Control board voltage problem
- Thread starter roccus
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It is an op amp coupled with a precision voltage reference and an open collector output transistor inside that TO-92 package. Not a resistor at all. It is a sophisticated integrated circuit.
You can test if it is bad Ray
by removing it from the circuit and replacing it with a new one. It is a standard TL431AI device.
First make sure you have -78V coming in on both left and right channels on PAD 12. If you are getting plus voltage on the negative regulator, that is likely a key suspect.
You can test if it is bad Ray
by removing it from the circuit and replacing it with a new one. It is a standard TL431AI device.
First make sure you have -78V coming in on both left and right channels on PAD 12. If you are getting plus voltage on the negative regulator, that is likely a key suspect.
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Checked out pad 12 on right and left channel right channel is good -83V but right channel is +3 volt looked at pico fuses on right channel backplane and the B- fuse is open... I know I don't have any of these around here so looks like my amp will be out of commission for at least another week or so to get replacement fuse 
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That fuse prevented the roasting of the predriver on the control board, ergo, it did it's job. As an assembler of a lot of control and backplane boards one of the first things I did was order 100 spare pico fuses. Unless a guy is doing a lot of it, it really doesn't make sense to stock up on these types of components..........................
BUT..... When you do encounter these types of problems, when ordering replacements , a few more doesn't cost much at all, but you probably already knew that....
BUT..... When you do encounter these types of problems, when ordering replacements , a few more doesn't cost much at all, but you probably already knew that....
i
This would be very helpful if you lived next door.. never a Lee around when you need one! lol But ya when I order a part I get a few extras I have hundreds of dollars of components kicking around here but still never have the part I need 
That fuse prevented the roasting of the predriver on the control board, ergo, it did it's job. As an assembler of a lot of control and backplane boards one of the first things I did was order 100 spare pico fuses. Unless a guy is doing a lot of it, it really doesn't make sense to stock up on these types of components..........................
BUT..... When you do encounter these types of problems, when ordering replacements , a few more doesn't cost much at all, but you probably already knew that....
BUT..... When you do encounter these types of problems, when ordering replacements , a few more doesn't cost much at all, but you probably already knew that....
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