That trace may be connected to the diode that shorted.
If the amp powered up and drew only 0.6A and the caps aren't shorted. you may have a problem in the regulated power supply or something feeding off of it.
Solder the legs of the rectifiers back into the circuit and power up the amp for as long as possible without allowing the power supply FETs to get too hot to touch. While it's on, check the temperature of all of the 8 pin op-amps. They should remain cool. By touching them, determine if one is getting hotter than the rest. With the limited supply you have, the op-amps shouldn't get hot enough to burn you but you should be careful.
If you don't find any that are hot, pull the input legs for the regulators (LM317, leg 3 and LM337, leg 2) from the board. Does it power up with those out of the board?
If the amp powered up and drew only 0.6A and the caps aren't shorted. you may have a problem in the regulated power supply or something feeding off of it.
Solder the legs of the rectifiers back into the circuit and power up the amp for as long as possible without allowing the power supply FETs to get too hot to touch. While it's on, check the temperature of all of the 8 pin op-amps. They should remain cool. By touching them, determine if one is getting hotter than the rest. With the limited supply you have, the op-amps shouldn't get hot enough to burn you but you should be careful.
If you don't find any that are hot, pull the input legs for the regulators (LM317, leg 3 and LM337, leg 2) from the board. Does it power up with those out of the board?
I've soldered the legs of the rectifiers back in the circuit and powered it up.
The OP-AMPs remain cool so they are good.
Pulled the input leads of the VRegs but the amplifiers still draws 3A. The Power LED goes on though.
Quick question, If I'd pull the leg of the rectifiers one more time the leg 'll probably break off, so the'd be unusable. The ones that are on the board are STPR1520D's. These weren't available @ Farnell so I cross referenced them and found these STTH1502D and ordered them. Are these any good?
The OP-AMPs remain cool so they are good.
Pulled the input leads of the VRegs but the amplifiers still draws 3A. The Power LED goes on though.
Quick question, If I'd pull the leg of the rectifiers one more time the leg 'll probably break off, so the'd be unusable. The ones that are on the board are STPR1520D's. These weren't available @ Farnell so I cross referenced them and found these STTH1502D and ordered them. Are these any good?
From chassis ground to the pad where the legs of the regulators were soldered into the board, what is the DC voltage? One should be positive, the other negative.
Is the voltage steady?
The fact that the op-amps are not hot doesn't guarantee that they are in good working order.
Those rectifiers should be OK.
Is the voltage steady?
The fact that the op-amps are not hot doesn't guarantee that they are in good working order.
Those rectifiers should be OK.
Op-amp failure is relatively rare. I happens a lot in amps that have regulators that fail but regulator failure doesn't happen in many amps. I replace 1 in 50 amplifiers (rough estimate). Don't start replacing them until we find that one is defective.
With the amp off, measure the resistance from pin 4 to pin 8 on the 8 pin op-amps.
Do you have any low value resistors (1-10 ohms) with wire leads?
With the amp off, measure the resistance from pin 4 to pin 8 on the 8 pin op-amps.
Do you have any low value resistors (1-10 ohms) with wire leads?
Solder one leg of the 10 ohm resistor to the solder pad and the other leg to the leg of the regulator that was soldered into the board. Power up the amp and measure the DC voltage across each of the 10 ohm resistors. If there is excessive current draw, the resistors may burn so be prepared to remove power quickly.
Green = Newly installed parts from Conrad (IRF640, IRF9640 and IRF3205)
Red = Parts not installed atm.
Purple = Parts installed that I got from Farnell:
D3 (1N4003)
Q1, Q2, Q3, Q4 (MMBTA56, MMBTA05)
R325, R225 (10 Ohm 3W)
R252, R275 (51 Ohm SMD)
R243, R245 (100 Ohm SMD)
R238 (47 Ohm SMD)
R264 (39 Ohm SMD)
Thats it for what I could remember. First thing I did was installing Q1, Q2, Q3, Q4.
When I installed those I checked if the amp would power up, result -> It draws 3A (Can't remember if the power LED went on but I guess it did).
After that I installed the other parts.
Soldered the input legs of the regulators back in the circuit.
R264 = 9,22V !!! Its heating up rapidly!! The solder has melted
I was touching some other resistors with my finger (with the power on) if they were getting hot and suddenly R328 went up in smoke !! For what I can see its a 1000 Ohm resistor...
What to do now? Unsolder them?
R264 = 9,22V !!! Its heating up rapidly!! The solder has melted
I was touching some other resistors with my finger (with the power on) if they were getting hot and suddenly R328 went up in smoke !!
For what I can see its a 1000 Ohm resistor... What to do now? Unsolder them?
That's where some of the current is going. Check the outputs to make sure none are shorted.
If none are, solder a jumper wire from leg 1 to leg 3 of one of the output transistors in each of the 4 parallel groups. Measure the resistance from leg 1 to leg 3 for all of the output transistors. Confirm that there are none that read more than ~110 ohms.
Then power up the amp to see if it will power up fully without drawing a continuous 3 amps. You should have more than ±50v on the input pins of the voltage regulators (317/337).
I don't think you need to do anything with the other resistors now. They will need to be replaced later if they're out of tolerance.
If none are, solder a jumper wire from leg 1 to leg 3 of one of the output transistors in each of the 4 parallel groups. Measure the resistance from leg 1 to leg 3 for all of the output transistors. Confirm that there are none that read more than ~110 ohms.
Then power up the amp to see if it will power up fully without drawing a continuous 3 amps. You should have more than ±50v on the input pins of the voltage regulators (317/337).
I don't think you need to do anything with the other resistors now. They will need to be replaced later if they're out of tolerance.
Alright. I've measured the outputs in circuit (Used your Checking Field Effect Transistors as guide):
Right channel (note that these are the original components.)
IRF640 (S+, D-)
Q316 = .510
Q317 = .510
Q318 = .510
Q319 = .507
Q320 = .507
IRF9640 (D+, S-)
Q311 = .863 and slowly rising (.001 every second)
Q312 = .863 and slowly rising (.001 every second)
Q313 = .857 and slowly rising (.001 every second)
Q314 = .883 and slowly rising (.001 every second)
Q315 = .891 and slowly rising (.001 every second)
Left channel (new parts)
IRF640 (S+, D-)
Q216 = .513
Q217 = .513
Q218 = .513
Q219 = .512
Q220 = .513
IRF9640 (D+, S-)
Q211 = .662 also slowly rising but much slower (.001 every 2~3 seconds)
Q212 = .666 also slowly rising but much slower (.001 every 2~3 seconds)
Q213 = .666 also slowly rising but much slower (.001 every 2~3 seconds)
Q214 = .663 also slowly rising but much slower (.001 every 2~3 seconds)
Q215 = .663 also slowly rising but much slower (.001 every 2~3 seconds)
With all the IRF9640 I measure what I think capacitance when the + probe is on Source and - probe on Drain.
Should I Pull the drain or gate pin on all the FETs to check for better measure results or are these measurement sufficient?
Right channel (note that these are the original components.)
IRF640 (S+, D-)
Q316 = .510
Q317 = .510
Q318 = .510
Q319 = .507
Q320 = .507
IRF9640 (D+, S-)
Q311 = .863 and slowly rising (.001 every second)
Q312 = .863 and slowly rising (.001 every second)
Q313 = .857 and slowly rising (.001 every second)
Q314 = .883 and slowly rising (.001 every second)
Q315 = .891 and slowly rising (.001 every second)
Left channel (new parts)
IRF640 (S+, D-)
Q216 = .513
Q217 = .513
Q218 = .513
Q219 = .512
Q220 = .513
IRF9640 (D+, S-)
Q211 = .662 also slowly rising but much slower (.001 every 2~3 seconds)
Q212 = .666 also slowly rising but much slower (.001 every 2~3 seconds)
Q213 = .666 also slowly rising but much slower (.001 every 2~3 seconds)
Q214 = .663 also slowly rising but much slower (.001 every 2~3 seconds)
Q215 = .663 also slowly rising but much slower (.001 every 2~3 seconds)
With all the IRF9640 I measure what I think capacitance when the + probe is on Source and - probe on Drain.
Should I Pull the drain or gate pin on all the FETs to check for better measure results or are these measurement sufficient?
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