Echo Base Build Report

[audioguy]

I can hear the echo, but its extremely distorted.
Feedback control is all or nothing- if I turn it all the way down, I get one slap back. If I adjust it at all it sends the unit into a feedback frenzy.

Volume control is extremely loud, but tapers fine. The rest of the controls seem to work well. Even with the distortion I can hear the modulation controls functioning, and the switches are good to go.

Substitutions:
I didnt have any 1n4148's so I used 1n914- could this be my Feedback control issue?
Used a 2n8087 (reversed) instead of the BC560- didn't have any on hand.
Used 5532's rather than TL072's- shouldnt be any issue with that.

I'm thinking my diodes are the issue- thoughts?

I'll take some measurements another time.
audioguy

[caress]

what do you mean by using the 2n8087 "reversed"?  it's a general purpose pnp so it shouldn't be a problem as a direct drop-in for the bc560... the gain of the transistor would likely be the only issue with a replacement, but if it's in the ballpark then you shouldn't have a problem...

[slacker]

Sorry you're having trouble with it.

Substitutions:
I didnt have any 1n4148's so I used 1n914- could this be my Feedback control issue?

Should be fine.

Used a 2n8087 (reversed) instead of the BC560- didn't have any on hand.

Do you mean 2N5087, if so they work fine.

Used 5532's rather than TL072's- shouldnt be any issue with that.

They will work, except they have a much lower input impedance than Tl072s, which might cause some tone sucking.

Is it just the delay that's distorted, if you turn the level all the way down or bypass the effect is the clean sound ok?
If it's just the delay then try tracing the signal to see where the distortion starts, and check the resistor values around pins 13,14,15 and 16 of the PT2399.
If you want to check your voltages have a look here http://www.diystompboxes.com/smfforum/index.php?topic=60662.msg498824#msg498824 there's also some other debugging info there.

If you're unlucky it might be a bad PT2399, someone else had similar issues and that was the problem, hopefully that won't be it though.

[slacker]

what do you mean by using the 2n8087 "reversed"? 

The pin out for the 2N5087 is reversed compared to the BC560 so following the layout you need to flip the transistor so the curved side is facing the other way.

[caress]

gotcha

[audioguy]

OOPS YES 2n5087

Yes, just the echo is distorted.... and come to think of it the 2399 was previously used... which means on my bench that the build it was in before failed... so that is a good possibility. I'll look after the holiday.

Thanks all!

[Michael Allen]

did you happen to use one of the PCB layouts from the other thread? I've etched a PCB of my layout and am curious if it worked out alright if you did use it.... i should fire mine up sometime next month.