Can anyone identify this diode?

[Onion Ring Modulator]

I pulled this out of an old distortion pedal I'm working on tracing, the Washburn A-D2 (precursor to their Stack in a Box). Neither my DMM or my Altas will recognize it, so I'm thinking it's bad and I have no fV reading to help me. It kind of looks like the D9B, but I don't think so because this pedal was manufactured in the mid 1980's and the diode was a part of the JFET switching system for the Boss-style footswitch involved. It looks like maybe the letter/numbers were double-struck. I can't read it with my old eyes. Any help appreciated!

[Rob Strand]

I pulled this out of an old distortion pedal I'm working on tracing, the Washburn A-D2 (precursor to their Stack in a Box). Neither my DMM or my Altas will recognize it, so I'm thinking it's bad and I have no fV reading to help me. It kind of looks like the D9B, but I don't think so because this pedal was manufactured in the mid 1980's and the diode was a part of the JFET switching system for the Boss-style footswitch involved. It looks like maybe the letter/numbers were double-struck. I can't read it with my old eyes. Any help appreciated!

I can't quite make out the text (is there more text wrapped around?).

To me it looks like a zener diode.   They look like germaniums but inside is solid, not a wiggly wire.

Probably for the low battery indication on the battery/LED circuit.

Usually these are 5.1V, maybe 5.6V but it does vary across pedals.   Often marked something like 5V6B, 5.6A, 5.6B

[Onion Ring Modulator]

To me it looks like a zener diode.  They look like germaniums but inside is solid, not a wiggly wire.

Probably for the low battery indication on the battery/LED circuit.

Usually these are 5.1V, maybe 5.6V but it does vary across pedals. Often marked something like 5V6B, 5.6A, 5.6B

I think you're right. It's right down there near the LED (D4 ?). Don't laugh too hard at this schematic, I've never tried to draw one of these switch systems before, so it probably looks wonky, but the connections are right. Not planning on using it anyway, just wanted to get the parts out of my way so I could concentrate on the audio section.

[Rob Strand]

I think you're right. It's right down there near the LED (D4 ?). Don't laugh too hard at this schematic, I've never tried to draw one of these switch systems before, so it probably looks wonky, but the connections are right. Not planning on using it anyway, just wanted to get the parts out of my way so I could concentrate on the audio section.

Tracing boards is hard.   I kind of predict what should be there then match that up with what is there, making small adjustments along the way.  When you trace something which doesn't have a recognizable circuit the schematics get more and more wonky and has to be redrawn later.

Not sure about the Washburn A-D2 but the Washburn A-D3 schematic is here in PDF form about 80% down the page,
https://www.freestompboxes.org/viewtopic.php?t=5887

A few schematics have been posted (here and on FSB) and I can't remember if the A-D2 was one of them.   The fact you have a PNP transistor does hint the A-D2 is slightly different.

When I look at your diode D4, it's looks like it's across the power supply.  Could be a zener for protection or a zener to regulate the supply rails.   I might expect a resistor in series with the supply rails somewhere.

[Rob Strand]

You are in luck,  I have a schematic for the A-D2,



Quality could be better and there's a few parts with impossible to read values.

Looks like normal silicon diodes from the schematic.

There is a protection diode but that's D3 (or is that D1 LOL! I think it is D1).  Can't always trust the schematics so maybe check what diode designator is what on the actual board.

[Onion Ring Modulator]

You are in luck,  I have a schematic for the A-D2,



Quality could be better and there's a few parts with impossible to read values.

Looks like normal silicon diodes from the schematic.

There is a protection diode but that's D3 (or is that D1 LOL! I think it is D1).  Can't always trust the schematics so maybe check what diode designator is what on the actual board.

Nice! Thanks much! Now I can tell how close I got with the audio circuit!  One of my biggest confusions was the Distortion pot. In the pedal I have, there was only one wire connected to it on lug 2, but I could tell there had been solder on lug 1 and got pulled off at some point. By this, it looks like the 4k7 goes into 3 and 1 goes to ground, but I'm not sure what the slash across 2 means. Does that mean not used, or does it mean 2 & 3 are bridged?

[Rob Strand]

Nice! Thanks much! Now I can tell how close I got with the audio circuit!  One of my biggest confusions was the Distortion pot. In the pedal I have, there was only one wire connected to it on lug 2, but I could tell there had been solder on lug 1 and got pulled off at some point. By this, it looks like the 4k7 goes into 3 and 1 goes to ground, but I'm not sure what the slash across 2 means. Does that mean not used, or does it mean 2 & 3 are bridged?

IMHO, it's an old and ambiguous short-hand symbol.   

As I recall that symbol means it uses the wiper and one of the other terminals but doesn't even say which one.   I'm fairly certain it never explicity means use three terminals - that would be the builder's choice/variation.

We know from the way the pedal works it must use 3 and 2, since the drive increases with clockwise rotation of the pot.  We are adding that meaning not the symbol.   As for 4k7 going to 3 or 2, there's nothing to say one way or the other.

You might find an explicit meaning in an old hobbyist electronics book from the 60's but I suspect that would be the author's interpretation more than reality!

[Onion Ring Modulator]

Just figured out the Distortion pot design. It has one wire connected to lug 2 which goes to the 4k7, and lug 3 is bent upward so it grounds out on the enclosure.

[fryingpan]

A resistor with an arrow across it is, yes, a variable resistor (technically you can call it a rheostat, I think).

[aion]

Very interesting! Looks like they started with a Dist+ and added a Big Muff tone stack to the end.

[Rob Strand]

Just figured out the Distortion pot design. It has one wire connected to lug 2 which goes to the 4k7, and lug 3 is bent upward so it grounds out on the enclosure.

It would be good to fix up that schematic.

I'm pretty sure both tone resistors are 27k (not 27k and 2k7);  based on the fact all the other decimal points are located at the bottom level of the text, also, it makes more sense for a Muff tone control (no guarantee).

Only about 80% certain the cap on the Tone control wiper is 47n (not 27n); based on 2 not being full height, the 47n at DIST pot has the bottom chopped off as well and all caps are E6 series steps.

[Onion Ring Modulator]

Oh yeah, I'm going to take your crusty old schematic and fix it up real nice. I'll post it here when complete, for future generations to ignore! 

Maybe AION wants to make a PCB, I know you did the Stack in a Box already.

I have a parts list I made from the actual pedal, and you are correct, both tone resistors are 27k and both of those caps are 47n.

The op amp in this one is a 1458. I have another one I got a few years ago that uses a 4558. All the transistors and diodes are the same as on your schematic.

[Rob Strand]

Oh yeah, I'm going to take your crusty old schematic and fix it up real nice. I'll post it here when complete, for future generations to ignore! 

Don't worry I've done about 200+ schematics for people to ignore  .

I have a parts list I made from the actual pedal, and you are correct, both tone resistors are 27k and both of those caps are 47n.

The op amp in this one is a 1458. I have another one I got a few years ago that uses a 4558. All the transistors and diodes are the same as on your schematic.

Thanks, interesting to know.

I keep racking my brains for a pedal which had a distortion+ like circuit with a muff tone control.    I'm out of the loop these days so I can't remember the details like I used to.

[sinthmart]

похож на Диод Д 9 Б

[bluelagoon]

"похож на Диод Д 9 Б"

Translated "similar to Diode D 9 B"

[sinthmart]

Yes, it looks like the very common Russian D9, but maybe the same ones (visually and structurally) were produced in other countries. I don't know for sure. I just saw a familiar detail and expressed my opinion.

[Onion Ring Modulator]

See cleaned up schematic by Rob below.

[sinthmart]

Maybe you can provide a sample of the sound? On solo, on chords.

[duck_arse]

your circuit diagram - R1 is wrong position - it should be between D1 Kathode and the VREF point. I aasume the VCC point sould be at the D1 K as well. both halves of the opamp are shown without bias. there should be a resistor from each (+) input to VREF, by convention.

ahh. R6 in the Emitter leg, is that correct? it looks like the sort of value that might be biasing the oppie, but it's way way too high for an emitter follower.

Q2 has Collector [late mail - Q1 has as well] connected to VREF - it should be VCC, that's why it is so named. and the R14 would be to VREF, but not to VCC. I'm not too sure about the Q2 base connections - they look like noise and scratch to me.

but mainly, recheck your opamp connections.

[Rob Strand]

Sharp eyes as usual!

your circuit diagram - R1 is wrong position - it should be between D1 Kathode and the VREF point. I aasume the VCC point sould be at the D1 K as well. both halves of the opamp are shown without bias. there should be a resistor from each (+) input to VREF, by convention.

Ah I see, yep R1 has a problem.  Move D1+C1 point to VCC, not VREF.

ahh. R6 in the Emitter leg, is that correct? it looks like the sort of value that might be biasing the oppie, but it's way way too high for an emitter follower.

R6 is 10k

Q2 has Collector [late mail - Q1 has as well] connected to VREF - it should be VCC, that's why it is so named. and the R14 would be to VREF, but not to VCC. I'm not too sure about the Q2 base connections - they look like noise and scratch to me.

Yes, good one.

but for R14, it's not there.
- the LEVEL pot connects to VREF
- R14 should be 470k and moved to bias the pin 5 of the opamp to VREF

Some more,
- C10 should be 10nF?
- R12 should go to VREF
- add another 100k from pin 2 of IC to C11.
- diode D1 isn't series protection it's parallel protection across the supply

Here's a clean-up.  I didn't clean up the text much since OnionRingModulator was doing the redraw.  It at least lets you see the connections.



with text: