Vintage amps full of insulated leads?

[Rhodesplyr]

I've run across a few 1950s amps that are full of components with leads carefully insulated with bits of tubing, often where it makes no sense, i.e., where leads aren't carrying higher voltages or aren't close together, etc...

So, I'm wondering, what was the thinking, if anyone knows, behind this build technique? Was the idea to protect people in case someone decided to go poking around inside, in which case, they could still touch the tube socket terminals, etc... It seems like a lot of trouble to go to for limited gains, especially in cases where someone was more likely to get zapped by a shorted "death cap" to the chassis ground.

[diagrammatiks]

It's the idea of doing something right just to do it right.

[Rhodesplyr]

It's the idea of doing something right just to do it right.

Pardon me if I'm being obtuse, but what's "right" about insulating component leads inside a chassis where there are still plenty of exposed dangerous voltages?

Is it similar to the practice of bundling wires together because it looks neat, even if it results in noise coupling?

[diagrammatiks]

how does bundling wires together automatically result in noise coupling?

Can you tell just by looking at pictures that all the low impedance lines were bundled with the high impedance lines?

Insulating material is required around leads in order to provide strain relief and vibration support.

[Jazz P Bass]

Insulating material is required around leads in order to provide strain relief and vibration support.

Now that makes sense.
I guess when you are assembling amps with the threat of nuclear annihilation hanging over your head, you go all out to ensure the product will survive a 1 megaton impact.
Kind of in the same vane as wrapping the leads around a terminal 5 gazzillion times (man I hate that!).
Wouldn't want that there wire coming off if Nicky desides to launch a few.

[diagrammatiks]

Now that makes sense.
I guess when your are assembling amps with the threat of nuclear annihilation hanging over your head, you go all out to ensure the product will survive a 1 megaton impact.
Kind of in the same vane as wrapping the leads around a terminal 5 gazzillion times (man I hate that!).
Wouldn't want that there wire coming off if Nicky desides to launch a few.

Leads should only be wrapped around a terminal a gazzillion times for solderless wirewrap connections.

turrets are supposed to be wrapped just enough so that the entire lead can be soldered without placing undue stress on the turret.

Not a big issue with lead and wire size found in most guitar amps these days but a few twists with 16gauge will torque the turret right out under stress.

[g1]

how does bundling wires together automatically result in noise coupling?

He didn't say "automatically". I believe he meant "occasionally" which is sometimes seen when form is given priority over function. Sometimes wires are run parallel in bundles when they should be crossing perpendicular to prevent noise issues. It is usually done because it "looks good". Hiwatt comes to mind, not sure if it is the best example.

Insulating material is required around leads in order to provide strain relief and vibration support.

Not in the case that Rhodesplyr is speaking of. The insulating material in these units does not provide any kind of strain relief or support.

I'm wondering if it was due to some (odd) safety regulations that required insulation of component leads but for some reason overlooked lugs etc.
Edit: Could also be a way of ensuring leads of various components were uniform length from unit to unit? Pre-cut sleeves would make this easier.

[Kazooman]

I know what you are saying and have faced it many times. I have an interest in vintage gear from the 60's (when I was a budding "rock and roll star"). I did manage to scrape together a good Fender Bandmaster, guitar, and reverb, but there were many things I coveted that I could not afford. I put all that behind me and went off to college, grad school, and a career. NOW, I can finally manage to purchase some of these toys and they are driving me CRAZY!!!

I have a real THING for early - mid 60's tape echo machines (Klemt Echolette / Dynacord, etc.). I grew up on the sound and would love to make it happen again. This is truly a "labor of love" or an indication of insanity. I own four Klemt Echolette S tape echos. Three are in "good to great" shape and one was a basket case that I have nursed back to some sort of life.

What a nightmare where electronics and mechanical systems converge to beat down the restorer.

More to the point of this thread, all of these units have "anal-retentive grounding and shield tubing". Several ground buses run throughout the units, making them a network of signal lines and many, many ground buses. There are a huge number of shielded cables used, often for no apparent reason other that "good measure". Most of these are wires enclosed in braided metallic shields and then routed through plastic tubing sleves. The final mess of wires is very carefully (and skillfully) stitched together with string to make a great appearance. I should note that the bundle of similarly colored tubes makes tracing a connection from A to B very difficult. In some cases, the shielded cables have two conductors and one is actually suppoesed to be grounded. Break one of those at the end of a cable run and good luck finding it!

I don't have an answer as to why they did things as they did, other than to say that it was probably well before most on this board were born and we should give them credit for what they accomplished with what they had in hand.

Here's one of many gut shots I take before messing with any unit.

http://i.pbase.com/g4/45/150145/2/14...5.sNaX4jvN.jpg

[diagrammatiks]

He didn't say "automatically". I believe he meant "occasionally" which is sometimes seen when form is given priority over function. Sometimes wires are run parallel in bundles when they should be crossing perpendicular to prevent noise issues. It is usually done because it "looks good". Hiwatt comes to mind, not sure if it is the best example.


Not in the case that Rhodesplyr is speaking of. The insulating material in these units does not provide any kind of strain relief or support.

I'm wondering if it was due to some (odd) safety regulations that required insulation of component leads but for some reason overlooked lugs etc.
Edit: Could also be a way of ensuring leads of various components were uniform length from unit to unit? Pre-cut sleeves would make this easier.

Well a couple of things..

regarding bundling: We'd have to agree that there is a right way and a wrong way to do things. Even novice builders get taught the first few "golden rules". You're supposed to twist your heaters and keep them away from signal lines.

If you made a giant bundle of your signal, power, and heater lines in the middle of the amp, it would be easy to say well that's not quite how that should go.

But at the same time just because certain wires shouldn't be bundled together doesn't mean that the 2 heater wires should be kept as far apart as possible.

Well, those guidelines exist for every type of lead and component in an electrical circuit and depending on what parameters you are looking to maximize or stabilize different wires will need to be put together and other ones will need to be placed far apart.

When you can figure all of that out before hand then it's very easy to make neat bundles that are electrically correct.

On the issue of lead insulation,

Remember that tube gear wasn't always just a hifi unit on a bookshelf or a guitar amp. Almost everything used tubes at one point.

Saying that because you can't insulate everything, nothing should be insulated is an intenable building principle. If that were the case then there would be no reason to insulate iec connectors, fuse holders, or anything that had a termination point somewhere else.

Some wiring guidelines required that insulation be used to minimize the number of potential contacts between connectors.

Insulation also helps to protect the covered wires from environmental factors.

Circuit density was also another qualifier. If you needed to put a lot of components close to each other then it was necessary to insulate the leads just in case the components shifted.

[Jazz P Bass]

Cannot view the picture.
Access Forbidden.

[diagrammatiks]

Cannot view the picture.
Access Forbidden.

this thread got me looking for pictures...

here's some random new production hifi amp i found.

[trobbins]

A schematic and a photo or two may be worth a thousand words about whether there is indeed a 'technique', or any technical credibility.

[Kazooman]

Sorry about the bad link. I keep forgetting that for some reason PBase doesn't let me link from here. It does with most forums.

Here's a pic.

[Jazz P Bass]

Whoa!
How would you like to do that all day, every day.

[Rhodesplyr]

He didn't say "automatically". I believe he meant "occasionally" which is sometimes seen when form is given priority over function. Sometimes wires are run parallel in bundles when they should be crossing perpendicular to prevent noise issues. It is usually done because it "looks good". Hiwatt comes to mind, not sure if it is the best example.


Not in the case that Rhodesplyr is speaking of. The insulating material in these units does not provide any kind of strain relief or support.

I'm glad someone understood what I meant. I'm working on a 1953 Multivox Premier 120. It's got lots of insulating tubing on resistor and capacitor leads, but some leads with little to no voltage on them are insulated, while some carrying plate voltages are not.

These are ALL component leads, not hookup wires.

However, I have seen cases (my Farfisa Compact Duo) where extra "strain relief" at the end of hookup wires actually made the wires more prone to breaking off--because it concentrated any motion of the wire right at the solder joint.

Bundled wires that cause noise coupling: Wurlitzer Electric Pianos, particularly the wiring to the front panel controls.