My VJR Voxy build didn't work, help?

[bluefoxicy]

So I built this...

http://www.turretboards.com/vjr/vjr_..._main_voxy.pdf

Except where C8 is, it's grounded to the case and isolated from the direct negative rail; rather than connect C5 to C7 as shown, I connected it to C8, then C8 to C7.

I have horrible hum. I also seem to overdrive FAST and then go silent, like my tubes are way off bias.

also I haven't grounded R16/R17 as shown yet... and I moved R1 across the input (connects to R2 rather than pin 2 of the 12AX7).

Thoughts?

[Albert Kreuzer]

Change your "excepts" to the original design and I bet the hum will be gone. Most important, ground R16/17. Also, there probably is a reason why C8 is not grounded at the same point with the other caps.
R1 will not make much difference.
The reason for the amp going silent may be a missing ground path from either pin 2 or pin 7. Check for ground on your input jack (isolated jack? Painted chassis?).

Cheers,
Albert

[bluefoxicy]

Fixed that and it was unstable.

I didn't solder down a capacitor and bias resistor on the first gain stage of the 12AX7, fixed that.

My solder joints are cold, some of them don't conduct at all. That amp's all @^*@$^@^$ up. It's totally unstable, but I traced it and it's lain out and soldered right. I need to reflow ALL the solder.

[Albert Kreuzer]

Although you probably know that:
Make sure your iron is hot enough and the tip is clean.
When you reflow the joints, add a tiny bit of fresh solder to get some flux in there.

Good luck
Albert

[Enzo]

And don;t melt solder into the joint from your iron tip - that is don;t feed your solder onto the tip and let it flow into the joint. Touch your iron tip to the joint itself - for example a turret and the wire around it. Then touch your solder to the other side of the wire. The iron should get the wire so hot that IT can melt your solder. That sounds harder than it erally is, the thickness of a wire is not very far from the iron tip.

[bluefoxicy]

And don;t melt solder into the joint from your iron tip - that is don;t feed your solder onto the tip and let it flow into the joint. Touch your iron tip to the joint itself - for example a turret and the wire around it. Then touch your solder to the other side of the wire. The iron should get the wire so hot that IT can melt your solder. That sounds harder than it erally is, the thickness of a wire is not very far from the iron tip.

Oh THAT'S why my iron didn't melt last time.

I've been tinning the tip but it takes 10 minutes to heat a joint that hot, so I touched the tip to get a tiny dot of solder and then quickly drew towards the joint and let the melted SOLDER melt the feed. Once it got hot enough, it just flowed properly. Once the tip was destroyed, it didn't get hot enough anymore.

I tried 4 irons, and destroyed the only one that can heat a joint. Screw this. The only other one I found that worked was a Radio Shack iron.. so I'm buying this now:

[ame=http://www.amazon.com/Weller-P2KC-Professional-Self-igniting-Soldering/dp/B000WOHSHM/]Amazon.com: Weller P2KC Portasol Professional Self-igniting Cordless Butane Soldering Iron Kit: Home Improvement[/ame]

[Steve Conner]

The butane ones are a bit "Meh." I've got one that I use in emergencies, and I can get by with it, but it's nowhere near as nice as something like a Weller TCP.

Weller WTCPT Soldering Station Product Reviews

The downside is that it costs about as much as a Valve Jr

[bluefoxicy]

The butane ones are a bit "Meh." I've got one that I use in emergencies, and I can get by with it, but it's nowhere near as nice as something like a Weller TCP.

Weller WTCPT Soldering Station Product Reviews

The downside is that it costs about as much as a Valve Jr

yeah those are nice. I've used butane irons (cheap ass radio shack one), they're fine. I had 5 irons on the table; the only one that worked ate itself, and the other 4 simply didn't get the joint hot enough despite being anywhere from 25 to 50 watts. The butane one worked best for me, so yeah.

If it gets the joint hot it's good enough. I prefer the form factor.