The shorted FETs were connecting the 47 ohm resistors in parallel causing you to read 47/4.
If they're shorted, they must be replaced.
If they're shorted, they must be replaced.
Wow. That explains the high current when we turn on the amp.
I was thinking they were good, because they looks good. Huge mistake from my part. I will change them now.
Here is the Diodes results:
Upper side:
D3: ~815 Ohms
D4: ~639 Ohms
D5: ~653 Ohms
Lower side:
D6: ~660 Ohms
D7: ~639 Ohms
D8: ~801 Ohms
I was thinking they were good, because they looks good. Huge mistake from my part. I will change them now.
Here is the Diodes results:
Upper side:
D3: ~815 Ohms
D4: ~639 Ohms
D5: ~653 Ohms
Lower side:
D6: ~660 Ohms
D7: ~639 Ohms
D8: ~801 Ohms
For future reference, probe placement on the terminals of a diode is important.
None read near 0 ohms so they may be OK.
It appears that your soldering iron may not be getting enough heat to the terminals. Cut the legs of the old FETs and remove them one at a time. Heat the board from the side that has the most copper for the terminal and remove the terminal when the solder is molten. Adding new solder before desoldering is generally helpful.
None read near 0 ohms so they may be OK.
It appears that your soldering iron may not be getting enough heat to the terminals. Cut the legs of the old FETs and remove them one at a time. Heat the board from the side that has the most copper for the terminal and remove the terminal when the solder is molten. Adding new solder before desoldering is generally helpful.
Perry.
Sure. I will do that on the future.
I will do too a better soldering job when i finish this amp. I will buy a better soldering iron later.
About the amp, well.. i changed all the FETs (i tested and no more shorted FETs) and the problem still happens.
Still the same problems: Noises on the toroid and very high current consumption.
Sure. I will do that on the future.
I will do too a better soldering job when i finish this amp. I will buy a better soldering iron later.
About the amp, well.. i changed all the FETs (i tested and no more shorted FETs) and the problem still happens.
Still the same problems: Noises on the toroid and very high current consumption.
And all resistors now have a normal reading. About 47 Ohms on all of them on the upper and on the lower side of the board.
Well.
I see 0.7 Ohm resistance the on some legs on ALL MJE 4353's on the upper channel. I tested them still soldered on the board.
Do you think this is a problem? Can i test them that way?
Doing more tests right now.
I see 0.7 Ohm resistance the on some legs on ALL MJE 4353's on the upper channel. I tested them still soldered on the board.
Do you think this is a problem? Can i test them that way?
Doing more tests right now.
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That may be the only shorted transistor. Desolder one terminal of that resistor and re-check the output transistors on that side.
All MJE 4353's on the upper side shows a very low resistance on two of their three legs.
I will desolder one of their legs and test.
I will desolder one of their legs and test.
Hi,
I removed the 0.33 ohm resistor (that was reading 8k before), no luck. Still the same problem. I put the 0.33 ohm resistor on the circuit again.
Going to remove the first terminal of each 4353 on the upper side of the amp.
I removed the 0.33 ohm resistor (that was reading 8k before), no luck. Still the same problem. I put the 0.33 ohm resistor on the circuit again.
Going to remove the first terminal of each 4353 on the upper side of the amp.
Hi,
I removed the right leg of all bipolar transistors (MJE 4353's) on the upper side:
I tried to turn on the amp with the current limiter, and nothing. Still the noise and high current consumption.
And, i can see one of this transistors are shorted, the one i've changed the resistor:
😕
I removed the right leg of all bipolar transistors (MJE 4353's) on the upper side:
I tried to turn on the amp with the current limiter, and nothing. Still the noise and high current consumption.
And, i can see one of this transistors are shorted, the one i've changed the resistor:
An externally hosted image should be here but it was not working when we last tested it.
😕
If you pull the first leg and the emitter resistor for that transistor, the amp will likely power up. Clamp all transistors before applying power
Hi Perry.
I pulled up the first leg and the emitter resistor, like you said.
I've soldered back all another transistors.. and still the same problem.
The amp powered up, no protection LED, just high current usage and toroid noise.
I pulled up the first leg and the emitter resistor, like you said.
I've soldered back all another transistors.. and still the same problem.
The amp powered up, no protection LED, just high current usage and toroid noise.
OK. I was hoping that the one with the open emitter resistor was the only one shorted.
When you had the other legs out, did you find any shorted transistors?
When you had the other legs out, did you find any shorted transistors?
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