Build Your Own Clone Message Board

There's a problem with my (old version) tremolo. I've been messing with the CLR values, as referenced in this thread:

viewtopic.php?f=9&t=34300


Well, now I've seem to have broken it completely. The LED lights, signal passes through, but there is no trem anymore. Not sure what to do next.

Well either the low frequency oscillator is no longer oscillating or you have fried the modulation FET. Assuming it is anything like the current Trem kit.

It's nearly exactly like the current trem. The things which have changed between versions are a few cap values and making the volume trimpot an external pot. No major changes in the circuit.

It's quite possible that one of your joints somewhere else was cold and just taking the board in and out of the enclosure to change the resistor aggravated it. I'd reflow joints first.

I never took the board out, so I think the above may be right. My question is, which components are the LFO and the modulation FET?

The modulation FET is Q3, the 2N5457 with its gate connected to the wiper of VR1. The LFO is all the bits associated with Q4. Its output connects to the top of VR1. if the LFO is still running you should be able to pick up a slowly varying voltage at the top of VR1. An old fashioned needle / analogue multimeter is best for this (or one of those new fangled DMMs with a pseudo analogue bar display). In fact, come to think of it, if the LFO is running surely the LED should pulse? Isn't that what it normally does?

Now I think more about it - you say you were messing with the CLR in series with the LED, so it is most likely the LFO not running that is your problem. Unlike almost all other BYOC kits the LED and its resistor are an integral part of the effect circuit - specifically of the Low Frequency Oscillator (LFO).

Changing R11 will affect the LFO. What did you change it to? Is the LED the original or did you blow it and have to replace it? Is the CLR now back to its original value? If not I would put the 10K back and see if the pedal works. Otherwise there is a strong possibility you passed too much current through Q4 and it is blown.

Incidentally - the input impedance is not 1M as claimed in the instructions. It is 330K.

All references in this post are to the current download circuit diagram included in the trem kit instructions.

I suspect it is perhaps the LFO then, as the LED will be solid -- meaning non-blinking -- if the rate is turned all the way down or up. Switching the effect off and back on again will reset it, but will re-occur when you min or max the rate.

I need to find a copy of the old version trem schematic so I can pinpoint which component you're referring to. Thanks so much for your help.

I really missed this pedal this past weekend at my gig, as I use it for several songs per night!

Apparently the differences between the two version of the trem are quite small. I think you should look for and try replacing the transistor that has its emitter connected to the footswitch. The base and emitter likely each go to non-polarised 1uF caps.

The schems and board layouts mapping te components are available in a sticky at the top of the non-BBD modulation lounge.

You're speaking Greek! Which component is that?

Greek is of course the language of electronics.

The transistor of which I speak so obscurely is, according to the schematic for the old trem (issue 2.2 PCB) - Q4. I have no idea what the manufacturers part number is for that because the old instructions are not yet in the old instructions archive. The new trem has a 2N5088 in that position - a general purpose NPN silicon high gain, low noise. I would think an MPSA18 would do and it has the same pin-out. The 1uF caps are C6,C7 and C9. They are in a side by side group of three, the largest caps on the PCB. Q4 is right next to them.

I see Charlie Hunter uses this trem - I am impressed.

The old version has the 2N5088 in that position, as well. There was just enough room under it for me to see the number. I'll replace it and see if there are any changes. Thanks!

Finally got around to taking a shot at this repair. First thing I did was replace the 10k CLR. That did the trick, it works fine again and is now back in action. Thanks everyone for the assistance!