Again. Left channel: to the ground
Tran. #6 R 1.57V L (-20)-(139)mV
The measurements on meter is jumpy
Tran. #6 R 1.57V L (-20)-(139)mV
The measurements on meter is jumpy
Sorry mistake in post above... Left channel not to ground. Must same from pin to left fork of Tran 6
You see that tran 6 on left channel only has 2.7mV.
Normally it should have around 26mV.
Now Tran 5 has 67mV which is to much.
This Tran 5 high current is because the parallel Tran 6 is not conducting.
Normally it should have around 26mV.
Now Tran 5 has 67mV which is to much.
This Tran 5 high current is because the parallel Tran 6 is not conducting.
So it looks like Tran 6 or the resistor of Tran 6 of the right hot channel is open = defective.
Before removing any transistor, first measure the resistor leading to it. The work/ not work problem points away from the FET.
Personally, I don't remember an open FET, they usually do a nice short.
If the transistor really is defective, the problem is to get a non fake replacement. Which may be a huge problem...
I hope AlphaAudio knows.
Personally, I don't remember an open FET, they usually do a nice short.
If the transistor really is defective, the problem is to get a non fake replacement. Which may be a huge problem...
I hope AlphaAudio knows.
So I understand it right?
Left channel Tran 6 = 22.7mV = ok
Right channel Tran 6 = 2,7mV = bad. And Tran 5 = 67,4mV = to high, because it compensates for Tran 6.
So tomorrow check resistor behind Tran 6 if it has 0,22 ohms or open.
Left channel Tran 6 = 22.7mV = ok
Right channel Tran 6 = 2,7mV = bad. And Tran 5 = 67,4mV = to high, because it compensates for Tran 6.
So tomorrow check resistor behind Tran 6 if it has 0,22 ohms or open.
We suspect an open resistor but open FET is also possible.
I once bought 2 working pa amps only for taking out the Fets and one FET out of 40 was open. 🙂
Does he use the amp in or use the pre? It is very important to use the amp in, so a possible, second problem doesn't mix up with the pure amp function.
That is why I wrote "personally". I'm a hobyist in electronics, so my experience is limited to a few dozen cases, others here may have much more experience.
I just wanted to point out that you should not butcher an amp if the problem is not 100% diagnosed.
This SANSUI is a beautifull build, even changing a FET is quite easy. They knew what they did.
I just wanted to point out that you should not butcher an amp if the problem is not 100% diagnosed.
This SANSUI is a beautifull build, even changing a FET is quite easy. They knew what they did.
There should be a small one for the input signal to the gate. Measure it too, not only the large 0.22R one. The difference in resitance are your measureing leads, which add to the 0.22 Ohms.
Ok, still from yesterday: resistor of Tran 6 on the good channel has around 25 mV ?
From now on everything is only about the bad channel Tran 5 to Tran 8.
Gate voltage about 2V on Tran 6 is ok ?
You could measure temperatures again.
Resistors and Trans 7 and 8 should have medium values.
Resistors and Trans 5 should be more hot.
Resistors and Trans 6 should be more cold.
As the resistor 6 is ok it all points to Tran6 is open.
From now on everything is only about the bad channel Tran 5 to Tran 8.
Gate voltage about 2V on Tran 6 is ok ?
You could measure temperatures again.
Resistors and Trans 7 and 8 should have medium values.
Resistors and Trans 5 should be more hot.
Resistors and Trans 6 should be more cold.
As the resistor 6 is ok it all points to Tran6 is open.