Hey all!
So this question has been bothering me for a while, how do I do it? What do I need to have? Do I need to know all the math behind them?
So as a 15 year old now that is my huge problem, it seems so hard, but i want to try to do it, is it possible?
So my first goal would be to wind 1:1 transformer (220V to 220V transformer) and an SE EL84 output transformer, and then maybe later 6V6 or EL84 PP OT.
What do I need to know to do this, what do I need to have? How to make an ideal guitar amp OT?
So I have already tried reading Wolpert manual but I find it too hard. Is there any other alternative of how to learn it? Any good website?
Thanks in forward for replying!
FireBottle
So this question has been bothering me for a while, how do I do it? What do I need to have? Do I need to know all the math behind them?
So as a 15 year old now that is my huge problem, it seems so hard, but i want to try to do it, is it possible?
So my first goal would be to wind 1:1 transformer (220V to 220V transformer) and an SE EL84 output transformer, and then maybe later 6V6 or EL84 PP OT.
What do I need to know to do this, what do I need to have? How to make an ideal guitar amp OT?
So I have already tried reading Wolpert manual but I find it too hard. Is there any other alternative of how to learn it? Any good website?
Thanks in forward for replying!
FireBottle
See this reference:output-trans-winding.html
When age 20 I tried to avoid the lathe and bobbin since the transformer I was re-winding had aluminum wire and I could save a lot of space with copper. One MUST use a mylar bobbon. I nicked the insulation, Class F polyurethane, and shorted a turn to core.
Actually, guitar amps are well supported on the guitar builder market, see tubesandmore.com for a selection of guitar amp transformers. I can't help you overseas, you'll have to search the net yourself. I saw builders in Australia for example on another thread, but haven't logged them since I don't live there.
One matches the input impedance of the output transformer to the shown output impedance on the push pull chart of the vacuum tubes you are using. One matches the output impedance of the transformer to the speaker. Many transformersfor sale have multiple speaker taps.
When age 20 I tried to avoid the lathe and bobbin since the transformer I was re-winding had aluminum wire and I could save a lot of space with copper. One MUST use a mylar bobbon. I nicked the insulation, Class F polyurethane, and shorted a turn to core.
Actually, guitar amps are well supported on the guitar builder market, see tubesandmore.com for a selection of guitar amp transformers. I can't help you overseas, you'll have to search the net yourself. I saw builders in Australia for example on another thread, but haven't logged them since I don't live there.
One matches the input impedance of the output transformer to the shown output impedance on the push pull chart of the vacuum tubes you are using. One matches the output impedance of the transformer to the speaker. Many transformersfor sale have multiple speaker taps.
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DrFireBottle,
A good "first test" transformer project would be to rewind a 12.6v transformer secondary to 5v, so you can power a rectifier tube even if the power tranny doesn't have a 5v winding. It involves a tiny bit of math to determine the number of turns per volt, but that's about it. The primary should be the inside winding and the secondary should be on the outside. You're only going to touch the secondary.
A 5v volt secondary at roughly 3 amps current would be perfect (which is close to 15VA), so find a donor power tranny that supports maybe 24 VA (a 12.6v @ 2 amps works nicely) for some wiggle room. Disassemble the I E laminations and then count the number of turns on the 12.6v winding as you remove them. Divide 12.6 into the number of turns, and the number you have is the number of turns per volt.
Obtain some transformer wire that will support the amount of current you desire and then multiply the number of turns times 5. Wind that number on to the bobbin, re-assemble the core and test.
Easy to do, and it will tell you whether you want to pursue rewinding any further. Audio trannys are a bit more complex if you want to make a good one, but this will give you a level-of-effort experience.
Dave
A good "first test" transformer project would be to rewind a 12.6v transformer secondary to 5v, so you can power a rectifier tube even if the power tranny doesn't have a 5v winding. It involves a tiny bit of math to determine the number of turns per volt, but that's about it. The primary should be the inside winding and the secondary should be on the outside. You're only going to touch the secondary.
A 5v volt secondary at roughly 3 amps current would be perfect (which is close to 15VA), so find a donor power tranny that supports maybe 24 VA (a 12.6v @ 2 amps works nicely) for some wiggle room. Disassemble the I E laminations and then count the number of turns on the 12.6v winding as you remove them. Divide 12.6 into the number of turns, and the number you have is the number of turns per volt.
Obtain some transformer wire that will support the amount of current you desire and then multiply the number of turns times 5. Wind that number on to the bobbin, re-assemble the core and test.
Easy to do, and it will tell you whether you want to pursue rewinding any further. Audio trannys are a bit more complex if you want to make a good one, but this will give you a level-of-effort experience.
Dave
At around age ten or eleven, I found a whole world of complexity lies in those two little sentences.
Working only with a few crude hand tools, and only a boy's strength, I shed plentiful amounts of blood attempting to disassemble some transformers. I shed more blood attempting to re-assemble them.
In the process I also realized that without some sort of press capable of exerting high pressure on a stack of laminations, there was no way I was ever going to get all those laminations back into the bobbin. Particularly since the struggle to extricate them from the original transformer had slightly warped a few.
I have built lots of oddball things for myself over the years, but transformers are one thing I decided to leave to those with the proper equipment.
I wish Firebottle well, perhaps he will have better results than I did. 🙂
-Gnobuddy
The next time you do this (??), remember that you "can" leave a few out.
The lam stack was sharp-pencil calculated to just do the job. The original job, original specs. You are re-winding because you want a *different* tranny, different specs. You should allow for the skill of the winders/stackers-- the sharp-pencil design allows perhaps 90% utilization of space. UN-skilled winder/stacker may not get 75% utilization. So start with a lump at least 1.2X as big as it would be if factory wound.
Thanks,
but is there any simple instruction manual on how to assemble transformers and how to calculate?
but is there any simple instruction manual on how to assemble transformers and how to calculate?
Since you don't have the mathematical skills needed to fully design a transformer yet, I suggest to look back in time to the work done when computer simulators and extreme cost optimizations needs were not a given. You may find useful information at this page VintageWindings Audio Transformer Design Coil Winding Collection V1 .pdf
DVD Page . I suggest to start with the "practical transformer design and construction (by C. Roeschke)" article from 1947 Radio News, it probably will match well with your current knowledge level and needs. Be careful while assembling EI laminations because you may easily cut yourself. If you want to start by modifing/disassembling an existing EI transformer, choose a vintage one because current production is almost always covered with resin/varnish and the wire will easily break while unwinding.
If you want a easier start, use a big power toroidal transformer such as RS components 1176060. Wrap 10 turns of wire around the donut, connect the primary to the mains, and measure the AC voltage on this makeshift temporary winding both without load and with a 10 ohm resistor. It should be something around 2-3 volts. Divide this voltage by 10 and you will know how many volts are produced at each turn. Now you can easily calculate the number of wire turns to wrap around the donut to generate all your required secondary voltages. Use Kapton tape to secure the enameled wire. This way is much faster than messing around EI cores because you only add to the transformer - no need to dismantle it. You can also use this toroid as a base for a guitar amp push-pull output transformer. It is not good for Hi-Fi use because frequency range will be around 12-16 Khz max and frequency response will not be flat. If you use a 115+115/115+115v transformer, just connect all the winding in series to get your primary, and add a secondary winding on top.
DVD Page . I suggest to start with the "practical transformer design and construction (by C. Roeschke)" article from 1947 Radio News, it probably will match well with your current knowledge level and needs. Be careful while assembling EI laminations because you may easily cut yourself. If you want to start by modifing/disassembling an existing EI transformer, choose a vintage one because current production is almost always covered with resin/varnish and the wire will easily break while unwinding.
If you want a easier start, use a big power toroidal transformer such as RS components 1176060. Wrap 10 turns of wire around the donut, connect the primary to the mains, and measure the AC voltage on this makeshift temporary winding both without load and with a 10 ohm resistor. It should be something around 2-3 volts. Divide this voltage by 10 and you will know how many volts are produced at each turn. Now you can easily calculate the number of wire turns to wrap around the donut to generate all your required secondary voltages. Use Kapton tape to secure the enameled wire. This way is much faster than messing around EI cores because you only add to the transformer - no need to dismantle it. You can also use this toroid as a base for a guitar amp push-pull output transformer. It is not good for Hi-Fi use because frequency range will be around 12-16 Khz max and frequency response will not be flat. If you use a 115+115/115+115v transformer, just connect all the winding in series to get your primary, and add a secondary winding on top.
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