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PostPosted: Sat Jun 22, 2019 6:44 pm 
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The reverse current thing puzzled me, too. That's why i said you may want to check w/ Coco. I think the ones on Amazon will work, but I'm NOT SURE that they will!

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PostPosted: Sun Jun 23, 2019 2:36 am 
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LEDs aren't that critical. Pretty much any 5mm LED will work for the pilot light. Blue would look good. If you think the LED you get is too dim or too bright, you can play with the value of the resistor feeding it. The lower the value, the brighter the LED will be.


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PostPosted: Sun Jun 23, 2019 1:16 pm 
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Thanks, Mitch! Wasn't certain I was giving Epifool the right advice.

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PostPosted: Sun Jun 23, 2019 3:24 pm 
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mitch m wrote:
LEDs aren't that critical. Pretty much any 5mm LED will work for the pilot light. Blue would look good. If you think the LED you get is too dim or too bright, you can play with the value of the resistor feeding it. The lower the value, the brighter the LED will be.


Thanks for this, I wondered how critical the led rating was. I just thought if no-one chimed in otherwise, I'd try to use the perfect rated one. Glad news to me, I can change the color.


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PostPosted: Wed Aug 21, 2019 7:40 am 
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Ok. I have the amp built, but no sound, even tried another 12ax7. Startup voltages are as follows
Line voltage- 119-120side ac
Rec pins, 646 to both ac
320 to ground, both sides Ac
50uf (c12?) Dc 90 @idle
Dc 440 @ max
50uf (c13) 454 @ idle
440 @ max
That's where my voltage readings stop. I get nothing on any pre amp tube pins to ground, or power tube pins, though both tubes are glowing orange. I get nothing from the 1000uf capacitor either, and so on. When I turn the amp off, and plug in a cable to the input, I have continuity from the cable tip to ground. I've waited what seems like forever to build this beautiful amp, now I gotta get it playing loud. Are there Any pics I can post that may be helpful diagnosing any problem? Or any other information I could supply?


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PostPosted: Wed Aug 21, 2019 1:47 pm 
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Yes, some pictures might help.

If you have no voltage readings at any of the power tube pins but they read OK at C12 and C13, check your connections to the 1k resistor on the terminal strip by the power tube. Also check the wire running from C12 on the board to the 1k resistor.

With a cord plugged into the input, you shouldn't see a short from tip to ground. If you see a tip to ground short with a cord plugged in, then check your wiring to the input jack. You should see a very low resistance reading from the tip of the cord to the input end of C1, though.

And with no cord plugged in there should be a short from the input end of C1 to ground.


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PostPosted: Thu Aug 22, 2019 7:39 am 
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I was missing a wire from c12 to 1k @power tube terminal. Now, I'm getting readings to all the big caps at least, and I get a little buzz when I'm turning up the vrm, but nothing from the speaker. I get a buzz when I'm doing voltage readings as well.


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PostPosted: Thu Aug 22, 2019 7:40 am 
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I'll go back through and read the voltages I couldn't get before, as soon as I get a chance.


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PostPosted: Thu Aug 22, 2019 12:25 pm 
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Check to make sure that your input at the input jack is not grounded...
(Plug in a guitar cable without a guitar to check to see if it is shorted to ground)
The shielded cable might have a cut/burn if the solder iron heated the wire up to much...
(No signal - no sound)

Andrew


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PostPosted: Fri Aug 23, 2019 4:57 am 
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Ok, went to look inside tonight, and found that the master volume pot wasn't connected to pin 7 on the power tube. I have sound now in both modes, but couldn't turn it up all the way, as everyone else in my house is sleeping. I'll post final startup voltages asap.


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PostPosted: Fri Aug 23, 2019 8:46 pm 
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Sounds like you might have it sorted. One tip I can give is to use the printed layout and working from left to right on the layout check-off every connection visually and physically for connectivity with a meter, then mark it off on the layout with highlighter pen. The time spent doing this might seem a real slog but can literally save hours of frustrating troubleshooting, and possibly even intermittent trouble in the future operation of the amp. Good luck with your Tramp, it's a great amp.


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PostPosted: Mon Aug 26, 2019 3:08 am 
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Yes, I think I'm sorted out now. I've played it thru a n eminence patriot @85? Watts, and even swapped the 6v6 out for an electro harmonix el34, and it sounded great either way. Can't wait to build the cab and push the vet 10 I bought for this build.


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PostPosted: Mon Aug 26, 2019 3:56 pm 
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Glad to hear it's working. That's good advice to make a copy of the layout drawing and highlight the wires after you check them for continuity. Missing or misplaced wires are easy to find that way. All the wires are important and the amp won't work right, or it won't work at all, if some are missing!

Have fun playing the Tramp. It should sound great with the Veteran speaker.


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PostPosted: Wed Sep 18, 2019 5:52 pm 
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Epi, think I led you astray, the Br-Blk-Y resistor (100K) on the preamp tube goes to the the gate of the MOSFET (between gate and blue wire to Power control) and Br-Bl-Or (10K) resistor should on the preamp socket. I figured this out when I started second build. Hope you already corrected it! :oops: Amp will probably work, but VRM won't work like Coco designed it. In process of correcting my first Tramp build.

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