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DIY Tavish Classic Burning Out Wall Warts!
DIY Tavish Classic Burning Out Wall Warts!
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Old 18th July 2018, 09:05 PM   #1
jphabc54 is offline jphabc54  United States
diyAudio Member
Join Date: Mar 2018
Default DIY Tavish Classic Burning Out Wall Warts!

​Hi all -- I've been working with the exceptionally responsive, helpful, and patient Scott Reynolds at Tavish Design to figure out what I did wrong to a Tavish Classic that I recently assembled. What I've learned from the experience is that I'd do business with Scott and Tavish anytime -- he is truly customer focused (even for me, a guy who just bought a PCB), but he and I are both a bit stumped figuring out exactly what I screwed up. I am hoping the community here can help me out.

Here's the issue. I built a Tavish Design Classic according to Scott's great build guide. Once I finished the build, I powered the unit up and was able to get steady, accurate voltage readings at all three locations (200v, 18.6v, and 6.3v). Everything checked out.

Once I completed that initial voltage check, I closed up the chassis, plugged the Classic in again, and all of a sudden the wall wart burned out. I'm not sure exactly what shorted, but the most likely candidate was the barrel jack (which was loose). At this point, the fuse blew and the 18vac/1amp Jameco wall wart burned out. Nothing else exploded, smoked, popped, or did anything otherwise abnormal.

After replacing the barrel jack with one that fit better and rewiring the AC-in, I purchased another Jameco 18vac/1amp wall wart and powered the unit up again. Everything powered up seemingly normal with the exception of the front panel LED that turns on after the mute relay triggers. That LED had previously come on during the initial, normal power up. This time it did not light, though I did hear the relay click.

Unfortunately by the time I was ready to check voltages again, this second wall wart died. Again, nothing on the board exploding, popping, getting excessively hot, or otherwise behaving oddly (other than the blue LED not lighting).

I'm including below some pictures of my build. Scott and I could not see anything clearly wrong with the wiring, so I'm wondering if anyone has any other theories that could be causing this kind of behavior. Note that I replaced the PC mount components with panel mount, and I have left U1 vacant and have not wired the MC out. Otherwise, it's built entirely to the Tavish BOM.

I tested most of the diodes and the transistors and didn't identify any clearly bad components, but I also did not desolder any of the diodes, ICs, or transistors to give them a full test. I have one more wall wart on hand to try, but I'm really hesitant to fire it up until I at least have a new theory about what's going wrong.

Here is a link to the Tavish Classic build guide. The schematics are located on pp. 19-22 if anyone has a theory. I'm hoping it's just a bad component, or even a wiring mistake. This is only my fifth build, so I'm very much still a newb at this--thanks for your patience with me!

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Last edited by jphabc54; 19th July 2018 at 12:11 AM. Reason: Fixing images
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Old 18th July 2018, 11:40 PM   #2
jphabc54 is offline jphabc54  United States
diyAudio Member
Join Date: Mar 2018
Just needed to correct the images and update that I must have gotten a bad reading on the fuse when I checked it. I just confirmed that it did blow when I powered it back up with the new wall wart..
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