BJFE-Baby Blue [traced]

[momo lab]

Hi, everyone，My English is very bad,Sorry about this.

this is bjfe-baby blue od， wonderful od pedal，I hope the disassembly process goes well.

For now, I have a question，I do not know the type of this diode，It's big，The character is S 2A 1200.

When I finish, I will upload the detailed layout, thank you all.

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[momo lab]

Looks like a schottky diode. Like ones used in switching power supplies. Has less voltage drop than a silicon diode.

Also Depends a little on where it is used in the circuit.

If it is in the clipping/clamping/feedback circuit, any schottky will probably work.
Maybe just try a good old 1N4148/1N914 (?)

[momo lab]

You could measure the threshold voltage of the diode in this way:

diodetest.JPG

I do not see an OP-Amp Pin layout on the PCB shot.
Is there an OP-Amp installed or is this only a transitor circuit?

[momo lab]

This job is difficult and slow，I mean，Really slow.

The threshold for this diode is 0.536v and 0.523v，It does not use the OP-amp, but the use of a JFET，Very simple and effective circuit.

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[Manfred]

What are the dimensions of the PCB-Board?

[momo lab]

What are the dimensions of the PCB-Board?

Its size is 55 * 22 mm, but its shape is irregular.
I have built an identical PCB plan,Although not perfect, but I am ready to use it，Suppose I copy the value of it.

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[Manfred]

This job is difficult and slow，I mean，Really slow.

I see, it is a tough piece of work, the tracing takes time.

[momo lab]

This job is difficult and slow，I mean，Really slow.

I see, it is a tough piece of work, the tracing takes time.

Sorry, a lot of work these days.
Schematic has been updated.

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[momo lab]

I just updated the layout, and sprayed the shell ready to clone it, thank you all.

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[fuzzbunny]

Thanks for your hard work!

Do you have any idea which JFETs the original circuit used? Any voltage readings on the original JFETs?

How about D3 & D4 ? What kind of diodes?

[Manfred]

The FET-Stage circuits of the Baby Pink Booster and Model_H drive are similar to the Baby Blue FET-Stages,
where the 2N5952 FET is applied.

In my opinion R6 should by 22k not 220k as in the schematic shown.

BJFE applies often the 1N400X diodes as clipping diodes.

[momo lab]

BBOD.JPG

[momo lab]

Thanks for your hard work!

Do you have any idea which JFETs the original circuit used? Any voltage readings on the original JFETs?

How about D3 & D4 ? What kind of diodes?

The FET-Stage circuits of the Baby Pink Booster and Model_H drive are similar to the Baby Blue FET-Stages,
where the 2N5952 FET is applied.

In my opinion R6 should by 22k not 220k as in the schematic shown.

BJFE applies often the 1N400X diodes as clipping diodes.

After I checked, R6 is indeed 22K, not 220K, 15K resistor should be 14.7K.
It uses diodes and JFETs I'm not sure, the diode has a clear character, S 2A 1200, but I do not know its model number.
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.

Earlier today, I tried to make a PCB and use it to test the BF244 as a JFET, frustrating that it did not work well, the gain was significantly lower, and the more frustrating thing was that I came from China, fake Very much, I'm not sure JFET in my hand is really BF244, in your country common 2NXXXX series I can not determine the hands of the real thing. I do not know where something went wrong, and now it's no longer sounding, ready to do a few more PCB tries, I will try to feedback in time, thanks again!

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[Manfred]

I have done some calculations and found that the value R5 ist to high.
Please check it again, maybe is the value 14.7 Kohms not 47 kohms.

Cool milling, who is the manufacturer of the milling machine?

Have look at this webside, this rectifier diodes look much alike.
https://www.ebay.com/itm/Diode-Rectifier-75-Amp-1200-Volt-Vintage-Restoration-Part-Tested-Qty-of-2-/321099522209

[momo lab]

I have done some calculations and found that the value R5 ist to high.
Please check it again, maybe is the value 14.7 Kohms not 47 kohms.

Cool milling, who is the manufacturer of the milling machine?

Have look at this webside, this rectifier diodes look much alike.
https://www.ebay.com/itm/Diode-Rectifier-75-Amp-1200-Volt-Vintage-Restoration-Part-Tested-Qty-of-2-/321099522209

Today I have reworked the PCB and tested it, except for the low gain, which worked fine.

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Schematic diagram before the ground fault. Has been updated in V2.

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This milling machine was made by myself three years ago, using only electric drills and saws. The production of a BB OD PCB about half an hour, but it is loud noise.

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I found in another old Emerald Green thread that it uses the same diode and does not think this red diode is the same as it.

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To make it easier to test for more diodes, I used a 24-segment switch to test more differently more quickly.

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Communicate with everyone I use Google Translate, which was unthinkable 10 years ago, thank you all.

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[marshmellow]

If you include a ground layer on your pcb, you would have to mill much less.

Print on the transistors is not readable?

[Manfred]

This job is difficult and slow，I mean，Really slow.

The threshold for this diode is 0.536v and 0.523v，It does not use the OP-amp, but the use of a JFET，Very simple and effective circuit.

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I want to know at which current the threshold has been measured?
Have you measured the voltages on the FET terminals in the original circuit?

[vovian]

Hello. Thank You for this big job. You made fantastic work. So what diodes is better for this project?

[KK Japan]

Please Comeback, momo lab!

[Nick123]

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