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Old 16th March 2016, 05:06 AM   #1
muhy3 is offline muhy3  Australia
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Smile 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
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Old 16th March 2016, 06:57 AM   #2
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Did you use the PCB or point to point?

Either way, first check continuity from the power supply output to the top(drain) of the top fet

Last edited by vladimirb0b; 16th March 2016 at 07:04 AM.
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Old 16th March 2016, 07:00 AM   #3
muhy3 is offline muhy3  Australia
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Quote:
Originally Posted by vladimirb0b View Post
Did you use the PCB or point to point?
The PCB version
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Old 16th March 2016, 07:10 AM   #4
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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?

Last edited by vladimirb0b; 16th March 2016 at 07:39 AM.
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Old 16th March 2016, 08:47 AM   #5
muhy3 is offline muhy3  Australia
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Quote:
Originally Posted by vladimirb0b View Post
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.
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Old 16th March 2016, 08:58 AM   #6
Rewind is offline Rewind  Sweden
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I had similar problems. I just took everything apart and resoldered according to the schematic. Mine was point to point so it was easier to desolder. Worked like a charm afterwards. Still have no idea what went wrong.
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Old 16th March 2016, 09:02 AM   #7
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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.
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Old 16th March 2016, 09:24 AM   #8
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A really dumb question: Are the jfets all 2sk170 or 2sk370?
I only ask because I recently saw a thread where it turned out the
wrong jfets were sent.

Good luck.

Dennis
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Old 16th March 2016, 10:05 AM   #9
muhy3 is offline muhy3  Australia
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Quote:
Originally Posted by Dennis Hui View Post
A really dumb question: Are the jfets all 2sk170 or 2sk370?
I only ask because I recently saw a thread where it turned out the
wrong jfets were sent.

Good luck.

Dennis
I just checked they are all 2sk170s. Thanks though
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Old 16th March 2016, 01:03 PM   #10
wdecho is offline wdecho  United States
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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.
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