Bunch of Questions, advice much appreciated

[Tim Hall]

Ok, I'm going to jump into my first from-scratch build this weekend. I have very little experience...just one small kit build before this. I'm really hoping some of you experienced builders can answer at least a few of my questions.

Soldering: I'm using rosin-core, silver-bearing solder. I've read that the key to a good joint is getting the joint plenty hot (I have heat sinks so not to burn caps). Should I be cooking this stuff on until all the rosin has completely carbonized, or is the yellow tinge of the just-melted rosin ok? I have a variable-wattage Weller.

Grounding: I've attached a PDF of my grounding scheme. Some of the values on the schematic have changed, but nothing is different as far as grounding goes. Maybe someone will have just a minute to to review it for me (?) The layout/chassis is pretty tight, so it's partially a function of where components have to be located. I tried following Aiken's tech info on star grounding as best I could.

Filament wires: Is there some protocol as to which gets juiced first - preamp heaters, power amp heaters, or 'ON' lamp? Or is it just a function of keeping them as short as possible?

I really appreciate any help! I'm aiming for less-than-a-disaster on this first effort.

Oh yeah, I know this probably taking it way too far, but is there any reason one can't paint the terminal board?

[bob p]

Soldering: I'm using rosin-core, silver-bearing solder. I've read that the key to a good joint is getting the joint plenty hot (I have heat sinks so not to burn caps). Should I be cooking this stuff on until all the rosin has completely carbonized, or is the yellow tinge of the just-melted rosin ok? I have a variable-wattage Weller.

Use heatsinks on your components, and heat the components until the point that the solder melts over them and flows freely into the joint. At this point the flux will smolder, but it should remain clear if its not overheated. If you add more heat and carbonize the flux, you're adding more heat than you need to use to establish the solder joint. That places your components at increased risk of thermal damage. In addition to running the risk of overheating your components, using enough heat to carbonize the flux makes the flux harder to remove from your solder joints. Many people skip this step, but you're supposed to clean the flux off of your solder joints after you make them.

HTH

[bob p]

Filament wires: Is there some protocol as to which gets juiced first - preamp heaters, power amp heaters, or 'ON' lamp? Or is it just a function of keeping them as short as possible?

If you run all of the heater leads using true parallel wiring (each stage has its own wire coming fdirectly rom the transfomer taps) it doesn't really matter.

OTOH, if you want to daisy chain your heater wires, order can be significant. The little preamp tubes draw a lot less current than the big power tubes, and most designs use heavier gauge wire for the power section compared to the preamp tubes.

IF you want to daisy-chain, most designs tend to supply the power section first, using large gauge wires, because the power section draws the most current. Then you can use smaller gauge wires to daisy-chain from the power tubes to the preamp tubes. At least that's my preference.

Regarding painting the terminal board: FIRE HAZARD!!!

[bob p]

Grounding: I've attached a PDF of my grounding scheme. Some of the values on the schematic have changed, but nothing is different as far as grounding goes. Maybe someone will have just a minute to to review it for me (?) The layout/chassis is pretty tight, so it's partially a function of where components have to be located. I tried following Aiken's tech info on star grounding as best I could.

It looks pretty good. BTW, that's a really nice drawing. What software are you using?

The only question I have about your grounding scheme is why the first stage's cathode isn't grounded to the board, where the rest of the preamp grounds are established. Instead, it goes to the chassis and meets the rest of the preamp grounds there.

[Tim Hall]

Bob,

Thanks for all the great info. With regard to the first cathode, I figured it will probably see much more voltage fluctuation than the input and tonestack, so I thought it best to keep it seperate. But that's the logic of inexperience...if you think it's best to ground it with the tonestack, I'll see if the layout permits.

Regarding the drawing - thanks. Drafted in ACAD. Cleaned it up, noted it, and drew the grounding scheme in Adobe Illustrator. I'm a technical/architectural illustrator by trade. My drawings might look good, but I'm not so confident about my amps

Thanks again.

[Tim Hall]

In Case Anyone Was Interested...

...finished the chassis yesterday morning.

Few things I learned: Having an accurate template AND accompanying schedule of diameters really pays. Polish your chassis AFTER you drill/dremel...I had the box to nearly-mirror finish prior to cutting holes. Now it's a "brushed" finish



It's a pretty tight squeeze in there. In fact more components will be soldered directly to the socket lugs than to turrets. The input jack will be connected directly to the first grid lug by nothing other than the grid resistor.

I got some 5-mil copper for shielding in different places. I figured it would be good to shield the ON lamp from the input, and I thought I'd place shields directly under the transformers. I also plan to shield the back side of the turret board, and keep all the power and heater wires behind it. Oh yeah, the other thing I learned is aluminum doesn't solder for all practical purposes. But I'm sure most of you already knew that

[Konny]

Dude that thing looks pretty nice!

Take some gutshots please.

[Tim Hall]

Dude that thing looks pretty nice!

Take some gutshots please.

Thanks. Will do when I have the guts together. This being my first from-scratch build I kinda when ape$#!? with "audiophile" components and such. I hope I can keep it clean with the solder. Like I said it's really tight inside there, and I'll have to a fair amount of soldering to do with the board mounted.

I'm still waiting on pots and the OFF-STNDBY-ON switch to arrive (the knobs were just taped on so I could see what it'd look like).

[Tim Hall]

This is all I could solder to the board before mounting



It looked much more organized and clean in the CAD drawing Everything else will have to be soldered inside the chassis. I suppose this wasn't the most brilliant design for maintenance.

I just couldn't resist coloring the board, so instead of painting it I "stained" it I sanded it a bit for some tooth, and applied a small amount of Prismacolor and Everclear (as thinner).

I hope it sounds decent. I'm really worried about the heater and power supply wires causing trouble since they'll be stuffed directly behind the left side of the board (directly below the PT). I managed to epoxy some copper foil to the back of the board...hope that shield things well enough.