fairchild mosfet taken from Mean Well TN 1500 inverter.

[73's de Edd]

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Sir aoud . . . . . . .

The basic number that you are looking for is that very bottom number

For the top numbers, they are suspect to be code date or production runs on the first part and the last two markings numbers are usually relating to pin treatment or casing variants.
In these units that would be the very end BF and AB aspects.

Here are three pics, two of them are your referenced units, while the FIRST unit is a real bona-fide, certified unit offered by Mouser in the UK.
Note the sharp defined lines of laser marking on the part number of the first unit.

The other two units look to be stamped on markings.
The center unit looks to be having the best marking of the right two.

Also note the mold flash extrusion divots similarity on the first two units. The third is entirely different.












I point out the above, because some popular POWER audio transistors and TV horizontal output transistors had a problem of inferior bogus / counterfeit units being out on the "black" market supply chain.

However many of these devices that your unit used (2? ) . . .replace them both (all).


73's de Edd




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[(*steve*)]

Here is yet another with different wrting on top :
http://m.ebay.ca/itm/272041748092?_mwBanner=1

Assuming they are genuine, they look to be ideal replacements.

As previously stated we don't know if this is all that is wrong with your device, but the replacement transistors seem cheap enough to give it a go. In addition you'll have spares if it turns out there's other things to fix and you blow up the replacements.

 

[aoud]

Assuming they are genuine, they look to be ideal replacements.

As previously stated we don't know if this is all that is wrong with your device, but the replacement transistors seem cheap enough to give it a go. In addition you'll have spares if it turns out there's other things to fix and you blow up the replacements.

You guys are god sent . For a moment i thought i got mr steeve mad . But there he is . Patient and helpful as always .
God bless you . I think i have enough to work with here . Thank you all so much .

 

[(*steve*)]

Not mad, just confused. If we're not understanding each other then I can't help you and you may get bad advice.

I really don't want to give you bad advice