Flyback/Cap replacement of Hantarex Polo 25” monitor

[Elias Blackman]

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I was using a Hantarex Polo 25” monitor connected to the power supply with a KI cable. Yesterday, unexpectedly few sparks were seen in my monitor and then suddenly it went off. I opened the monitor and saw that a flyback was burned and that was where the sparks must have come from. I tried replacing the flyback from the spares which I had, but it didn’t work. I tried working on the trial picture but nothing was displayed on the screen. Instead a strange clicking sound was heard coming from the connection where the neck and anode cap is connected. There is no problem with the chassis arcing. I tried adjusting the settings of the screen, but nothing helped. Does anyone have any ideas, about what must have gone wrong?

[Amy_i3]

You can get a polo kit, which will have the required connecting parts in it. You can use them to create a new connection between the neck and the anode cap. From my experience I can tell you that the pin of the flyback that comes in the polo kit is broken. You will need to check the pins before you do anything or else it will burn again causing more damage than before. Before you work on the circuit, swap the vertical deflection ICs and take its readings. This might come helpful when you’ll need to check if the connection is working properly or not.

[Hayley]

Did you check the flyback that caused problem properly. I am saying this because many manufacturers don’t connect the bare wires it has to the prongs. They just hook it around the corner which creates the connection. Maybe the connection just came off. If this is the case, you can simply attach it back without having to solder or try the hardcore hardware solutions. For future safety, you can solder the prongs and the hooks so that they don’t come off easily in future. Also after you connect the prongs and the hook, check the flow of electricity using the light bulb method.

[ddj]

I recommend you that you should put an insulator sheet on all transistors and ICs. Before you power up the monitor, you must check all the caps you insulated for any fluctuating power supply. The base and the emitter must be shorted together and must be grounded to protect from any problem that can be caused due to short circuit of the connections. After you swap the vertical ICs and after the testing is done, you put it back, check if there is no leak or short of voltage.

[BonnieT]

You must take special care where you have shortened the base and emitter as it becomes the most vulnerable area after the new connections are set. Many manuals suggest that the damper diode is best for this purpose, but I personally think that they are not of much use when it comes in creating a new connection.

[Girr]

I think that the problem must be the Horizontal deflection circuit. If the power supply is fine and the problem lies only with prong and the hook of the flyback in discussion, then problem lies with the circuit that control the horizontal deflection circuits. You can use the light bulb method to measure the voltage at different points on the Horizontal deflection circuit and its control circuit. You start checking the values at 3 of ic104. If you find any leak in the voltage or any inconsistency, then it will be the faulty area.

[KumaraVel]

As mentioned in one of the replies, the pin that is missing from the flyback from the polo kit doesn’t mean it is faulty. The set is tested and then packed. The so called missing pin is actually folded below the cap of flyback. It is no defect, but just some pieces are manufactured that way. First thing, in such situations you need to replace the HOT before changing the cap of flyback. This has to be done, even if the cap tests well. Never try shorting the HOT as it might again cause the flyback to break connection under stressful conditions.

[Bageshri27]

I suggest you to test c172, c173, c174 and qnd172 caps. These caps are the one which generally get killed or burned under stress. They are actually inter connected to each other. So if you are replacing any one of them, then you will need to replace all of them.

[Oms-waroop]

Before you proceed with troubleshooting of the board, check all the connections properly. Also check the connections that you never worked on or were never had any problems. The large solder joints must be check thoroughly. If any similar problem occurs repeatedly, then it might cause bigger problem to the hardware. If while troubleshooting, any problem is seen in the connections that you have worked on then it can be an issue of wrong numbering or wrong placement of the cap or joint.