I Grabbed this amp from a previous owner who tried to repair it, And did a horrible job and i suspect used the wrong output mosfets.
The 12v and ground wires get extremely hot very fast, Assuming its due to high current being drawn.
It draws excessive current (40) at idle with and without remote voltage.
Wondering where to start with this one ?
The 12v and ground wires get extremely hot very fast, Assuming its due to high current being drawn.
It draws excessive current (40) at idle with and without remote voltage.
Wondering where to start with this one ?
it does draw current without the remote wire.
Ive taken a few mosfets off and the current has dropped significantly.
I Had a single Q4469 or O4469 that looked like the former owner added, I removed that so far.
I'm also getting very weak voltage on all rails
Ive taken a few mosfets off and the current has dropped significantly.
I Had a single Q4469 or O4469 that looked like the former owner added, I removed that so far.
I'm also getting very weak voltage on all rails
Check the rail voltage again (on the center legs of the rectifiers). Place the black probe on the secondary center tap. If you still have very little voltage, post the DC voltage on all of the pins of the KA7500. Place the black meter probe on the amplifier's ground terminal for this. Place the red meter probe on the point where you need to measure the voltage. When measuring the voltage on the KA7500, either monitor the temperature of the heatsink mounted components very closely or clamp them to the heatsink.
IC#
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:
Pin 15:
Pin 16:
IC#
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:
Pin 15:
Pin 16:
i went to test ka7500.
Before i had a chance to test the chip, one of my gate resistors blew out. Smoking pretty badly and i got a pop.
The amp was powered on for roughly 5-6 seconds before this happened.
The blue "rear led" did turn on though for the first time since pulling the mosfet that didnt belong on the board to my knowledge (Q4469 or O4469)
Before i had a chance to test the chip, one of my gate resistors blew out. Smoking pretty badly and i got a pop.
The amp was powered on for roughly 5-6 seconds before this happened.
The blue "rear led" did turn on though for the first time since pulling the mosfet that didnt belong on the board to my knowledge (Q4469 or O4469)
It's likely Q, not O. Q is the prefix generally used for transistors.
Was the gate resistor for an output or for a power supply FET?
Was the gate resistor for an output or for a power supply FET?
it was a gate resistor for a power supply fet
I got 11.8v rail voltage on both the rails on the output side
No voltage reading on the rails on the power supply side
I got 11.8v rail voltage on both the rails on the output side
No voltage reading on the rails on the power supply side
That sounds like you may have a shorted power transformer.
If the gate resistor failed for one of the power supply FETs, it's likely that all of the power supply FETs have failed.
If the gate resistor failed for one of the power supply FETs, it's likely that all of the power supply FETs have failed.
It turns out my power supply was at fault and not the rails.
I now have between 13.93 and 13.96 volts on every rail.
I now have between 13.93 and 13.96 volts on every rail.
the resistance is 991 without power
The amp idles fine without remote voltage, I haven't hooked the remote up again to see if it draws excessive current
The amp idles fine without remote voltage, I haven't hooked the remote up again to see if it draws excessive current
'Idling' typically means that the amp is powered up (remote included) and is producing rail voltage.
hooked it up to see if it idled and its still pulling excessive current, And it blew two power supply mosfets within 10 seconds.
They had the heatsinks on as well.
unhooked it right away as im afraid to blow anything else. Everything that is blowing when i try to let the amp idle is on the left side of the board if that makes a difference.
They had the heatsinks on as well.
unhooked it right away as im afraid to blow anything else. Everything that is blowing when i try to let the amp idle is on the left side of the board if that makes a difference.
I think a few more things need to be clarified.
Can you post a photo of the transistor you removed?
Was the Q4469 or )4469 silkscreened on the board or was it on the face of the transistor?
Can you post a photo of the transistor you removed?
Was the Q4469 or )4469 silkscreened on the board or was it on the face of the transistor?
Its apparently not a o or a q, but im assuming its a C
Because it looks exactly like this : http://www.electronic-spare-parts.com/pics/2/2sc_4468-1.jpg
The C4468 is the only mosfet that looks to be out of place on the board, Everything else looks correct.
Ive removed multiple burned IRFP054N's and IRFP064N's as well as the blown gate resistors (3 burned up gates)
Ive cleaned the board with acetone and a toothbrush and checked everything over as best as i can by eye.
Because it looks exactly like this : http://www.electronic-spare-parts.com/pics/2/2sc_4468-1.jpg
The C4468 is the only mosfet that looks to be out of place on the board, Everything else looks correct.
Ive removed multiple burned IRFP054N's and IRFP064N's as well as the blown gate resistors (3 burned up gates)
Ive cleaned the board with acetone and a toothbrush and checked everything over as best as i can by eye.
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