The simplistic Salas low voltage shunt regulator - Page 512

merlin el mago · 8th July 2012, 03:37 PM

Why have you connected collector BC547 to GND? you have to follows exaqctly Salas schematic.

Salas · 8th July 2012, 03:46 PM

Quote:

Originally Posted by studiostevus

Funny stuff here... My 4 salas shunts seemed to be working correctly.... However one of them has a problem: the bc547 gets really hot and eventually burns (after several hours)

Specs:
Bib version, but on my own pcb, using irf610 for ccs and irf620 for shunt
Vout=15v
Vin=25v
Ccs=130mA
Iload=50mA tda1541a

Any ideas?

The other 3 regs on the board (5v, -5v, 3.6v) all work fine

See if the 170 on top of it feeds it too much current. Could that 170 got shorted dead? See if something oscillates in the particular unit if all its semis are healthy.

studiostevus · 8th July 2012, 06:53 PM

Quote:

Originally Posted by merlin el mago

Why have you connected collector BC547 to GND? you have to follows exaqctly Salas schematic.

The GND connection I mean is the 'S0' connection. This connection is according to the schematic.

studiostevus · 8th July 2012, 06:57 PM

Quote:

Originally Posted by Salas

See if the 170 on top of it feeds it too much current. Could that 170 got shorted dead? See if something oscillates in the particular unit if all its semis are healthy.

Do you mean U$22 in my schematic?

I have replaced it yesterday, as I thought it was the reason for the trouble I had. It turned out that the BC547 was the problem. After I replaced it (yesterday), regulation was back, however after listening to the unit for some hours today, again the voltage was drifting upwards as the bc547 got hotter and hotter...

Salas · 8th July 2012, 07:45 PM

U$23

agussug · 9th July 2012, 03:47 AM

@Studiostevus : What BC547 did you use?
@Salas : Is it possible to see oscillation without oscilloscope?

Regards

Salas · 9th July 2012, 04:22 AM

If you move a portable AM radio over an oscillating circuit it can pick it up given its strong and high enough. Not reliable, kinda Mad Max world solution.

studiostevus · 9th July 2012, 05:04 PM

Quote:

Originally Posted by agussug

@Studiostevus : What BC547 did you use?
Regards

Plain BC547's...

I just noticed that on both my negative regs, the bc547's get really hot

studiostevus · 9th July 2012, 05:36 PM

I just checked on the scope: the -15V reg (the troubling one) is absolutely not stable. The output voltage moves irregularly down, on the scope visible as the trace pulling several mV's down. It's very irregular, i can't see any particular pattern, it's more like flickering, and goes instantly

Salas · 9th July 2012, 05:54 PM

The error amp or the Vref must be having an intermittent condition. Any semi for that matter.

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8th July 2012, 03:37 PM	#5111
merlin el mago diyAudio Member Join Date: Sep 2009 Location: Catalonia new Europe state	Why have you connected collector BC547 to GND? you have to follows exaqctly Salas schematic.

8th July 2012, 07:45 PM	#5115
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	U$23

9th July 2012, 03:47 AM	#5116
agussug diyAudio Member Join Date: Jul 2010	@Studiostevus : What BC547 did you use? @Salas : Is it possible to see oscillation without oscilloscope? Regards

9th July 2012, 04:22 AM	#5117
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	If you move a portable AM radio over an oscillating circuit it can pick it up given its strong and high enough. Not reliable, kinda Mad Max world solution.

9th July 2012, 05:36 PM	#5119
studiostevus diyAudio Member Join Date: Oct 2009 Location: Brunei	I just checked on the scope: the -15V reg (the troubling one) is absolutely not stable. The output voltage moves irregularly down, on the scope visible as the trace pulling several mV's down. It's very irregular, i can't see any particular pattern, it's more like flickering, and goes instantly

9th July 2012, 05:54 PM	#5120
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	The error amp or the Vref must be having an intermittent condition. Any semi for that matter.