SD-1 diode swapping.

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bigtone23
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Re: SD-1 diode swapping.

Post by bigtone23 » Sun Jul 03, 2022 3:36 am

Old_Iron wrote:
Sat Jul 02, 2022 6:51 pm
I found this page and it is a little bit of information to help who is looking for a certain kind of sound in the most known Boss "drive" pedals, with visual examples (frequency response analysis and some comments about it).

https://guitarpedalsvisualized.wordpress.com/
That's a cool find! I really like seeing the waves and and the analysis.

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fernieite
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Re: SD-1 diode swapping.

Post by fernieite » Tue Nov 22, 2022 11:51 pm

I don't know if this is the right thread to post in, but here goes:

I just opened up my old beat-up May 1982 SD-1 to see what's under the hood. It looks like I have the JRC 4558D chip with the black stripe/ band clipping diodes. Sounds great! 8-) It's the 1st revision to the circuit. (B)

Is there much of a difference between the 1981 circuit (A) compared to the (B)? Thanks.

My May 82 SD-1 - Copy resize.JPG
My May 82 SD-1 - Copy resize.JPG (472.87 KiB) Viewed 216 times

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Old_Iron
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Re: SD-1 diode swapping.

Post by Old_Iron » Wed Nov 23, 2022 11:03 am

fernieite wrote:
Tue Nov 22, 2022 11:51 pm
Is there much of a difference between the 1981 circuit (A) compared to the (B)? Thanks.
Let's play Where's Waldo (Wally at some places)? :lol:

Here is a side by side picture of my earliest version "A" (0300 FEB 1981) and "B" (126000 NOV 1981).

The only difference I found is at the lower left corner of the solder's side, to accommodate the bigger D1 zener diode.

Image

Image

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fernieite
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Re: SD-1 diode swapping.

Post by fernieite » Thu Nov 24, 2022 1:05 pm

Great photo comparison Old_Iron!

It's also fantastic to see a 0300 silver screw on the inside! Thanks for posting these. :ugeek:

Did the SD-1 get anymore revisions over the years? (C, D, E, etc )

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Old_Iron
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Re: SD-1 diode swapping.

Post by Old_Iron » Thu Nov 24, 2022 1:50 pm

fernieite wrote:
Thu Nov 24, 2022 1:05 pm
Great photo comparison Old_Iron!

It's also fantastic to see a 0300 silver screw on the inside! Thanks for posting these. :ugeek:

Did the SD-1 get anymore revisions over the years? (C, D, E, etc )
Nope, up until it became SMT/SMD there are only two versions, A and B.


Chips and diodes combo (to my knowledge) :

NEC c4558c, black stripe and yellow stripe diodes.

JRC 4558D, black and yellow stripe diodes.

Mitsubishi 5218, black stripe diodes.

JRC 4558DX, blue stripe diodes.

JRC 4558DD, black, yellow and blue stripe diodes.


Yellow stripe diode = Rohm 1S2473.

Blue stripe diode = Toshiba 1S1588.

Black stripe diode = ???

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fernieite
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Re: SD-1 diode swapping.

Post by fernieite » Sat Dec 03, 2022 2:56 pm

Old_Iron wrote:
Wed Nov 23, 2022 11:03 am
fernieite wrote:
Tue Nov 22, 2022 11:51 pm
Is there much of a difference between the 1981 circuit (A) compared to the (B)? Thanks.
Let's play Where's Waldo (Wally at some places)? :lol:

Here is a side by side picture of my earliest version "A" (0300 FEB 1981) and "B" (126000 NOV 1981).

The only difference I found is at the lower left corner of the solder's side, to accommodate the bigger D1 zener diode.

Image

Image
I did the Waldo thing, and I think you're right. The only difference is the larger diode at the bottom right of the B board. (Assuming the values of the other components didn't change) Are the transistors the same? I can't make out the numbers clearly.

I also noticed that our B boards have the same inspection or build stamp too. (O) :geek:

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Old_Iron
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Re: SD-1 diode swapping.

Post by Old_Iron » Sat Dec 03, 2022 9:07 pm

fernieite wrote:
Sat Dec 03, 2022 2:56 pm
I did the Waldo thing, and I think you're right. The only difference is the larger diode at the bottom right of the B board. (Assuming the values of the other components didn't change) Are the transistors the same? I can't make out the numbers clearly.
I also noticed that our B boards have the same inspection or build stamp too. (O) :geek:
Components, resistors and capacitors, have the same values.

Transistors, like chips, may vary but with same characteristics. Those pedals in the picture have different transistors in the flip-flop circuit (bypass), and same ones in the signal part of the circuit.

I never payed much attention to transistors in SD-1, OD-1, DS-1... And never seen anything about they influence in the tone.

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