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PostPosted: Thu May 07, 2020 8:26 pm 
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Normal Channel works fantastic... TMB channel volume is incredibly low (like you can barely hear it over the les paul acoustically). You can hear enough to tell that the volume, TMB/G pots affect the tone, but not enough to tell if they are working correctly.

Done the highlighter test (:)) have redone my input jacks and validated ground/resistance/continuity for coax and jumpers. I've attached the voltage chart and pics...

If anyone out there spots a problem/mistake please let me know...


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PostPosted: Thu May 07, 2020 8:31 pm 
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oops forgot to post the voltages :) here that is..


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PostPosted: Fri May 08, 2020 2:13 pm 
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The pictures look good. The power supply, power amp, and normal channel preamp are all working properly. Sounds like there is just a bad connection somewhere in the TMB channel.

You are on the right track with your troubleshooting. Keep checking for bad solder joints. Sometimes bad ones can look pretty good. Use a multimeter to make sure you have continuity between everything that should be connected. Put the probes on the component leads or terminals rather than the solder joints to make sure you are measuring through the solder joints.

Check for coax shields that touch the inner wire. Check for accidental shorts in the signal paths. Make sure the input jacks are wired properly.

The tubes seem to be working, although the voltages on V2 are higher than expected. Try swapping the 12AX7s around to see if anything changes.


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PostPosted: Sat May 09, 2020 1:28 am 
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I've tried everything I can think of here... re-ran all coax (input jacks and gain for tmb channel) tested/swapped input jacks between tmb and normal channel... reflowed every solder joint, validated all resisters/caps against the schematic and layout... tested continuity as suggested above (good point about from the component rather than turret by the way!)... chopsticked the living hell out of this thing and nada jumped out as a problem.

I keep going back to V2 where my voltages seem to run high at pin 1 (207 vs 145). After reflowing solder that actually got worse now is 215. I'm starting to wonder if there isn't something wrong with the layout or if I'm misinterpreting the 100k resister installation from Pin 1 to 6 &7. This is the only red flag I'm able to come up with here...

I will say that while I was testing voltages, I accidentally connected pin 1 to pin 2 (resistor to coax for gain) and sound did come out of the speakers. musical sound from my guitar.... which is why I'm asking about the layout for V2. Other 18 watt models seem to do this tube differently and I'm wondering if there isn't a misprint or something for this one.

could use a 2nd set of eyes here if anyone has the time. Let me know if more pictures would help...


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PostPosted: Sat May 09, 2020 1:33 am 
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shot of layout for V2


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PostPosted: Sat May 09, 2020 5:38 am 
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So... 2:30 AM... became obsessed with this thing... resoldered everything like 8 times... took alllmost every voltage reading I could think of then decided to check a few more at random... Noticed that the "Fat" switch wasn't registering.09 volts like the schematic showed.. and then I took an even closer look at the switch trying to figure out if maybe I wired it upside down or shorted something out with my over soldering...

Noticed that there is a jumper shown across the top of the switch... wasn't' 100% that I wasn't imagining the jumper on the layout and took a shot anyways... and Boom goes the dynamite this thing woke the F$#% up!
omg she sounds nice... beautiful cleans and nasty crunch.. I love it. no noise no hiss no cycles ... (slight hiss at high volumes...but meh)...

this is exactly what I was hoping to get out of this kit. The unfortunate need to recheck everything 30 times taught me more than i would have probably learned eslewise but the end result ... pay off with instant gratification. This thing kicks @ss!..

Seems like I did a lot of talking to myself in this thread (Thanks to Mitch for responding!) but maybe the next guy/girl will be able to take a shorter path than I.

Thinking tweed is next :)


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PostPosted: Sat May 09, 2020 2:22 pm 
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Joined: Sat Dec 04, 2010 3:42 pm
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Glad you got it working!

Yes, I see the problem now. Without that little jumper on the Fat switch, there would be no connection to the cathode of one of V2's triodes and it couldn't work.

The higher than normal voltages on pins 1 and 3 of V2 was the clue. I looked at V2's wiring in your photos and nothing seemed to be wrong. It's easy to see that the jumper on the Fat switch wasn't there, though, if you know what to look for. Unfortunately, I didn't have the layout drawing earlier to see how the switch is supposed to be wired.

It's nice if an amp you build works the first time, but as you said, you learn a lot more about it if you have to spend some time troubleshooting a problem.
Good eye spotting that missing jumper. It's pretty subtle on the layout drawing.


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PostPosted: Sat May 09, 2020 11:29 pm 
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It’s tough to troubleshoot from afar. Which is why the voltages are so important.
Glad you got it going. Nice to talk to you as well. Now you know a heck of a lot about your amp!

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