OLD THREAD DAC End by Andrea Ciuffoli - Page 92

Salas · 26th February 2010, 05:41 PM

Problem. Exchange Q15 first, and then Q14 if no cigar. Also watch their orientation. I hope it will not have to be Q16.

adamus · 26th February 2010, 06:08 PM

15 and 14 replaced... no cigar.

Must be the mosfet. bugger!

Ryssen · 26th February 2010, 07:16 PM

Quote:

Originally Posted by quanghao

Yes the Salas shunt I still have some PCB!

Ok,money sent for 2 pcb´s.

adamus · 26th February 2010, 08:19 PM

replaced q16 and still the same.... hmmmm

Salas · 26th February 2010, 09:06 PM

Look on its correctly functioning (?) twin +5V for parts orientation, correct types and values on parts, connections and copper lines underneath, measurements. There must be a bug somewhere in your build. Vgs (gate to +V) of the Mosfet must be around 4V and drop across Q14 must be existing. Is R15 actually 47R?

le´flu · 26th February 2010, 09:11 PM

Hi Salas,
if i understand you right...you recommend to skip the tl431
Regulator and only regulate from salas-reg pointed at 5V
and -5V. Right?
Would you suggest matching of LED´s? To what current should
they be matched each?

Greetings Ulf

Salas · 26th February 2010, 09:16 PM

Its not my design, I don't recommend. I just thought aloud. This must come officially from the maker and GB holder, or any other successful tweaks from the builders. As for the part that they adopted, namely the 5V SSV1.0 reg array, no you don't need to match leds, since you got trimmers.

Regards

adamus · 10:16 PM

the gate of q16 is sat at the output voltage. so surely it points the finger at q14.... trouble is i have already replaced it.

I'll try replacing again.

edit, replaced and no joy. I'll try q15 again..... this has me stumped.

Salas · 26th February 2010, 10:17 PM

I repeat, is R15 correct value?

adamus · 10:25 PM

yep, 47ohms.the 47ohm bc550 junction measures 338mv.

26th February 2010, 09:57 PM	#918
adamus diyAudio Member Join Date: Apr 2008	the gate of q16 is sat at the output voltage. so surely it points the finger at q14.... trouble is i have already replaced it. I'll try replacing again. edit, replaced and no joy. I'll try q15 again..... this has me stumped. Last edited by adamus; 26th February 2010 at 10:16 PM.

26th February 2010, 10:19 PM	#920
adamus diyAudio Member Join Date: Apr 2008	yep, 47ohms.the 47ohm bc550 junction measures 338mv. Last edited by adamus; 26th February 2010 at 10:25 PM.

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26th February 2010, 05:41 PM	#911
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	Problem. Exchange Q15 first, and then Q14 if no cigar. Also watch their orientation. I hope it will not have to be Q16.

26th February 2010, 06:08 PM	#912
adamus diyAudio Member Join Date: Apr 2008	15 and 14 replaced... no cigar. Must be the mosfet. bugger!

26th February 2010, 08:19 PM	#914
adamus diyAudio Member Join Date: Apr 2008	replaced q16 and still the same.... hmmmm

26th February 2010, 09:06 PM	#915
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	Look on its correctly functioning (?) twin +5V for parts orientation, correct types and values on parts, connections and copper lines underneath, measurements. There must be a bug somewhere in your build. Vgs (gate to +V) of the Mosfet must be around 4V and drop across Q14 must be existing. Is R15 actually 47R?

26th February 2010, 09:11 PM	#916
le´flu diyAudio Member Join Date: Mar 2004 Location: Hoexter	Hi Salas, if i understand you right...you recommend to skip the tl431 Regulator and only regulate from salas-reg pointed at 5V and -5V. Right? Would you suggest matching of LED´s? To what current should they be matched each? Greetings Ulf

26th February 2010, 09:16 PM	#917
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	Its not my design, I don't recommend. I just thought aloud. This must come officially from the maker and GB holder, or any other successful tweaks from the builders. As for the part that they adopted, namely the 5V SSV1.0 reg array, no you don't need to match leds, since you got trimmers. Regards

26th February 2010, 10:17 PM	#919
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	I repeat, is R15 correct value?