The $20 delay (Fab Echo mods photoessay) 56K warning!

[moertz]

ok this is the closest i got with my camera http://www.bilder-hochladen.net/files/8t1j-1-jpg.html. the repeat knob works as usual with one repeat when i turn it down but just about four when i turn it up. the fourth is already barely audible. it is limited to one repeat only when i remove one of the two solder bridges. i don't know what else could be contacted by the bridges .. i also resoldered them multiple times. i thing i'm buying another fab echo anyway so i'll see if i get it working then. do you think it's possible that it just doesn't work on some?
thanks for the quick help!
 

[earthtonesaudio]

Hm... Not sure why it's not working.  Other than the fact that I left my 12k resistor in place, and shorted the 4.7k instead, it looks alright.  My best guess is that one of the two solder joints is not complete.  Try and test for continuity with a meter and see if there's any high value (>1k) where there should be a short.  It's easy to make a cold solder joint when re-working something.  Those tend to make strange problems.

[Ssmit]

Thread Resurrection!

So I took my Fab Echo apart to do the infinite delay mod, and maybe plot out the delay time knob positioning, and I found out I have a different "delay module" board layout than most of the pics posted; the PT2399 chip is on the TOP of the board (the pot side). I'll try get some pics up tomorrow, but for now, I'm just going to leave it alone (wouldn't want to break anything  ). So, is anyone else have this revision?

[Ssmit]

Bottom


Top, with PT2399

[Ssmit]

Anyone? I'd really like to get this done

[krellmusician]

Just did two of the three mods (infinite repeats and mix; delay time pot will be added tomorrow) and I'm not sure if I might have done something wrong.  The mix pot is acting more like a pure wet level control, that is, I hear no dry sound at any setting of the control.  To be honest, I don't remember exactly what it sounded like stock, but I know that I used to get an output with the mix control turned all the way down.

Any ideas?  Or am I just imagining things?

[earthtonesaudio]

@ Ssmit: Locate the resistor coming from pin 6 of the pt2399 and going to ground, remove it and replace it with a pot for adjustable delay times.  For infinite repeats, take a look at the datasheet: http://www.datasheetcatalog.org/datasheet/PrincetonTechnologyCorporation/mXyzsyzt.pdf
And notice the 50k pot under the "Echo Application Circuit" schematic diagram.  The 50k pot corresponds to the "mix" control on you delay unit, and the 18k resistor attached to the wiper of that pot is what keeps it from doing infinite delay/self oscillation.  Reduce the value of the corresponding resistor on your Fab Echo (anywhere between zero ohms and 10-12k should do it) and it should work.  HOWEVER, the circuit might be slightly different (instead of the 18k resistor attached to the wiper, a similar value may be in series with lug 3 of the 50k pot) so take a good look, draw a schematic from what you have, and you'll be able to make a better decision from there.  Good luck!


@ krellmusician: That sounds like something's wrong.  I think at minimum, the mix pot should either let full "dry" signal and no "wet" through, or maybe mostly dry and a tiny bit of effect.  I'd look for solder bridges first.

-Alex (Earth Tones Audio)

[Ssmit]

@earthtonesaudio: thanks! I'll be getting to it soon (have a lot on the go at the moment)

[The Tone God]

There is a fairly easy way to do a true 100% wet/dry mix but the one draw back is you lose the bypass function. If you are true bypassing it then this is no big deal.

Any interest ?

Andrew

[AM]

There is a fairly easy way to do a true 100% wet/dry mix but the one draw back is you lose the bypass function. If you are true bypassing it then this is no big deal.

Any interest ?

Andrew

I would be interested. I just got one of these and want to mod it. Thanks in advance

[The Tone God]

I'll take some pic later to outline the mod.

Andrew

[The Tone God]

Sorry for the late response. Okay here we go.

Wet / Dry Mix Mod

The Fab Echo does not have true bypass but instead switches the delay signal in and out and leaves the clean buffered signal always connected. To disable the clean signal from always passing cut the trace between the jumper connection and the SMD resistor:



Note: An easy way to cut the trace is with a sharp knife. You can test to make sure the trace is cut by measuring with your meter.

To get the clean signal connect a wire to the jumper connection on the board. This is a good place for example:



To get the wet signal wire a connection to the wet side of the mix pot on effect board:



Note: Do not forget to turn down the pot attached to the board otherwise it will interfere with the mod.

Connect the clean signal to one end of a 100K linear pot. Connect the wet signal to the other end. Connect the wipe of the pot through a 1uF capacitor and a 33K resistor.

Go ASCII graphics:

Code:

Clean
   |
   |
   |
   P    1uF      33K
   O----|(----/\/\/\/\----Board
   T
   |
   |
   |
  Wet       

Connect the wiper to the orange capacitor at this spot on the board:



You now have a 100% wet / dry mix pot. If you want you can decrease the 33K for more output then put a volume pot on the final output of the effect as a level control.

Since the clean signal is disable the bypass function will not work anymore. If you want to force the pedal into effect mode all the time then perform this mod.

Always On Mod

Cut the trace at this point:



Connect a wire from the switch's board connection to the resistor:



The pedal will now always be on. You can install a true bypass switch.

Enjoy.

Andrew

[AM]

Thanks,
This is very nice of you. Step to step instructions together with photos!!!!!

[The Tone God]

Thanks,
This is very nice of you. Step to step instructions together with photos!!!!!

No Prob. Let me know if you need anything else.

Andrew

[Br4d13y]

wow. i got one at the gc for 5 buks used yesterday, and did the delay time pot mod

this thing has longer delays than my dd-3?! and the slightly lo-fi breakup at long delays sounds way kool!!

this has a place on my pedal board, im just mystified that a dano, other than my fish n chips, is there!!!

[lolalola]

Aaaaah, I want one! Anyone want to sell me one? Puh-lease? I so do not have the brain capacity to make one, so if you're bored of yours, please email me! x

[lolalola]

Aaaaah, I want one! Anyone want to sell me one? Puh-lease? I so do not have the brain capacity to make one, so if you're bored of yours, please email me !

[Quackzed]

you can get the fab echo on ebay for a reasonably low price... 

[DjFrontBum]

wotto, just got 1 from CPC/Farnell for £26 including UK delivery,

[AudioMime]

Indeed, I got one at my local music store for 15  dollars.

Well I found this out while I was roaming through the pages, and I remembered I got one for christmas a year ago.  So I whipped it out and unscrewed it. So far I was able to take off the first board, but the second board with the pots is really annoying to get out. Any suggestions to get the knobs off?

BTW this is a pretty cool mod for a really cheap echo/delay. Thanks you guys.