Many years ago I built the wonderful Tom Hollis Easy Vibe circuit and put it into a pedal enclosure. Used it for many years. I fried it by accidentally switching my pedal power supply to 18volts on the output the Easy Vibe was connected to. It promptly fried the pedal. I'd like to get it working again. I'd assume resistors and capacitors are all fine? Start with the ICs and then LEDs? Any advice would be great. I am okay with reading a circuit and populating a board, but my understanding of how the circuit works is rudimentary at best, and so is my knowledge of where to start troubleshooting.
This board has been a real asset to the community and I would covet any direction and guidance on where to start troubleshooting.
Edit:
(http://www.hollis.co.uk/john/easyvibe.jpg)
Project page: http://www.hollis.co.uk/john/circuits.html (http://www.hollis.co.uk/john/circuits.html)
Link to the circuit layout here: http://www.geofex.com/PCB_layouts/Layouts/easyvibe.pdf (http://www.geofex.com/PCB_layouts/Layouts/easyvibe.pdf)
10V was risky anyway. Looks like he relied on the right,and well regulated
power source. So smoothing electrolitic cap from 9Volt to ground ,470uF,
is fried. Its late here so I'm not sure about the 2 leds in series
The most likely parts to fry are the 4xLEDs which light-up the LDRs.
All the other stuff is probably OK.
Even those LED might be OK!
Perhaps post some voltages.
Thanks guys!
I'll change C10, the smoothing electrolitic cap from 9Volt to ground 470uF first. Then I'll check the 4 leds first as those leds and LDRs were mounted in sockets. Don't know why I didn't think about that before. What about the dual opamps?
QuoteWhat about the dual opamps?
Anything is possible. Start with the most obvious things and work down the list.
The voltages help pin-point where the problems are and remove the guessing.
OK. Thanks guys. I'm not really experienced with measuring voltages. I have a meter and can give it a try. I'll start by replacing and looking at the most obvious ones that you guys already mentioned. I'm guessing it's the filter cap, as I remember it dying right away when I inadvertently plugged it in to my power supply with the voltage toggle switch in the wrong position.
Most op amps are designed to work in circuits where they are effectively seeing 30V (+15/-15). There are not too many that will die if hit with 18V. If you used the TL064 specified, it is one of the few that won't like 18V. I think I would be tempted to try something less noisy like a TL074 if you are replacing the op-amps. If you are running from a power supply then you don't care about battery drain.
Quote from: DIY Bass on October 18, 2022, 06:34:12 AM
If you used the TL064 specified, it is one of the few that won't like 18V.
Are you sure? This TI datasheet says +/-18V like most other op-amps:
https://www.ti.com/lit/ds/symlink/tl064.pdf?ts=1666025207302
Quote
I think I would be tempted to try something less noisy like a TL074 if you are replacing the op-amps. If you are running from a power supply then you don't care about battery drain.
+1 agree. Less noisy would be better, and unless you're running it from a battery, the extra current won't be an issue.
Quote from: ElectricDruid on October 18, 2022, 08:51:48 AM
Quote from: DIY Bass on October 18, 2022, 06:34:12 AM
If you used the TL064 specified, it is one of the few that won't like 18V.
Are you sure? This TI datasheet says +/-18V like most other op-amps:
https://www.ti.com/lit/ds/symlink/tl064.pdf?ts=1666025207302
I can assure you that TL064 can run up to over 38V, as DC amp, without any issue.. :icon_wink:
Boy, if that had happened to me (like it never has, ha ha!), I'd be sure to fit some polarity protection in there while I had it apart... :)
Quote from: Rob Strand on October 17, 2022, 08:55:15 PM
The most likely parts to fry are the 4xLEDs which light-up the LDRs.
All the other stuff is probably OK.
Even those LED might be OK!
Perhaps post some voltages.
I think Rob might be right. The LEDs in the voltage divider that creates the bias voltage for the LDRs have a 470uF cap across them. With that 10K resistor, the 470uF cap means the bias voltage takes 18secs to come up to 98% of its final value, so you'd get away with connecting it to 18V for probably at least ten seconds!
The ones in the LFO that drive the LDRs could be dead. That would explain why nothing works.
The main 470uF power cap should definitely have a bit more leeway than 10V on a 9V supply. Is 16V really that much more money?!? 25V or even 50V would be much better. And I second what Gibson said - while you're messing with it, you could add a protection diode (it wouldn't save you from 18V, but it'd save you from reversed power) and a little resistor (47R? 68R?) so that that 470uF power cap is actually doing some proper filtering.
Quote from: ElectricDruid on October 18, 2022, 08:51:48 AM
Quote from: DIY Bass on October 18, 2022, 06:34:12 AM
If you used the TL064 specified, it is one of the few that won't like 18V.
Are you sure? This TI datasheet says +/-18V like most other op-amps:
https://www.ti.com/lit/ds/symlink/tl064.pdf?ts=1666025207302
Quote
Darn it. That's what you get for reading datasheets at bedtime.