Pass B1 Buffer Preamp help

Hi all,

I've assembled my B1 buffer, powered it up, and I only get sound coming from one side (left channel). I have tried swapping leads and used that process to identify which input channel works.

I only have a multi-meter and don't really know what I need to be inspecting to see which component may have failed (if indeed there is one which has failed).

Please let me know what photos or information I can provide which will help with fault finding. I am open to suggestions too, in case there's a process or something I can apply to further investigate where the fault is occurring.

Thank you all in advance :)

Regards,
Vlad
 
If you have continuity there then go to the fet datasheet and make sure it is oriented correctly

edit:
Now I realize you can probably just compare jfet orientation between working and non working side.

Where did you get your fets and have they been matched or otherwise tested?
 
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If you have continuity there then go to the fet datasheet and make sure it is oriented correctly

edit:
Now I realize you can probably just compare jfet orientation between working and non working side.

Where did you get your fets and have they been matched or otherwise tested?

I purchased the PCB and jfets from the pass website. I am assuming they were tested and working.
 
So either a part is bad or the board is bad... but I would hope the PCB is fine.

If you have tested the things suggested above you could try to see if you need to reflow any component legs, or just reflow them all.

And you might want to measure the resistances of the resistors to make sure you haven't switched them accidentally. Also make sure the capacitors are oriented with the + where it should be (if not they can get burned out) and have infinite resistance across them.
 

wdecho

Member
2014-10-28 11:45 am
I had the same problem on a tube build yesterday. I took some resistance readings of both channels at connection points comparing the two channels and found my problem. Most problems are incorrect parts or cold solder joints. Take your soldering iron and go over all the joints of the bad channel. That is the first thing I would do. I played around with some of the Chinese assembled boards a few years ago and the ones I bought that did not work right worked fine when I did this.
 
Take a picture from above which shows clearly, all the wiring, to both volume pots as well as rca plugs, etc. There really isnt much to go wrong.

Russellc

Hi Russell, please see the photos taken of the board and associated connections from both sides. Please let me know if you want any close-ups.
 

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