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Heatercathodeshort · 20th Jan 2018, 11:22 am

Philips certainly did supply later type diode split transformers not all of which were robust.
Toshiba used them in their portable range from 1989 and I replaced large numbers supplied free from Toshiba even when out of guarantee.

Mullard certainly supplied Ferroxcube cores to most makers together with scan coil core assemblies in pairs, in fact just about every transformer lamination employed in high frequency television receivers was superseded by Ferroxcube by the mid 60's. 'Iron' was still in used in mains/sound/frame output transformers probably due to the low frequency and high currents associated with these circuit requirements.

The cores were supplied from Mullard in boxes each core separated by a cardboard rectangle to prevent chipping and damage. There were many differing shapes but the majority of the LOPT cores looked identical but had very different characteristics.
Using the wrong core would result in all sorts of weird effects. The FX number was stamped on the long arm of the 'U'.
All this takes me back 57 years when I used to make EKCO transformers from scratch.

Cut newly fabricated Paxolin sides and top from large sheets with a lethal band saw.
Rivet the 4BA studs and anti corona cups to hold it all together.
Layer wind the underwind [primary]each layer interleaved with special tissue. [on the Ekco a separate winding]
Wave wind the overwind,[EHT] both windings on Paxolin bobbins.
Vacuum impregnate windings.
Form a [TYRE] around perimeter of overwind to seal off and prevent flash over.

This was simply done by employing an old style OXO tin with a couple of slots cut in the sides. This was filled with pitch and heated from below by a small gas flame to a depth that was just enough to allow the overwind to just dip into the pitch with the dowel resting on the slots. The overwind was taped to a short length of dowel and 'spun' in the bath forming a neat tyre around an 1/8th of an inch in depth.

Assemble Ferroxcube cores and windings not forgetting the gaping papers.
Fit assembly into Paxolin case using threaded rod to hold it all together.
Solder lead out wires to anti corona cups.
Fit Paxolin top and secure with 4BA nuts.
Loop two turns of EHT cable around underwind to supply EHT rectifier U25 heater [2V]
Picture test in Ekco television chassis. [Long leads and crocodile clips]
Finally dip top in hot pitch to help prevent tracking under very damp conditions.
There was of course many other steps in manufacture, mostly minor mechanical such as attaching a more substantial lead from the high end of the very thin overwind to the anode cup of the EHT rectifier. A bit fiddly but you soon got the knack of it!

I know one forum member that has a TMB272 with one of my transformers still working well!

Happy days. John.

20th Jan 2018, 11:22 am	#19
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Dismantling LOPT's Philips certainly did supply later type diode split transformers not all of which were robust. Toshiba used them in their portable range from 1989 and I replaced large numbers supplied free from Toshiba even when out of guarantee. Mullard certainly supplied Ferroxcube cores to most makers together with scan coil core assemblies in pairs, in fact just about every transformer lamination employed in high frequency television receivers was superseded by Ferroxcube by the mid 60's. 'Iron' was still in used in mains/sound/frame output transformers probably due to the low frequency and high currents associated with these circuit requirements. The cores were supplied from Mullard in boxes each core separated by a cardboard rectangle to prevent chipping and damage. There were many differing shapes but the majority of the LOPT cores looked identical but had very different characteristics. Using the wrong core would result in all sorts of weird effects. The FX number was stamped on the long arm of the 'U'. All this takes me back 57 years when I used to make EKCO transformers from scratch. Cut newly fabricated Paxolin sides and top from large sheets with a lethal band saw. Rivet the 4BA studs and anti corona cups to hold it all together. Layer wind the underwind [primary]each layer interleaved with special tissue. [on the Ekco a separate winding] Wave wind the overwind,[EHT] both windings on Paxolin bobbins. Vacuum impregnate windings. Form a [TYRE] around perimeter of overwind to seal off and prevent flash over. This was simply done by employing an old style OXO tin with a couple of slots cut in the sides. This was filled with pitch and heated from below by a small gas flame to a depth that was just enough to allow the overwind to just dip into the pitch with the dowel resting on the slots. The overwind was taped to a short length of dowel and 'spun' in the bath forming a neat tyre around an 1/8th of an inch in depth. Assemble Ferroxcube cores and windings not forgetting the gaping papers. Fit assembly into Paxolin case using threaded rod to hold it all together. Solder lead out wires to anti corona cups. Fit Paxolin top and secure with 4BA nuts. Loop two turns of EHT cable around underwind to supply EHT rectifier U25 heater [2V] Picture test in Ekco television chassis. [Long leads and crocodile clips] Finally dip top in hot pitch to help prevent tracking under very damp conditions. There was of course many other steps in manufacture, mostly minor mechanical such as attaching a more substantial lead from the high end of the very thin overwind to the anode cup of the EHT rectifier. A bit fiddly but you soon got the knack of it! I know one forum member that has a TMB272 with one of my transformers still working well! Happy days. John.