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Old 1st Jun 2021, 3:03 am   #1
nzoomed
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Default Winding a new output transformer for a Philips B5G64A Radio

I have a Philips B5G64A Radio that has the primary open circuit thanks to "THAT" capacitor.

I left the OT with a transformer winder a couple of years ago but he has been too busy to look at winding a new one, so I'm going to collect it from him and have a go at winding one myself since I have since acquired a winding machine and a supply of wire and laminations.

I believe it needs a 5K primary, and can't remember what the impedance of the speaker is for the secondary so need to take another look at the speaker.

I was hoping i could disassemble the transformer and unwind it and count the turns, but it is all gunged up with pitch, I'm wondering if this is why the guy I left it with has avoided looking at it for so long?

So basically I need to know how many turns Im looking at to wind my own and what wire gauge, etc.

I'm not sure what impedance the centre tap is tapped on either, its an unusual design.

TIA.
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Old 1st Jun 2021, 6:40 pm   #2
Ed_Dinning
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Default Re: Winding a new output transformer for a Philips B5G64A Radio

Hi, dunk in a sealed container of petrol (observe all safety precautions) for a while and the pitch will dissolve.
When vapor has gone carefully extract lamination's. If this is a single ended output you should find the lams are all butted one way, not interleaved. Note that there may be a thin paper spacer between the lams, measure thickness in case you need to replicate.

Measure thickness of sec wire , note that this is the overall dia , not the copper dia and count the number of turns.
Measure dia of pri wire and count the number of turns, or multiply up by the ratio from the sec turns
Ratio is given by the SQRT of the valve Rl (not Ra) to speaker R (typically 3R and will be in the typical range of 20 to 50:1

Make cheeks for the bobbin unless you are lucky enough to have a molded one as it make winding much easier

As you mention a tap and it is a Philips set I'm guessing it is a hum bucking winding. This is typically about 5% of the total sec turns.

Ed
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Old 1st Jun 2021, 10:42 pm   #3
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Default Re: Winding a new output transformer for a Philips B5G64A Radio

Thanks for that, I'll give it a go.
I have boxes of bobbins and pretty much everything that's required. I have been trying to find the computer program the old guy had who gave this gear to me that could calculate turns ratios and that would save me a lot of time if I could just calculate the turns and wind a new one from scratch.
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Old 2nd Jun 2021, 5:36 am   #4
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Default Re: Winding a new output transformer for a Philips B5G64A Radio

Here's some photos for your reference, I'm going to soak it in Naphtha overnight and hopefully I can get all the pitch dissolved.

You're right, the laminations are not interleaved, I thought they only did this with chokes?
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Old 2nd Jun 2021, 12:19 pm   #5
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Default Re: Winding a new output transformer for a Philips B5G64A Radio

No, they also do it for output transformers with a net standing DC in the primary as in single ended class A. P-P can be interleaved since the dc in each half of the primary balances out to give a net zero flux in the core.
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Old 2nd Jun 2021, 8:27 pm   #6
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Default Re: Winding a new output transformer for a Philips B5G64A Radio

Hi, as you do not know the core parameters it would be easier to count the turns on your existing transformer. Then providing your core was at least as large there should be no problem

Ed
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Old 2nd Jun 2021, 10:39 pm   #7
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Default Re: Winding a new output transformer for a Philips B5G64A Radio

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Originally Posted by Herald1360 View Post
No, they also do it for output transformers with a net standing DC in the primary as in single ended class A. P-P can be interleaved since the dc in each half of the primary balances out to give a net zero flux in the core.
Interesting, I didnt know this. Makes me want to check the custom wound transformers I had made for a single ended class A build a few years ago!

Quote:
Originally Posted by Ed_Dinning View Post
Hi, as you do not know the core parameters it would be easier to count the turns on your existing transformer. Then providing your core was at least as large there should be no problem

Ed
Yeah, I expect so too.
Hopefully its easy to unwind. Looks like the pitch is dissolving away.
Doesnt look like its got much core (or wire for that matter)
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Old 3rd Jun 2021, 6:41 pm   #8
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Default Re: Winding a new output transformer for a Philips B5G64A Radio

They tended to be a low cost component in these sets anyway

Ed
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Old 21st Jun 2021, 9:21 pm   #9
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Default Re: Winding a new output transformer for a Philips B5G64A Radio

So I have had this transformer soaking in petrol to dissolve all the pitch for two weeks now and have unwound it last night.

Its a very basic transformer, no interleaving at all, the secondary was wound on first and the primary on top.
There was a thin piece of paper between each layer of wire.

I was told that a single ended el84 transformer should be about 3000 turns, and this is close to that at around 3500 turns.

The "humbucker winding" seems to be much lass than that however at only about the first 90 turns.
Is the 5% value based on the amount of turns or the actual impedance?

Im thinking of splitting the primary into two and putting the secondary in the middle, I was told this is usually acceptable.

Not sure what varnish to dip the transformer in when wound, i think its polyurethane that is being used from what I can tell from the smell of new transformers ive bought in the past.
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Old 21st Jun 2021, 10:25 pm   #10
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Default Re: Winding a new output transformer for a Philips B5G64A Radio

Splitting the primary into two and placing the secondary will give you better coupling. You can use thin yellow polyester tape for the interleaving insulation. For the final dip you can use poly U but I hate the stuff. For a little transformer such as yours beeswax can be used with perfect success.

Joe
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Old 22nd Jun 2021, 7:53 am   #11
Edward Huggins
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Default Re: Winding a new output transformer for a Philips B5G64A Radio

Re. Post#1, the typical voice coil impedence for a Philips speaker of this period is 5 ohms. With the tropical coating removed, you say the actually tranny does not look to be of much substance. Even so in the Radiogram version using this same chassis, it does still sound very good.
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Old 22nd Jun 2021, 8:55 am   #12
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Default Re: Winding a new output transformer for a Philips B5G64A Radio

Quote:
Originally Posted by nzoomed View Post
I was told that a single ended el84 transformer should be about 3000 turns, and this is close to that at around 3500 turns.

The "humbucker winding" seems to be much lass than that however at only about the first 90 turns.
Is the 5% value based on the amount of turns or the actual impedance?
If it's an output transformer that has a hum cancelling winding then the ratio of the main primary turns to the hum cancelling turns should be the same ratio as the valves anode impedance to the value of the resistor that's connected to the output side of the hum cancelling winding (the HT filter resistor)

Lawrence.
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Old 22nd Jun 2021, 9:18 am   #13
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Default Re: Winding a new output transformer for a Philips B5G64A Radio

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Originally Posted by joebog1 View Post
Splitting the primary into two and placing the secondary will give you better coupling. You can use thin yellow polyester tape for the interleaving insulation. For the final dip you can use poly U but I hate the stuff. For a little transformer such as yours beeswax can be used with perfect success.

Joe
Yes ive seen people use beeswax. Ive also read that people use nitrocelluose.
Anything has to be better than that horrible sticky pitch right? lol
I guess there is no harm in interleaving it in two?

Quote:
Originally Posted by Edward Huggins View Post
Re. Post#1, the typical voice coil impedence for a Philips speaker of this period is 5 ohms. With the tropical coating removed, you say the actually tranny does not look to be of much substance. Even so in the Radiogram version using this same chassis, it does still sound very good.
Yes 5 ohms sounds about right, obviously they were nothing audiophile grade and mass produced, but i can only assume it will sound better if i interleave it.

Quote:
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Quote:
Originally Posted by nzoomed View Post
I was told that a single ended el84 transformer should be about 3000 turns, and this is close to that at around 3500 turns.

The "humbucker winding" seems to be much lass than that however at only about the first 90 turns.
Is the 5% value based on the amount of turns or the actual impedance?
If it's an output transformer that has a hum cancelling winding then the ratio of the main primary turns to the hum cancelling turns should be the same ratio as the valves anode impedance to the value of the resistor that's connected to the output side of the hum cancelling winding (the HT filter resistor)

Lawrence.
OK, well im assuming it must be about right at the 90 turns ive got.
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Old 22nd Jun 2021, 8:17 pm   #14
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Default Re: Winding a new output transformer for a Philips B5G64A Radio

Hi, I think your figures should work just fine, interleaving will only improve matters and as Joe says the yellow polyester tape is great for insulation between windings.
You can use grade 2 (double enamelled) wire for both pri and sec, but many winders simply use grade one on the output transformers where insulation requirements may be lower.

You should check your core, if it was not interleaved laminations and they were only butted together, there is often a layer of paper about 2-3 thou thick to create a slight air gap and reduce core saturation.
Candle (paraffin) wax that is not coloured also works as an impregnant.

Ed
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Old 22nd Jun 2021, 10:51 pm   #15
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Default Re: Winding a new output transformer for a Philips B5G64A Radio

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Originally Posted by Ed_Dinning View Post
Hi, I think your figures should work just fine, interleaving will only improve matters and as Joe says the yellow polyester tape is great for insulation between windings.
You can use grade 2 (double enamelled) wire for both pri and sec, but many winders simply use grade one on the output transformers where insulation requirements may be lower.

You should check your core, if it was not interleaved laminations and they were only butted together, there is often a layer of paper about 2-3 thou thick to create a slight air gap and reduce core saturation.
Candle (paraffin) wax that is not coloured also works as an impregnant.

Ed
Ive always wondered where you buy that special yellow tape from thats used on transformers, it seems to have a different type of adhesive unlike sellotape.
I was going to use kapton tape if thats something you recommend?
I didnt realise there was a double enamelled wire, i really need to go through mine and take a closer look, many rolls have had the labels fall off.
Im just going to use my digital calipers to measure the wire, im assuming that should be near enough, although the enamel thickness on this older wire could be alot different than modern wire.

Candle wax could be a good option, I had also been exploring glyptal which is supposed to have good insulation properties and was made for this purpose.
Eventually I want to get a vacuum chamber set up for this too.
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Old 22nd Jun 2021, 11:52 pm   #16
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Default Re: Winding a new output transformer for a Philips B5G64A Radio

Over the ditch its made by Tesa tape. Its available from many many sources in Asia, all over, and is cheap from there. I have used the non branded stuff and I would swear its identical to Tesa tape. Its available in perhaps 100 widths, starting at about 1/16" wide.

There is double enamelled wire. There is single enamel with single silk. There is single enamel with double silk. There is double enamel with single silk, etc etc. Some of it can be VERY expensive. Whatever enamelled wire you have will be fine in your situation as the voltage across it will be fairly small. When measuring enamelled copper wire, its normal to remove the enamel and just measure the copper NOT the insulation as well. If you have double enamel its going to measure much thicker than the copper itself. I normally burn it off with a lil gas torch, then using very soft steel wool I remove the residue and then measure. DONT be over fussed about polishing the copper, just remove the residue. Traditionally a micrometer is used to measure copper wire, but a modern digital calipers should be close enough, especially if they are good quality.

There are hundreds of uchoob videos showing transformer winding from the cheapest nastiest build to way over the top audiophoolery supreme eccentric style.

Modern insulation, ( say from last 20 years ) is mostly poly u as well and is called "solderable " enamel. You can burn it off with a hot soldering iron. I have used it mainly because good old fashioned enamel has not been available in guages I needed. There is a very old "black enamel" wire that is a disaster. Its basically shellac ( made from Lac beetles) and you can pick it by scraping the so called enamel off with your fingernail. If you have any, GET rid of it or you will end in disaster.

There is also enamelled Eureka wire which is NOT copper, but resistance wire. Different guages means different resistances!!. BUT with different chemical mixes the same guages can be very different resistances. If you have inherited this wire, it would be a good idea to check before you start.

Keep asking questions You are about 2% into learning about transformers, wires, and laminations. I have been doing it more than 50 years and I am still a rank beginner.

Best of luck

Joe

Keep the questions coming.
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Old 23rd Jun 2021, 8:31 am   #17
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Default Re: Winding a new output transformer for a Philips B5G64A Radio

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Originally Posted by joebog1 View Post
Over the ditch its made by Tesa tape. Its available from many many sources in Asia, all over, and is cheap from there. I have used the non branded stuff and I would swear its identical to Tesa tape. Its available in perhaps 100 widths, starting at about 1/16" wide.

There is double enamelled wire. There is single enamel with single silk. There is single enamel with double silk. There is double enamel with single silk, etc etc. Some of it can be VERY expensive. Whatever enamelled wire you have will be fine in your situation as the voltage across it will be fairly small. When measuring enamelled copper wire, its normal to remove the enamel and just measure the copper NOT the insulation as well. If you have double enamel its going to measure much thicker than the copper itself. I normally burn it off with a lil gas torch, then using very soft steel wool I remove the residue and then measure. DONT be over fussed about polishing the copper, just remove the residue. Traditionally a micrometer is used to measure copper wire, but a modern digital calipers should be close enough, especially if they are good quality.

There are hundreds of uchoob videos showing transformer winding from the cheapest nastiest build to way over the top audiophoolery supreme eccentric style.

Modern insulation, ( say from last 20 years ) is mostly poly u as well and is called "solderable " enamel. You can burn it off with a hot soldering iron. I have used it mainly because good old fashioned enamel has not been available in guages I needed. There is a very old "black enamel" wire that is a disaster. Its basically shellac ( made from Lac beetles) and you can pick it by scraping the so called enamel off with your fingernail. If you have any, GET rid of it or you will end in disaster.

There is also enamelled Eureka wire which is NOT copper, but resistance wire. Different guages means different resistances!!. BUT with different chemical mixes the same guages can be very different resistances. If you have inherited this wire, it would be a good idea to check before you start.

Keep asking questions You are about 2% into learning about transformers, wires, and laminations. I have been doing it more than 50 years and I am still a rank beginner.

Best of luck

Joe

Keep the questions coming.
OK, thats good to know, ill burn the insulation off this stuff first, I think there wont be much in it anyway.
I know what you mean about the black shellac wire, that stuff was crap!
Ive come across the odd roll of it and it was all cracking.

Yes I know I have a lot to learn and have no idea where to begin for winding my own output transformers for a future project!
Im hoping there is some sort of chart out there with all the data for turns ratios and core sizes for common impedances.
The math for working it out is way over my head!

Power transformer theory is much more simple and there is computer software that calculates it all for you.


I forgot to mention ED, yes your right, the transformer laminations are not interleaved and there was a piece of paper separating the E and I sections.
There were also two strips of brass which is not magnetic that was holding it all together by the bolts on each corner.
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Old 23rd Jun 2021, 8:44 pm   #18
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Default Re: Winding a new output transformer for a Philips B5G64A Radio

Thanks Joe, saved me typing!

Yes the paper gap is important, but not critical, I often use thin tissue paper or 1 layer of yellow tape.
The brass strips are probably not totally necessary in this set

Ed
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Old 23rd Jun 2021, 10:52 pm   #19
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Default Re: Winding a new output transformer for a Philips B5G64A Radio

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Thanks Joe, saved me typing!

Yes the paper gap is important, but not critical, I often use thin tissue paper or 1 layer of yellow tape.
The brass strips are probably not totally necessary in this set

Ed
Well it needs something to hold the "I" sections in place since they are not interleaved and if it was steel, it would defeat the whole puropse im assuming?
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Old 23rd Jun 2021, 11:15 pm   #20
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Default Re: Winding a new output transformer for a Philips B5G64A Radio

Is there not a crimped on steel band around the whole transformer? The I's are normally held in place by that band.

These pictures show one of my transformers. Its a single ended line output transformer so very similar to what you need. The I's are placed into the top of the crimp band, the E's are placed into the band facing upwards. The whole thing is then crimped. When crimping on this band its essential not to grimp with pliers or similar, but a good quality vise with straight and parallel jaws will do the job OK. If you use pliers they will crimp only the edges of the steel band and will not press the whole thing together. That is guaranteed to cause lamination rattle. When doing this crimping dont be tempted to "squeeze the life out of it", just enough pressure to close down the steel band.

Hope this clarifies

Joe
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