SOLVED: my EH Screaming Bird wiring problem

[throw2k]

EDIT: the issue was solved, scroll down for an updated wiring diagram.

I got a Screaming Bird from a friend around 1991, and I don't think it ever worked. I remember taking out the OFF/BOOST switch and disconnecting all of the connections, because I believed it was broken (probably wasn't).

Anyway, so I've been working on rebuilding it. I am a novice at this kind of repair, but am eager to learn.

I'm using this schematic:

as it has the closest measured values could find to my Screaming Bird. I did use my DMM to check the resistor values against the diagram, and they are in spec.

So I drew a diagram that shows how I think it's supposed to be wired:


Can someone check my diagram for me?

One thing that throws me conceptually is how the +9V is tied to what I would this is usually ground (jack sleeve, pot case, etc.). From the picture of other LPB-1 and Screaming Bird (below), you can see how the battery + is wired to the pot case.

I also wonder if I got pin 2 of the pot wired to the correct spot. I can't make out the connections from the pictures, but I may have done it wrong. Now I'm thinking that the .002u cap connecting to the 2N5088 base should go to switch pin #4, and pot pin 2 should go to the tip output.

I've been staring at it this diagram long that I'm starting to hallucinate  

I tried comparing my wiring to some other photos of Screaming Birds wirings that I found, but they aren't clear enough to see all the connections.



I did connect it to my 9V power, and tried it out; I get signal when the switch is set to OFF, but no sound at any pot position when set to BOOST.

Thanks in advance for your help!

[throw2k]

Never mind, I solved it. Yes, as I suspected pin 2 of pot, like the schematic, should go to the tip at output. Also, the .002u cap connects from DPDT switch pin 4 to the base.

I unsoldered, used gator clips as temporary jumpers between the new proposed connections, fired it up and it worked! Went back and soldered, tested again and buttoned it up.

I like the sound, granted the lack of true bypass makes this pedal quite a tone-suck. Also when the volume is all the way down, there is no sound coming thru the pedal. It's got a nice bright sound with some punch (tried it on my Tele), and was a lot less noisy than I thought it might be.

Here is an updated wiring diagram, for anyone that needs it:



The values listed vary from Jack Orman's LPB-1 schematic (which were the same as the ones in my Screaming Bird), as these were measured & observed values (e.g., resistor & capacitor markings).

[PRR]

Welcome.

> an updated wiring diagram

Much more likely.... glad you got that sorted......

> lack of true bypass makes this pedal quite a tone-suck

Yeah, the Vol pot permanently loads the line even in bypass.

Also, I dunno how it was done in the Old Days, but today we usually don't kill power when the effect is not-effecting. Cold-starting pops. We switch power on when we set up (often with a stray finger on the input jack) and leave it on the whole set. Do that, and you can use the second pole of that DPDT switch to disconnect the effect output so it dont tone-suck. (Yeah, then you wonder "is it engaged?", which leads to a 3PDT switch so you can switch an LED.... this is all standard stuff for nearly any pedal.)

[throw2k]

Thanks Paul. Yeah you're right. In it's current form this pedal really isn't practical for live use. I'd probably re-build another version in a more modern case, and switch it using true bypass. To use it in its current "vintage" form I'd probably run it using a true-bypass effect loop.

Best,
Pete