hello all!
i have a problem with a steg 310.2, it was working but it had the usual problem on the potentiometer wich made noise in the output, and unbalanced volumes in output..
so i desoldered it, cleaned and resoldered, after 5 minutes it goes in protection..
i checked the mosfets and teh Q64 was burn!, checked them all and replaced all the 6 mosfets on that side from the IRF540a with FQP33N10 as mentioned in the service manual..
but after 5 minutes of play i got protection again: this time was the Q63, replaced that one only, and after 5 minutes of music not at full volume same thing, q63 burn..
can it be a defective gain potentiometer the cause??
excepting from the unbalanced output it worked great form months!
i have a problem with a steg 310.2, it was working but it had the usual problem on the potentiometer wich made noise in the output, and unbalanced volumes in output..
so i desoldered it, cleaned and resoldered, after 5 minutes it goes in protection..
i checked the mosfets and teh Q64 was burn!, checked them all and replaced all the 6 mosfets on that side from the IRF540a with FQP33N10 as mentioned in the service manual..
but after 5 minutes of play i got protection again: this time was the Q63, replaced that one only, and after 5 minutes of music not at full volume same thing, q63 burn..
can it be a defective gain potentiometer the cause??
excepting from the unbalanced output it worked great form months!
Post or send me the service manual if you have it.
Many times, a plastic-bodied pot will be damaged when desoldered from a board, especially double-sided boards.
Many times, a plastic-bodied pot will be damaged when desoldered from a board, especially double-sided boards.
Did you replace the resistors indicated on the second diagram for the audio circuit when you changed the outputs to the 22p10s and the 33n10s?
Are the gate resistors and the source resistors within tolerance for the FETs that have failed?
Did you reset the bias after replacing the FETs?
Were the FETs clamped to the heatsink when they failed?
Are the gate resistors and the source resistors within tolerance for the FETs that have failed?
Did you reset the bias after replacing the FETs?
Were the FETs clamped to the heatsink when they failed?
the amplifier was already repaired (bought it this way) and all the amplifier has the old mosfet type except for the Q63 to Q68 new type, i also saw that all the resistors marked in the sm remained the same except R219 and r20 wich are 6,8k
and it worked this way for months in my hands!
the gate and source resistors are all within tolerance
yes, the FETs where clamped and the amplifier was assembled all the times they failed
and it worked this way for months in my hands!
the gate and source resistors are all within tolerance
yes, the FETs where clamped and the amplifier was assembled all the times they failed
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Having mixed parts in a parallel group of transistors won't generally be reliable. It's typically not reliable when the transistors are of the same part number but of a different production batch.
in the meantime i ordered a new potentiometer, do you think the cause of the fail was not the gain selector?
what should i do? install all the new fets type and resistors like showed in the service manual? or install in the amplifier the old type FETs keeping the standard resistors?
what should i do? install all the new fets type and resistors like showed in the service manual? or install in the amplifier the old type FETs keeping the standard resistors?
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I don't know if the pot could cause the problems. In some amps, an intermittently open potentiometer can cause problems, especially if it causes the amp to oscillate.
If all of the 9540s survived, I think it would be easiest to go back to using the IRF540s.
Does the 6.8k resistor appear to be a factory installation or does it look like someone changed it?
Before applying power, you need to set the bias pots fully CCW to prevent excessive current flow through the outputs.
Gain selector? Pot?
If all of the 9540s survived, I think it would be easiest to go back to using the IRF540s.
Does the 6.8k resistor appear to be a factory installation or does it look like someone changed it?
Before applying power, you need to set the bias pots fully CCW to prevent excessive current flow through the outputs.
Gain selector? Pot?
i was thinking about the pot because it's the only thing i removed before the amplifier died... it worked without problems before and i get intermittent values when testing it with a multimeter
yeah, the 9540 are ok, so i'll go back with the IRF540!
the 6.8k resistors appear to be factory installed, the amplifier is a later revision (Black limited edition), probably that's the cause
ok, i'll set the bias when i'll replace the FETs as showed in the SM.
yeah i named gain selector the pot 🙂
sorry but i'm italian 😀
yeah, the 9540 are ok, so i'll go back with the IRF540!
the 6.8k resistors appear to be factory installed, the amplifier is a later revision (Black limited edition), probably that's the cause
ok, i'll set the bias when i'll replace the FETs as showed in the SM.
yeah i named gain selector the pot 🙂
sorry but i'm italian 😀