Q17 - an audiophile approach to perfect sound

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#961
tvicol said:
Which BS250 are you using ?
https://www.vishay.com/docs/70209/70209.pdfTake care on DGS

Regards,
tibi
Click to expand...
I am using this transistor - https://in.element14.com/diodes-inc/bs250p/mosfet-p-ch-45v-0-23a-150deg-c/dp/3405170

The datasheet is https://4donline.ihs.com/images/Vip...7-1.pdf?hkey=52A5661711E402568146F3353EA87419

Comparing against the Vishay from your link the DGS seems to be different on the Diodes inc. but I followed your PCB marking which says DGS and put the D to D, G to G and S to S against the one of Diodes Inc datasheet. So I think I soldered the right way.

Thanks
 
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#962
Vishay BS250

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Diodes Inc BS250
1645116343915.png
 
#963
manniraj said:
Sorry Tibi, I thought you looked at my earlier posts when I started testing using a simple bulb tester. To put in perspective the step by step approach here you go:
Amp has all the good quality parts from element14 and rsdelivers distributors. OPA1641 is the smd opamp which I used directly on the amp board.
1. Using a 22vac 300VA trafo and LT4320 CRC psu board but the R is shorted per your suggestion for this kind of class B amp. Gives around +/-33vdc stable.
2. Used a simple bulb tester to run the initial tests of the amp, and now the rails show around +/-10.12vdc
3. On power up with the bulb tester, the bulb initially glows for a flash of a second and then goes off and then immediately comes back blinks for 2-3 seconds and glows fully does not get switched off so I presume the current is being drawn by the amp board.
4. Checked the voltage across R10/12 having 47/1W and its around 2.82v and 3.12v corresponds to around 60mA current flow so I guess the input stage is good.
5. Offset was hovering around 0.5-1.4mV and slowly dropping towards 0
6. But the LEDs were not lit and Stef suggested that i need at least 24vdc or optimal 30vdc on the rails for them to glow. As I am using a bulb tester the current/voltage is being limited, so I am fine with the LEDs for now.
7. Power transistors are not hot but maybe very slightly warm at this stage.
8. Now I used a 0.1R/5w BPR resistor in series with the positive rail on the amp and checked for the voltage across it. This is around 152mV with the input signal being open and being shorted/closed its around 173mV. So the amp is drawing around 1.52A to 1.73A.

Need your suggestions to look for any issues with my above results or is it good to remove the bulb tester and test the amp!

Here are some of the pics for your reference

View attachment 1026334

Thanks
Click to expand...
As you can see @tvicol I put the BS250 correctly following the data sheet of Diodes Inc where I got them from.
 
#965
@manniraj

Hello,
I first tested my Q17mini boards
With a 60W light bulb

The light bulb is connected in serial with the primary of the power transformer

I have ~240V at home, and my transformer give me after rectification +/- 50V

When I plug(one board), the light flash (charging capacitors) then light off...
With 2 boards the light bulb glows a little...
Idle consumption is really low...

Regards,
Julien
 
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#969
juju35135 said:
@manniraj

Hello,
I first tested my Q17mini boards
With a 60W light bulb

The light bulb is connected in serial with the primary of the power transformer

I have ~240V at home, and my transformer give me after rectification +/- 50V

When I plug(one board), the light flash (charging capacitors) then light off...
With 2 boards the light bulb glows a little...
Idle consumption is really low...

Regards,
Julien
Click to expand...
Thanks Julien for the confirmation, then my board has some issue as with 240vac primary and 22vac winding I get around +/-33vdc and now with bulb tester the bulb glows after the initial hiccup which you rights described as charging the caps on the psu. But the bulb I was expecting to either reduce the glow or switch off but not sure here its always glowing.
 
#972
manniraj said:
Also one observation on this board is Q11 the D & G are shorted and I checked the solder pads for any dry solder or flux. Also my blank pcb too has those pads shorted on the pcb itself.
Click to expand...
This is normal, as Q11 is part of a current mirror.

Opamp is correctly mounted. Does the LED's emit any light or are completely off ?
Please let me know rail voltages and before and after opamp regulators.

Regards,
Tibi
 
#973
tvicol said:
Пожалуйста, дайте мне знать напряжение на шинах, а также до и после регуляторов операционных усилителей.
Click to expand...

manniraj said:
Теперь, используя тестер ламп для первоначального включения, лампа сначала гаснет, а затем быстро включается с миганием, а затем светится оптимально. Я проверил шины постоянного тока, и они упали до +/- 10,5 В постоянного тока с помощью тестера ламп. Но красные светодиоды на плате усилителя не светятся при включении питания, и перед пайкой я проверил стандартную полярность: более длинная нога к кругу, а короткая — к квадратной.
Click to expand...
 
#979
tvicol said:
This is normal, as Q11 is part of a current mirror.

Opamp is correctly mounted. Does the LED's emit any light or are completely off ?
Please let me know rail voltages and before and after opamp regulators.

Regards,
Tibi
Click to expand...
Thanks for the Q11 clarification. Regarding the LEDs they do not emit any light and I got the same ones per the BOM from element14 site. I tested the spare 2 more leds using DMM and they do light up but fairly low which is fine. Rail voltages are +/-33vdc and with bulb tester they drop to around +/-10.5vdc. When you say "before and after opamp regulators" not sure I get what you are asking sorry.

Also I am using 1845 transistors for Q3/7/12 whereby the pcb silk screen says use 2SC2240 as well as the schematic. Also using KSA992 in place of 2SA970 for Q2/10. But the guide says Q2 as 1845.
The github layout and your content guide bom values does not mention anything for Q3. I went with the pcb marking and looking at your schematic.

1645123735329.png
 
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