Build Your Own Clone Message Board

Hi, hoping you can help.

I've just completed this build but when I power it up the bass only LED lights up fine but nothing else works,

In bypass mode, the signal is fine, when engaged, no sound.

My first suspicion is that it has something to do with the wiring on the footswitch. But then it could be likely it's the result of poor soldering throughout, which would obviously be more serious.

Couple of points.
1. I'm running it off a 9v battery at the moment, as its easier to take the PCB out of the enclosure
2. I haven't connected the aux output, as I seem to have managed to cross thread the nut on it.

Any help would be much appreciated

Well the Bass only LED is directly switched through the Bass only foot switch.

The Bypass LED is indirectly switched using a 'millennium bypass' circuit based around Q8 qnd Q9. This relies on the tiny leakage current through D8, the reverse biased 1N4148 diode, to turn on the MOSFET BS170 when the switch SW1 tags 8,7 and 9 is in the open, effect active, position. When the switch is flipped to effect bypass the gate of the BS170 is pulled low through the various resistances of the circuit, it is turned off and the LED goes out.

To operate correctly this circuit relies on the very small leakage current through D8 being enough to overcome any other leakage currents which for example might pass through flux or other contamination on the surface of the PCB. It also requires that the base to collector diode provided by Q8 is much lower leakage than D8. Silicon transistor b to c diodes normally are very low leakage but you just might have a bum one. Anyway I would clean your PCB surface first to remove any leakage paths through surface contamination. The other possibility is that you have blown the gate of the BS170 from static electricity while handling. For some reason BYOC does not warn that MOSFETs need careful handling to avoid static damage. I'm assuming that you do actually have the BS170 in the right place on the PCB.

All of the above is just to address the problem of why your bypass LED does not light and doesn't even start to look at why you have no effect sound. All of your ICs appear to be in the right place and the right way round on the PCB. You could check that you have the right voltages present. Check pins 1 and 7 of IC1,2 and 3 are at 0V and that pins 4 of all the 558s are at -9 and pins 8 are at +9. The -9 supply is provided by the MAX1044 charge pump IC and if that is not operating properly you will have no -9, the DC conditions throughout the entire pedal will be way off and it won't pass audio.

Further to the above, and assuming that your problem turns out NOT to be a lack of the +9 and -9 power rails ...

I have been looking again at the divided octave circuit and I notice that once the signal passes through the input pre-amp IC1b it splits into two audio paths one of which goes through a half wave rectifier then to a phase switcher which is driven by the CMOS logic dividers to produce the low octave components. The other path goes to a Green Ringer octave up (full wave rectifier) circuit based around Q1 and Q2, and then gets mixed back in to the output signal. Since you aren't getting any output at all that means the signal isn't getting through EITHER path. That in turn leads to the conclusion that the signal goes AWOL either very near the input, or near the output bits of the circuit, before the two paths split or after they are mixed back together.

If signal loss rather than wonky power rails turns out to be your problem the best way to fault find it is to use an audio signal probe to follow the signal paths through the circuit and home in on the point it gets lost.

Thanks very much for your help. I tidied up some of the dodgier solder joints, re soldered a few of the wires on the foot switch, and cleaned the board with isopropanol, with the result that the effect now works (partially).

I should have time at the weekend to do a bit more troubleshooting and test some values of the ICs, but I've listed below what does and doesn't work in case anyone can easily see what's wrong just by seeing these symptoms.

When engaged, there is an octave down mixed with the dry signal (with a fairly noticeable drop in volume - although I suspect this may be normal having read some other posts).

There is less octave down volume than I would like (a maximum of about 40/60 octave/dry signal with the mix pot turned counter clockwise). I suppose it could be possible that this is due to the little 10 watt practice amp I played it through.

The stabilizer appears to work

The mix control works (although the volume increases as it is turned clockwise)

The bass only switch changes the sound but doesn't give a bass only effect (still a mix of dry signal and octave down)

Pretty sure neither the green ringer or tone control do anything.

The main effect LED still does not light.


Any suggestions on what may be wrong or components I should be testing would be very welcome. Please be gentle, I'm a complete newbie who's probably bitten off more than he can chew...

To start with your last problem first - No effect active LED

Refer to my last post - the LED is controlled only by the small group of components around Q9 the BS170 MOSFET. Those include D8, Q8 and R64 1K. When the bypass switch is in the active position nothing should be connected to the input of that small circuit. The tiny leakage current through D8 should turn the MOSFET on, it allows current to flow through R64 and the LED and the LED lights up. With the foot switch in bypass the input to that circuit is pulled low by R34,35 or R16,17 (depends on the position of the Bass switch) and the LED goes out. Q8 acts as super low leakage diode, its just there to protect the MOSFET.

Possible problems with that circuit are - LED in backwards or a bad LED, static blown MOSFET or a bad diode or bad Q8. Or a bad solder joint or short somewhere. Note that some of the PCB tracks are on the top side of the PCB. If there is a bad plate through hole they may not be making connection with the tracks on the underside.

You can check the LED is working by using a short piece of wire to temporarily connect the LED lead on the flat side of the plastic shell to ground. If the LED does not light either the LED is bad, in backwards or there is solder joint problem with the LED or with R64 the 1K.

Using a small amp obviously won't help the bass. The Bass switch should leave you with just the divided bass but the reason it doesn't work properly is likely connected with why the ringer doesn't work. The ringer is based around Q1 and Q2 and is mixed with the clean signal by IC1a. The input signal from the output of IC1b pin 7 may be making it through to the output of the ringer (C19) but then getting lost.

You may need to build a simple audio probe to trace the signal through the effect circuit (a jack lead into your amp with the other end split into live and ground. A reasonable sized cap should be connected in series with the live of this lead and the other end of the cap to a metal probe which can be touched to any selected point in the circuit under test. Any audible signal on that point will be heard from the amp).

Success!!
It turned out that I was a bit shy with the solder on some of the resistors. I didn't realise that solder had to flow through to the top side of the PCB for some of them to work. I resoldered R64 and the main LED started working. I then had a good look at the rest of them and resoldered any which looked suspect. Pedal now works a treat.

Anyway, thanks very much for taking the time to troubleshoot and diagnose the problems for me, I really appreciate it.

>> I didn't realise that solder had to flow through to the top side of the PCB for some of them to work. <<

Well in theory it should not need to. Double sided PCBs usually have plated through holes where before the tracks on either side are etched copper is electrolytically deposited in the holes and is supposed to connect the tracks on both sides together. This process is quite critical and is not always successful. PCB manufacturers are supposed perform quality control checks to see that the through plating is properly formed but this is cost related.

With through plated PCBs two things can happen - either there is a surface film on the component lead that does not break down when the lead is soldered on the bottom of the PCB. Re soldering with the solder wicking through the the top pad covers a longer section of the component lead and allows longer for the solder to make a connection. Or - The through hole plate has failed and the extra solder and heating allows the solder to create a bridge between the top and bottom pads. This only matters at points where there are bottom and top tracks that need to be connected together. I suspect that at least some of the 'bad joint problems' with BYOC kit builds are due to improperly formed through holes.