BJFE-Baby Blue [traced]

[Jone the Bone]

I think I have found an error in the last schematic.
Only the wiper of RV2 should be grounded.

There is no error. In this circuit it doesn't matter, it's only an another way to connect a potentiometer.

[momo lab]

Hi everyone, I'm back!Sorry for not coming so long, but our country has a “Great Wall firewall”，So I have to resort to some network tools to normal visit。
BBOD I have completed the test, 1N4XXX diode for the circuit sound will be bright and thin, so I had to modify the EQ part.Parallel into a 102 capacitor will sound almost exactly the same。
I wish you have fun, thank you.

[Manfred]

Hi momo lab,

I would very much appreciate it if could you measure the drain and source voltages an give the read values to us.

[momo lab]

Hi momo lab,

I would very much appreciate it if could you measure the drain and source voltages an give the read values to us.

QQ截图20180304185035.jpg

[Manfred]

Hi momo lab,

I would very much appreciate it if could you measure the drain and source voltages an give the read values to us.

QQ截图20180304185035.jpg

Thanks for the hint, I checked the topic twice, but I have overlooked.

[Manfred]

After the measurement, the first stage FET voltage is 4.62V and 1.72V, the second stage FET voltage is 4.72 / 1.68 and the third stage is 5.55 / 1.44.

I got a bunch of 2N3822 FETs, which are almost equal as the 2N5952 FET, except the maximum voltage and current values.
I ran a curve traces of it, to drawing in the resitor values in found characteristic curves graphic.
The graphical soultion gave values in the vicinity of the read values of momo lab's measurement,
therefore the 2N5252 seem to be the right choice.

[ray86]

Fairly straight forward JFET circuit with hard clipping in the 2nd stage

[Dingleberry]

It looks to me that the diode is 2A / 1200V diode, most likely rectifier diode or schottky of some kind.
That's probably the obsolete part of that pedal because the production was stopped because of parts shortage (or at least that's what I have heard).

[Manfred]

It looks to me that the diode is 2A / 1200V diode, most likely rectifier diode or schottky of some kind.
That's probably the obsolete part of that pedal because the production was stopped because of parts shortage (or at least that's what I have heard).

Have a look at the post further up, mom lab measured the original diodes

The threshold for this diode is 0.536v and 0.523v

I traced an obsolete rectifier diode found in an old tube amplifier as a part of a HV brigde amplifier.
The case has a rectangular shape and no imprint.
The traced values are surprisingly close to the measured values.
I therefore believe that it is rather a rectifier diode than a schottky type.

OldRectifierDiode.jpg

By comparison, the interpolated curve of a BY133 diode.

BY133.jpg

[Manfred]

Retrospectively, I have to say that the BY133 does not produce the desired value,
I am continuing to seek for the matching diode.

[Dingleberry]

Found an inside-view picture of the new One Control Baby Blue from a japanese site.
Most likely those diodes in the One Control version are BY448V diodes. It's a 1500V 2A diode.
Kind of correlates to the 2A1200 of the original BJF unit. High voltage 2A rectifier diodes in both of them.

[Manfred]

Most likely those diodes in the One Control version are BY448V diodes.

Thanks, it helps me, I will buy some and trace the curves.

[Manfred]

Today, I received my ordered Diodes.
The BY448 Diodes were difficult to get and are very expensive,
that's why I bought a bunch of 40 BY458 diodes for a favourable price.
The diffrence between the both types is only the maxium reverse voltage.
The PN-junktion curve in the common data sheet is the same for both.
The measuring of all diodes results in a mean value for the threshold voltage of 0,608 Volts at 5 Milliamps,
with a deviation of 0.006 Volts.
The threshold voltage at ~0,9 Milliamps is.0,516 Volts, which is close to the measured original values of 0.536 and 0.523 Volts,
so the BY458 should be functioning well.