First Time Build Problems

[dwilliamsaudio]

Hi everybody. This is my first post here. It looks like a great forum. I am in the process of completing my first amplifier build, but I am experiencing some problems. I am hoping somebody on here with more experience has some ideas. The kit I chose was the TubeDepot kit. I figured it was a good starting point for a beginner. Here is the layout.

https://d1sjrnpi226dnf.cloudfront.ne...pdf?1400188816

The problem is, the amp is perfectly clean all the way up. It simply does not sound like a 5e3. It gets plenty of volume, and the clean is beautiful, but I am looking for that raunchy 5e3 sound. Also, I discovered something that concerns me and took a video of it. If I have the bright volume at 12 and get the normal volume up around 8, one of the power tubes does something strange.

https://youtu.be/xSc_s2CmMZc

Here is a picture of my build.


Any help would be greatly appreciated. I am happy to post voltage readings if anyone is interested.

[eschertron]

Hi! From one relative newcomer to another, welcome to the place. You will get lots of help and friendly analysis here

I'm not familiar with the tube depot kit, but it looks nice!

What tubes are you using in V1 and V2? Different mu tubes will produce more or less gain.
I watched the video. On the cheap laptop speakers I have here, I thought I heard a click or sputter, but could see nothing. If the amp is doing something strange, then double-check the wiring, look for bad solder connections, take voltage readings, maybe swap tubes to see if the problem follows the tube; be specific with your conditions, including things like whether there's anything plugged into the input.

[dwilliamsaudio]

Sputter is a good word for it. I am using JJ 12AX7 tubes in V1 and V2. My power tubes are JJ 6V6 and the rectifier is a JJ GZ34. I know people like a 12AY7 in V1 for more headroom. I may decide to do that later, but right now headroom is not my problem at all. I have swapped the power tubes to see it was a bad tube, but which ever one is in V4 flickers like that on certain settings. I also tried a pair of Chinese 12AZ7s that I had laying around just for fun. I have a Weber 12A125A that I will be putting in at some point, but I want it to be working properly first. I will post some voltages when I get a chance. Probably tonight.

[dwilliamsaudio]

Ok, Here are my readings.

Rectifier
2- 359.6 DC
4- 307 AC
6- 307 AC
8- 359.6 DC

V4
1- 321 DC
2- 2.9 AC
3- 352.7 DC
4- 317.4 DC
5- 0
6- 0
7- 2.88 AC
8- 19.4 DC

V3
1- 318 DC
2- 2.88 AC
3- 350 DC
4- 317 DC
5- 0
6- 0
7- 2.86 AC
8- 19.34 DC

V2
1- 167 DC
2- 0
3- 1.267 DC
4/5- 2.86 AC
6- 208 DC
7- 14 DC
8- 46 DC
9- 2.89 AC

V1
1- 178 DC
2- 0
3- 1.19 DC
4/5- 2.89 AC
6- 175 DC
7- 0
8- 1.18 DC
9- 2.88 AC

[nosaj]

Can you get the voltages on the power tubes when the noise is happening? And a closer gut shot of the board and pot wiring.
If it's too clean maybe check the polarity of the first bypass cap? (just wildly guessing.)

Your voltages seem inline. The voltages on my 5e3 junk box build were much lower primarily because of my transformer and it gets real nasty( in a great way) with humbuckers.

nosaj

[Jazz P Bass]

Here is a 5E3 with voltages at specific test points.
Oval voltages are Vac. (signal)
Rectangles are Vdc (static)

57 Deluxe, Fender 57 Schematics (01 JUN 07).zip

I do not know why one tube socket would act up.
There is nothing inherent in the circuit.

Triple check your work.

To add: these amps need a good hot signal to be driven hard.
There is no indication of what your input signal is.

[Justin Thomas]

Missing connection on cathode bypass cap(s)? And more concerning me than the sputter is the flashing inside that tube... arcing? Short?

Justin

[TimmyP1955]

Are the power tube grid stoppers on the board or on the sockets? If they aren't on the sockets, JJs might misbehave as yours are.

[eschertron]

The problem is, the amp is perfectly clean all the way up.

The voltages on my 5e3 junk box build were much lower primarily because of my transformer...

Subbing a 5Y3 for the current rectifier tube might lower voltages enough to get some grunt? (But fix the power tube circuit/socket problem as a priority!)

edit: do the heater voltages seem low to anybody else?

[nosaj]

Yes 5.87v does a little

[nosaj]

Can you elaborate on this, please?

Thanks,
nosaj

[dwilliamsaudio]

I reworked a few solder joints. The power tube no longer cuts out. Yes, this build does have screen grid resistors on the power tube sockets.

Thanks Jazz P Bass for the schematic. I will take a look at those test points now that I seem to have fixed my problem at V4. As far as my input signal, I've just been trying it with a few of my guitars. Both single coil and humbuckers.

[Jazz P Bass]

Just remember that you need a good hot signal from the guitar.

That means, no screwing around, guitar volume maxed.

[ThermionicScott]

That video clip sounds like an old car or boat that won't start because the choke is open.

dwilliamsaudio, are you in a country with 220/230/240V power? Using the 240V primary winding in a country that only has 220V or 230V at the wall could explain the globally-low voltages. Many of us think 350V is about perfect plate voltage for a 5E3, but I imagine the 5AR4 is the only thing propping up your B+.

Paradoxically, I think the voltage situation could be to blame for the overly-clean sound -- the 5AR4 is preventing the output section from sagging, but the low heater voltage could be reducing gain up front.

[dwilliamsaudio]

Actually, I am in the US. I am using this power transformer.
https://d1sjrnpi226dnf.cloudfront.ne...pdf?1382030387