FET Cross Reference
If you have decided to join this repair field, i suggest that you get a good semiconductor data book for reference. This cross reference book comes in handy and you don’t need to log in to internet whenever you want to search for a particular specification. More and more electronic equipments are using FET in the circuit thus having the databook will give you an added advantage to look up for comparison part number fast.
If you have the time to do your own research in terms of comparison of each part number for FET in a particular circuit such as B+ circuit, you can come out with a universal part number that can be use in all CRT Monitor. Lets take the CRT Monitor that have the boost circuit (not buck circuit), for a 14, 15 or even 17″ B+ boost circuit i can actually use the IRF640 as replacement regardless of what original part number used in the Monitor. For a 17″ or higher CRT Monitor you can use IRF634A as replacement. As for the data for IRF640 and IRF634A i will let you do some homework as what are the spec is. You can search from the internet or from a data book if you have one in your workshop.
If i don’t use this IRF640 part number then i will be having a hard time of tracing the original part number from electronic suppliers. Your precious repair time would be wasted every time you search for the original part number. I do came across some weird FET part number and there is no way you could trace the data even from the internet. So the best way is to use the replacement part number as suggested above.
Spend some of your good time and you will be able to find a universal part number for power circuit, Buck circuit or even the S-correction circuit too.