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PostPosted: Wed Jan 22, 2020 12:59 pm 
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After a couple years of playing my tramp it started to act up the other week. Signal was getting weak, cutting in and out and sounding otherwise fizzy/grossly distorted. The problem seemed to be intermittent, so I suspected the input jack. I swapped out the input jack with a switchcraft as I’ve been wanting to do for a while. The problem persisted. The tramp began to regularly act this way on both tweed and tude settings. I suspected maybe a tube had worn out. I put in a new 6v6 and 12ax7 set, now it sounds fine in tude mode but the problem remains in tweed mode. I also get some popping sounds when I turn the dial. Maybe a bad pot? Re-tension the 12ax7 socket? I’m thinking of reflowing some solder joints along the tweed part of the circuit, but that doesn’t really explain all the previous symptoms, maybe just the current ones. Any other suspects or places to check? I’d appreciate the advice!


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PostPosted: Wed Jan 22, 2020 7:23 pm 
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I did a voltage test on V1 pins 2 and 6, they are each getting around 195 volts. B+ is measuring just over 400 at the 50 uf filter caps with VRM on full. I notice as I turn the knob up in tweed mode the pot feels smooth and the signal is quiet, as I turn it back down it makes a pop around the 3-4 positions. Any insight would be appreciated :D


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PostPosted: Thu Jan 23, 2020 6:52 am 
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Hi Herby. I'm no expert, but I wonder if you could get some insight by checking the other DC voltages called out in the Tramp schematic (i.e., bias voltages on V1 pins 3 & 8, and bias voltage on V2 pin 8 ).

If those measurements don't turn anything up, do you have a way to put a known signal on the input? For example, could you connect a laptop headphone output to the Tramp input jack, play back a tone, and adjust the laptop volume to get the voltage you want? I just took a bunch of AC measurements on my (presumably working) Tramp with a 1kHz, 10mV input, and I'd be happy to share them. We could compare, and maybe see where in the circuit your numbers start looking different than mine.


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PostPosted: Thu Jan 23, 2020 11:07 am 
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Thanks for the help lighthouse! I’m not quite set up to play a signal through my amp, I wouldn’t have the right adapters. I will check the bias voltages. For some reason after I checked the B+ Voltages on the plates (pins 1 and 6 not 2 and 6 as I miswrote earlier) the problems seem to have gone away. I’ll do some playing and testing today and see if anything acts up. The intermittent nature of it sure doesn’t help try to solve it!


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PostPosted: Thu Jan 23, 2020 1:19 pm 
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I checked all DC voltages marked out on the layout of the tramp and everything looks reasonable.
425 volts on the 50 uf filter caps with VRM on full. V1 pin 1 is 186 and pin 6 is 183. Bias on pin 3 is 1.76 and pin 8 is 1.71. Bias on pin 8 of V2 is 32. I did a bit of playing and so far all symptoms seem to be gone. I guess time will tell. If it starts acting up again I will have to try out your input signal method lighthouse, see if it is something in the AC signal chain. Until then perhaps this problem has resolved itself. For some reason I believed I had the tramp set up with the loudest tube in it (confusing that the 6v6 is louder than a 6l6) and now that I realize my error I am going to set a 6l6 in there, flick over the bias switch, and when I take my tramp over to jam next week I think the others will be shocked that it’s back alive and well and apparently with a vengeance!


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PostPosted: Fri Jan 24, 2020 2:56 am 
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Good luck with the Tramp. Intermittent problems that show up after an amp has been working well for a couple of years are usually due either to a bad tube or a bad connection. You are on the right track to change the tubes, check the voltages, and reflow any solder joints that don't look good.

You can also poke around (carefully) with a chopstick and see if you can get the amp to act up, or clear the problem if it's acting up already. Pay a lot of attention to the tube socket connections if the problem went away after you probed them to check the voltages. Check the switch and pot connections, too.

We use chopsticks because they are long, wooden and non-conductive. You can probe around safely without shorting anything or getting too close. Don't use a pencil because the graphite inside can conduct electricity.


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PostPosted: Fri Jan 24, 2020 12:25 pm 
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Thanks Mitch! Good point about the connections on the tube socket, when I built my tramp it was my first time soldering so some connections don’t have the lug filled with solder as I was concerned of damaging things if I held the iron on too long. I will go through the amp and improve any weak spots I see.


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PostPosted: Mon Feb 24, 2020 5:22 pm 
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Well, I touched up some solder joints and put new tubes in. No more fizzy sound. I do still have one problem though. The amp seems very quiet!

In tweed mode I don’t get any sound from the amp unless master volume and pre amp volume are above 5 and even then it is still not loud. Tude mode is louder but not as loud as it used to be. I put a 6L6 tube in and the bias switch is running both resistors in parallel as it should be, yet the amp is quieter than it was with a 6v6 before. Any suggestions on what to check? Hopefully it’s not the OT going...


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PostPosted: Mon Feb 24, 2020 8:55 pm 
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I think I figured it out. Important lesson to learn: don’t test your newly worked on amp with an old questionable patch cord. Everything seems fine now!


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PostPosted: Tue Feb 25, 2020 3:43 pm 
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Glad you got the amp working. Bad cords are a guitar player's nemesis!


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PostPosted: Wed Feb 26, 2020 12:50 pm 
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Thanks for helping me along Mitch. Always appreciate the support.


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