Baja MDR Overdrive vero layout - Input Buffer Follow Up

Frank_NH · Post by **Frank_NH** » 21 Mar 2018, 13:44

This is for the Baja MDR Overdrive vero layout at tagboard effects. Just want to post here that the 1M bias resistor at the JFET input buffer in in fact included in the current layout and should be OK.

Here's a link to the layout:

https://tagboardeffects.blogspot.com/20 ... drive.html

sixthfloor · Post by **sixthfloor** » 22 Mar 2018, 16:16

Looks like I marked the topic where I reported the problem I had too quickly. Sorry for that

In my build, following exactly the vero layout from tagboard effects does not work currently, I still need to bypass the buffer to get the circuit working.

Could it be the PSU being overloaded ? I've got around ten pedals connected to a 9v 1A supply. I don't think it is likely though, the other pedals have no problem.

Frank_NH · Post by **Frank_NH** » 22 Mar 2018, 19:09

Check the voltage on the gate and source of the JFET. Gate shouls be 4.5V and the source a little below the bias voltage (maybe 4 V) but stable. Also, check your build for possible solder bridges - I've been bitten by that before!

The JFET buffer shouldn't cause any trouble as far as I can see, and it's already been used in many of the Bajaman designs posted here.

sixthfloor · Post by **sixthfloor** » 24 Mar 2018, 13:37

Agreed, the JFET buffer works perfectly in the Baja UBS I built.

I've checked for solder bridges using a multimeter, no problem there - its something that happened quite often to me too. In the end, the culprit was a bad contact between the transistor socket and the veroboard, the source voltage was stable only when the transistor was firmly held into the socket. Reflowing the solder there solved the problem, I guess it hadn't glued well with the socket.

Now everything is working fine with the buffer. Thanks again for the help Frank ! Alex can mark the layout as verified