First channel of the pearl soldered today. I have a nice short somewhere, would be great if somebody could shortly take the time and help me a bit!
Being a genius, I left out R8 connecting the regulator with the actual amplifying stage to test first the regulator.
Surpassing myself I also forgot to solder Q2 and Q12.
The result was that R2 and R3 start to get cookingly hot (the 3 Watters of the regulator).
After disconnection and soldering in Q2 and Q12: no change (now circuit fully populated).
I don't even get proper voltage of the toroid, seems the voltage completely breaks down because of a short.
Measuring the resistance between PAD1 and PAD2 (where the psu-board leads connect to the pearl) I get a resistance of 9.5 Ohms indicating that the short is after the 2 power resistors (being 4.7Ohms each).
So what's wrong?
First I thought that I soldered the snapin elcos with far too much solder so that it made a short with the above lying ground plane (btw I failed desoldering them ARRGG), however this shouldn't be possible due to the laquer on the pcb.
Shorted diode also nay, since there would be still the 3k32 resistor R5 giving a higher resistance than I measured.
Any tips greatly appreciated! Thanks a lot guys!
Cheers, Hannes
PS: btw the rail (coming from psu-board) is unloaded 39.9V DC.
Being a genius, I left out R8 connecting the regulator with the actual amplifying stage to test first the regulator.
Surpassing myself I also forgot to solder Q2 and Q12.
The result was that R2 and R3 start to get cookingly hot (the 3 Watters of the regulator).
After disconnection and soldering in Q2 and Q12: no change (now circuit fully populated).
I don't even get proper voltage of the toroid, seems the voltage completely breaks down because of a short.
Measuring the resistance between PAD1 and PAD2 (where the psu-board leads connect to the pearl) I get a resistance of 9.5 Ohms indicating that the short is after the 2 power resistors (being 4.7Ohms each).
So what's wrong?
First I thought that I soldered the snapin elcos with far too much solder so that it made a short with the above lying ground plane (btw I failed desoldering them ARRGG), however this shouldn't be possible due to the laquer on the pcb.
Shorted diode also nay, since there would be still the 3k32 resistor R5 giving a higher resistance than I measured.
Any tips greatly appreciated! Thanks a lot guys!
Cheers, Hannes
PS: btw the rail (coming from psu-board) is unloaded 39.9V DC.
Polarity is ok.
Well, what I know now is that the short is after the 2nd 4.7Ohm resistor (R3). After this R3 I measure zero resistance between signal and ground. Resistors R5, R6, R7 measure ok. The IRF has no short (and does not have a connection to ground anyway).
I think one of the big 10mF caps is shorted. I don't know wether this happens now and then, but I see at the moment no other possibility.
I desoldered the R3 and the voltage after the 1st 10mF cap is fine (40V DC).
At least I learned now to measure also the big caps before soldering them in.
Desoldering snap-ins is really a pain.
Cheers, Hannes
Well, what I know now is that the short is after the 2nd 4.7Ohm resistor (R3). After this R3 I measure zero resistance between signal and ground. Resistors R5, R6, R7 measure ok. The IRF has no short (and does not have a connection to ground anyway).
I think one of the big 10mF caps is shorted. I don't know wether this happens now and then, but I see at the moment no other possibility.
I desoldered the R3 and the voltage after the 1st 10mF cap is fine (40V DC).
At least I learned now to measure also the big caps before soldering them in.
Desoldering snap-ins is really a pain.
Cheers, Hannes
How about pulling out the most expensive components (transistors) and apply a low voltage with high current. Then the short might suddenly show it ugly face... 
EDIT: If you supply something like 2V you can trace your way to the short by measuring different points in reference to supply +. When the voltage diff gets higher, you are closer to the short with your probe.
EDIT: If you supply something like 2V you can trace your way to the short by measuring different points in reference to supply +. When the voltage diff gets higher, you are closer to the short with your probe.
Thanks for your help!
I don't have any standoffs at the moment - the board is resting on newsprints at the moment.
If you mean the heatsink...that guy is isolated from the fet using a silpad and a nylon screw.
No, grounds are not connected at the moment. But I thought the grounds meet at the output rca-connectors as stated in the pdf?
Cheers, Hannes
I don't have any standoffs at the moment - the board is resting on newsprints at the moment.
If you mean the heatsink...that guy is isolated from the fet using a silpad and a nylon screw.
No, grounds are not connected at the moment. But I thought the grounds meet at the output rca-connectors as stated in the pdf?
Cheers, Hannes
Further news: I also desoldered the heatsink and the fet Q1 (the regulator fet).
Further R5 is now also desoldered.
I also attached a new pic with the changes made.
Still shorted
Cheers, Hannes
PS: can I make money with this? Selling it to scientists? Proofing Kirchhoff wrong?
Further R5 is now also desoldered.
I also attached a new pic with the changes made.
Still shorted
Cheers, Hannes
PS: can I make money with this? Selling it to scientists? Proofing Kirchhoff wrong?
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