Need help with Madbean/VFE Mini Mu Issue

[pedalbob]

 Hi all-

Built a Madbean/VFE Mini Mu with the newer style "TrueSoft" relay switch board (one they currently sell v3.4). Not sure if anyone has had any experience with these.  I've used the older version and never had an issue. The newer version has a bunch of SMD pre mounted parts when you buy it and logic is programmed into one of them ... older version came with a separat Dip 8 chip that was pre-programmed.  The newer one has a selectable buffer too between true bypass and buffered bypass with a little slide switch.

Effect worked great when effect is on (LED lights up, all pots and switches do their thing ... sounds great) but when I click to bypass while the LED goes out no guitar signal comes thru to the output (i.e no sound at all in bypass mode).

I checked everything multiple times and even built a 2nd True Soft board and tried that with same issue.  All of the important parts (relay, jacks, semi conductors, etc. came from Mouser and I checked everything else with my Peak passive component tester before installing).

The Mini Mu uses a split rail design so there is a voltage inverter on the True Soft board too and the effect board uses +9v and -9v from that ... I assume since the effect works fine that the power supply side of the board is good.

I posted pictures and same above info on the Madbean Forum a few weeks ago and have not received any useful suggestions.  It seams to me looking at the schematics bewteen the two boards that the issue needs to be on the True Soft Board since only the momentary footswitch has pads on the effect board and it seams to be doing its thing fine.

I also tried bypassing the relay switching by putting/taking guitar signal input and output directly from output board and using my test rig board jacks but so far just get hum noise so soemthing not right with my logic.

Any suggestions on troubleshooting ? I can post schematics from madbean site if that helps.     

[idy]

May be more helpful to post pictures... If taking the bypass board out does not fix the problem, it probably isn't the problem. It is more likely some error or solder bridge on the bypass board, and maybe some other error when you use your test rig.

[ElectricDruid]

Yes please, photos.

Sounds like a wiring issue, rather than a problem on the PCBs.

[pedalbob]

Hi-
Thanks for the interest. I was out of time for a few days so didn't have ability to upload photos. Anyway the wiring is pretty foolproof with these ... there is an 8 conductor ribbon cable that goes between the Relay Switching/Power Supply board and the Effect Board. Power Supply and I/O Jacks are board mounted.  Only other connection is a two lead momentary switch. So I'm pretty sure I didn't mess that up in either of my builds ... but here is a photo

[idy]

OK. So this has a switchable buffer? You can turn it off... then check, in bypass mode, for continuity from input jack tip to output jack tip. Also make sure one or both are not shorted to ground...
IT seems like you will not presently find that continuity. So check continuity from input jack to switch board, to relay terminal. Do the same for output jack. To the switch board, to the relay. We're pretty sure both jacks connect to the switch board....In true bypass they should connect t together. This connection is missing at some point. You can find that point.

[pedalbob]

Yes ... there is a little switch to go from buffered bypass to true bypass. 
Documentation/Schematic for the Switching/Powersupply board is here :

https://www.madbeanpedals.com/projects/_folders/VFE/pdf/VFE_TrueSoft.pdf

I'll check the continuity path as you suggest and report back.

There is also a "latching" relay which is to preserve the last state when you depower the pedal ... You can build it either way but I happened to have only latching relays on hand so I built it that way. I suspect my problem lies there either in the logic they put in the controller chip (comes preprogrammed and prepoulated as one of the SMD bits on the board).

Thanks so much for the reply !! ... I built 3 of these switching boards with the same result (one for another effect and one for the 2nd mini-mu I was going to build for a friend)... So frustrated at this point I can't even think of the logical troubleshooting like continuity

[ElectricDruid]

Are the jumper wires set the right way for the latching relay? Is the relay the right way around?

[pedalbob]

Hi-

Yes jumpers are installed per build instructions and the marking on the PCB for Latching Relay.

Relay installed with end line on same side as marking on PCB and also looks correct per photo in build instructions.

I checked continuity per above suggestions and there is no continuity between input and out put jack tips which makes sense with the no bypass signal.

There is continuity to the True/Buffer switch from the input jack tip (which makes sense per schematic).
There is continuity to corresponding pins on Relay from input jack and output jack sleeves.

Trying to figure out what pin to pin continuity on the relay should be in energized and unenergized states ...

Thanks.