PLEASE HELP: EH Slapback Echo w/Filter Switch. . . .

[Joe Kramer]

Hi Friends,

Found an old EH Slapback pedal in not-working condition, some wires disconnected.  Only schematic I can locate is here:

http://sites.google.com/site/electroconducive/EHXSlapBackDelayEH-4700.jpg

But my pedal is an earlier version with the FILTER switch, not the DELAY switch.  I'm trying to find where on the PCB a wire coming from one pole of the FILTER slide switch is supposed to be connected.  Anyone have one of these he'd be willing to post a few guts shots of?

Any help much appreciated!

Regards,
Joe

[Scruffie]

Could you post gut shots of your pedal? As for one, i'd quite like to see inside it as I didn't know there was a version with a Filter Switch and Two... might help to spot where the wire came from 

I'll have a look to see if I can help you out though.

[Joe Kramer]

Sure, I'd be happy to post some pix.  But since I have no webspace to host, I guess I'd have to start up a gallery profile here?

BTW, I studied the PCB with a magnifier for a while, and still couldn't see where the wire might have broke loose from.  No dedicated PCB holes/pads, just wires soldered to the traces, that's EH for ya. . . .

   

[Scruffie]

Sure, I'd be happy to post some pix.  But since I have no webspace to host, I guess I'd have to start up a gallery profile here?

BTW, I studied the PCB with a magnifier for a while, and still couldn't see where the wire might have broke loose from.  No dedicated PCB holes/pads, just wires soldered to the traces, that's EH for ya. . . .

   

Or you can set up an account on Photobucket and Link here (There's a button to do it below the Italics symbol above in the reply section).

But that'd be very appreciated.

Haha, that is indeed EH for ya, but it might help to trace through a bit and see what it was doing before.

[Joe Kramer]

Or you can set up an account on Photobucket and Link here (There's a button to do it below the Italics symbol above in the reply section).

Ah, I see now, thanks!  Might be a day or two before I can take some pix. . . .

Meantime, there's these:

http://www.effectsdatabase.com/model/eh/slapbackecho

Unfortunately, no help to me.  On mine, looking at the guts with the bottom off, the wire in question comes from the middle pole on the right side of the slide switch (closest to the right outside edge of the pedal); or, looking at it from the top, the middle pole on the left side of switch (closest to the left outside edge of the pedal).  These pix don't show that. . . .

[Mark Hammer]

Here you go:

[theehman]

If you still need help, LMK.  I have one sitting here I can take pics of.  Is there a resistor mounted on the switch?

[Joe Kramer]

That's it!  Okay, I see it just changes the knee of the post-filter by putting some extra caps in parallel there. . . .

Brilliant Mark--thanks and I owe you a bagel!  (And I mean a GOOD bagel, not one with seams around the edges like at Noah's. . . .   )

-------------------------

Hi Ron,

Thanks for your help offer.  No, there's no resistor mounted on the switch; mine looks to correspond with the schemo from Mark.  I will attempt the fix shortly, get back with a report, and let you know if I still need pix/help.  Thanks again.

[Mark Hammer]

All thanks go to CJ Landry, who drew and posted it, but I'd be happy to split the bagel with him. 

[cjlectronics]

WOW, I don't remember drawing that schematic.  I better save it 'cause I don't know what happened to the original. (probably on one of the scrap HDD in my lab)

I can't find a good New York bagel in Texas.  Maybe for the same reason you can't find good Texas BBQ in New York.  

CJ Landry

[Joe Kramer]

All thanks go to CJ Landry, who drew and posted it, but I'd be happy to split the bagel with him. 

Bagels for both of you then!  But hold the cream cheese a minute. . . .

. . . Thanks to the schemo, I was able to find a home for the loose wire.  By process of elimination, I came upon one of the .0047 caps with one lead soldered to a small copper trace connected to nothing else.  Sure enough, when I desoldered the trace, there was the little bit of wire broken off from the original piece.  Reconnected it, and now the FILTER switch is working properly.  However, in the process of tracing things out, it looks to me like the 9.1K resistor in the schemo is actually in the feedback loop of that op amp, in series with the filter caps; the switching of the caps is essentially the same as drawn.  Only a small error, and I mention just for the record.  Otherwise, grateful for the help guys!

I can't find a good New York bagel in Texas.  Maybe for the same reason you can't find good Texas BBQ in New York.

Actually, what I'd be interested in finding here in LA is some of that legendary New York pizza they're always getting all misty about around here. . . .

Thanks again for all the help,

Joe