect. It can also be flyback, corrupted eeprom data, bad h/v oscillator or even bad ceramic capacitor.




Hi Jestine,

Thanks for the quick reply.  I had the PS working into an amateur transceiver (abt 2 amp) when the voltage started fluctuating–it would ho from 13.8 down to about 4 volts, then up, etc.  Sometimes it would work ok for a couple hours, sometimes it would not go above 4 volts from the start.

Before it started acting up, it would feed the transceiver on transmit at 20 amps with no problem.

Hope you can help me.



Hi Charles,

I’ve got the schematic-thanks.
1) Just to check when you said the 13.8 output are you referring to the +Vo in the schematic?
2) Is the FAN + voltage stable and accurate?
3) Have you check the filter cap at C6, C7, C8, C9, C17, C39, C18 ,C19  and C28 with ESR meter?
4) Check also C10 and C11 with a digital capacitance meter
5) Try direct replace D7 because if it is leaky it could cause intermittent problem.
6) Check also for VR1 for intermittent problem. Try adjust and see if the output voltage will gradually increase/decrease. If the voltage output is erratic then direct replace the VR1.
7) Check also if there is any decayed glue in the circuit board. If they are there then you need to clean it with thinner solution.

Please keep me update on this repair case-thanks.






HI Jameel,
It could be the problem of lcd panel or the t-con board have problem. I suggest that you check /replace the t-con board first. Before that make sure all the voltages in the t-con board are good.



Hi Jestine ,

It a round fuse but i replace it with a pico fuse and the amp was higher that the original one. When i didn’t connect the power board through mainboard and test it i got 5 and 12 volts at the secondary side

Hi Chong,

You can’t replace it with pico fuse because it can’t handle the big current draw by the big fat capacitor and the main board. Put in a 3 amp slow blow fuse and retest. Before that make sure you have replaced with the original parts for those bad components.




hi mr jestine what is the best way to analyzed the logic circuit board and their function what is your technique to analyzed them. in the coffee machine main board lot of program and logic ic that you need to analyzed.


You need to download the manual and schematic in order to understand/analyze it.



Hi sir can i replace an electrolytic cap value 39uf 6v dc working by a 47uf50v its for a pocket transistor Radio supply voltage 6 volt please help thank.

Yes you can but it will be too big. Try replace with a 47uf 10 volt.



It was interesting to note the web site for the capacitor replacement technic. In this regard i want something to be clarified: Can the 1uf 160v capacitor in the Horizontal circuit be replaced with 2.2uf 250v without affecting the circuit or another example can 1uf 250v be replaced with 3.3uf 250v or 330v cap? i appreciate you Mr Jestine. Thanks

In certain sensitive circuit that involve timing and frequency the best is to replace with the same value.




Hi Jestine

One question please. Going through my repair books I could not find what I am  looking for.
I am repairing a tv and seem to think the problem is the electrolyte capacitor in the primary side of smps. Reason being of a small bulge on top of capacitor. Measurement show capacitor has stopped functioning as it should. It is a 400 v 220 uf.

However I have a capacitor at my disposal to use as a replacement but it is 450 v 150 uf

Can I replace 400v 220uf with 450v 150uf

Thank you

Hi Gasant,

It is recommended to replace with a higher UF like 330uf. Yes you still can use 150uf but I’m afraid it would not last long.



What is the volts that goes through flyback transformer thick output cable to tv. Is it the same as b+ input from smps (which in my case is 77v). Does the voltage
increase somehow to energize  the  tv.


Hi Gasant

first you need to understand the function of flyback. The primary winding takes in 77volt and at the same time the HOT switch. This will cause AC to be produced at the secondary side. Since the secondary winding have more loops than the primary thus the ac that you get will be boosted and this AC will pass through few internal high voltage diodes and the end result you get is 24 kvdc (The thick output cable).



HI Victor,

I just got a monitor.the problem is the on/off doesnt go off when i press the power button.what can i change here?

Check the on/off switch as some on/off switch could be rusted and have continuity.

Secondly,i received a monitor.the problem is screen.i replaced it with a good one compatible with the original but to my surprise,i saw burning smoke and smell coming frm the good screen.i am afraid of putting another one.i want to let you know first.

You mention compatible and not the exact lcd screen and this could cause problem. You need to have the original one. If the compatible one can be used this mean you may have connected wrongly and you need to recheck on the wiring/connection.

Lastly,i asked you the components in the power supply board i can test for voltages during troubleshooting and you replied that i need a question is what is a voltmeter?is it different from my analog meter which i am using?

Voltmeter meaning is the range to test the voltage. You can have ac or dc voltmeter. You analog meter has a dc and ac volt range. Just set the range to DC and you can now check on the voltage.

For the printer question i asked.yes the output jack has about 3 output holes with the pins how can i test the voltage?

Although it has few pins some do not have voltage and some have lesser voltage. Check the spec of the power adapter and it if says 19vdc output then place your black probe at the metal of the jack and red probe to one of the pins. If you get 19 vdc then it is good.





Hope you are doing well. My friend has got a TV, you can hear the sound of people talking on it, but the problem is the picture that doesn’t show up. It only show the redish colour on the screen, Can you please help me out here, what components should I look at that might course the problem.

Kind Regards



Hi Bheki,

It could be the red transistor in the crt has shorted or the picture tube have problem. Try compare the voltage of the RGB transistor. If there is a different in voltage or signal then you can start troubleshooting from that point.



Hi jestine,

i just bought your book about switch mode power supply.
my switch mode power supply is connected throught an isolation transformer.  when i try to put the oscilloscope ground to primary ground of the power supply ( hot ground)
there is a  spark and i already burnt  a rectifier bridge.
can you help me please

kind regards


HI Mohammed,


Try open up the isolation transformer and make sure the ground cable inside is not connected. If it is connected then cut it away. I have seen many isolation transformer where the designer have the ground cable install and this will defeat the purpose of the isolation transformer.



Jestine Yong works as an Electronics Repair Lecturer in Kuala Lumpur Malaysia and his training website is You can check out his repair blog at