trinityamps.com

Well after I built a TC-15 without a hitch I thought a Tramp was going to be a cinch but it seems I was sadly mistaken. After finishing things up and triple checking everything I took the DC voltage at the first 50 uf filter cap with the VRM in idle and without the tubes and I came up with a whopping 69 VDC. Obviously, something's wrong. Ideas anyone? This is my third amp build but the first time I've needed to do any trouble shooting so this is uncharted territory for me. Here are some pictures and I have many others if there's something more specific anyone needs to see.

http://i239.photobucket.com/albums/ff15 ... 103317.jpg

http://i239.photobucket.com/albums/ff15 ... 084618.jpg

http://i239.photobucket.com/albums/ff15 ... 213241.jpg

http://i239.photobucket.com/albums/ff15 ... 213211.jpg

http://i239.photobucket.com/albums/ff15 ... 213203.jpg

Hi Demo,

Here's a snippet from my build thread where I started taking voltages, it may be the same thing as is catching you.



Snowy

Everything sounds good so far!

Nice looking build

_________________
http://pdfelectronics.com

Very good call Snowy, that's exactly what I did! I read "first" capacitor in the build guide and saw that "400" number in the layout at C12 and obviously tested the wrong capacitor. This morning before I ran out the door for work, I grabbed my multimeter and tried again but this time at C13 and came up with 451VDC. Maybe someone can tell me if this is a bit high but it's certainly better than 69. While I was at it I checked the filament voltages and came up with 3.1 at each pin to ground and 6.7 accross the heater wires on the 12ax7. For the 6V6 3.2 to ground and 6.6 across the heater wires. Are these within the acceptable range?

I thought I would throw in a picture for good measure.

http://i239.photobucket.com/albums/ff15 ... 114309.jpg

I put the tubes in and plugged in a speaker and checked the voltages:

Plate 6V6 pin 3 = 406
Cathode = 29
R8/C6 = 326
V1 pin 1 = 170
V1 pin 6 = 165

I then plugged in a cable but I'm getting no hum or static ground. Nothing. (Cable and speaker are good. I checked.) I've looked for bad connections and poor solder joints but nothings stands out. I spent some time poking around with a chop stick but no luck. Any advice on what I should do from here?

Voltages are good

Check jumpers, pot wiring and tube socket wiring.

_________________
http://pdfelectronics.com

Hi Demo, I could be way off here but I can't see the wires I've circled in the pic of the Layout, are they there on your board?

http://pecdm2.dyndns.org/mail/photos.ns ... ngPic1.jpg


http://pecdm2.dyndns.org/mail/photos.ns ... ngPic2.jpg


Snowy

Looks like that wire goes under the board.

_________________
http://pdfelectronics.com

Thanks for looking Snowy. Yes, Kurt has it. One of those two green wires going to the Pre-amp ground connects under the board. The other red wire just kind of blends in with the board in the picture but it's there.

I've examined the jumper, pot, and tube wiring and everything seems to be in the right place and well connected. I'm going to post some more pictures and maybe someone can spot something I'm not.

Here are those pictures. Can anybody see where I'm fouling up?

http://i239.photobucket.com/albums/ff15 ... 160610.jpg

http://i239.photobucket.com/albums/ff15 ... 160743.jpg

http://i239.photobucket.com/albums/ff15 ... 172720.jpg

http://i239.photobucket.com/albums/ff15 ... 172908.jpg

http://i239.photobucket.com/albums/ff15 ... 173924.jpg

http://i239.photobucket.com/albums/ff15 ... 173950.jpg

http://i239.photobucket.com/albums/ff15 ... 211824.jpg

http://i239.photobucket.com/albums/ff15 ... 211927.jpg

http://i239.photobucket.com/albums/ff15 ... 212050.jpg

nvm,,,

_________________
http://pdfelectronics.com

By this you mean "nevermind" and not VMR right?

Nevermind

Thought I saw something but I was wrong. Nothing is popping out at me.

Try touching pin 5 then 6 of the output tube with your DMM hear anything? If yes then touch pins 1 then 6 of the preamp tube. Hear anything?

_________________
http://pdfelectronics.com

Thanks. I've give it a try after work and report back.

Can you list all your voltages? Specifically interested in the per amp cathode voltages.

If they're good, might be the input cable.power amp seems good per measurements provided.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

So I took Kurt's advice and started with pins 5 and 6 on the power tube. I gave them some light pokes and heard the "pops" I was hoping for. I turned to the 12ax7 and touched pin 6 with my DMM and heard another pop. I moved to pin 1 but this time heard nothing. This it seemed was at least part of the problem. Now since I built my first amp I've been working on reading schematics. To be honest my efforts have been pretty limited. But before I asked here I thought I would try on my own to read the schematic and follow the signal path the best I could from pin 1 to see if I could locate the source of the problem. I looked at the schematic and going back to the layout this is what I came up with going from and back to the 12ax7.

http://i239.photobucket.com/albums/ff15 ... 185608.jpg

Starting from pin 6 I followed the path backwards checking it with my probe as I went. When I poked the the shielded cable on lug 2 of the volume I didn't hear anything. I checked to make sure the shielding wasn't making contact with lug 2 but it wasn't. That didn't seem to be the problem. I checked the other end of the cable and cut the heat shrink off of it and this is what I found.

http://i239.photobucket.com/albums/ff15 ... 193614.jpg

I foolishly didn't leave a little insulation to keep the shielding away from the copper wire. From my years of building guitars I know better than to do this but I just must have spaced it. The funny thing is when I checked this connection with my probe it didn't seem like a problem. The probe must have moved the shielding away from the wire enough so that I got a "pop" when I checked it. But once I took the probe away and checked the other end I lost the signal. So I replaced the wire and this time I did it correctly.

http://i239.photobucket.com/albums/ff15 ... 193536.jpg

After I went back to pin 1 and tested it I got that "pop" I was looking for. VICTORY!

I plugged in a guitar and everything now works perfectly. Quiet as a church mouse and great tone. Kids were already in bed so I didn't play for long. Tomorrow when they're at school I'm going to crank the sucker up and have some fun. I'll report back tomorrow after I have some more time with the amp.

Great troubleshooting mate, glad you found the problem and thanks for the details on how you worked through it too. Anyway, you better go play her for a while now. These Tramps are just great little tone machines I love mine more every day I play it.

Hope you enjoy it.

Snowy.

Indeed nice troubleshooting!

I’m glad you understood my advice and my logic behind it. You’re just injecting a signal (a pop from the DMM) to places where the signal should be. You start at the end and work your way back to the beginning. You can then pinpoint exactly where things are going wrong.

That shielding/shorting issue is a common one. It’s happened to me a few times before so I’ve come to look for it. At least now you know!

_________________
http://pdfelectronics.com

Yes, it sounded like the input was a good place to check. Congrats!

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Here are some build pictures of the combo cab I built for my son's Tramp.

Some plywood left over from another cabinet project.



Always fun to have an opportunity to use the crosscut sled.



Sides cut.



When I was a kid I always wanted a red Marshall stack. I never got it but at least my kid gets a red Tramp. I was a little nervous about the color before I applied the Tolex but I really like the way it turned out.



Putting the corners on before placing the amp in.



I built the cab to hold both an 8" and a 10" speaker. I only have the 8" in now but eventually I will wire the the thing run the single 8", the single 10", or both in parallel. I've become a big fan of marching two different size speakers. With both the speaker and the tube options, this will be one versatile little amp. I think my boy's going to have a lot to play with here.



We took the amp over to my friends martial arts studio Sunday morning and cranked the thing up. Great fun.





And back at the house here is the little Tramp next to big daddy TC-15. Father and son. I think they look good together.