A quick question for anyone who knows about these things- I have an old PT that I was thinking as using for a first "learning" attempt at winding , for a 6l6 SE amp. Unfortunately the lams are drilled in the middle as well as the corners and the tongue trimmed on its corners , am I right in thinking that this will be useless when butted?
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No, it was a working one, was it not..So no effect from drills etc.
And buy a transformer, not worth learning for a one off.
And buy a transformer, not worth learning for a one off.
There should only be *two* of those funny looking E lams from the 2nd pic. Those are supposed to go on the outside. The inner ones are straight. Half of the time, I end up sacrificing one of those outer lams just to get the disassembly process started. It gets mangled.
Don’t try to learn winding on a SE trafo. Getting the gap right is not trivial. It’s best to learn on *power* trafos, then move on to PP OPTs. Power trafo lams are often not good enough quality for anything better than a guitar amp. Thickness and material matter for all OPTs, anything works at 60 Hz. You don’t need to mess with interleaving power trafos, in order to get good HF response you *do*. If you are dead set on learning OPT winding with this, start with PP and relatively low Ra-a (say, 4K), and don’t try to make ridiculous power. They get harder to do right the higher the Z.
You have the plastic bobbin for it? If this is your first, and if doing by hand don’t try to use a paper former (you’ll get frustrated and just give up). If this is your first amp build, do not wind the OPT or PT - buy or salvage.
Don’t try to learn winding on a SE trafo. Getting the gap right is not trivial. It’s best to learn on *power* trafos, then move on to PP OPTs. Power trafo lams are often not good enough quality for anything better than a guitar amp. Thickness and material matter for all OPTs, anything works at 60 Hz. You don’t need to mess with interleaving power trafos, in order to get good HF response you *do*. If you are dead set on learning OPT winding with this, start with PP and relatively low Ra-a (say, 4K), and don’t try to make ridiculous power. They get harder to do right the higher the Z.
You have the plastic bobbin for it? If this is your first, and if doing by hand don’t try to use a paper former (you’ll get frustrated and just give up). If this is your first amp build, do not wind the OPT or PT - buy or salvage.
I hope it's not a one -off , as I said it's a learning experience and I'm OK with learning from my mistakes. Thanks to wg_ski , I checked and it's just the end lams that are cut on the corners. I'll press ahead with it , it' a guitar amp and I'm just following my interests- I've already wound pickups for my guitars so I'm not coming into it cold , and at least trafo wire is THICK and doesn't snap on a whim like pickup wire!
That.
The rounded center leg ones are mostly cosmetic, real ones (99% of them) are flat tops.
Wind it if you wish, agree that you are starting with the most complicated of them all, SE requires a defined gap, typically by inserting an *thin* sheet of Mylar or Pressphan, you can not trust raw irregularities which are absolutely uncontrolled.
A quality OT also requires well designed interleaving.
Design is not simple, at all, absolute best case you will need a tried and true project, already designed by somebody experienced, or, say, clone some recommendation from an old Philips manual or Wireless World project from the 50´s or 60´s (tops) which used to give you detailed winding instructions.
I would start with a *power*transformer and climb the ladder step by step.
The rounded center leg ones are mostly cosmetic, real ones (99% of them) are flat tops.
Wind it if you wish, agree that you are starting with the most complicated of them all, SE requires a defined gap, typically by inserting an *thin* sheet of Mylar or Pressphan, you can not trust raw irregularities which are absolutely uncontrolled.
A quality OT also requires well designed interleaving.
Design is not simple, at all, absolute best case you will need a tried and true project, already designed by somebody experienced, or, say, clone some recommendation from an old Philips manual or Wireless World project from the 50´s or 60´s (tops) which used to give you detailed winding instructions.
I would start with a *power*transformer and climb the ladder step by step.
A bass guitar low frequency starts at just above 40Hz.
A lead guitar amp typically has harmonics to about 7kHz (as do lots of speaker driver units that roll off at very high frequencies).
For a guitar amplifier, you do not have to have 20Hz to 20kHz frequency response.
But do not expect the amplifier to be Hi Fi without a really good output transformer, and circuit topology, etc. to match.
But first you need to determine how you will use the 6L6 (or the higher max dissipation 6L6GC) . . .
Beam Power Wired (high power, but speaker damping requires negative feedback; Triode Wired, low power, dampens the speaker without negative feedback; Ultra Linear (the characteristic of power and damping falls in between Beam Power and Triode modes, but you have to have Ultra Linear taps of the primary windings).
Quiescent Plate voltage and plate current.
Primary turns, primary DC current, laminations, air gap thickness, versus inductance and early saturation.
Global negative feedback can be real tricky, if not impossible, with unknown output transformer characteristics.
An early design popular guitar amplifier uses a 6V6 in Beam Power mode. It does not have any negative feedback.
And I bet the very small output transformer does not have any interleaving of the primary and secondary windings.
If you really want to wind your own, go for it!
Just my opinions
A lead guitar amp typically has harmonics to about 7kHz (as do lots of speaker driver units that roll off at very high frequencies).
For a guitar amplifier, you do not have to have 20Hz to 20kHz frequency response.
But do not expect the amplifier to be Hi Fi without a really good output transformer, and circuit topology, etc. to match.
But first you need to determine how you will use the 6L6 (or the higher max dissipation 6L6GC) . . .
Beam Power Wired (high power, but speaker damping requires negative feedback; Triode Wired, low power, dampens the speaker without negative feedback; Ultra Linear (the characteristic of power and damping falls in between Beam Power and Triode modes, but you have to have Ultra Linear taps of the primary windings).
Quiescent Plate voltage and plate current.
Primary turns, primary DC current, laminations, air gap thickness, versus inductance and early saturation.
Global negative feedback can be real tricky, if not impossible, with unknown output transformer characteristics.
An early design popular guitar amplifier uses a 6V6 in Beam Power mode. It does not have any negative feedback.
And I bet the very small output transformer does not have any interleaving of the primary and secondary windings.
If you really want to wind your own, go for it!
Just my opinions
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Have a go, but expect to rewind it a few times. One of the trickiest things with E I lams is bobbin fill, it's hard to get right. Brocott - Enamelled Copper Magnet Wire do wire and insulation tape and varnish.
If you need any transformers to play with let me know, I'll send a few for the price of postage.
Andy.
If you need any transformers to play with let me know, I'll send a few for the price of postage.
Andy.
Depending on your winding machine and technique, there is a parasitic factor called "bowing" and it occurs in rectangular 90 deg edge bobbins only. It is occurring in the first layers and it manifests as a bulging, the first layers not entirely following the rectangular shape of the bobbin, but slightly rounding off. To the most extent it is fixed by applying a counter-arc shape to the wire just before laying it on the bobbin, using your thumb if done by hand, or adjusting feeding angle when working on a machine.
Most importantly, you must take into account this bowing when calculating if your coil "will" fit.
As mentioned, the exact type of bowing will depend of your winding technique. In my designs I add an absolute minimum of 1mm, but sometimes it can reach 4mm. Usually the thicker is the diameter of the first layers wire, the more the bowing is.
My most recent work was two types of nanocrystalline C core chokes with two bobbins.
-One choke has a 19x60mm core with an overall window of 25mm. Shape plays a role too. Theoretical filling windows is maxmum 21.7, considering some core irregularities. 25 - 21.7mm = 3.3 overall bowing, considering there are two coils, we can assume 1.65mm bowing per single coil.
-The other choke has a 16x45mm core, 19.5mm window. Theoretical filling is 16.58, leaving us with 2.92mm overall bowing or 1.46 per coil.
Most importantly, you must take into account this bowing when calculating if your coil "will" fit.
As mentioned, the exact type of bowing will depend of your winding technique. In my designs I add an absolute minimum of 1mm, but sometimes it can reach 4mm. Usually the thicker is the diameter of the first layers wire, the more the bowing is.
My most recent work was two types of nanocrystalline C core chokes with two bobbins.
-One choke has a 19x60mm core with an overall window of 25mm. Shape plays a role too. Theoretical filling windows is maxmum 21.7, considering some core irregularities. 25 - 21.7mm = 3.3 overall bowing, considering there are two coils, we can assume 1.65mm bowing per single coil.
-The other choke has a 16x45mm core, 19.5mm window. Theoretical filling is 16.58, leaving us with 2.92mm overall bowing or 1.46 per coil.
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easier if you have bobbins to use for those....you can scramble wind...just make sure interlayer insulations are used using nomex and at least two laps to eliminate chances of pinholes..