I have received several emails from techs who come to me for some guidance in relation to at what point should one suspect an ic is faulty. In this article I wish to shed some light on this issue in relation to CRT television. (Of course you can use the same knowledge in other equipment using ics)
In CRT Television we have several ics like Audio I.C, Vertical ic, RGB amplifier ic, control ic in the power supply and lastly the jungle and micro processor ic.
The latter ics are quite expensive and therefore it is very important to very sure that indeed it is the ic which is faulty and not related components causing the problem.
The word integrated in Basic English means included there in. Such as active components like transistors and passive components like resistors, capacitors in order for it to function.
So in I.C like the micro processor or jungle ic expect many components both active and passive which form circuit with different functions within that particular ic.
So one clue that an ic is bad is function failure, Take for example the micro processor part of the circuit which produces tuning pulses for channel selection in CRT television. If this particular circuit fails then you will find the TV is not able to do channel auto searching.
If you get this symptom and you find the entire external component associated with turning are OK, then you can conclude that the micro has failed partially because you will find sometimes other functions of the micro will be okay.
If you find NO function of the micro is working, then first check if the micro is getting power. Power supply is very important for any ic/circuit to work and therefore should always be checked to see if it is present and correct value.
Another common occurrence on these ic is actually dry joints on the components around it and also actual ic pins.
Sometimes a technician can change the whole ic when actually the problem was dry joints. So when you replace the ic its like you have re-soldered and hence if the TV work you will imagine that actually it was the ic faults while it was just dry joints problem.
This will waste your time and also lower your profit margin, from my experience I have seen these main ic(the micro and jungle ic) are quite reliable and highly protected from static discharge and power surges and therefore should be last on your suspect lists.
Below you can see a diagram of a TV micro, before you replace it consider checking the fuses around this ic, you never know they were fast enough to open to protect the micro and changing only one of them can cure the problem.
One good symptom of a bad ic is that they usually get HOT and also the VCC voltage goes down(Nb you expect 5 volts but you are getting 2volts
To learn more on how to troubleshoot and repair CRT television like a professional click the link below…
Author CRT Television repair course