Hmmmm...
I've just finished the P06 ESP phono preamp and I am getting a large voltage readings on the phono-in section. I've built a couple similar phono pre's and my voltage readings are 0 volts at the inputs. I'm having trouble sleuthing the problem, looking for ideas.
I built the variable EQ version for 78rpm EQ, so it is a bit different than the straight ahead build.
Getting voltage readings around 12.5 Volts at the inputs and no sound.
When I plug in my test turntable to voltage drops to around 2 Volts.
I've attached schematic of the version I built.
Any advice welcome!
I've just finished the P06 ESP phono preamp and I am getting a large voltage readings on the phono-in section. I've built a couple similar phono pre's and my voltage readings are 0 volts at the inputs. I'm having trouble sleuthing the problem, looking for ideas.
I built the variable EQ version for 78rpm EQ, so it is a bit different than the straight ahead build.
Getting voltage readings around 12.5 Volts at the inputs and no sound.
When I plug in my test turntable to voltage drops to around 2 Volts.
I've attached schematic of the version I built.
Any advice welcome!
Attachments
Don't connect the turntable until this is fixed. Can you unplug the op amps?
It could be a construction mistake. Remove the input op amp and ohm out each
pin connection per the schematic. Possibly all the op amps are connected wrong.
Are you numbering the pins clockwise from pin 1 on the bottom (not the top)?
It could be a construction mistake. Remove the input op amp and ohm out each
pin connection per the schematic. Possibly all the op amps are connected wrong.
Are you numbering the pins clockwise from pin 1 on the bottom (not the top)?
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I can unplug the op amps.
I installed them as he shows in his directions and as I have seen in several photos.
I also tried different op amps to see if that was the problem, had same result.
hmmmmmm
I installed them as he shows in his directions and as I have seen in several photos.
I also tried different op amps to see if that was the problem, had same result.
hmmmmmm
Think you must have a wiring problem, especially since both channels have the same problem.
Get out the DVM, remove the op amps, and check all the connections. Don't connect the turntable
any more until you are sure the problem is fixed, as the cartridge could be damaged. Luckily,
the R2 may have protected the cartridge. Could the power supply be connected backwards?
Get out the DVM, remove the op amps, and check all the connections. Don't connect the turntable
any more until you are sure the problem is fixed, as the cartridge could be damaged. Luckily,
the R2 may have protected the cartridge. Could the power supply be connected backwards?
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Power supply is connected correctly.
I have an amp, speakers and beater turntable I use for my testing-equipment I don’t mind losing-just for this kind of situation.
I’m just gonna go through it with a super fine tooth comb after looking away from it for a day.
I have an amp, speakers and beater turntable I use for my testing-equipment I don’t mind losing-just for this kind of situation.
I’m just gonna go through it with a super fine tooth comb after looking away from it for a day.
Did you build this using Rod's PCB or did you role your own? Point-to-point?
When you say "on the phono-in section" I assume you are talking about the voltage across R1?
What op amps have you been using?
With the op amps removed are you still seeing voltage on the input? Where do you connect the power ground to the signal ground in the circuit (if rolling your own). Are you using a standard +/- supply or are you trying to use a single supply?
When you say "on the phono-in section" I assume you are talking about the voltage across R1?
What op amps have you been using?
With the op amps removed are you still seeing voltage on the input? Where do you connect the power ground to the signal ground in the circuit (if rolling your own). Are you using a standard +/- supply or are you trying to use a single supply?
Thanks everybody, I just figured it out!
In a bout of insomnia I decided to get up and start looking over the board.
The little wire that connects V- to ground, wasn't showing continuity consistently, it would, then wouldn't, it visually looked fine.
Put in a new one and now everything measures perfectly.
In a bout of insomnia I decided to get up and start looking over the board.
The little wire that connects V- to ground, wasn't showing continuity consistently, it would, then wouldn't, it visually looked fine.
Put in a new one and now everything measures perfectly.