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Post by PinkFloyd on Dec 12, 2006 15:24:08 GMT
Are you there xerxes? what happened / is happening with the Corda? if you can't get it going I'll be happy to have a look at it man.
Mike.
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xerxes
Been here a while!
Posts: 1,115
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Post by xerxes on Dec 12, 2006 17:00:35 GMT
Hi Mike, I replaced the buffers, which I thought I might have damaged by overheating them, but got exactly the same result with the new ones which I was very carefull not to get too hot. I've scrubbed the circuit board, held it up to the light and made as good a visual inspection as possible. I also checked the circuit with a voltmeter and this is what I get: [ It would appear that everything is fine up to the point before the buffers, I assume that while the 1.4 voltage difference between -15v and -13.6v after the 3k3 resistor would not cause the amp to not work completely or account for the -12.5v DC offset at the headphone jack. The fact that both channels are the same is also odd and suggests that the same fault is present on both channels, or that the problem is "further back" in the power supply part of the circuit, but basically I'm all out of ideas and patience.
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rickcr42
Fully Modded
Rest in peace my good friend.
Posts: 4,514
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Post by rickcr42 on Dec 12, 2006 21:07:47 GMT
are you getting +/- 15 volts at the op amps ? If low only at the buffers then yes,that is the area with the problem but if you are getting a low voltage reading at both stages your regulators are not "regulating" which usually means they are in backwards
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rickcr42
Fully Modded
Rest in peace my good friend.
Posts: 4,514
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Post by rickcr42 on Dec 12, 2006 21:29:45 GMT
more on the above..... Early on when I first began using three terminal regulators for some reason i more often than not "flipped" the package (or screwed up the negative V-Reg layout the pin-out being different ;D ) and at first had no clue that I did it even though the measured voltage was low. My thinking at the time was "well it is passing a voltage so obviously not the problem" and because of this it was a real bitch to finally recognise my mistake,a mistake made worse by the nature of reversed regulators to STILL pass a voltage even though in backwards ! Once I "got it" my life became a lot more simple because NOW I was armed with knowledge (even though still not smart enough to always put the little pricks in right the first time ) so every time I got a low voltage reading my first reaction would be to check the V-Regs instead of my former way of of they being last on the list of suspects and usually meant I tore everything up in the process of elimination,especially circuit board traces (vaporised more than a couple in my life ) Tought me to build and test the entire power supply section before proceeding on to the actual operational circuit being built because everything rolls from there and if that aint right nothing that follows can be
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xerxes
Been here a while!
Posts: 1,115
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Post by xerxes on Dec 12, 2006 22:48:26 GMT
The VRegs are in the right way round. Thinking about it, why don't they make some of these components so that they can only go in the right way round? It would be very easy to do, with the TO-220 packages, simply move one leg further out, so you have 2, or 4 legs equally spaced and the last one with a larger gap, that way it will physically only fit one way round. Similarly with DIP packages, simply move one pair of legs further apart from the rest.
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