Looks like this is a "rare" amplifier? Not much information out there on it. I have been running it as my 3rd spare LOL.
Started doing a weird thing where there would sometimes be no audio, but if I turned the volume way up it would start to play for a while, then stop. Figured I'd open it up and see what's going on.
One of the MOSFET's (looks like the power supply section) let out the magic smoke. 2 more have bad solder joints. Seems simple enough, but I am not sure what is the correct part.
Silk screen on the board says T3055, Part itself is BUZ71A. T3055 is kind of generic, lots of parts come up. BUZ71A has some more specific results, but seems to be obsolete. Found one site that had STP16NF06 as an x-ref.
I understand it is risky buying parts on Ebay, but what about Amazon?? Or, best to stick with the reliable part houses (Mouser, Newark, etc.)
Looking for someone smarter than me with experience to suggest the best route for replacement part?
Thanks!
Started doing a weird thing where there would sometimes be no audio, but if I turned the volume way up it would start to play for a while, then stop. Figured I'd open it up and see what's going on.
One of the MOSFET's (looks like the power supply section) let out the magic smoke. 2 more have bad solder joints. Seems simple enough, but I am not sure what is the correct part.
Silk screen on the board says T3055, Part itself is BUZ71A. T3055 is kind of generic, lots of parts come up. BUZ71A has some more specific results, but seems to be obsolete. Found one site that had STP16NF06 as an x-ref.
I understand it is risky buying parts on Ebay, but what about Amazon?? Or, best to stick with the reliable part houses (Mouser, Newark, etc.)
Looking for someone smarter than me with experience to suggest the best route for replacement part?
Thanks!
I'd recommend only reputable electronic components distributors (not ebay or amazon).
The Z44s may work but it depends on the drive circuit and the gate resistor value.
The Z44s may work but it depends on the drive circuit and the gate resistor value.
Not clear if you suggest I look for an original BUZ71A? or if STP16NF06 will work?? I guess it is not worth the risk to put in the Z44.
Does it drive the gate resistors directly, through a diode and transistor or through an emitter follower pair?
Photos of the drive area?
Photos of the drive area?
I see what looks like one driver but can't see the other. I don't have the diagram for your amp but the circuit should be similar to the attached diagram. D21/Q23 is one driver. D31/Q33, the other. If yours is the same, the Z44s are perfectly fine.
Attachments
You must replace all that are in parallel. If there are two banks of 4 FETs, that would mean 4 FETs. There's no reason not to change all of them. The Z44s are dirt cheap.
The PNP drivers may have failed.
The PNP drivers may have failed.
Hmm. Then I might have to wait because I am down to two 47 ohm 1W resistors.. Looks like the ones on the board are 1/4W, which I thought I had ordered a while back, but they look smaller- like 1/8W.
But yes, it looks like 2 banks of 4 FETs for each bank. The amplifier still worked, so I don't think the driver is bad. Guessing I just overheated it, and blew the one FET that is visibly damaged.
But yes, it looks like 2 banks of 4 FETs for each bank. The amplifier still worked, so I don't think the driver is bad. Guessing I just overheated it, and blew the one FET that is visibly damaged.
How many gate resistors burned? You only need to replace the ones that are out of tolerance.
They are 1/4w.
They are 1/4w.
Well, one was visibly burned- for sure replacing that one, and the one next to it... Because that "pair" had one FET that was physically burned, and the other looked like it may have gotten hot too. The other two resistors in that bank look fine, but I will test them.
Yes, the ones on the board are 1/4W.. But are my new ones 1/4W? Are modern resistors smaller?! LOL. Thought physics would dictate how much heat something could dissipate for its size.
Yes, the ones on the board are 1/4W.. But are my new ones 1/4W? Are modern resistors smaller?! LOL. Thought physics would dictate how much heat something could dissipate for its size.
Right. The physical size generally determines the power rating unless they are made of special materials that can take more heat than normal. Those are rare.
Gate resistors dissipate VERY little power. 1/8w resistors would be good enough.
If the second gate resistor got hot, that FET failed as well. The resistors won't burn unless the FET fails (the gate typically shorts to the drain).
Gate resistors dissipate VERY little power. 1/8w resistors would be good enough.
If the second gate resistor got hot, that FET failed as well. The resistors won't burn unless the FET fails (the gate typically shorts to the drain).
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