Sundown SFB-8000D What are these transistors?

[redbaron1007]

I had a Sundown SFB-8000D amp come into the shop yesterday that wasn't giving any output. The guy who brought it in said he bought it off some crack head on Facebook marketplace for a good price, but bought it knowing it was broken. Apparently the original owner was cutting out the transistors to the right of the ones pictured whenever one would blow and take the output out. Best I can figure he also cut the legs on the S5 and S6 ic's as well and soldered them back together.

My problem is Sundown decided in the factory to remove the original markings on the IC's and now I can't figure out what the transistor is supposed to be. Looking around on other forums I managed to find the missing transistors (which are labeled D1 instead of having part numbers) are IRFP90N20D and the driver IC's (which are also burnt up) are Irs20957s.

The transistors in the photo aren't testing faulty I just don't like the idea of taking all the time to source the missing and blown components and leaving these in in their current state.

I appreciate any and all help. I also have this same question posted on a couple of audio specific forums so if someone on one of those knows what the part is I'll be sure to update everyone here. Figured it couldn't hurt to cast as wide of a net as possible on this one.

[petehall347]

Re: Sundown SFB-8000D What are these transistors?

IRFP90N20D according to datasheet is for smps circuit .https://cdn.badcaps-static.com/pdfs/...17da90848f.pdf

[redbaron1007]

Re: Sundown SFB-8000D What are these transistors?

IRFP90N20D according to datasheet is for smps circuit .https://cdn.badcaps-static.com/pdfs/...17da90848f.pdf

I know that's the part number for the ones that are missing. I don't think these two transistors are the same. On the other side of the board there's still all of the D1(IRFP80N20D) and the package looks slightly different than the one for the S5 and S6 transistors.

I'll take another picture of the other side and upload it later today when I can get into the shop for a little bit.

[redbaron1007]

Re: Sundown SFB-8000D What are these transistors?

Here's the follow up picture of the other side where the IRFP90N20P is still present. They have slightly different package appearances and I can't imagine they would have used only different looking transistors in the the s5 and s6 locations.

Looking closer at the picture I noticed the emitter of S5 and the emitter of Q16 are connected. The capacitors are definitely connected to the transistors I just don't know to which pins since I haven't pulled the board out of the housing yet.

Yesterday and today are my days off work so I probably won't be able to update anything about what the capacitors connect to until tomorrow morning when I go in.

I did some reading up on amplifiers in the interum though and am thinking maybe the S5 and S6 transistors are a darlington pair but I haven't connected this thing to power yet to figure out what the voltages would be. Haven't really wanted to power it with all the fets missing on half the board and all of the fet driver IC's visibly blown.