Hello all
Ive posted a few things about this pain in the arse , So i thought i would start a new post
Brief History
It came in dead.
I found Q19 and Q20 burnt up
Replaced them and tested the amp. Amp working but running hot and couldn't bias down. Cutting a long story short
Found o/c R38 and a short between B-E on Q17. Removed Q17 and Q19. Transistors were ok. Cleaned the board/Area and short went away, Replaced with 2 new transistors Short gone
Must of been a solder splash ?? Biased the amp as the Schematic states.10MV ( J3)
Anyway tested the amp sounds good no issues apart from when you turn master and gain up, 12 oclock Ish the amp goes into protection and LED goes red, Wait 1-2 seconds and its back working again
seems to be worse if you use the drive function
I have monitored the Voltage rails no issues, when goes into protection , They remain stable
all voltage rails are correct as the schematic states
schematic below Page 15 - 206-211-A3
I have checked just about everything,
Hoping one of you more experienced techs can help and shed some light on this for me
Many thanks in advance
gallien-krueger_mb150-iii_pwramp_sch.pdf
Ive posted a few things about this pain in the arse , So i thought i would start a new post
Brief History
It came in dead.
I found Q19 and Q20 burnt up
Replaced them and tested the amp. Amp working but running hot and couldn't bias down. Cutting a long story short
Found o/c R38 and a short between B-E on Q17. Removed Q17 and Q19. Transistors were ok. Cleaned the board/Area and short went away, Replaced with 2 new transistors Short gone
Must of been a solder splash ?? Biased the amp as the Schematic states.10MV ( J3)
Anyway tested the amp sounds good no issues apart from when you turn master and gain up, 12 oclock Ish the amp goes into protection and LED goes red, Wait 1-2 seconds and its back working again
seems to be worse if you use the drive function
I have monitored the Voltage rails no issues, when goes into protection , They remain stable
all voltage rails are correct as the schematic states
schematic below Page 15 - 206-211-A3
I have checked just about everything,
Hoping one of you more experienced techs can help and shed some light on this for me
Many thanks in advance
gallien-krueger_mb150-iii_pwramp_sch.pdf
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