ABDUCTOR II DELAY.

[deadastronaut]

Ok man. Check that switch too....it only lengthens the delay to
For extreme long delays....or standard delay time.

[BetterOffShred]

Ok well I've been going over this with a fine tooth comb and it's getting the best of me.  After messing with it, delay 1 does not seem to work at all and delay 2 generates hiss.  The other 2 "work" but they all only repeat once no matter the feedback knob position ..  It's got to be something mad simple at this point.  All the PTs have 4.7V on pin 1.. I checked the 2N3904 pinouts.. tested known PTs..   the volume works,

I'm not great at troubleshooting delays, but if 1 isn't working I'm guessing that's causing the rest of the issues    anyway here are some pics. Any ideas ? 

[duck_arse]

I don't seem to have the build docs that match your board, but I do have 2 questions - what value resistor have you fitted at R37? what value resistor have you fitted to the left of IC5, where it says "1k"? I don't know these are the problem, but they might be pointers.

[BetterOffShred]

Yeah definitely had a 10k in R4..  looked in my bin and there's like 20x 10k in the 1k slot      that's why you don't stock parts while watching a movie and drinking. ..

R37 was a 7.5k..   swapped both to correct values and tested it out, still the same problems. 

And now my soldering iron is shocking me again!  Wtf..   I guess I'll take the controller and open it up.. maybe something obvious .. otherwise I'm out $140.  Great.

Thanks for looking Duck

[BetterOffShred]

So a few more days of troubleshooting and I'm still having problems.  The delay time knob works as it's supposed to, the switch works as it's supposed to, the modulation works, the volume works .. but
Delay 1 does not work
Delay 2 adds hiss when turned up
Delay 3 and 4 work and follow as I think they are supposed to
The feedback knob does nothing, only one repeat always.

I tried directly grounding pin 1 of feed, direct jumper from pin 3 feed to pin 3 vol 1.. no difference.

Based off these symptoms is there a section of the circuit I should be looking at?

I've checked over all the little through holes and there doesn't seem to be any solder bridges or anything. 

Any insight would be appreciated

[deadastronaut]

hi have you got other pt2399's to try..

the 3 at the bottom, look weird...really large notch.  never seen them like that.

if 1 2 3 aren't working properly then the repeats wot work either.

[BetterOffShred]

Ok so give that man a chicken dinner!  I pulled those PTs out, tested them in a different circuit I haven't boxed up yet (Bluffchill hyperlite 1.0) and they all work, but I fished out 3 new ones with the tiny slot... and now it all works.   So I guess there's something with those other chips the Abductor does not like!   Well I'm happy,  thanks everyone for looking and helping out. It's a really fun delay.  I appreciate it all.

[deadastronaut]

Yay....yeah they looked a bit moody for sure...

Excellent. 

[BetterOffShred]

I'll be sure to remember this when I build my dream time hehe 

[BetterOffShred]

Finally got my box painted up and it's looking good, about to box this one up and I was just curious..  Will using a smaller value time pot, say a B1M shorten the overall possible delay time?

[deadastronaut]

yup.....

looking forward to seeing it man...

[Aharon]

Hey Robert,sorry to use the forum to ask I tried emailing but somehow my email provider is not compatible with your yahoo,do you have stock of chasm and abductor II boards?
Thanks
Aharon

[deadastronaut]

Hi. Strange....yes i have . No problem..

Rob.

[iefes]

Hi all, after my original thread didn't get any attention I figured I could try it in the main Abductor II thread here. Maybe you folks can help me. I'll paste the text from the original topic:

"after working on a tube amp the last months, I got back to my effects pedals a few days ago and noticed some serious hiss being produced by the abductor delay in my signal chain (the hiss was also present the last time I tried it, I just didn't care too much about it). Despite the fact that this is an absolutely great delay pedal that I really love, the hiss is something I'd be happy to sort as it would be even more usable for me.

I have googled a bit and found this thread over at madbean https://www.diystompboxes.com/smfforum/index.php?topic=111625.20 . This guy had a similar issue so I tried some of the suggestions, without any luck so far.

I probed the signal path using an audio probe and found out that the hiss is only very subtle on the input stage (IC5 / pins 3,2,1) and on pin 6, but is very strong on the output of the output-buffer stage - pin 7. Most of the hiss goes away when I pull the 78L05 voltage regulator supplying the PT2399s. When doing these tests I turned down the volume-controls of all the delays to ensure no PT2399 noise gets fed to the mixing/output-stage.

After I noticed that the regulator gets quite hot, I tried a (properly adjusted) LM317 in its place, without an improvement. Additionally I moved the diode D1 before C1 to ensure the resistance of the diode forms a HPF with the capacitor to shunt power supply noise. No improvement. Then I tried a 100n cap from several points in the power supply to gnd and from pin 5 to gnd without any success. I tried a different opamp (OP275) instead of the TL072, no success. I also tried two different power supplies without success.

The only thing that helped was to put a large-ish cap in the feedback path of the mixing stage. When I used a 10n cap the hiss was at the same level like on pin 6, however this did also result in some treble roll-off which is not very convenient.

That's all I could think of up to now. Are there any other things that could try? Or is this something I have to live with? I've build loads of pedals but never had such a strong hiss going on. I have to admit, however, that's one of the most complicated builds so far.

Attached is an image of the schematic I used to build this beast.

Thanks heaps!"

I should add that I used the PCB that had no part-markings on it and that has the issue with the output-volume poti. However, building this worked like a charme and the delay is really sweet, except the hiss.

Thanks!
Yves

[rankot]

If your regulator gets too hot, then probably you have a short somewhere.

[deadastronaut]

hang on, i'll find the 'fix ' mod image.  it was on here, but dropbox changed my links...

do this fix...no hiss.  ( the input opamp was reversed on those boards. ...)

the 78l05 should be fine...as rankot said, check for a short.

[iefes]

Thanks for the quick responses!

I will definitely check for shorts somewhere on the bottom of the PCB. I will have to take it out of the enclosure though which is a little complicated, but I'll check it out.

Rob, I inspected the PCB and it is a different layout than the one in the fix you posted (picture attached). There's already a 1k on the input of pin 3 and R6 is already 1M. What is the jumper supposed to do? Does it connect Pins 1 & 3? At the moment, pins 1 & 2 are connected as per the schematics. If I would connect pins 1 & 3, all three of the first opamps pins would be connected, which isn't what we want, right?

Thanks for your help!

[deadastronaut]

Ahh i see, yeah so it is ok then...thought it was a much older board....so shouldnt be hissy.

have you got any other pt2399's to try.  those ones with the big notch are dodgy...

see previous posts.

1+2 should be connected yes ...

[iefes]

Okay, I just tried it without any PT2399 inside and there was still quite some hiss. I also tried some small-notch PT2399s but with them in the hiss was even stronger than with large notch ones. Then I pulled just IC 4 which resulted in some oscillation. Same when I pulled just IC 1.

So, anything else I could try? The hiss is really only present from pin 7 of the IC, not on pin 6 (or just very quiet).

[iefes]

I still haven't found a solution to the hissing issue. Right now I have a 2n2 cap across pins 6 & 7 of IC 5 to get the hiss down to an acceptable level, even though this means a significant treble roll-off. I'll rewire it to True Bypass for this reason.

I'm still very curious to find out why the noise is so prominent here. Do you guys have any more ideas? It seems that it's really only present from pin 7. The gain of the last stage isn't really high enough to amplify hiss that is produced earlier in the circuit to these annoying levels, is it?

However, any more ideas are highly appreciated. I love this delay but it's giving me a hard time.