50's technology

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50's technology

Post by corsair on Sun Jul 16, 2017 1:00 am

So. The lap steel has been playing up a little in that when I went to change the tuning to G6 to C9 that the machine heads were quite hard to turn and getting harder, so that plus the fact that the pots are quite scratchy lead me to this...



... the thing stripped down and on the bench. This main bit is an aluminium casting with chromed tin plate and steel parts for the art deco accents and bridge/tailpiece.

Gonna have to continue this when we have decent interweb  - the .servimg is hopelessly slow!

Later...



It has a wooden base, as well as a piece of wood underneath the "fretboard".



The tailpiece, bridge, circular magnet that sits directly underneath the pickup and a piece of chrome trim.



Pickup from above. These instruments were all handbuilt at this stage in the companys' life- not hand finished! - in a shed in Taihape, NZ by a panelbeater called Bunny Milne and sound really very good! That celluloid is glued onto a thin piece what feels like bakelite; he didn't need to do this for anything other that aesthetic purposes, but evidently thought it might look nice!



The pickup revealed. I don't know whether Bunny wound his own or sub-contracted the work out - I suspect he may well have rolled his own - he was a very skilled tinkerer. The pole pieces screw through the coil straight into the body; the outside screws are insulated in a sleeve of undetermined but electronically inert material. The thing itself sounds immense, yet reads only 7.4kΩ.



The loom. Many years ago, I replaced the proprietary jack socket - which was some sort of orphan thing as the 6mm phone plug hadn't been standardised at that stage in NZ - with a normal socket... which barely fits. Look at the size of those pots - British made and both 500k log pots...



Monster cap, eh!!



One of the exposed gear machines showing the wear and tear on the cog - they're all like this and I actually have a set of machines to replace them with... I just need to drill out the teeny tiny holes that are there to allow a 10mm ferrule!



The bridge, such as it is, which sits underneath the tailpiece, and above that honking great magnet: that thing will pull the fillings right out of yer teeth!!

Would someone please tell me what purpose it serves there? And whether or not replacing the electronics with a modern audio taper pot for the volume, and a log pot for the tone with a modern capacitor will affect the sound in any meaningful way?? The pickup stays as I like the noise it makes...









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Re: 50's technology

Post by Barry on Sun Jul 16, 2017 12:53 pm

Wow John, what a funky geetar! A beauty in it's own strange way.
Nothing routine about working on this one eh?

I'm thinking that perhaps the magnet may be acting as a kind of noise canceller, similar to what Leo Fender did on the Tele with the wrap around bridge + "ashtray" cover?? Something to do with the donut shape of the pickup and the magnetic field generated by it??

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Re: 50's technology

Post by Westbone on Sun Jul 16, 2017 4:23 pm

Interesting, like the art deco style....  Smile

Have a Kalamazoo 1935--40 lap steel, drab looking thing but sounds great.
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Re: 50's technology

Post by Barry on Sun Jul 16, 2017 4:54 pm

Re: changing the electronics.
As a rule, "if it ain't broke...etc" Unless the cap is leaking or summit I'd be inclined to leave the big ass thing alone.

Theoretically there shouldn't be a change but sometimes if you mess with a component, especially in a circuit this old you can mess up the Mojo, ya know?

Jesper would be the fellow with the definitive answer if he's still about. I don't know anyone who's ripped apart more electronics than he has.

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Re: 50's technology

Post by Westbone on Sun Jul 16, 2017 6:09 pm

If it ain't broke don't fix it
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Re: 50's technology

Post by corsair on Sun Jul 16, 2017 10:19 pm

I have no intention of disturbing that particular circuit; rather, I will put another one together with modern components and see what happens...

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Re: 50's technology

Post by Barry on Sun Jul 16, 2017 10:53 pm

Clever lad.  Wink

p.s. While yer at it see if that magnet is easily removable and if it affects the sound/noise in any way.

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Re: 50's technology

Post by corsair on Tue Jul 18, 2017 6:18 pm

That magnet just slops about in the hole, eh; easily removeable - I really need to do some more research...

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Re: 50's technology

Post by Barry on Tue Jul 18, 2017 10:23 pm

It's a new one on me. Can't think of anything else useful it could be doing there. Thinking

edit: just found this: LINK


and this video:

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Re: 50's technology

Post by gittarasaurus on Tue Jul 18, 2017 11:05 pm

please pardon my geek out... geek

it seems "that honking great magnet" the only magnet present?
can you tell if the magnet is oriented up/down or side-by-side?
are the bridge and the tailpiece made of steel or other alloy that is magnetic?

a "pickup" is only just a magnetic field and a coil of wire. the strength and shape of the magnetic field in relation to a coil of wire is the crux of how a signal is created in a circuit. vibration of the magnetic field is what induces the signal into the wire coil/circuit.

you have the gauge of the wire and the number of wraps that translate into ohms. smaller gauge wire requires fewer wraps to reach the same resistance reading as more wraps of larger gauge wire.

the body is aluminum so will not affect the magnetic field, but the other parts that are magnetic, and their relative position with respect to the coil and the orientation of the magnet, would seem to be integral to the special sound it produces.

my theory is; 

the bridge and the strings become directly coupled and part of the magnetic field. concentrating all the vibrations of the strings at the bridge directly through a very strong magnetic field induces a strong and clear signal to the coil, and produces a big output signal.

Don\'t Know.... end of geek-out.... time for another beer and another bud... Twisted Evil
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Re: 50's technology

Post by Barry on Tue Jul 18, 2017 11:53 pm

Um, er, right. What Mike said. Wine Drinker

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Re: 50's technology

Post by corsair on Thu Jul 20, 2017 8:18 pm

You beauty... cheers Mike! So what I'm seeing here with the wire coil and magnet is just the pickup in it's single components? That is pretty damn cool; that's a pretty concise description of pickups magetism principles, too - thank you!

Right. I've set to and stripped it right down and cleaned and polished the body; I have to restock on the metal polish beofre I take on the tinplate Art Deco embellishments! I have, however, found an unused set of black tulip buttoned tuners which, on measuring the height of the posts of the OEM ones, will do the job.

If only it were that easy! The wood insert in the headstock sits about 1.5mm below the level of the body. so the machine heads weren't sitting flush, and short of removing the wood and making a whole new one in exactly the correct depth, I opted for the cheaper option of using 10mm washers modified to fit where they needed to be! it works a treat  - as you'll see when the photos I took arrive on the desktop!



... stealth hardware!! Cool Laughing



.. the cheap option!



The pins that hold the "fingerboard" and tin plate to the body look to be dress saddlers nails, but I've found some M2 bolts on the web, so I'll do that instead.

Electronics have been ordered - once again via eBay - though I'm humming and ha-ing about the cap; oil in paper or ceramic? I feel sure that it's not what the thing is made of, but its' value that makes the difference?! Discuss.


Last edited by corsair on Fri Jul 21, 2017 6:53 am; edited 1 time in total

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Re: 50's technology

Post by Westbone on Fri Jul 21, 2017 3:43 am

Ceramic(cheap), don't be fooled about all that baloney regards 'oil in paper' 'bumblebee' crap! that's all they had/used at the time. Voltage doesn't matter.

I'd keep everything original (excluding your experimental circuit) as it was. Won't a load of lube free up the tuners,they tend to bind on the shaft/ferrule.

Still it's yours to do as you please... Smile
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Re: 50's technology

Post by Westbone on Fri Jul 21, 2017 6:07 am

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Re: 50's technology

Post by corsair on Fri Jul 21, 2017 6:56 am

Westbone wrote:Check this out... Cool
https://www.youtube.com/watch?v=XvKbbDBeBNo

Nice!! Gilmour does 'One of these days' on a lap steel... it's cool to see instruments pushed a little out of their comfort zones, so to speak!

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Re: 50's technology

Post by corsair on Fri Jul 21, 2017 7:03 am

Westbone wrote:Ceramic(cheap), don't be fooled about all that baloney regards 'oil in paper' 'bumblebee' crap! that's all they had/used at the time. Voltage doesn't matter.
So, you're saying that the type of cap doesn't matter? Just the value, i.e .050µF @ 350MVD??

Westbone wrote:I'd keep everything original (excluding your experimental circuit) as it was. Won't a load of lube free up the tuners,they tend to bind on the shaft/ferrule.

I intend keeping the original circuit as it came out of Bunnys' shed, yes and re. the tuners - you'd think so, wouldn't you, but no; these have chewed out their cogs beyond what some lube is capable of fixing. I'll keep 'em aside for any future owner but I'm looking for ease of tuning and stability which modern ones will do better than old slogged out ones!

Westbone wrote:Still it's yours to do as you please... Smile

... and I shall!!

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Re: 50's technology

Post by Westbone on Fri Jul 21, 2017 8:06 am

corsair wrote:
Westbone wrote:Ceramic(cheap), don't be fooled about all that baloney regards 'oil in paper' 'bumblebee' crap! that's all they had/used at the time. Voltage doesn't matter.
So, you're saying that the type of cap doesn't matter? Just the value, i.e .050µF @ 350MVD??

Yours is .05uf  @350 vdc

It's the value not the volts that matters. 50/100/350/400 volts will make no difference whatsoever.
With the tone full up the capacitor is redundant anyway.
I'd stick a treble bleed on it, much more useful.
Try a 220k ohm resistor with a 680pf cap as a treble bleed.
A tone capacitor of your choice.

Here's a shot of the old Kalamazoo circuit
.03pf cap, 400vdc.
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Re: 50's technology

Post by corsair on Fri Jul 21, 2017 8:44 am

Westbone wrote:Try a 220k ohm resistor with a 680pf cap as a treble bleed.
A tone capacitor of your choice.
Cool!! That sounds like the sort of thing I'd like to have a go at!

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Re: 50's technology

Post by Barry on Fri Jul 21, 2017 9:13 am

Westbone wrote:Check this out... Cool
https://www.youtube.com/watch?v=XvKbbDBeBNo
That's incredible technique! I've never seen anyone roll the steel slide like that. What beautiful playing.

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