De-Ticking a Shaky Jimi Univibe - help please

[Regis]

I need an effect pedal expert. Someone who can help me de-tick this damn Shaky Jimi univibe. It's a great sounding vibe, but useless to me unless I can make the tick go away, if it's even possible. I'll take advice from anyone.

I had done some reading and tried putting 100r resistors inline in the plus and minus from the power supply to the pedal, but no dice.

The op amps are Tlo62's.

Here are above and below shots of the board, thanks for any help!

[Jazz P Bass]

Did you replace the opamps?

[Regis]

No, it came with the TLO62CN's in it.

[Jazz P Bass]

The reason that I asked about the opamps is I had a MXR Phaser that was letting the phase thump through.
I changed out the TL062 & that fixed it.
Just a thought.

[52 Bill]

I assume that the ticking follows the speed control? If you have a scope, can you see the pulsing on the power supply line and or the bias supply? Is it better or worse with a battery or wall wart?

[pdf64]

Try bypassing all the electrolytics (with new / tested good ones of similar value); maybe one has developed high ESR?
Pete.

[Regis]

I assume that the ticking follows the speed control? If you have a scope, can you see the pulsing on the power supply line and or the bias supply? Is it better or worse with a battery or wall wart?

Yes it follows the speed control. Don't have a scope, Bill. It doesn't happen with a battery.

Try bypassing all the electrolytics (with new / tested good ones of similar value); maybe one has developed high ESR?Pete.

This is a brand new pedal, Pete. I know caps can be bad but how likely? I found something by Mark that sez to bypass the power supply rail on the LFO with a resistor and cap, but I'm too dumb to figure out which IC is the LFO. Thanks,Regis

[J M Fahey]

Best desire to help, but no schematic plus no scope makes the task difficult.
Yet, we might follow the "PSU=tick" lead.
Out of the tip of my head, I can imagine 2 possible problems (there may be a thousand others, for all I know).
1) poor jack grounding, relative to battery terminals grounding.
to test it, come with 2 wires (red and black) from the PSU and tack solder them to the exact same pads where the battery terminals are soldered.
2) the PSU actual voltage is not 9V (usually quite higher).
Regulate it down to exact 9V.
If it has, like most cheap wall warts, say, 10 or 11V no load, you have not enough margin for a 7809 , but use a nominal 12V PSU (which will be 15/16V) to begin with and you'll be fine.
Soldering it straight to the battery terminals as before will not hurt, of course.
Good luck.

And by the way, how's your back/ribs going?
Hope you recovered fully.
Double good luck.

[52 Bill]

JM does point out one thing here, have you tried different wall warts?

If you follow the traces from the speed control it should lead you to the LFO circuit, which appears to be the chip closest to the power supply jack.

[Regis]

JM does point out one thing here, have you tried different wall warts?

If you follow the traces from the speed control it should lead you to the LFO circuit, which appears to be the chip closest to the power supply jack.

Yes, a one spot, a Boss, and a GFS, all regulated. They all do it. Thanks for the tip on the LFO, The remarks I found that Mark H. authored say to isolate the LFO Chip. I'll have a look at that chip and see what I can do. Thanks!


About my back where the tumor was, I guess you can say I am steady state. I have to wear a wrap around brace to keep my guts in because they say I have a "surgically created hernia". Meaning my guts droop because there are no ribs to hold them in. If I go without the brace it starts to be very sore very fast, and eventually it becomes painful. So, it looks like I have to wear this thing for the rest of my life. The docs say they are reluctant to go back in and fix it because they aren't sure they can. The only time I don't wear it is when I am sitting down, watching tv, or sleeping. Even wearing the wrap, when I am jamming with the fellas I have to stop after four or five songs and go sit down.

I am going to see the plastic surgeon soon and have a frank talk with him about the possiblity of a fix, but I'm not gonna get my hopes up.

[Mark Hammer]

I heard my name called.

The ticking arises out of the very sudden current draw that the LFO has. Those 2-op-amp LFOs produce a square wave, and then turn the square wave into a triangle. That sudden rise on the leading edge of the square wave is what causes the issue, but putting spikes on the shared power lines in the pedal.

So what can be done?

1) Reduce the amount of current it needs to do its job. That seems to be already done. YOu'll often find low current chips like the TL022 or LM358 used for such LFOs because they draw much less current than something like a 4558 or TL072. I don't know chapter and verse on the TL062, but my understanding is that it is very much at the TL022/LM358 end of the spectrum rather than the other end.

2) Turn that square into a trapezoid. Boss uses this trick in soe of their pedals. Remember, it is the instantaneity of the current draw that produces the spike. If the "square wave" takes a couple of milliseconds to rise, and a couple of milliseconds the fall, the current draw is not nearly as sudden. You can read more about how Boss does it in this old Stompboxology newsletter about tremoloes: http://moosapotamus.net/files/stompb...-mo-tremlo.pdf

3) Provide the chip a "current cushion". This is what the "isolation"/"decoupling" is about. You appear to have done part of it, from your comments, but I need confirmation that you've done ALL of it.

Running a small-value resistor between the V+ line and the +power pin on the chip, in tandem with an electrolytic cap between the power pin (pin 8) and ground, does two things. First off, that electrolytic cap acts like a little teeny weeny uninterruptible power supply for the chip - assuming you treat a couple milliseconds as akin to an eternity. It stores charge that is available on demand to the chip, and clearly, if the chip is gonna suck current from anywhere, that electrolytic cap is a more efficient route than having to go through that godawful 100 ohm resistor to the power supply.

So, by virtue of the manner in which it stores a wee bit of reserve supply for the chip, and series resistor assures it will draw from the cap in a pinch, rather than the supply. That softens the immediate power needs of the op-amp stage producing the square wave, such that spikes don't show up on the power line shared with the audiop path.

The other thing that RC pair do is serves as a sort of ultra-lowpass filter, such that when it does pull current from the supply to produce a square wave, the "treble response" of that power line will be way way down. To illustrate, a 100R resistor, with a 10uf cap to ground provides a 6db/oct rolloff above around 160hz. A 160hz signal takes roughly 6.25 msec to go from midpoint, all the way up, all the way down, and back to midpoint, so 3.12msec to go up then back to midpoint. That's roughly equivalent to the little trapezoid-wave shift I referred to earlier; enough to make any sudden current draw not so sudden as to produce spikes.

So, there you go. Hope it was clear. Did you already use the electrolytic, or did you only use the series resistor?

[R.G.]

It appears from a glance at the photos that this is a commercialized Easyvibe circuit. Same de-ticking should apply.

Ticking with one of these is nearly always decoupling or layout related.

Here's a thought: if it's a brand new pedal, it appears to me to be defective and replaceable under warranty. If you bought a new car and it had out-of-round tires that thumped each time they rolled over...

[Regis]

Mark, R.G., thanks for the replies and education. I haven't tried the cap between the +9v and ground pins on the ic, what size? You mention 10mf but other things I've read state that up to a 1000mf cap should be used. I don't think I have any 1000mf caps small enough, I'll have to get one on Monday if needed. Does the +9v to the LFO chip have to be completely isolated from the other chips? The power feed runs from that chip to the other chips as far as I can tell. R.G., I knew of the EasyVibe but not in detail, yes it looks like clone/ripoff/copy of it. I can't send it back because I've had it for a few months, and have already hacked the board some. I probably won't get to working on it until Sunday or Monday due to the honeydo list, yard work, binge drinking, etc. I'll let you know what happens. Thanks again for all the help. sorry about the run on sentences, for some reason the text editor for the replies is stripping out all my carraige returns.

[Mark Hammer]

4.7-10uf should be sufficient to do what needs doing.

[Regis]

Mark, R.G.,I added a 10mf cap to the chip and it did reduce the ticking but it is still there some, mostly when I step on an overdrive. The resistor didn't seem to help much either way. I want to thank you for your detailed help and instructions, it's always a learning experience with you guys. thanks againRegis