Hi agithegreat ,
before destroy furthermore Mosfets with worth of plenty pounds here the way I do repairworks on DC converters in car amps.
unsolder the secondairies of the toroid to the rectifier diodes. Replace them against a load resistor with a equivalent value to substitute the idle current of the amp circuitry . For example, assume the converter deliver 2x30V and the amp need 100mA idle current. The substitute resistor should be 300 ohms. Next standard value is 270 or 330 Ohms. Choose one with 10W .
Never power an amp under repair from a car battery or other storage batteries. Even you put a small fuse into the power lead. The inrushing current due to a fail or possible short while poking with tool into the circuit is faster than any fuse. In other words the current rise time is measured in microseconds as the fuse need ages to melt , say milliseconds. Time enough to destroy Mosfets diodes or even the control chip.
Use a Bench power instead , one with an adjustable current limiter.
If you are in lack of such power supply , use a small storage battery and insert a current limiting device into the feedline. A recommed thing is a 21 W brake or indicater light or a 35W headlight bulb. The input voltage does not decrease und 11 V.
Furthermore remove the huge filter caps from the power input and replace them against a small value say 470 µF.
If you remove the heatsink from the trannies, check the temperture of the them . If the converter is working well the trannies stay cool. even with the base load of the resistor.
If the converter works basicly but blow up when the associated amp is driven with music program.
one ore more mosfets have a damaged drain/source path simply named they are leaky.
The secondary rectifiers have a bad current capability, the latching up at high currents.
The control chip ( TL494 , SG3524) are bad. It is difficult to trace especially without the proper measurement eqipment. So since these chips are not expensive its quite easy to change them if you are in any doubt of its conditiion.
Check also the trannis of the mosfet driver. For each group of the push pull outputs there are two small signal trannies connected as chargíng pump for the mosfets. If the Power trannies are gone they often blow up together with them. If you did´nt check them, you blow up the new power mosfets.
If you like to repair more the this amp in the future , look out for a bench power and an oscilloscope
A oscilloscope is a helpful instrument to trace al the faults.
regards from rainy Hamburg
Wolfgang
DF6ZC
before destroy furthermore Mosfets with worth of plenty pounds here the way I do repairworks on DC converters in car amps.
unsolder the secondairies of the toroid to the rectifier diodes. Replace them against a load resistor with a equivalent value to substitute the idle current of the amp circuitry . For example, assume the converter deliver 2x30V and the amp need 100mA idle current. The substitute resistor should be 300 ohms. Next standard value is 270 or 330 Ohms. Choose one with 10W .
Never power an amp under repair from a car battery or other storage batteries. Even you put a small fuse into the power lead. The inrushing current due to a fail or possible short while poking with tool into the circuit is faster than any fuse. In other words the current rise time is measured in microseconds as the fuse need ages to melt , say milliseconds. Time enough to destroy Mosfets diodes or even the control chip.
Use a Bench power instead , one with an adjustable current limiter.
If you are in lack of such power supply , use a small storage battery and insert a current limiting device into the feedline. A recommed thing is a 21 W brake or indicater light or a 35W headlight bulb. The input voltage does not decrease und 11 V.
Furthermore remove the huge filter caps from the power input and replace them against a small value say 470 µF.
If you remove the heatsink from the trannies, check the temperture of the them . If the converter is working well the trannies stay cool. even with the base load of the resistor.
If the converter works basicly but blow up when the associated amp is driven with music program.
one ore more mosfets have a damaged drain/source path simply named they are leaky.
The secondary rectifiers have a bad current capability, the latching up at high currents.
The control chip ( TL494 , SG3524) are bad. It is difficult to trace especially without the proper measurement eqipment. So since these chips are not expensive its quite easy to change them if you are in any doubt of its conditiion.
Check also the trannis of the mosfet driver. For each group of the push pull outputs there are two small signal trannies connected as chargíng pump for the mosfets. If the Power trannies are gone they often blow up together with them. If you did´nt check them, you blow up the new power mosfets.
If you like to repair more the this amp in the future , look out for a bench power and an oscilloscope
A oscilloscope is a helpful instrument to trace al the faults.
regards from rainy Hamburg
Wolfgang
DF6ZC
Perry Babin said:
I'm just about to desolder them now.
I have these model numbers, C1027 is the upper transsitor. The bottom one is A1023. These are in 4 sets, so they split the 20 into 4 sets of 5 and a 'pair' of C1027 and A1023's are attached to the gate resistor circuit.
As i said above the only thing left on the power side now is a few resistors by the driver transistors, the toriods and the SMPS board.
Ok i get 15v (supply voltage) across the centre pads of 4 of the transistors ( the C1027)
The other 4 transistors ( the A1023) i get 0v.
I have reason to believe that the centre pin may not be the gate, however, as i get ~5.6v across all top pads of the transistors.
What does that conclude then?
Thanks for all your help btw, Perry.
The other 4 transistors ( the A1023) i get 0v.
I have reason to believe that the centre pin may not be the gate, however, as i get ~5.6v across all top pads of the transistors.
What does that conclude then?
Thanks for all your help btw, Perry.
The pin configuration for the driver transistors is emitter, collector, base.
http://sigma.octopart.com/108441/datasheet/KEC-KTC1027.pdf
The center leg of the PNP drivers will be connected to ground (0v).
The center leg of the NPN drivers will be connected to B+ and will have ~12v DC.
The bases will be connected to the output pins of the driver IC and should have ~5-6v DC when read with a multimeter (actually ~50% duty cycle square wave).
When the drivers are working properly, the emitter will have approximately the same DC voltage (read with multimeter) as the base. The emitters drive the gates of the FETs via the gate resistors.
http://sigma.octopart.com/108441/datasheet/KEC-KTC1027.pdf
The center leg of the PNP drivers will be connected to ground (0v).
The center leg of the NPN drivers will be connected to B+ and will have ~12v DC.
The bases will be connected to the output pins of the driver IC and should have ~5-6v DC when read with a multimeter (actually ~50% duty cycle square wave).
When the drivers are working properly, the emitter will have approximately the same DC voltage (read with multimeter) as the base. The emitters drive the gates of the FETs via the gate resistors.
So it looks like the driver transistors have blown then?
However the rest of the board is ok as i get 0v across 4 of the middle pins on the transistors, but supply voltage across the other 4 middle pins.
I assume this means that the smps board is ok?
I'll replace the driver transistors, then see if i get the above said value across the then hopefully working, transistor, emitters legs
However the rest of the board is ok as i get 0v across 4 of the middle pins on the transistors, but supply voltage across the other 4 middle pins.
I assume this means that the smps board is ok?
I'll replace the driver transistors, then see if i get the above said value across the then hopefully working, transistor, emitters legs
These are components manufactured by KEC. The prefix is KT, not 2S.
http://www.keccorp.com/data/databook/pdf/KTC/Eng/KTC1027.pdf
http://www.keccorp.com/data/databook/pdf/KTA/Eng/KTA1023.pdf
If you can't find exact replacements, the BD139 and BD140 have worked for me when I needed a sub for a PS driver. The leads are a bit larger but have fit in all of the boards I've used them in. Someone mentioned ksa916 and ksc2316 which should also work but I haven't tried them.
http://sigma.octopart.com/28364/datasheet/ON-Semiconductor-BD139.pdf
http://sigma.octopart.com/139431/datasheet/Fairchild-KSA916OBU.pdf
http://www.keccorp.com/data/databook/pdf/KTC/Eng/KTC1027.pdf
http://www.keccorp.com/data/databook/pdf/KTA/Eng/KTA1023.pdf
If you can't find exact replacements, the BD139 and BD140 have worked for me when I needed a sub for a PS driver. The leads are a bit larger but have fit in all of the boards I've used them in. Someone mentioned ksa916 and ksc2316 which should also work but I haven't tried them.
http://sigma.octopart.com/28364/datasheet/ON-Semiconductor-BD139.pdf
http://sigma.octopart.com/139431/datasheet/Fairchild-KSA916OBU.pdf
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