Help with first build - JTM 45 quiet *edit problem fixed!

[lespaulplayer]

So I just built my first tube amp. It's a JTM 45 with a master volume.

The problem is I get sound out of it but it's really quiet. I've traced all my connections like 100 times and everything is wired correctly. I went through and re-hit all my connections on the circuit board with the soldering iron to make sure there wasn't a cold joint. I tried replacing all the preamp tubes with some old ones that I know work, and it's still quiet - so it's not preamp tubes.

What else should I be looking for? I'm getting really frusterated.

[bcmatt]

A high quality photo would help. Show us the guts, and we can avoid pestering you with needless questions that we can see the answer to.

My thoughts would be things like making sure there is no speaker jack grounding out, checking the values of your resisters... But we could see some of that in a good pic.
If you have a pedal, you could try inserting signal mid-circuit somewhere to see if the problem is before or after that point.

[Phil_S]

+1 on the request for pictures. We only need the inside ;-}. It helps to have an overview picture of the whole chassis and then close-ups of the board and anything else you might think is relevant.

A common error is selecting the wrong value resistor...100K where you need 1K or vice-versa. You may have a simple wiring error, a missed ground, or an unintended ground.

If you have traced the work, do it one more time. This time, start at the other end of the schematic and meticulously work your way through it, marking the schematic with a highligher for parts and wires as you verify them. If you can't find it, don't skip over hoping you'll find it later. When I build, after putting it all together, I verify right to left and then again left to right.

[lespaulplayer]

It's built from a triode amp kit.

Here is the wiring diagram:
http://site.triodestore.com/JTM45LAYOUT.pdf

I did this master volume mod:
http://site.triodestore.com/MASTERVOLUM ... lume-1.pdf

Here are some pics of the inside:

[IMG:800:600]http://img.photobucket.com/albums/v605/ ... 91177b.jpg[/img]

[IMG:800:600]http://img.photobucket.com/albums/v605/ ... 26f5dd.jpg[/img]

[IMG:800:600]http://img.photobucket.com/albums/v605/ ... 76764d.jpg[/img]

[IMG:800:600]http://img.photobucket.com/albums/v605/ ... bc0e5b.jpg[/img]



[IMG:800:600]http://img.photobucket.com/albums/v605/ ... ad81f9.jpg[/img]

[lespaulplayer]

Here's a couple up close shots of the circuit board.

[IMG:800:600]http://img.photobucket.com/albums/v605/ ... f423c8.jpg[/img]

[IMG:800:600]http://img.photobucket.com/albums/v605/ ... e4a20c.jpg[/img]

[Reeltarded]

First thing I am confused about is the PPIMV because it's not clear how it's wired in the pics..

Still looking.

Where is the ground to V1 cathode?

[lespaulplayer]

One thing I do have a question about. On the JTM 45 diagram it shows having the wire from the 16 ohm tap on the impedance selector going to the circuit board. Which is how I have mine.

But on the master volume mod it shows a JTM 50 diagram, and they have the wire from the 8ohm tap going to the circuit board.

I figured that was just for the JTM 50. Do you think that could be what my problem is? Should I try running the wire from the 8 ohm tap to my circuit board instead of the 16 ohm?

[Reeltarded]

No, that only selects where NFB is set.

Check above. Look at cathode V1. Is it grounded?

[lespaulplayer]

Are you talking where the yellow wire connects to the first preamp tube? Sorry if I sound dumb, but I'm not hip on amp terms. But yes that goes to ground if thats what you're talking about.

[lespaulplayer]

I think I just found my problem. On the second preamp I have pin 6 and 7 connected with the 100K instead of pin 1 and 7. Gonna fix that and see what happens.

[lespaulplayer]

I verify right to left and then again left to right.

doing this is what helped me see I had those pins ass backwards on the second preamp tube. This baby is roaring and loud now! Thanks for the help everyone!

[martin manning]

I've traced all my connections like 100 times and everything is wired correctly.

These are famous last words... Glad you found it ;^)

[Structo]

Yep, sometimes the best thing to do is walk away from it for awhile or overnight.
Come back fresh and you will notice things you didn't before.

[tictac]

That type of Master Volume really needs to be capacitor coupled on the input AND the output. IMHO having your negative bias on the Master volume pot is a really bad idea and an amp failure waitng to happen....

Isolate the MV from the power tube inputs with capacitors, like you did for the PI and it will work better and be safer....

TT

[randalp3000]

I really like to wire the screen and grid backwards on half of the PI..