New Build - Express

[M Fowler]

18 awg for heaters because of high current (amperage).

[Picker]

Thanks! Not the answer I was hoping for, but much appreciated.

[T Wilcox]

I honestly dont know what the voltage or the amperage for that matter is at the wire in question.
I personally would just replace it with a 18 or even 20 to be sure. Atleast make sure the 22 is as thick of wire or thicker than the lead coming off the 25watt resistor it ties to, to be safe.

Todd

[Picker]

Thanks guys. I was able to desolder with less difficulty than I thought. The hard part was actually getting both 18 gauge wires to go through the hole once I removed the other wire. For that I had to get a little creative. Since I could only fit 1 wire through I ended up running the main wire through and wrapping the 2nd wire around the one I put through and soldering it to that. (sort of like using the bare wire where it goes into the insulation as a turret.)

It wasn't pretty maybe, but I think it works well, and I know have 18 gauge where it should be.

I'm getting close to the finish line now. I just have to assemble and wire the cap stack and I'll be done. Can't wait.

[amplifiednation]

it's a bit of a buzzkill, but i would go through and check all your solder joints and connections from the input to the speaker jacks.

i have found a few wires that didn't get soldered correctly at that final check and saved myself a heck of a lot of troubleshooting. Especially places like the tube heaters where you might have two wires stacked in one hole and the solder didn't flow to the bottom, or there wasn't a great mechanical connection

make sure to use the light bulb limiter during your initial power up and get ready to have your ear drums blown out.

[Picker]

Thanks. I plan on doing a final walkthrough of all my soldering points before I fire it up. Last night I assembled the Cap Stack and hopefully can start on wiring it up tonight if I have time. At least by the end of the weekend I hope to be up and running.

[Picker]

Incidentallly... This is more of a curiosity question.

Regarding the cap stack, the build guide says, "A black ground wire goes to the solder lug in front of the cap stack and is soldered to the right most 40uf cap lead - but wait until the whole stack is done to attache the wires"

The pictures and the layout confirm this.

The question is, why go to the right most 40uf cap, which is the furthest away? All three 40uf caps are connected to each other. Why not make the connection at the closest point instead of running the wire all the way around the stack to the far cap?

Just curious.

[Picker]

Another question.

Why do the leads on the standby switch seem to be reversed between the Build Guide and Francesca? The layout shows the leads from the cement resistor and the transformer going to the lower lug on the switch, while the photos show them going to the top lug?

[selloutrr]

the pics of the undocumented express might help?

[amplifiednation]

It doesn't matter. The switch just connects the terminals. Follow the build guide, there are no errors that haven't been addressed. Only worry about the direction the switch flips, you want "on" going "up" like the power switch. Spst only does on and off

[amplifiednation]

And the rightmost filtercap is grounded first because the other caps aren't in the circuit until you flip the standby switch. That is how I see it at least. That filter cap and the cap next to it carry the highest voltage; they are wired in parallel. I would think since they get b+ first you also want them getting a direct path to ground

[amplifiednation]

Double post

[selloutrr]

great points.

I was thinking in the view of authentic but you are correct!

[Picker]

Well, I got a bit over zealous and did a few foolish things. The good news is that she is finished (in a completed, but untested sort of way). I ran through the checks, and being a bit uncertain what to look for I glossed over a few things. Finally got though to making sounds and it sounded Wonderful!!! for about 30 seconds.... Then I red-plated one of the power tubes and blew the fuse.

.... For you other newbies following along... Don't do that.

Now I'm taking a more measured approach (literally) and asking as I go through testing if I'm not sure.

I think the problem initially was that I discovered I had not fully soldered in the MOV resistor on the power switch. That is now corrected as well as touching up a few other solder joints that looked like they could be improved. Now I'm running though the first checks with the blub limitor and no tubes.

The first test is the one that I am questioning the most. I measured the Max negative bias voltage following the build guide and came up with -22. The guide says it should be between -35 to -50.

What would cause this? How should I proceed?

I ran through the other initial checks and got the following

1. Max negative bias votage = -22
2. Heater votage between pin 4 and 9 on v1 = 5
3. Across PT secondaries = 460
4. Voltages on B+1 trough B+5 are all about 320 (range from 314-326)
5. DC voltage at plate V1-V3 = 290-296 V4 and V5 = 328

I think everything checks out except the max bias voltage, but could use advice before I run the next tests.

Thanks

[T Wilcox]

Heater voltage is 5v?

Todd