If you want to find the right substitute number
for field effect transistor, you have to look for a transistor substitution
data book and not the Philip semiconductor master replacement guide. Most of
the transistor substitution book will list out the specification of a
particular component such as the type of component, volt, ampere, watt, ohm,
frequency and recommended substitution number. From experience, the number
that the data book suggest are not 100 % correct. If possible learn how to
find the right number by yourself rather than
depending on the data book. It is same with horizontal output transistor
(HOT) spec which is doesn't mean the bigger spec the better the replacement
number is. In field effect transistor, look at the ohms value which is
provided by the data book besides the volt, ampere and the watt. Always find
a replacement with the same
or higher reading in volt, amp and watt but not in the case of ohm. The ohms
value have to be as near as possible. Assuming the original fet is 1 ohm
then replace it with a fet that have the ohm values between 0.5 to 1.5 ohm.
Don't replace it with a too high or too low ohms as this will make the fet
run hotter and eventually blow the fet itself. Though you have a higher
volt, ampere and watt with too low ohms value the fet will still blow after
running for sometimes.
True case example- Epson printer came in for repair with no power symptom.
Upon checking found the power fet shorted. I do not have the original number
and replace the fet with a higher volt, amp and watt and a higher ohm value
than the original. It runs perfectly but won't last long. After two weeks
the customer came back with the same printer complaint no power again. I
found the fet shorted again. Replacing with another fet number that have the
similar specification solve the no power symptom.
Conclusion- Bigger volt, amp and watt doesn't guarantee you the replacement
fet can work. If you
take ohms value into consideration chances are very high the replacement fet