Newbie needs help w/Voxy VJ

[soulsamurai]

BINGO! I replaced the mini fuse at the 3 prong, I hadn't even noticed that one before this morning. Thanks Dave!

Now I have power at the switch, the amp comes on but there's still annoying hum/buzz. I got some low volume (but ugly distortion) with my guitar plugged in, and the volume control isn't working - there's no change as I turn it up and down. The tubes look redder/hotter than usual too.

I have a couple questions - if you check the photos I posted earlier in this thread you'll noticed I ran the black wire from the volume control to the preamp tube under my turret board to keep it out of the way, also the two red wires from the PT to the rectifier diodes I also ran under the board and connected to base of the turrets - is there any reason I should have kept them all on top and not done that? Does anything else look suspect?

What do you suggest I should check next?

Thanks again everyone.

[soulsamurai]

I've still got the nasty hum/buzz. The EL84 (I swapped the stock Sovtek with a new JJ but that didn't seem to make much difference) seems to be quite red/hot. Here are some measurements anyway - these seem to have fluctuated slightly from this morning +/- a volt or two in some cases. I hope somebody can help me out:

EL84:
pin 3 - 10v
pin 7 - 302v
pin 9 - 278v

12AX7:
pin1 - 165.5v
pin3 - 1.3v
pin6 - 165v

C1 - 165.5v
C2 - 165v
C5 - 10v
C6 - 359v
C7 - 293v
C8/C11 - 272v
C9 - 319v

[BBQLS1]

There is a mini fuse located in the 3 prong power socket. I bet that fuse blew, since you don't have any power "at" your switch.

Dave

Good tip!

[BBQLS1]

I've still got the nasty hum/buzz, here are some measurements:

EL84:
pin 3 - 10v
pin 7 - 302v
pin 9 - 278v

12AX7:
pin1 - 165.5v
pin3 - 1.3v
pin6 - 165v

C1 - 165.5v
C2 - 165v
C5 - 10v
C6 - 359v
C7 - 293v
C8/C11 - 272v
C9 - 319v

Does the kit/board maker have a layout or schematic with the voltages?

[soulsamurai]

There's a layout here:

http://www.turretboards.com/vjr_layout_main_voxy.pdf

It pretty much follows the recommendations elsewhere on this site for the Baby Vox mods.

FWIW I also bought a Heyboer OT from Turretboards.com that was specifically made to upgrade the Valve Jr. It's primary is 6.6 however, which is slighter higher than the recommended 5 for a SE EL84. I also have a Hammond 125ESE which may be a better match - so if I can get the amp working I intend to compare the two OT's to see which one I like better. For now the Heyboer is installed.

[dram56]

If you look at the layout you'll see the "ground" side of the circuit starts at the top of the diodes to the top of C6, then to C9, then to C7. Then it is jumpered under the board to C5/R14/R5.

With the power off, check for continuity starting at the top of the diodes to each of the points I just mentioned. I would bet you have a bad connection somewhere in that path. Probably at the jumper that goes from C7 to C5.

If you have power coming in along the bottom of the circuit getting to the EL84 tube, but no power at pins 1 & 6 of the 12AX tube, you will get the symptoms that you are describing. Just a lot of hum, no input coming from the guitar and the hum doesn't change with the volume pot.

Just start at the beginning of the chain and work your way through. You'll find it.

Dave

[soulsamurai]

Thanks for the suggestions, I sure appreciate it. - I'll try again tomorrow morning.

[Strat]

It's a little difficult to see from your pics buy have you got the ground point on the chassis between the vol pot and input jack? One of the outer legs of the pot goes there. I might be tempted to add another by the input jack and ground the sleeve securely rather than relying on the chassis face.

[Mooncar]

Hey Soul,
You can give me a call tomorrow at the shop. We should be able to get it going pretty quick.

Ken