Voltage between Gate and Source of the FDP.
That's the two outer pins of that MOSFET.
Voltage difference is 4,8 to 5 V
That's the two outer pins of that MOSFET.
Voltage difference is 4,8 to 5 V
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So its wide open.
Now, what is the voltage between the output and the reference voltage on pin 3 of the opamp? Be careful not to short anything!
Can you also verify that the voltage between the output and pin 2 of the opamp is zero? Again, be careful!
Jan
Now, what is the voltage between the output and the reference voltage on pin 3 of the opamp? Be careful not to short anything!
Can you also verify that the voltage between the output and pin 2 of the opamp is zero? Again, be careful!
Jan
Now, what is the voltage between the output and the reference voltage on pin 3 of the opamp?
>>>>> It is 0,9V
Can you also verify that the voltage between the output and pin 2 of the opamp is zero?
>>>> It is 0 V
>>>>> It is 0,9V
Can you also verify that the voltage between the output and pin 2 of the opamp is zero?
>>>> It is 0 V
Jan, are there any other measuring point that I can check to encircle the reason for that curious behavoir. By the way, I have another T-Reg perfektly working in my phonostage. Works great.
Could the reason be that I put the FDP at Q 7 position only and there are only 30 mA running through?
Could the reason be that I put the FDP at Q 7 position only and there are only 30 mA running through?
No that should be OK. If the output is higher than the ref voltage, the opamp output should draw the Vgs of the FDP down, which isn't the case in this unit.
Just to exclude everything, can you verify that the opamp is installed in the correct orientation? And the FDP in Q7, should have the metal tab facing outward (which is the opposite for when it is mounted on the PCB heatsink).
Jan
Jan,
the T-Reg feeds in this case directly into a interstage transformer only. Could this be the issue, because it sees only a small resistance and a inductance?
Many thanks
René
the T-Reg feeds in this case directly into a interstage transformer only. Could this be the issue, because it sees only a small resistance and a inductance?
Many thanks
René
Could be, what is the DC current taken from the T-reg then?
You can check with 30k to 50k load resistor temporarily added, at 170V?
Jan
You can check with 30k to 50k load resistor temporarily added, at 170V?
Jan
Jan I have put a 1K8 Resistor between the T-Reg and the Interstage transformer, now it is running. DC Current is 30 mA.
1 is stable running, the second may be has shot the IC, but I will figure out
1 is stable running, the second may be has shot the IC, but I will figure out
Well done!
But I hope you are not pulling 30mA through the interstage? Can you show that part of the circuit?
Jan
But I hope you are not pulling 30mA through the interstage? Can you show that part of the circuit?
Jan
the Interstage Lundahl 1671 is set up as line out. It is fine with 30 mA.
I have no drawn circuit. It is a circuit similar to the MIR Preamp of Kevin at K+K audio the MIR, but with a 12P17L instead of the 4P1L tube
I have no drawn circuit. It is a circuit similar to the MIR Preamp of Kevin at K+K audio the MIR, but with a 12P17L instead of the 4P1L tube
I have a new set of boards coming in this week, expected to be delivered Wednesday.
In the mean time, our friend EUVL has discovered that when the regulator is switched on without load, there is a chance that the opamp non-inverting input is driven outside its limits. The way to prevent that is to replace zener diode D7 (see attached) by two reverse-parallel small signal diodes, preferable Schottky. A good part would be Mouser 511-BAT43 or 511-BAT42.
There should be no problem with the current PCB but I will adapt the next version of the board. I will also post this on the Linear audio website and note it in the BOM.
Jan
In the mean time, our friend EUVL has discovered that when the regulator is switched on without load, there is a chance that the opamp non-inverting input is driven outside its limits. The way to prevent that is to replace zener diode D7 (see attached) by two reverse-parallel small signal diodes, preferable Schottky. A good part would be Mouser 511-BAT43 or 511-BAT42.
There should be no problem with the current PCB but I will adapt the next version of the board. I will also post this on the Linear audio website and note it in the BOM.
Jan
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