Simplistic NJFET RIAA - Page 311

merlin el mago · 11:49 PM

Wrong channel
C5 not connected to GND & R5 connected to R7

R7/GND 0.68V
Drain Q5/GND 10.50V
If I have to change Q6 I only have one SK170BL max. 10.02 Idss, can I use it?

Ok channel
R7/GND 10.14V
Drain Q5/GND 21.4V

Salas · 10th March 2010, 11:53 PM

OK channel perfect. You can use your spare as Q6 no problem. But double check and fix everything for connections first. Use the OK channel as total prototype to review and correct the wrong channel.

merlin el mago · 11th March 2010, 12:09 AM

Ok tomorrow I will check twice the connections & after I will change Q6.

Changing Q6 will increase the voltage between Drain Q5/GND to 21V?

Salas · 11th March 2010, 12:21 AM

No, Q6 has to do with feeding the LEDs only. When you will fix ''Wrong channel
C5 not connected to GND & R5 connected to R7'' there is chance 2nd and 3rd stage will work if nothing had burned. Leave Q6 change last after you review every tiny connection from in to out and voltages will be measured once more.

P.S. Did it ever get more than 45V during your shunts problems?

Anyway, Merlin The Wizard in the end can lift spell.

merlin el mago · 12:49 AM

Seems that the dual njfet lsk389 is bourned, due to the fact after connecting C5 to GND & disconnect R5 from R7 I measured R7 to GND 0.68V & Drain Q5 to GND 10.50V. To change lsk389 I have two options: one lsk with 11.23 Idss + 11.29 Idss or other lsk with 9.74 Idss + 9.72 Idss, wich one could I use it?

Can't remember during shunt process if voltage exceeded 45V.

Yes, always I have the last chance in the end to lift spell.

Salas · 11th March 2010, 12:35 AM

Quote:

Originally Posted by merlin el mago

Changing Q6 will increase the voltage between Drain Q5/GND to 21V?

Quote:

Originally Posted by Salas

No, Q6 has to do with feeding the LEDs only.

Salas · 11th March 2010, 12:45 AM

Quote:

Originally Posted by merlin el mago

Seems that the two njfets lsk389 is bourned, due to the fact after connecting C5 to GND & disconnect R5 from R7 I measured R7 to GND 0.68V & Drain Q5 to GND 10.50V. To change lsk389 I have two options: one lsk with 11.23 Idss + 11.29 Idss or other lsk with 9.74 Idss + 9.72 Idss, wich one could I use it?

First option.

merlin el mago · 11th March 2010, 12:51 AM

Thanks & good night.

merlin el mago · 11th March 2010, 03:57 PM

After checked 4 times the connections I replaced the dual LSK389 (Q2 & Q5) for the new LSK389 & the voltages follows the same Drain Q5/GND 10,50V & R7/GND 0.68V.

I suspected about the resistors values for R9, R10 & R11 so I checked:

R9 100R4 instead 100R
R10 2K37 instead 2K4
R11 6K12 instead 6K2

Salas · 11th March 2010, 04:18 PM

Is your trimmer under Q2 connected and set as in the working channel?

10th March 2010, 11:47 PM	#3101
merlin el mago diyAudio Member Join Date: Sep 2009 Location: Blanes - Costa Brava	Wrong channel C5 not connected to GND & R5 connected to R7 R7/GND 0.68V Drain Q5/GND 10.50V If I have to change Q6 I only have one SK170BL max. 10.02 Idss, can I use it? Ok channel R7/GND 10.14V Drain Q5/GND 21.4V Last edited by merlin el mago; 10th March 2010 at 11:49 PM.

11th March 2010, 12:34 AM	#3105
merlin el mago diyAudio Member Join Date: Sep 2009 Location: Blanes - Costa Brava	Seems that the dual njfet lsk389 is bourned, due to the fact after connecting C5 to GND & disconnect R5 from R7 I measured R7 to GND 0.68V & Drain Q5 to GND 10.50V. To change lsk389 I have two options: one lsk with 11.23 Idss + 11.29 Idss or other lsk with 9.74 Idss + 9.72 Idss, wich one could I use it? Can't remember during shunt process if voltage exceeded 45V. Yes, always I have the last chance in the end to lift spell. Last edited by merlin el mago; 11th March 2010 at 12:49 AM.

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10th March 2010, 11:53 PM	#3102
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	OK channel perfect. You can use your spare as Q6 no problem. But double check and fix everything for connections first. Use the OK channel as total prototype to review and correct the wrong channel.

11th March 2010, 12:09 AM	#3103
merlin el mago diyAudio Member Join Date: Sep 2009 Location: Blanes - Costa Brava	Ok tomorrow I will check twice the connections & after I will change Q6. Changing Q6 will increase the voltage between Drain Q5/GND to 21V?

11th March 2010, 12:21 AM	#3104
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	No, Q6 has to do with feeding the LEDs only. When you will fix ''Wrong channel C5 not connected to GND & R5 connected to R7'' there is chance 2nd and 3rd stage will work if nothing had burned. Leave Q6 change last after you review every tiny connection from in to out and voltages will be measured once more. P.S. Did it ever get more than 45V during your shunts problems? Anyway, Merlin The Wizard in the end can lift spell.

11th March 2010, 12:51 AM	#3108
merlin el mago diyAudio Member Join Date: Sep 2009 Location: Blanes - Costa Brava	Thanks & good night.

11th March 2010, 03:57 PM	#3109
merlin el mago diyAudio Member Join Date: Sep 2009 Location: Blanes - Costa Brava	After checked 4 times the connections I replaced the dual LSK389 (Q2 & Q5) for the new LSK389 & the voltages follows the same Drain Q5/GND 10,50V & R7/GND 0.68V. I suspected about the resistors values for R9, R10 & R11 so I checked: R9 100R4 instead 100R R10 2K37 instead 2K4 R11 6K12 instead 6K2

11th March 2010, 04:18 PM	#3110
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	Is your trimmer under Q2 connected and set as in the working channel?

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