Eyelet/Turret Board Soldering

[xm52]

I wanted to make a general comment about solder technique.

How components are connected and soldered in an amp is very important. Solder is not the best conductor, it's best to not rely on it as a conductive element in the signal path. Let me explain.

I see too many amps where component leads are placed in the center of an eyelet and soldered. Amps seem to sound better if the leads are wrapped around the outer edge of the eyelet, making good contact with the eyelet, then soldered. The solder should act as a glue to hold the leads in place against the eyelet, not as a bridge between the lead and the eyelet. The same holds true for turrets. Wrap the lead around the turret to ensure good contact, then solder. On pots, solder bridges between the case and terminal is not good technique. See the attached image.

For those that recall the days of wire wrap construction, wires were tightly wrapped around square terminals, solder wasn't even used.


Here is a useful link to NASA Workmanship Standards: http://workmanship.nasa.gov/lib/insp/2%20books/frameset.html

There are other good references listed here: https://nepp.nasa.gov/index.cfm/5544.

[shooter]

NASA Workmanship

I was sent to a 3wk NASA soldering school in the NAVY, toughest school I ever had, made it to wk 3 then got cut when they broke out the 20X microscopes!

[John]

Amps seem to sound better if the leads are wrapped

Hmmm. 

[kagliostro]

http://el34world.com/Forum/index.php?topic=14655.msg139882#msg139882


 


Franco

[PRR]

Solder is an acceptable conductor. 1/32" inch of solder conducts better than the 6 inches of wire it connects.

Solder is a terrible Mechanical material. Weak. You wrap so that "no" strain comes on the solder.

You can't wrap a round terminal so it "makes contact" reliably.

Wire-Wrap is different thinking. The terminals are square. The wrapping tool applies high force to "smear" the wire onto the terminal corners, also breaking tarnish and giving a gas-tight joint; and about 28 such joints per terminal.

[HotBluePlates]

All that said, I think the original point of "make a good mechanical connection, only use solder to hold the part/wire in place" is still valid.

[xm52]

Radio Shack used to sell a lead/tin/silver solder that I really like. I wish I could still buy it.


Nothing wrong with a small solder bridge but direct contact is better. Even with plated through circuit board holes, I like to wrap leads and wires onto the pads before soldering. It's the globs like illustrated in the image on the pot that are all to common, especially in some vintage amps.


Perhaps I go overboard, but I use a Mr. Clean sponge to remove oxidation from wire leads, then clean with alcohol prior to soldering. With components that have been sitting around for a while, a lot of black comes off leads as seen on the sponge.


It seems that the military/NASA soldering courses leave an impression with those that have take them. 


As was mentioned, it never hurts to have good technique for consistent results.

[eleventeen]

For old style DIP-chips, wire wrap is awesome. Ahh...the 80's. Backplanes!


I believe I read a carefully done study that showed the MTBF of a wire wrap joint was better than that of solder joint.

[shooter]

Ahh...the 80's. Backplanes!

Fresh batteries, spool of wire and I could *fix the world*, at least til proper replacement parts showed up!

[HotBluePlates]

Yes, but for our southern friends, how do you solder a "turlet" properly?

[PRR]

> MTBF of a wire wrap joint was better than that of solder joint.

Yes-- and the new-joint defect rate is far lower.

A telephone central office has millions of joints. Wiring-up a CO with techniques that fail 1% of the time means ten thousand bad joints to find and fix. Good soldering will tend toward a thousand bad joints. Best WireWrap work, under a hundred.

This depends on the RIGHT terminals, wire, and tools. It may not apply to low-price terminals, certainly not to non-Wire terminals, untrained hand-tool work, old WireWrap wire, etc.

[vibrolax]

Radio Shack used to sell a lead/tin/silver solder that I really like. I wish I could still buy it.

I picked up a couple rolls of RS's silver-bearing solder right after their latest bankruptcy event, then started looking for a replacement.
What I found was this 2% silver solder at Newark:http://www.newark.com/multicore-loctite/dlmp22-250g-reel/solder-wire-lmp-250g/dp/13J8468

I bought two 250g rolls during a sale for about $50, which looks like a lifetime supply at this point.  Per ounce, it's less expensive than Radio Shack's, and seems to behave very much the same.

[shooter]

how do you solder a "turlet" properly?

I clean the copper with *brillo pads*, make sure the pipes are dry, add flux, heat with torch, then quick, smoothly, apply solder,  Martha she's flushing again

[PRR]

> two 250g rolls .., which looks like a lifetime supply

Probably. I'm still on a pound (455g) I bought decades ago.

[PRR]

> how do you solder a "turlet" properly?

I'm surprised anybody south of NYC would make that joke.

You don't solder a turlet. It's a lead pipe cinch.

[xm52]

Thanks for the link to the silver solder.

[xm52]

These are sweep generator modules from an aircraft radar system. I bought them some time ago from Surplus Sales of Nebraska. I good source for vintage parts BTW. The construction is interesting. All wires and leads are wrapped, none down the center rim of the turlets.  . Note how they economized on space by using two boards. Distances to the tube socket terminals are short. I also like the idea of a pluggable module. Imagine using this to build a preamp. Different designs could be swapped in and out of an amp.

[xm52]

For those who have worked on tube radios and TVs, you used to see wire wrap to and from the circuit boards. Here is an example of a Philco TV. The brown module next to the tube is interesting. Resistor and capacitor networks were mounted on a substrate ad encapsulated. This saved time in manufacturing. One manufacturer was Centralab: Centralab Printed Electronic Circuit (PEC) - Nostalgic Kits Central


Interesting to note that Ampeg used these modules in many amps in their James tone stages.

[xm52]

Another very crude example of tube related wire wrap. This is a display board mounted literally on a board. The pins look like square nails. An inventive approach to circuit construction. I recall some crystal radio kits used to come with a board as a base.

[vibrolax]

These are sweep generator modules from an aircraft radar system. I bought them some time ago from Surplus Sales of Nebraska. I good source for vintage parts BTW. The construction is interesting. All wires and leads are wrapped, none down the center rim of the turlets.  . Note how they economized on space by using two boards. Distances to the tube socket terminals are short. I also like the idea of a pluggable module. Imagine using this to build a preamp. Different designs could be swapped in and out of an amp.

6 or 7 years ago Randall marketed their MTS (Modular Tube System) amp and preamp line.  Commercially they weren't too successful.  I have no idea about the quality of their technical execution.
https://www.google.com/search?q=randall+mts+modules&espv=2&biw=1834&bih=1293&tbm=isch&tbo=u&source=univ&sa=X&sqi=2&ved=0ahUKEwjjhtvb3NjOAhWBUyYKHckRACgQsAQIOA
Egnater seems to have acquired Randall, or at least run with the modular plug-in idea some more.

Salvation Audio has this:http://salvationaudio.com/index.php?page=modifications

I've built a few 1U preamps semi-modular, but not connectorized.  I make them this way for ease of assembly and troubleshooting, rather than for instant swap-out.  It also left me the option to "swap" a module in an hour if I were so inclined.  Modules need to be connectorized including the controls to be really swappable.

I suppose we could design guitar / bass amps using the API rack module form factor if we wanted that sort if modularity without having to create the whole mechanical system.  Maybe somebody already did it.

BTW, I bought a used Soundcraftsman HiFi preamp about 25 years ago that used wire wrap for all the module and control interconnects.  It was a noisy mess that I returned for refund.  Yes, wire wrap can be awesome and reliable, but I've never seen it done well in a consumer product.  I think my Adcom preamp also had wire wrap interconnects.  It also turned into an unreliable mess, but that could have been the quality of the PCB's as well. Lateral stress on the wire wrap pins would break the pad/trace where they were soldered onto the PCB.

Thus I am happy to build on 1/8" G10-FR4 with large Keystone turrets.  I'm a guy who usually uses the hollow turret holes, but I'll do the external wrap for builds that need to be qualified for spaceflight.

[xm52]

The commercial modular amps are interesting. I've never had a chance to try one. They seem pretty rare.


I'm thinking that a modular approach would be useful to use in a studio where chasing tone and options are is so important. Being able to plug in different tone stages is useful. Same for different pre-amp stages. It can help keep the signal path uncluttered. Modular design is common in recording consoles because so much is repeated and it helps with service turnaround. Downtime can be expensive.


There are some interesting images of a channel strip designed by EMI like the ones used at Abbey Road: http://vintageking.com/blog/2015/11/emi-strip. They used a combination of printed circuit boards with small turrets. The TG12345 is a transistor based design. You can see the bus lines running perpendicular to the boards. They sure knew how to build a good sounding desk.


A modular approach is helpful in designing amps. Switching in and out modules helps quickly A/B different approaches. It's also nice to have a sub-assembly handy in case you want to try it. Circuit boards are nice but a fast turnaround and multiple revisions gets costly fast.  Circuit boards are done closer towards the end. Turrets are attractive because they are fast and dirty.


I know what you mean about those older consumer products that used wire wrap pins on the circuit boards for external connections. Some of them were fairly low end. Using wire wrap certainly cut down on manufacturing time and cost. Today we have a lot of good quality connectors that can serve that purpose.


I have a Mesa Boogie amp that has all kinds options. I tend to dial in a good tone and leave it. The amp is complicated and it takes time to muck around with it. Overly complex can be a negative.

[xm52]

Here is an example of a wire wrap octal socket. Same as some PCB sockets but with longer terminals. They are available from Tube Sockets - Apex Jr., item 8.

[Champ_49]

Found this interesting topic. It's a bit of an old topic but thought I'd chime in. All of this makes sense.  However,  the way I did it was I did solder the leads into the holes. That is so I could easily change out components if need be such as replacing or swapping out different values.
One thing I DID do was bend the lead at less than 90 degrees so that when you place the leads (both ends) into the hole both leads make contact with the turret and stays in place while soldering. It gives  it an extra bit of force on either side as the leads push out against the inside of the turret.