Amp building tips and techniques

[sluckey]

I thought I'd start a thread where we can share some of our favorite building tips and techniques. If this thread becomes popular I'll move it to a more appropriate forum, maybe even to the archives.

Please share your ideas, complete with pics if you have them. I'll kick start with a couple tips I've learned thru the years...

TIP #1. I keep a printed copy of my drill template/jumper guide handy when installing jumpers on a board and I use a highlighter to mark jumpers as I install them. I've never had to troubleshoot a problem due to missed or incorrectly installed jumpers.

TIP #2. I usually don't like under board jumpers but sometimes it's just the right thing to do. I use bare tinned 22 AWG buss wire (available at Radio Shack) for all board jumpers. And I use Teflon (PTFE) insulation stripped from my hookup wire when a jumper needs to be insulated. I push the end of an under board jumper completely through the turret and hook it back over the top of the turret before trimming to length. This not only makes a good mechanical connection but also ensures that the jumper will not accidentally fall out some time later.

TIP #3. I keep a copy of my layout and schematic pinned to my workbench in a convenient but out of the way location during the entire build. I never have to hunt for it or move a bunch of stuff just to see it.

[Willabe]

I do the same for #1 and #2.

I have plastic parts bins along the back of me work bench so.....  maybe I could use some blue painters tapes to tape them the parts bins temporally? Hmmm.....


            Brad   

[Jack_Hester]

I don't have pictures of them, but I keep a couple sizes of hole countersinks on the bench.  I use them as hand reamers for small holes in aluminum, thin sheet steel, and turret boards (in particular).  De-burrs the backside nicely, after drilling.

I use a handle when reaming metal, but only the countersink held in my fingers, on turret boards.  The top side of the board, where the drill enters, is usually pretty clean.  However, the bottom side always needs cleaning.  And, the finished hole has a nice chamfer for the turret to swag to. 

They can be found in Home Depot or Lowes.  I can't remember which one, as I've had mine for quite a while.

Jack

[kagliostro]

Looks like you are a professional Steve

GREAT idea this tread 

Many thanks for sharing

Franco

[triode]

I wrote this a long time ago for people who purchased board kits. It may be of use to beginners.

http://www.theairtightgarage.com/gallery/tipsforboardinstall.pdf

[tubenit]

For those who like experimenting with different amp designs and mods ..................

(I probably would not use these tips for a "clone")

#1
I like using Doug's board material and making a board of paralleled turrets.  Having them paralleled allows for  lots of options for modifying and changing things (as opposed to a set/fixed position turret board like one would use on a clone).

#2
I like using different colored wires from the sockets to the board  (black/cathode, white/grids, red/plates, etc...).  And I use color coded wires from board to pots.   I do this so at a glance, I can trace where things go.

#3
Having a cap and/or substitution box is very useful for me in tweaking things to the tone I like.

#4
On higher gain amps, I use lower value cathode cap values in the preamp such as 5uf or lower.

#5
Use the minimum amount of shielding wire to start with.  I usually have shielded wire to V1-2.  And I use shielded wire when it is truly a long run across the chassis.  I am amazed at how little shielded wire that I can get away with and have a very quiet amp.

#6
On higher gain amps, start the build with a mindset that you are NOT going to dime all the knobs & in fact, that you might find your best and most harmonically sweet tone with pots set between "4" - "7".  I believe this has been an important mindset in the success of some of the higher gain amps I've built.

#7
I number each row of turrets with a permanent marker.  AND since I draw up my own layouts, I number the turret rows on the layout drawing also.

With respect, Tubenit

[terminalgs]

I do this on eyelet boards for layouts.  This lets me sit the caps I'm planning to use on the actual board to make sure I've got enough space/clearance.   I can also install the board in the amp to visualize proximity to tube sockets, pots, jack, etc.   When I need to correct something, I can overlay more tape.   Once I decide on the final eyelet locations, I circle them in red.   Then its off to the drill press.  after drilling holes, I'll peel off the tape as one piece and stick it to a piece of paper to use as the layout guide to later populate the board. 

[eleventeen]

A lot of this has to do with whether you are building an amp...
 
a: from a schematic only, with no particular layout, specifically without a pre-fabbed turret board a la Hoffman which almost forces you to place (but not wire) the components correctly.....you might do this for a point-to-point build.
b: building an entirely laid out "kit" with a turret board and all parts specified, with a pictorial diagram....
c: building on a *generic* parts board, just two sets of parallel terminals.

I have never been in category "b".

Most amps I've built have been from schematic only, with only rough sketches as to how to lay out a generic parts board, or, I've just surrounded the tube sockets with plenty of terminals strips, not caring if I have a few extra terminals.

Personally, I believe the most critical element is having some kind of system where you "highlight" a wire on a schematic as you make the connection and have a wire-by-wire "done" map as you make every connection. The idea is to acquire perfect certainty as to what is done and what is undone, and the get the "done" out your head. To do this efficiently, the schematic has to be on a clip board or a music stand...it absolutely can't be a loose piece of paper on your bench.

I don't like the word "highlight", though, because it implies you are using a highlighter (eg; a fluorescent felt-tip marker) and I think that's not a good approach....because you can't correct it if you make a mistake. Better, to me, is a colored pencil.

And there are several little subtleties. Consider the following, which is the B+ wiring for an AB763 amp. The B+ coming from the power supply node "D" feeds five locations, all of them happen to be 100K plate resistors that then feed 12a_7 plates. [My Paint program is not letting me color lines and text today, apologies]



If it turns out that you would be wiring the plates of the first triodes first, in other words, connecting your "master" B+ feed to node "a" before having made any connection to node "b" or or "node "c"....can your system accomodate that? Stated another way, after you have wired B+ to node "a" but before there is any connection from node "a" to either node "b" or "c"...how do you draw (or not draw) that? (I'm not looking for an answer, I have it worked out for me)

Likewise, what if you wired up the B+ feed to a terminal somewhere but you had not installed the 100K resistors yet?

As to nodes "a" and "b" and "c"...these happen to be dots on the schematic but are connection or tie points that the circuit itself does not care about. Yes, the connections have to be there but there need not be a specific "dead" terminal.

I'm trying the following on my next build to make a generic parts board more user-friendly: glue a short single row of turrets down the center, where I need to cram in more parts. 

 

[Fresh_Start]

+1 on color coding wire by function. There are industry standards but whatever works for you is fine as long as you're consistent. As an example, here's mine:

Red - B+
Blue - plates
Orange (or brown) - grids
Yellow - cathodes
Green (or black) - grounds
Violet/purple - bias supply
White - control runs (although multiple colors can help here)

Ground connections are critical. I use Doug's round ring terminals for chassis grounds. Always clean and then sand metal surfaces on both sides around hole. I put those star washers that bite into the metal on both top and bottom to get best possible mechanical connection to chassis.

Sorry if that is too elementary, but I learned the hard way on my first build.

For under-board wires, I always drill an access hole next to both turrets and bring the wire up to the top to solder it to the turret. That way I can SEE the connection and test continuity, etc.  

Oh, and those little bent needle nosed pliers are great for lacing up a turret board. Two pairs are even better.

De-soldering braid is priceless.

Old fashioned flux works when soldering to a pot or bare copper ground bus.  hole

Ground connections are critical. I use Doug's round ring terminals for chassis grounds. Always clean and then sand metal surfaces on both sides around hole. I put those star washers that bite into the metal on both top and bottom to get best possible connection to chassis.

Sorry if that is too elementary, but I learned the hard way on my first build.

Oh, and those little bent needle nosed pliers are great for lacing up a turret board. Two pairs are even better.

De-soldering braid is priceless.

Old fashioned flux works when soldering to a pot or bare copper ground bus.

[EDIT: Cleaned up duplicate paste]

[Platefire]

Another take on turret under board jumpers. I have been drilling a hole adjacent to a jumper destination turret and run my jumper through the hole and make my connection above board by wrapping around the bottom of turret. I feel better about having the solder connection above board so I can see it and have access to the solder joint. Platefire

[terminalgs]

On the subject of under the board jumpers.   I always end up regretting them to varying degrees, so I've recently  changed over to using "over the board jumpers".    They aren't as pretty, and you need to be careful not to let the mast of the soldering iron accidentally burn the insulation of one of these wires when working elsewhere,   but those seem to be the only downsides.   the benefits:  you see everything, can be changed/modified/etc.

[sluckey]

I prefer jumpers on top too. I also use teflon insulation and don't worry about burnt insulation. I also switched over from RG-174 to RG-316 for the same reason.

[shooter]

I build straight from the schematic also, point to point, (I’m an abstract artist:) NOT recommended for the new builder.
I do  sketches an mock-ups for the physical layout, drill, cut, mount everything but electronics.  I spent the most time here, mostly in my head and on paper so there are very few surprises later.  I check tube temp specs, try and find min distance specs between tubes.  Once I’m happy with the layout, I prime, paint, clearcoat, then re-mount all the pieces.

1.   dido on the colored wires, red anode, yellow grid 1, white grid 2, black cathode, 2 color twisted for fil.
2.   I always lay out the filaments first, that way I can make sure anything crossing them is at right angles and in the 3rd dimension.
3.   I tick the schematic with a pencil each part AFTER I solder it.
4.   If I build from a tag board I “layout” each tubes parts, anode, grid(s), cathode in that order, then I solder my colored wires, run a piece of shrinkwrap down that tubes bundle till it’s close to the board n write 1a, 1b etc.
5.    I try and elevate any power resistors off the board by ½” or so. 
6.   TIME is the most important element, take plenty of it, double check, triple check, then move on.  I average 1 mistake per build, most have been the old eyes looking at the Chinese colors on resistors n not verifying with a meter.

[birt]

-i draw everything on paper first. layouts, schematics... some of get digital versions, others stay on paper and i just make a copy to highlight or change things as i'm building.

-jumpers under a board are also drawn with permanent marker on top of the board.

-get a dentist mirror (small mirror on a stick) to watch under boards and behind components. you'll use it a lot doing repairs.

[Ed_Chambley]

Couldn't think anything cool that has not been offered, but I do use steel wool on every resistor and cap and get then shiny.  I also measure every one before making a nice mechanical connection.

On soldering in the event of PCB.  If new to it, it is best to keep some old boards from dead equipment.  This will let you get you heat correct and practice a bit before.  Keep in mind PCB boards are different thicknesses, so keep a few different ones.  Practice on this doing the same job as you want to do on your Hot Rod Deluxe.

Better to make the holes in the scrap PCB than your amp, and you will be soldering PCB eventually.

Also, if it your build, be proud of it and try to take your time.  I know the excitement very well and I know how much it cost to replace a Power Transformer because of it.  It is your work of art and it takes time.  Go ahead and get those Jupiter caps if you want them.  It is true no one will see them, but if it is cool to you then is it way cool.

Be careful and power down and drain those caps, even if you are only going to do this one little thing.  If an amp ever grabs you, it will love you to death.  I got stories and was very lucky.

[tubenit]

I do use steel wool on every resistor and cap and get them shiny.

I genuinely mean this respectfully .......... since I don't know you or your sense of humor ............    (I tend to have a dry sense of humor and people often don't get it).

Are you serious or kidding? 

I'm not at all being critical of doing something like that. I've never had the thought to do something of that nature? I'm trying to envision how that would work out & one would do that logistically?

With respect, Tubenit

[sluckey]

He's serious. I do too. He's talking about knocking the crud and oxidation off the resistor leads. Make'em shine and the soldering will work much better. Oxidation is very common on the old CC resistors. There's always been a 0000 pad on my bench. See pic...

[eleventeen]

Well....some these extra steps seem very OCD at first, but as they become habits, there isn't much thought nor effort involved.

I can see Ed's point. If you really get a kick out of having the thing you are building look great....then you also know that even though they are tinned from the mfr, R & C leads or turrets, sometimes they get a coating of skin oil or whatever that just won't cooperate. So here you are, you've made 37 textbook-ideal solder connections and are cooking right along....and suddenly, one of them just will not take solder! So you have to heat it and re-heat it and re-heat it and next thing you know the connecting wire is melting through its insulation or the turret gets loose in the backing board. And then your jewel has a bruise. And when all the other solder joints are ideal, then one scabby one stands out like a sore thumb.

I think a better example is perhaps lining up the row of holes in which the pots go. You are in most cases going to be doing this (chassis work) first, before any electronics are built. You start out, you want it perfect of course. Then you screw something up. Now, your jiggly row of pots looks amateurish and kind of colors your attitude all throughout the rest of the project: "compromise is OK.... well I could only get it that good and no better" 

I never used to even think about measuring components before soldering them in...just never thought about it....now I do it because I can't read the danged color bands on resistors. Or if I'm using used parts, certainly it makes sense to check them. I mean....if they came out of tube gear there's literally no way they aren't 40-50 years old, right? And I have definitely encountered backwards-marked diodes in my travels.

I'm not that obsessive about appearance, but I like an overall nice look. You gotta do what makes you happy, and if Sluckey's extra application of liquid flux and Ed's steel wool treatment does the deed, All I can say is, have at it.

[HotBluePlates]

I do use steel wool on every resistor and cap and get them shiny.

Are you serious or kidding? 

The Xicon carbon comps always have a lot of oxidation on the leads. I don't use steel wool, but have used a razor blade to quickly scrape it off.

Now flux is supposed to dissolve off this oxidation, and maybe I'm wasting my time, and maybe it doesn't make a material difference. But it makes me feel better to do it, so I do.

I don't do it with all parts (or even all parts from a given brand), as some come more oxidized than others. But if the leads don't shine like a new-minted coin, I quickly scrape them with the razor blade.

[tubenit]

I am totally embarassed by this ...................   

I wasn't even thinking about the leads, I was thinking about the "body" of the cap and resistor. Like making Orange Drops brighter orange.
 

Really .......... I missed the obvious that badly.   

[Ed_Chambley]

I am totally embarassed by this ...................   

I wasn't even thinking about the leads, I was thinking about the "body" of the cap and resistor. Like making Orange Drops brighter orange.
 

Really .......... I missed the obvious that badly.   

Jeff, I got to tell you buddy, that is the funniest thing I have ran into today.  Not making fun, but we can laugh at ourselves.

I do joke around a lot, but I wouldn't in a topic such as this.  You made my day.  I consider you a top shelf builder and designer.  Please take this as fun.

[Ed_Chambley]

Sluckey, please tell me the solder and flux you have in the photo. Do you use solid core solder?  Kester rosin 60/40?

If that rosin is what I think it is, I have not seen it in years and cant recall the brand.  I want to get some.

[rzenc]

Couldn't think anything cool that has not been offered, but I do use steel wool on every resistor and cap and get then shiny.  I also measure every one before making a nice mechanical connection.

+1.

I also use scope to determine the outer foil on coupling caps. Helps a lot with background noise.

With everyone posting techinics on this topic, I believe it will become a serious archive to help our community.
Great Idea!

Best Regards,

R.

[sluckey]

Ed, my solder is Kester 63/37 rosin core. I can't recall the brand (or even if there is one) on that can of flux paste. It came from Robins AFB back in the 70s. It is rosin paste.

I grew up with Burnley soldering paste back in the 60s. You can still find it on eBay for stupid vintage prices...

http://www.ebay.com/sch/i.html?_trksid=p2050601.m570.l1311.R5.TR7.TRC1.A0.H0.Xburnley&_nkw=burnley+soldering+paste&_sacat=0&_from=R40

[lego4040]

  This is some great info guys, I follow most of this stuff already like shining up leads, checking off things Ive done..etc I think my old man still has that can of paste too. I like both those ideas of bringing the underboard leads thru turret and bending over top & drilling hole next to turret and wrapping around base. I have some turrets on this AC15 build that wont let me bring anymore leads thru them and I will use the other option idea. I will write the color chart down for sure, I do alot of control wiring in HVAC and color code helps as well as numbering.

[eleventeen]

I am totally embarassed by this ...................    BangHead

I wasn't even thinking about the leads, I was thinking about the "body" of the cap and resistor. Like making Orange Drops brighter orange.

Hilarious! 

"I'll be right there, Honey, just shining up my Orange Drops! "

[tubenit]

just shining up my Orange Drops! "

What don't you guys shine yours up??  I just never have thought of using steel wool to do that before. 

 

I don't think anyone could have laughed at my goof harder than I have. 

With respect, Tubenit

[Willabe]

I use steel wool also.

Tubnit good thing winter is about over, you need to take some time off and go fishing with your grandson.


            Brad      

[HotBluePlates]

... I have some turrets on this AC15 build that wont let me bring anymore leads thru them ...

I have a tip for an X-Acto handle that's like an awl. Turrets are tinned brass, so when I need to put 3 component legs into a single turret opening, I put that awl tip into the turret and rock it it a circular motion. That flares open the top somewhat. Then I use diagonal cutters to trim the component lead into a short point that will stick into the flared turret.

I can generally get 3 parts into a single turret. Sprague Atoms are an exception, and you'll generally only get 1 of those in any turret, regardless.

[sluckey]

I have some turrets on this AC15 build that wont let me bring anymore leads thru them

And that's the real reason I used those blue metal film resistors on that layout. I can easily poke 5 of those skinny leads in one of Hoffman's turrets. Fat leg components get their own dedicated turret. How many of those Dales can you get in a turret?

[Ed_Chambley]

Ed, my solder is Kester 63/37 rosin core. I can't recall the brand (or even if there is one) on that can of flux paste. It came from Robins AFB back in the 70s. It is rosin paste.

I grew up with Burnley soldering paste back in the 60s. You can still find it on eBay for stupid vintage prices...

http://www.ebay.com/sch/i.html?_trksid=p2050601.m570.l1311.R5.TR7.TRC1.A0.H0.Xburnley&_nkw=burnley+soldering+paste&_sacat=0&_from=R40

Burnley, that is what I was thinking of, but I think for that price, what I have is fine.  I knew what you had had been around a while as the cup is flatter now.

I use the 63/37 as well.  I just know your joints are real clean of contaminates.  You must really keep a clean tip, but that is the trick anyway.  Clean tip, really wipe it every time.  Hey another tip, clean you tip and do not rub the coating off it.  A nice wet sponge should be all you need.

[sluckey]

I just know your joints are real clean of contaminates.

The first thing I do when I pick up my iron is wipe it on the wet sponge. Only takes a couple seconds. I rarely solder more than a couple joints before wiping again. But, my boards still have flux splatters. My boards are completely loaded including 99% of the interconnecting wires before the board ever goes in the amp. This allows me to wash the board with mineral spirits and a variety of acid/paint brushes. The MS will remove the rosin flux. Then the board gets blow dried with my air compressor. Next I will wash the board again with denatured alcohol, brush, and blow dry again. Finally, the squeaky clean board gets bolted into the chassis. The whole cleaning process only takes about 5 minutes. I had some good depot level training at Robins.

[Ed_Chambley]

I just know your joints are real clean of contaminates.

The first thing I do when I pick up my iron is wipe it on the wet sponge. Only takes a couple seconds. I rarely solder more than a couple joints before wiping again. But, my boards still have flux splatters. My boards are completely loaded including 99% of the interconnecting wires before the board ever goes in the amp. This allows me to wash the board with mineral spirits and a variety of acid/paint brushes. The MS will remove the rosin flux. Then the board gets blow dried with my air compressor. Next I will wash the board again with denatured alcohol, brush, and blow dry again. Finally, the squeaky clean board gets bolted into the chassis. The whole cleaning process only takes about 5 minutes. I had some good depot level training at Robins.

Another great tip.  I guess the components are much tougher than I thought,

[Voxbox]

I worked for a while in Ferranti where they made military spec equipment. Inertial Navigation and Attack systems for fighter jets in particular where I was.
I spent some time with the wiremen who used to use ordinary multicore solder (don't recall which type) but they would always dab some flux onto the joint area on the pcb before applying the urn. Brilliant shiny joint every time. They would have to clean the excess flux off with a cleaner afterwards as it was a bit corrosive.

Regarding component legs, I'll give the cruddy ones a wipe on wet and dry paper, but I usually re-tin them before soldering, even if they look ok.

Wiring tip for stranded wire - twist and tin the tip of the wire before making the mechanical joint that you make before soldering. The wire doesn't splay out then. I always do it before inserting a stranded wire into connectors like XLRs as well.

All the best, VB

[Mike_J]

Something that has helped me a lot in making amps is the free online Inkscape vector graphics program.  It allows me to email my faceplates and backplates to the local print shop and have faceplates and backplates made for about $5 each.  I put + signs in the center of the jack, pot, etc locations which makes it much easier to align/drill holes in the chassis. This in conjunction with some step drill bits and a jig saw allows me to make any size chassis I like.
 
Another huge benefit is once you develop a style for your amps they can look very uniform and your amps take on a consistent and professional look.

If anyone can tell me how to post a pdf file I will show you what one of my faceplates looks like.

Thanks
Mike

[HotBluePlates]

... If anyone can tell me how to post a pdf file ...

Ahem... the Forum How-to's Board.

[PRR]

> making Orange Drops brighter orange.

Resistor makers quietly admit that their leads may not be "solderable" (in commercial terms: no duds in a million joints) after a few months. In DIY we have parts 6 to 600 months old.

I would lean toward COPPER wool. It's in the kitchen cleaner aisle.

Also the 3M "scrubbie" plastic pot-scrubber.

Or plumber's emery cloth. Or a knife, carefully (careful on the lead AND your finger).

Specs of iron can be trouble in soldering.

Copper wool is also good for cleaning the tip of the soldering iron.

Elsewhere I've argued that LIGHT is the technician's secret weapon.

[jojokeo]

Hmm, not sure where to start but I'll add to others' comments first:
a) I color code wires, put my layout & schem on the bench while working, use above board jumpers almost always
b) on suspect parts/leads/older wire, new pot lugs and switches, un-tinned wire, heat sensitive components, etc. I always flux & tin these first beforehand
c) I will pre-assemble and/or wire anything possible before mounting to chassis such as input jacks, presence pot, VVR components, ppimv pot, etc. where practical
d) I use Kester 44 solder, do not use or advise using silver solder - it doesn't bridge gaps. I use stainless steel wool more than a sponge since I've read about micro fractures and other stuff re. wet sponges
e) I set my iron higher for faster on/off times and better heating but you do not want your solder to "boil" by holding the iron on too long, it takes experience to get your own feel
f) whether drilling, soldering, sanding - anything - let the tools do the work and do not force things. This is where injuries happen and breaking of parts
g) it is great practice as Ed mentioned to measure all your components beforehand, you will find something out of tolerance or completely marked wrong occasionally. Ounce of prevention...
h) it is beneficial to test & mark outside foil of caps beforehand especially on high gain designs as rzenc, tubenit, & others have discovered but I'll just send my caps to Ed for the extra personal touches, lol.
On scratch building:
a) I draw actual sized board & layout on paper to assure proper spacing & fit for all parts I'm going to utilize
b) this then serves as the actual template for drilling turrets or eyelet board
c) I do the same for all faceplate & backplate components to exact spacing & fit
d) I place all trannies, board, tube sockets, etc. to size & orientation for chassis layout before drilling
e) I place the PT & OT on opposite sides of chassis whenever possible or use a DIY "listening device" beforehand for quietest placements and do not place PT laminations toward power tubes
f) always punch circuit board and chassis before drilling
g) on chassis, I use 1/8" bit for preliminary holes then use a step bit for final size of component. This allows for very accurate hole placements

a few example photos from some above comments using good old reliable Sheriff amp.
hope this helps, Keo