Working on a Hifonics HFi1500D, amp that is going into protect. Power supply is fine (tested with rectifiers out). All output fets seem good (none are shorted, but i did not remove to test). Perry's guide suggests the two transistors on the output board Q6 and Q7 (see close up pic) to replace in this instance. I do not happen to have any MMBTA42 transistors, and I don't have any sil-pad to make a heat sink, so I was wanting to replace them with a TO-92 (or the slightly smaller size) transistor and then use some E6000 to secure them so they do not break off. This would fix the board and have better heat handling. Looking at the MMBTA42 specs I see a VCEO of 300V and that alarmed me some, this board appears to drive 2 sets of paired transistors to drive the fets gates, so i would think it would not need high voltage rating on this small transistor. Looking for advice on a standard NPN to use. This is the first time repairing this style Class D and just looking for some peace of mind before I try this. Thanks!
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I own the amp, but will probably sell it once fixed because I have no need for it. I buy lots of dead amps to learn on (its a hobby for me, my day job is programming PLCs and VFDs, 480 volt sutff). I was trying to figure out a solution to the heating problem these have without use the binder clip and sil-pad. Got some in the Mouser cart now.
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