Help an old guy identify this pcb...

[sixstringphil]

I turned 40 this week and my memory was already bad enough. I was going through some old pedal parts this week and found this little pcb. I believe its just a simple booster, does anybody recognize the layout? The design probably came from this forum years ago when I was active and building. Thanks for looking!

[Mark Hammer]

The transistor is a J201 FET, and the resistor values are obvious.  But what are the values of the two caps?

[sixstringphil]

10uF and 22nF

[mth5044]

That looks like a PCB John Lyons would have made - he had etched me quite a few a long time ago, but the he's the only one I recall getting blue boards from. Not sure if that gets you anywhere.

[Kevin Mitchell]

Sure does resemble a buffer daughter board.

-KM

[Rob Strand]

At first I though it was a booster but  there's a 1M resistor from the gate to ground and *also* a 1M resistor from the gate to the drain.   That's not a common biasing scheme for a JFET.  I would be thinking MOSFET or BJT but the pinouts look wrong to be those!

So from that I'd say the part under the cap should be a link to +V and it's a buffer.

But there's a problem.  There's a link next to the 3k3 resistor and that shorts output side of the buffer's output cap to ground.  (When I was thinking booster I thought it might be a cap bypassed source resistor.)

So over all it's looking like a buffer with a wrong part on the board.

There's a few other weird things:
- There an isolated divider 47k + 100k.
- A lot of connection points.
- Why is there wire for a direct connection (DC coupled) to the source?

(The board might be layed out for a combination chicken booster and buffer depending on what parts are loaded.)

[sixstringphil]

That looks like a PCB John Lyons would have made - he had etched me quite a few a long time ago, but the he's the only one I recall getting blue boards from. Not sure if that gets you anywhere.

While its possible that it was John's design, I etched it myself. I purchased some of the blue pcb from him and was printing my own boards.

[Rob Strand]

The circuit might be from here, about 3rd ckt down,
http://www.muzique.com/lab/buffers.htm

[GGBB]

Looks like:

The circuit might be from here, about 3rd ckt down,
http://www.muzique.com/lab/buffers.htm

Yes - very similar:



But the right jumper appears to ground the output - I think that should be a pulldown resistor.

And what's the unconnected 47k/100k divider for? Maybe there's an off-board pot involved for setting/varying Vin to the JFET drain.

[sixstringphil]

I was looking back through the gallery and found a pic of a BMP w/ Blend I made for a bass player.


The mystery board is the Buff 'n Blend circuit, and I used the layout from this page...
https://www.aronnelson.com/gallery/main.php/v/BarcodeVeroLayouts/album120/

It worked great in that pedal and he still uses it to this day. If anybody would like this circuit I'd be happy to pass it along for the cost of postage!

[Rob Strand]

The mystery board is the Buff 'n Blend circuit,

Well done.  It had to be something specific like that.

[GGBB]

I was looking back through the gallery and found a pic of a BMP w/ Blend I made for a bass player.


The mystery board is the Buff 'n Blend circuit, and I used the layout from this page...
https://www.aronnelson.com/gallery/main.php/v/BarcodeVeroLayouts/album120/

It worked great in that pedal and he still uses it to this day. If anybody would like this circuit I'd be happy to pass it along for the cost of postage!

Note to buyers - replace the jumper (the one that's not under the cap) with 100k "R4": https://www.aronnelson.com/gallery/main.php/v/BarcodeVeroLayouts/album120/buffnblendPCB.gif.html - if you want it to work.

[sixstringphil]

Note to buyers - replace the jumper (the one that's not under the cap) with 100k "R4": https://www.aronnelson.com/gallery/main.php/v/BarcodeVeroLayouts/album120/buffnblendPCB.gif.html - if you want it to work.

Yeah, that still has me stumped. Not sure why I would have put a jumper there. I'm usually pretty OCD about checking my work. I'll swap it over in case anybody decides they want it. I'm gonna try and get hold of the BMP I built and make sure it was right. I know it worked well so I must have just missed this one.