Identify problem with Aleph P

loovet · 28th January 2008, 07:32 PM

Something went wrong

I’ve had my Aleph P up and running for a while. But today, when I tried to measure the current of the pre amp itself, I ran in to trouble. Either I quickly shorted the circuit after the power supply or I did something wrong when I tried to do the measure itself. When I tried to measure the current I heard two small clicks, probably when one or two transistors blew up

This is not as bad as one could think since it’s just a prototype board and I will soon order new PCB’s.

But never the less, I have no problem to copy a schematic and make my one PCB and get an amp like this up and running. My problem appears when it is not function as it should or when as in this case, one or more components ran in to failure due to my one mistake. I really have a hard time to locate the problem itself, and I actually do not know where to start. And maybe someone could be nice and give me some hints where to start.

I actually do not know how to control if a transistor (9610, 610 ZTX450, ZTX550) is working as it should when it’s still stuffed to the board, or if it’s even possible to do so.

What I have measured so far is that I have a drop over R73 (original schematic, the first 3 Ohm resistor the current flows through from the PS) of 56 V on one channel and 48 V on the other channel.

I would be extremely happy if someone could give me some tips where to start.

BR

/loovet

Manu · 28th January 2008, 08:11 PM

Check R73. They must be at leat 1W or so.

Bill Fuss · 29th January 2008, 02:37 PM

I'm not sure I understand how you are measuring the current flow. If you are measuring the voltage drop across a 3ohm resistor with 60ma running through it you should be reading around 0.18v. If it's much higher than that you have blown the 3 legged fuses in the circuit. The higher the current the higher the voltage drop.

Bill

culture · 29th January 2008, 02:51 PM

Quote:

Originally posted by loovet

What I have measured so far is that I have a drop over R73 (original schematic, the first 3 Ohm resistor the current flows through from the PS) of 56 V on one channel and 48 V on the other channel.

Check the fets in the psu circuit... don’t really remember the values i measured when i
connected my psu board the wrong way around but i belive it measured something similar

cheers,

c

Bill Fuss · 29th January 2008, 03:05 PM

Hi Culture, are you assuming he is measuring the voltage from the PS neg to the resistor? If he's reading 48v like that then he's dropping 12v across the resistor, which would be 4 amps.

Bill

Bill Fuss · 29th January 2008, 03:12 PM

Is it possible that you have set your meter on amps and connected it across your PS and blown your PS board?

Bill

culture · 29th January 2008, 04:21 PM

Quote:

Originally posted by Bill Fuss
Hi Culture, are you assuming he is measuring the voltage from the PS neg to the resistor? If he's reading 48v like that then he's dropping 12v across the resistor, which would be 4 amps.

Bill

Oops, you're right...after taking a look at the schematic (and reading the post more careful) i realized i made some assumptions a bit too fast. i was measuring 60v plus and measuring between ps neg an the resistor indeed.

c

loovet · 29th January 2008, 08:46 PM

Manu,

you where right it was the R73s.

I've changed them and now it's up and runing again.

Thanks to all of you who have given you inputs.

Thanks

/loovet

Bill Fuss · 29th January 2008, 08:55 PM

That's very good news, glad things worked out.

Bill

Manu · 29th January 2008, 09:07 PM

Quote:

Originally posted by loovet
Manu,

you where right it was the R73s.

I've changed them and now it's up and runing again.

...
/loovet

Glad to hear that.
You're welcome.

Manu

28th January 2008, 07:32 PM	#1
loovet diyAudio Member Join Date: Sep 2002 Location: Outside Stockholm	Identify problem with Aleph P Something went wrong I’ve had my Aleph P up and running for a while. But today, when I tried to measure the current of the pre amp itself, I ran in to trouble. Either I quickly shorted the circuit after the power supply or I did something wrong when I tried to do the measure itself. When I tried to measure the current I heard two small clicks, probably when one or two transistors blew up This is not as bad as one could think since it’s just a prototype board and I will soon order new PCB’s. But never the less, I have no problem to copy a schematic and make my one PCB and get an amp like this up and running. My problem appears when it is not function as it should or when as in this case, one or more components ran in to failure due to my one mistake. I really have a hard time to locate the problem itself, and I actually do not know where to start. And maybe someone could be nice and give me some hints where to start. I actually do not know how to control if a transistor (9610, 610 ZTX450, ZTX550) is working as it should when it’s still stuffed to the board, or if it’s even possible to do so. What I have measured so far is that I have a drop over R73 (original schematic, the first 3 Ohm resistor the current flows through from the PS) of 56 V on one channel and 48 V on the other channel. I would be extremely happy if someone could give me some tips where to start. BR /loovet

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28th January 2008, 08:11 PM	#2
Manu diyAudio Member Join Date: Nov 2002 Location: Vienna, Ostrich	Check R73. They must be at leat 1W or so.

29th January 2008, 02:37 PM	#3
Bill Fuss RIP Join Date: Oct 2005 Location: Central Florida	I'm not sure I understand how you are measuring the current flow. If you are measuring the voltage drop across a 3ohm resistor with 60ma running through it you should be reading around 0.18v. If it's much higher than that you have blown the 3 legged fuses in the circuit. The higher the current the higher the voltage drop. Bill

29th January 2008, 03:05 PM	#5
Bill Fuss RIP Join Date: Oct 2005 Location: Central Florida	Hi Culture, are you assuming he is measuring the voltage from the PS neg to the resistor? If he's reading 48v like that then he's dropping 12v across the resistor, which would be 4 amps. Bill

29th January 2008, 03:12 PM	#6
Bill Fuss RIP Join Date: Oct 2005 Location: Central Florida	Is it possible that you have set your meter on amps and connected it across your PS and blown your PS board? Bill

29th January 2008, 08:46 PM	#8
loovet diyAudio Member Join Date: Sep 2002 Location: Outside Stockholm	Manu, you where right it was the R73s. I've changed them and now it's up and runing again. Thanks to all of you who have given you inputs. Thanks /loovet

29th January 2008, 08:55 PM	#9
Bill Fuss RIP Join Date: Oct 2005 Location: Central Florida	That's very good news, glad things worked out. Bill

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