I removed all the leaky caps and decided to check the output and power supply transistors at the same time.
Outputs tested fine, the power supply however was a different story-
Q27, Q28, Q31, Q32 dead short across all 3 legs, I pulled all 4 and they were still dead short. The part number is STP60NF0
before I order 4 new transistors, should I replace all 8 as Q25, Q26 Q29 and Q30 are the same component however they checked out fine on the board?
Outputs tested fine, the power supply however was a different story-
Q27, Q28, Q31, Q32 dead short across all 3 legs, I pulled all 4 and they were still dead short. The part number is STP60NF0
before I order 4 new transistors, should I replace all 8 as Q25, Q26 Q29 and Q30 are the same component however they checked out fine on the board?
OK thanks Perry, will do.
On a side note - I also have a GT24 with exactly the same issue, I stripped it down last night as I was curious to see if it had the same problem and to my surprise it had 4 blown power supply fets part no 75339P3, the capacitors were fine though.
So am I missing something here? did I just end up with 2 amps that were possibly installed by someone who somehow blew both (came from the same home) or are there other underlying issues?
These GT amps look well made and they sound great? the only thing I could think of was the placement of the cooling fans, both amps had the fans mounted on the output side of the heatsink - the fans can be moved to any point on the heatsink so maybe the power supply fets weren't being sufficiently cooled?
On a side note - I also have a GT24 with exactly the same issue, I stripped it down last night as I was curious to see if it had the same problem and to my surprise it had 4 blown power supply fets part no 75339P3, the capacitors were fine though.
So am I missing something here? did I just end up with 2 amps that were possibly installed by someone who somehow blew both (came from the same home) or are there other underlying issues?
These GT amps look well made and they sound great? the only thing I could think of was the placement of the cooling fans, both amps had the fans mounted on the output side of the heatsink - the fans can be moved to any point on the heatsink so maybe the power supply fets weren't being sufficiently cooled?
It's common to have power supply FETs fail. What's uncommon is to have 1/2 of the FETs fail in a power supply. Generally, when any single FET fails, it causes all in that power supply to fail.
The fans were likely mounted behind the output transistors because they produce significantly more heat than the power supply FETs in a class A, B or AB amp.
The fans were likely mounted behind the output transistors because they produce significantly more heat than the power supply FETs in a class A, B or AB amp.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.