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PostPosted: Mon Jan 18, 2016 3:41 pm 
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Though it's not a problem we see here very often, occasionally someone will post that they're not getting output signal in bypassed mode. The good news is that this condition greatly restricts the number of possible causes and is fairly straightforward to troubleshoot.

One important point to make at the very outset is that what we'll be describing here pertains only to true mechanical bypass (TMB) pedals. That covers almost every BYOC kit but a couple. A lot of it will apply to non-TMB pedals, too, but these will have other portions of the pedal circuit that remain connected to the bypassed signal path, and those would need to be identified and checked out, as well.

Keep in mind that for these TMB effects, bypassed mode should give an output signal even when no power source is connected to the pedal. This is not the case with many commercial effects that use an electronic switching system, like the majority of pedals from Boss, DigiTech, Ibanez/Maxon, etc.

1) The first thing to check if you don't get a signal in bypassed mode is the silly stuff that we all do from time to time. Forgot to take your amp out of standby? No cable plugged into the guitar? Or into the amp? Left your tuner pedal on? Instrument and patch cables are confirmed functional and plugged in all the way? Etc., etc., etc. So let's assume you've eliminated those possibilities, and it's definitely something in the pedal. What now?

2) The next thing to check for is a wiring error. Carefully check all your I/O jack and footswitch wiring against the wiring diagram you're using for your build. A wiring mistake is a very common cause for the lack of a bypassed signal. In particular, look for a mistaken swap of the connections for an I/O jack's tip and its sleeve (or ring, for the stereo input jacks).

3) If the wiring checks out as being correct, then the next step is to check the bypassed signal path for a circuit discontinuity. For the typical BYOC kit, the bypassed signal path is as follows:

For kits with top-mounted I/O jacks--

    Input jack tip --> wire to IN eyelet at top of PCB --> PCB trace from IN eyelet to #4 eyelet above footswitch --> wire to F/S lug 4 --> jumper wire to F/S lug 9 --> internal F/S connection to lug 8 --> wire to #8 eyelet above footswitch --> PCB trace from #8 eyelet to OUT eyelet at top of PCB --> wire to output jack tip

For kits with side-mounted I/O jacks--

    Input jack tip --> wire to F/S lug 4 --> jumper wire to F/S lug 9 --> internal F/S connection to lug 8 --> wire to output jack tip

In either case, in bypassed mode, you should have continuity all the way from the tip of the input jack to the tip of the output jack. Start by checking this. Put the pedal in bypass and disconnect the power source. Select the continuity measurement mode on your DMM (THIS symbol). If your meter doesn't have a continuity setting, set it to its lowest resistance range. Touch one meter probe to the tip of the input jack (or its solder tab) and the other to the tip of the output jack. If you have continuity between those two points, the meter should beep or buzz; if using the resistance mode on your meter, it should read almost zero resistance, certainly no more than a couple of ohms.

If you get positive continuity, then look closely at the contact between your instrument cables and the jack tips. A bent tip or the presence of corrosion on the tip or the cable plug could be causing your signal discontinuity issue. Another thing to check is if there is also continuity between any point in the bypassed signal path and ground; if such continuity is present, the signal will go to ground and kill the pedal output. If this condition is found, the point of connection between the bypassed signal path and ground needs to be found and corrected. Conduct a thorough visual inspection of the pedal, focusing on that bypass signal path. Things to look for include a long component lead or errant wire strand touching something it shouldn't (the enclosure, the back of one of the control pots, a grounded footswitch lug, an I/O sleeve tab, etc.) or a solder bridge to an adjacent grounded PCB eyelet. Carefully inspect both sides of the PCB and all of the jack and switch connections.

It's more likely that you'll find no continuity. Now it's a matter of going through the appropriate above bypassed circuit path and finding where the break is occurring. Keep one probe on the tip of the input jack. Then move through the bypass circuit connection points in the order they are listed. Keep going until you get a no continuity result, which will tell you what connection needs repair. Two common points of continuity failure in the bypassed signal path are:

  • The jumper between lugs 4 and 9 of the footswitch (assuming the usual footswitch wiring used in BYOC kits). Check the solder joints on each lug.
  • The internal footswitch lug 8 - lug 9 connection. Defective footswitches do occasionally happen, and it's also possible to damage the footswitch by putting too much heat into the switch during soldering operations.

If none of these troubleshooting measures pan out, by all means, post your problem here in the forum and we'll do our best to help you track it down.

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PostPosted: Sun Mar 08, 2020 2:56 pm 
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Hi, I am building the Envelope Filter & Fixed Wah. Everything works fine except I have no signal in bypass mode. I traced the continuity as described in this post, and found no continuity between lug 8 and 9 on the foot switch. Does this sound like a defective switch?
Thanks

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PostPosted: Mon Mar 09, 2020 7:40 am 
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Sounds like an overheated switch if you have effect but no bypass or continuity between 8 and 9. Are you sure the switch was in bypass mode when you tested it?


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PostPosted: Mon Mar 09, 2020 9:00 am 
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Thanks for the reply. Yes I double checked it was in bypass when I tested it.


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PostPosted: Mon Mar 09, 2020 10:41 am 
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With the pedal in bypass, try shorting the 8 and 9 footswitch lugs with a screwdriver and see if your signal comes through.

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PostPosted: Mon Mar 09, 2020 3:28 pm 
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Yep, the signal comes through when I short out 8 and 9.
Thank you


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PostPosted: Mon Mar 09, 2020 6:36 pm 
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Time for a new footswitch!

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PostPosted: Mon Mar 09, 2020 7:28 pm 
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Okay, that’s what I was thinking. Thanks for the help.


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PostPosted: Mon Mar 09, 2020 8:02 pm 
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Since it never worked correctly, I'm quite sure that BYOC will replace it for you at no cost. Just contact sales@buildyourownclone.com and tell 'em you received a defective footswitch. They'll send a new one right out to you.

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PostPosted: Tue Mar 10, 2020 5:59 am 
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That’s great! Thanks again.


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PostPosted: Fri May 29, 2020 12:04 pm 
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I am having a similar problem my pedal works fine but once I put it in bypass mode I can’t hear anything. But then tried turning the amp up all the way I and I could hear the bypass but at low volumes,
What is going on do I have a bad switch?


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PostPosted: Fri May 29, 2020 1:26 pm 
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Hello Hemo, I would suggest making your own topic in the tech support section under the appropriate effect type sub category. This way all replies can be to your specific case. Please include large well lit photos of both sides of the PCB as well as a detailed account of how the pedal is acting.

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