Reverb coil rewinding AWG

[diydidi]

Hi.
Anyone have an idea what wire gauge to buy for reverb tank coils? I can get 42AWG and 43AWG. Which one will be better suited?
I also noticed the 'in' winding uses different thickness wire than the 'out' winding for the coils. Maybe someone can elaborate on this...
Regards.

[J M Fahey]

Which end?

For the output coil, "as thin as you can handle" , because you want highest output possible and it will always drive a high impedance load.

For the drive coil, it depends on impedance desired.

Really, it's an inductor so impedance varies linearly with frequency, but there are 2 ways to state it:
1) if you have an RLC bridge, you measure impedance at 1kHz and that's it.
2) if not, you label your tank with roughly 10X the DC resistance , it's a reasonable value.

I suggest you get the thinnest wire you can handle without undue breaks, which will also be good to rewind a couple pickups , so maximum bang for the buck.

A drive coil wound with such thin wire will be easy to drive with a humble TL072 or similar simple circuit.
As said above, best bang for the buck.

2X or 3X as thick wire will be about right for low impedance drive coils such as tube/transformer driven ones in Twin Reverb, etc.

I think the pickup guys will have a lot to suggest in this area.

Personally I'd start with the thin wire, rewind a couple coils, measure them (mounted and driving a spring) and post results.

Then you can scale that to other desired values, remembering that in a full coli resistance varies with the cube of wire diameter , so 2X as thick means 1/8 the DCR ; other parameters scale accordingly.

Not rocket science but sharp eye, patience, and steady pulse.

I did manufacture my own reverb tanks, long ago, including pressing and cooking my own tiny hollow magnets, but it amounted to an admission ticket to Bedlam, so eventually I stopped , not worth the effort.

[diydidi]

Thanx JM!!
I can get 42 & 43 AWG from Stu-Mac. Is 43 too thin to work with? Buying both will be a costly affair for me with shipping and all. I have to choose between the two.
Luckily I have a paper that gives all the static DC resistances for various well known tanks. Is there a way to determine coil impedance using a scope and signal generator?
For some reason the output coils seem to fail. Must be the thinner wire.

[Enzo]

Considering the labor involved in rewinding one of those, assembly and disassembly, compared to the low cost of a new pan, I'd be hard pressed to justify the project.

[Jazz P Bass]

I will admit that it never entered my mind to 'rewind' a reverb coil.

Not at 25 bucks for a new pan.

[g1]

Some of the oddball vintage pans are unobtainium. And some collector types would jump at the option of repairing their original pans, regardless of price.
There's a guy online somewhere refurbishing corvette radios for $600 a pop.

[J M Fahey]

Considering the labor involved in rewinding one of those, assembly and disassembly, compared to the low cost of a new pan, I'd be hard pressed to justify the project.

Not at 25 bucks for a new pan.

Price: $24.95 + $5.95 shipping

That's true ... in USA.
Don't know about South Africa (guess not too different to Argentina) but ordering a reverb tank here costs:

* actual tank: U$25

according to Amazon, for shipping purposes a long tank (think for Fender Deville or similar) measures and weighs:

Product Dimensions: 16.8 x 4.4 x 1.3 inches
Shipping Weight: 1.3 pounds

whose shipping costs are:

* at FEDEX, estimated arrival and freight:

Tue Apr 14, 2015 by 6:00 PM FedEx International Economy® U$137.45

* at UPS , same data:

Ship To:
CAPITAL FEDERAL, 1166 ARGENTINA
Residential
Ship From:
TEMPE, AZ 85283 UNITED STATES
Commercial
Shipment Date:
Wednesday, April 8, 2015
Customs Value:
25 USD
Duty Type:
01 - Dutiable

Showing Retail Rates Results For:
TEMPE, 85283, UNITED STATES to capital federal, 1166, ARGENTINA


Service Details

Print

UPS Worldwide Saver - zone 406

Guaranteed By :
By End of Day
Friday April 10, 2015

Rates
UPS Worldwide Saver
143.10 USD
Declared Value Free
Fuel Surcharge
6.80 USD
Shipment Total: 149.90 USD

* by USPS:

Priority Mail International® Total $41.90
Expected Delivery Date 6 - 10 business days to many major markets

USPS looks way cheaper but they have their own quirks:
* they love to deliver envelopes (duh) , not happy with packages, so they either prefer you use one of their own (none fits) or no dimension is less than 5.5" so the original reverb tank package won't do by itself, so:
* it must be inserted in another box with USPS approved dimensions.
* It also must be dropped at an USPS office by somebody, who will also have to:
* fill the "green stamp" Customs declaration (so they can't send one of their Deltas but a Beta or at least a trained Gamma)

this either results in the classic "NO INTERNATIONAL SHIPPING" (except to Canada and maybe some European Countries) or "shipping by DHL/Fedex/UPS ONLY" or plain adding $20 to $40 to delivery costs (nobody does extra work for free)

***The reverb tank oddyssey, chapter 2***

when it arrives to Argentina, there's 2 paths, depending on who brought it in:

* Private Company (DHL, etc.) : they pay the Customs fee for me, a flat 50% above CIF cost (C-ost , I-nsurance , F-reight) and then bill me.
They ring my bell and a sharp dressed guy, in the Company colours, driving a same colours van, delivers it without further trouble, of course asking for Customs Duty they paid on my behalf:

* FEDEX: U$(25+137.45)*1.5= 243.68U$ <--no f*cking kidding

* UPS: U$25+149.90)*1.5= 262.35U$ <-- same here

of course, we prefer the State Mail , so by USPS it is less unreasonable:

U$25 (tank) + U$42 (actual shipping) + U$20/40 (estimated surcharge for more complex shipping)=U$67*1.5 (duty on "visible" cost) + U$20/40 (International delivery/extra packaging surcharge , is billed on the International Credit Card but appears nowhere on the actual package, so we will still pay it but no extra Duty) :U$101.25 + 20/40U$ ... about half the private Courier cost ... although it implies no door to door delivery:
Argentine Post sends a nice pink form stating when and where can I go pick the package, have it inspected and pay duty.

That day I wake up early, go to Customs Office carrying a Thermos loaded with coffee, a couple sandwiches and a good book, I have to pay admission (think a Cinema ticket value), sit in a comfortable chair surrounded by 700 to 1200 people who are there for the same reason as me.

4 to 8 hours later they call me , they X Ray the package before me (in case it has a b o m b connected to the lid or some a n t r a x envelope (thanks, USA paranoia ) and they open it.

They may agree on the stated price or not, anyway it's almost impossible to lie (if it's actually an expensive product, say a $3500 Les Paul claiming to be a $199 cheap copy) because they google it .
If they agree, they print a receipt which must be payed before actually getting the package.

I GUESS NOW IT'S CLEAR THAT REWINDING THE D*MN COIL IS THE QUICK, CHEAP, SENSIBLE OPTION

Now you will not find surprising that I wind my own transformers, make my own speakers, cut/punch/paint/silkscreen my own panels and PCBs, had dies and molds made for my own corner protectors, strip handles, knobs, rubber feet and even made magnetic reverb tanks and horn drivers (cloned the ubiquitous Fostex horn).

FWIW I am HAPPY with that situation, because I can work manufacturing amplifiers, speakers, cabinets and accessories, and repairing stuff which in USA would be prime landfill.

Instead of flipping a burger at some fastfood place, which would be the option if cheaply made stuff could enter freely.

@DIYDIDI: don't waste money ordering 2 such close sizes; if your main problem is output coils, get the thinnest one, if you also rewind driver coils, get 2X that diameter for a mid impedance coil; if you need nominal 8 ohms coils (I doubt they fail having the thickest wire) which have close to 1 ohm DCR, I guess any transformer winder will have a suitable one (since it will be a more "normal" diameter) and sell you a little.
Anyway ask the pickup guys, they eat, breath and dream thin gauge wire.

[MarkusBass]

Is there a way to determine coil impedance using a scope and signal generator?

I think that if you connect the coil in series with a resistor of a known value and provide 1 kHz signal from the generator, you will be able to determine the impedance simply by measuring voltage drop on the resistor. This is usual way to measure an impedance - nothing difficult. In this case it would be nice to have an oscilloscope with cursor measurements capabilities.
Another simple way to do it is to put a potentiometer in series with the coil, provide 1 kHz signal to the circuit and set the pot to get voltage drop by 2 and then measure the potentiometer resistance. There are many ways to do it.

Mark

[diydidi]

WOW. Great reply guys.
I think JM hits the nail on the head. Many people don't realise it, but for most people simply getting a new tank, speaker or whatever, isn't as easy if your'e living on the other side of the world where these type of things aren't manufactured at all. Let alone a third world country.

[diydidi]

I think that if you connect the coil in series with a resistor of a known value and provide 1 kHz signal from the generator, you will be able to determine the impedance simply by measuring voltage drop on the resistor. This is usual way to measure an impedance - nothing difficult. In this case it would be nice to have an oscilloscope with cursor measurements capabilities.
Another simple way to do it is to put a potentiometer in series with the coil, provide 1 kHz signal to the circuit and set the pot to get voltage drop by 2 and then measure the potentiometer resistance. There are many ways to do it.

Mark

So correct me if I'm wrong. If i use the pot method as described, and adjust for 1/2 the full signal across the coil, measure the pot, this is the impedance of the coil at 1KHz. This is not the Inductive reactance of the coil (XL). Right?
The inductive reactance is where the signal will be -3db down, and not -6db as with the pot method as described?

[g1]

In this case I believe impedance is equal to X(l). There is no X(c) to complicate things as far as I can tell.

[MarkusBass]

So correct me if I'm wrong. If i use the pot method as described, and adjust for 1/2 the full signal across the coil, measure the pot, this is the impedance of the coil at 1KHz. This is not the Inductive reactance of the coil (XL). Right?
The inductive reactance is where the signal will be -3db down, and not -6db as with the pot method as described?

You asked about impedance. Now, you introduced a new term: "inductive reactance" and ask about it. If you want a nice explanation of the difference between impedance and inductive reactance, I suggest to go here: http://www.electronics-tutorials.ws/...inductors.html and read it. Both terms are explained. There is even suggested circuit described (resistor in series with a coil).
But apart from scientific terms it is very easy to check the circuit on your own. I've built the circuit in about 10 seconds and made the measurements in about 40 seconds (so everything in less than 1 minute) . I used 1 kHz signal (sinusoidal and not square), 10 kOhms potentiometer, Accutronic reverb tank (input coil) and Rigol oscilloscope (with cursors measurements to make life easier). To get a half of the input signal across the pot, I had to set it to 590 Ohms. I think that the manufacturer lists the input impedance of the tank as 600 Ohms so my results are very close. If I measure DC resistance of the coil I get 49 Ohms. The smaller DC resistance, the closer are impedance and inductive reactance. If fact you can ignore 49 Ohms which is much smaller that 600 Ohms and say that the impedance of the input coil is 600 Ohms and it is almost the same as the inductive reactance of the coil.
I also wouldn't measure the signal in decibels since all you have to do is to set half of the input signal on the pot. This is much easier with plain numbers. For example, I set the amplitude of the signal to 700 mV, and set the pot to get 350 mV across it. Isn't it easier?

BTW, I agree with you that guys in the States have no idea how life in other countries looks like. Few months ago I had to pay $100 for two pots for a bass guitar only due to the fact that they were available only in the States and the company that was selling them knew only one method of goods delivery: FedEx. And FedEx charged me $70. Luckily reverb tanks are only $30 here so not that expensive as in Argentina .

Mark

[J M Fahey]

I imagined something similar.

FWIW k6mz said that shipping electronic stuff straight to Russia was a Customs nightmare, and he usually preferred to have it sent to Finland, driving a couple hundred miles and picking it up personally; then bringing it back in the trunk of his car.

[Enzo]

Agree that shipping from the USA would be prohibitive, but at least around here, most places that sell tubes also sell reverbs. The reverbs themselves are not made in the USA, they are imported. So there may not be any importers in SA, or Argentina, but in many other places around the world, there are local distributors as Mark points out.

[epis]

Just to share my experience, once I rewound input coil of reverb tank, simply I got higher impedance solid state driven tank from old organ and needed low impedance for my tube amp project.
So I took apart the transducer, counted the number of turns, calculated needed turns and wound the coil with thicker wire. ( I had the impedance data for the tank)
It worked like a charm.
I don't remember anymore of these numbers, but original magnet wire was something like 42 awg.
And about the shipping expenses from US, it became ridiculous even to Canada, for a $25 tank, I would have to pay $40 shipping most likely.