@cybercow
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Once you voltages are corrected, you’ll want to focus on that internal trimpot. The sweet spot for that trimpot is a very narrow and us=ually somewhere around 11:00 on the dial. Move it in tiny increments while testing for the effect.
As Barry pointed out, I’d start with a solder re-flow session. Then, fire it up and test for +9V at pin 11 of the IC and 4.5V (VB) at the junction of R13 & R14.
If the voltages are correct and the unit is still not functioning, start a ‘signal trace’ and/or continuity testing session and follow the schematic to see what might be wrong in that manner.
You may also want to check continuity on the PCB in and around those locations where the solder mask has been scratched off/up. The traces beneath are very thin and are subject to being scratched completely thru – breaking continuity.
Let us know what you find.
With careful planning, measuring and drilling, the Mini-Me, even with Wilkie1’s mods, can be mounted into a 1590B enclosure with all top-mounted jacks . . . .
The Mini-Me’s Rate pot is like Anderton’s version A and the Mini-Me’s Depth pot is like Anderton’s version B.
Note that the Rate pot does NOT share a ground connection. So be mindful of the wiring.
I use Photoshop to work up my artwork over drill templates. From there, I either do up a waterslide or have then enclosure professionally drilled and painted at a fab house (AmplifyFun) in Portland. Here’s a prototype Stereo/Dual Chorus done up in waterslide and clear coat. Inside are two highly modified Mini-Me chorus circuits.
After ensuring both grounds are properly connected, if it still doesn’t work, please proved more detailed info and some good clear photos of both sides of the PCB and all the wiring.
Del – welcome to the group!
I recently procured a Hantek 2D42 Handheld Oscilloscope 40MHz Waveform Generator Multimeter 3 in 1 Multifunction Tester, replacing my DMM, sig gen, and bench scope. Got it on Amazon for under a 150 zorkmids. Haven’t looked back.
theurbaner – yes, one could use a long-shafted dual-gang A100K pot on an expression pedal to simultaneously control the “WET” and “DRY” controls. Just need to be sure to wire one of gangs reversed from the other so one goes up while the other goes down.
In addition, R12 could also be replaced with an A100K pot to act as a master volume.
No idea what a “Cody switch” is. Can you please clarify?
And the Roto-Tone Deluxe does not support 8 device options – only 4.
We need more information on what you’re chasing.
Those cheap Chinese testers don’t do JFETs well at all. The symmetrical nature of JFETs confuse them. As Barry points out, a Peak Atlas DCA75 is far more accurate and reliable. And even then the symmetrical nature of JFETs can confuse a DCA75.
I’ve used all the variants possible with the Mini-Me build. MN3007, MN3207, XVive MN3007 and even the NTE1641 (MN3007 eq) all work fine. There is a bit difference in how the chorus sounds with the NTE1641 – it tends to sound a bit more brittle as far as chorus goes.
Barry – I’m pretty sure the orientation of the LEDs is not a signal killing issue. Whether they are backwards or both oriented identically, the signal should still pass – albeit somewhat horrible if both are oriented the say way. They form one of the clipping options and even if they are oriented wrong, at worst, they would be performing in an asymmetrical manner. As they are, they should really be fine. I suspect something else is afoot.
Stewart – if the bypass LED is working, that suggests the pedal is getting power. A good clear shot of the solder-side of the PCB would be good too. We would also like to know what voltages you have at the pins of the 4558 opamp. Also, the color of your pics seems a bit lack-luster and I’m not able to make out the values of the resistors. Good idea to dbl-check all the resistor values because it is so easy to insert a 100K where a 1K (or vise versa) goes. Also, with a 9V supply applied, ensure there is about +4.5V DC at the junction of R17, R18 & C11
Welcome back to the community. And congratulations on the Rat.
As far as not building pedals to save money goes, that’s pretty much what got me re-started in pedals & electronics. I didn’t want to pay the exorbitant prices just to hear how a certain effect would work & sound in my rig. So far, I’m only about $3300 in the hole.
And using existing circuits to get clues about related circuits has always been a part of my paradigm. So, you’re not alone.
