You might be able to identify the midpoint of each winding without removing the half winding.
See my previous posts describing the method.
Another unhelpful post?
See my previous posts describing the method.
Another unhelpful post?
Thank you for reply!
If you mean that post than you mention toroidal trafo there. And it suppose the secondary has one layer. But I think 51V secondary is quite a lot for one layer windings..
So I suppose to add 10-20 windings for measuring V by wind and calculate number to unwind. Am I on right way?
If you mean that post than you mention toroidal trafo there. And it suppose the secondary has one layer. But I think 51V secondary is quite a lot for one layer windings..
So I suppose to add 10-20 windings for measuring V by wind and calculate number to unwind. Am I on right way?
Finally i have in my hand 10 pcs of NJL 1302&3281. I used the schematic from Builders manual to measure Hfe and Vbe.
Vbe is very consistent between 0.610 and 0.614 V for NJL 1302 and between 0.623 to 0.627 for NJL 3281. (measured directly Vbe with Dmm while transistor was installed in the test rig).
Regarding hfe i have obtained for NJL3281 values between 110 and 115
and for NJL 1302 hfe is from 112 to 118.
What do you think are my values close enough? Also are my measured values close to what should be ?
Regards,
Adrian
Vbe is very consistent between 0.610 and 0.614 V for NJL 1302 and between 0.623 to 0.627 for NJL 3281. (measured directly Vbe with Dmm while transistor was installed in the test rig).
Regarding hfe i have obtained for NJL3281 values between 110 and 115
and for NJL 1302 hfe is from 112 to 118.
What do you think are my values close enough? Also are my measured values close to what should be ?
Regards,
Adrian
Adrian, the HFe values of your transistors look quite good, but I remember Mihai's advise to not use the NJL3 - series transistors,
since they have another type of compensation diode installed.
Find the description of the differences in Bob Cordell's book: "Designing Audio Power Amplifiers" on page 305.
The NJL4 - series would have been a better alternative!
If you want to stick to the NJL3 - transistors, build a compensation scheme like the ones Bob describes on the following pages.
Best regards - Rudi
since they have another type of compensation diode installed.
Find the description of the differences in Bob Cordell's book: "Designing Audio Power Amplifiers" on page 305.
The NJL4 - series would have been a better alternative!
If you want to stick to the NJL3 - transistors, build a compensation scheme like the ones Bob describes on the following pages.
Best regards - Rudi
Measured my 10pcs of NJL0281 i have:
Vf (diode)
0,503
0,510
0,510
0,509
0,509
0,509
0,504
0,507
0,506
0,507
Do you think i will be able to use 5 of them ?
Vf (diode)
0,503
0,510
0,510
0,509
0,509
0,509
0,504
0,507
0,506
0,507
Do you think i will be able to use 5 of them ?
I think Roender called for 1/2w resistors, it is quite difficult to get 1/2w resistors for all the values wanted and also too big to fit into the PCB.
can 1/4w do the job? if not, which ones in particular need 1/2w?
can 1/4w do the job? if not, which ones in particular need 1/2w?
You can use them , the 3 0,509 on one side and the 2 0,507 with the 0,506 on the other side. They don't have to be matched side to side, just the ones in the same side.
At what test current?
Much more important to match the Vbe @ 185mA and ~hFE (+-5%) @ 185mA than to select for Vf.
I've attached the test rig recommended to me by Rudi and the testing current is close to the one recommended by you.
Vbe is pretty consistent and is ranging between 0.630 and 0.638V among the 10 transistors under test.
Hfe obtained after calculation was:
86,09
94,65
90,90
91,24
92,90
92,90
95,25
88,80
91,77
85,76
Now i wait some NJL0302 from a fellow diy-er from Poland to how they measure.
I have also some good matching pairs of 3281/1302 but i understood that they sound a bit different that the recommended 0281/0302.
Vbe is pretty consistent and is ranging between 0.630 and 0.638V among the 10 transistors under test.
Hfe obtained after calculation was:
86,09
94,65
90,90
91,24
92,90
92,90
95,25
88,80
91,77
85,76
Now i wait some NJL0302 from a fellow diy-er from Poland to how they measure.
I have also some good matching pairs of 3281/1302 but i understood that they sound a bit different that the recommended 0281/0302.
Attachments
That is the really important parameter.
A 3pr output stage MUST have the three devices with very close Vbe
I consider +-1mVbe to be too high, a 1mV spread is preferable.
For measuring Hfe of 15034/15035 is needed the circuit that i've attached above in #672 to have a higher test current ?
I'm asking this because i've measured them on my DMM and i have different ranges for PNP and NPN something like 120-170 vs 212-218 and i can't see any chance to select some pairs. I have 10 pcs of each.
I'm asking this because i've measured them on my DMM and i have different ranges for PNP and NPN something like 120-170 vs 212-218 and i can't see any chance to select some pairs. I have 10 pcs of each.
Hi,
Can anyone help, what could be a reason of fc100 amp shorting after powering it up with 40W light bulb tester?
Used it with 30VDC main PSU and 37VDC fronted PSU. They are work fine alone.
Can anyone help, what could be a reason of fc100 amp shorting after powering it up with 40W light bulb tester?
Used it with 30VDC main PSU and 37VDC fronted PSU. They are work fine alone.
Last edited:
Andriyol, the power dissipated by a FC-100 channel in idle status is about 35W.
Add to this about 5W for the frontend shunt, and you will see: a 40W bulb tester is too small.
Moreover: please connect the bulb tester only to the backend, when you power-on both the shunt and a FC-100 channel.
Best regards - Rudi
Add to this about 5W for the frontend shunt, and you will see: a 40W bulb tester is too small.
Moreover: please connect the bulb tester only to the backend, when you power-on both the shunt and a FC-100 channel.
Best regards - Rudi
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