Stuck IFT cores - UK Vintage Radio Repair and Restoration Discussion Forum

Tractionist · 20th Oct 2023, 11:42 am

Hi All -

I'm currently looking at a pair of Perdio 'Piccadilly' trannies - both of which seem to be pretty deaf. (I've been all the way through one and re-capped it etc.). The 'final touch' was going to be an alignment check but ....... the Toko style IFT cores [they aren't Toko by the way] in both sets seem to be pretty much 'stuck' - complete with perished rubber locking threads pretty much disintegrated too (but doubtless still inside the core tube etc.).

So ..... my question is: what is your favoured method of freeing-off these cores without causing unnecessary damage?.

G6Tanuki · 20th Oct 2023, 5:08 pm

When you say "Toko style" IFTs, do you mean the small quare stamped-brass cans with a hole in the top through which you can access a broad slot in the upper part of the ferrite pot-core?

Usually with different colours on the cores [red, yellow, green] to distinguish the function?

Have never seen these with rubber locking filaments, the adjustable locking was in my experience done with wax.

Perhaps you could try gentle heat?

radiomobile · 20th Oct 2023, 5:16 pm

I have never encountered Toko IF transformers with locking threads. The type in the Perdio Piccadilly look more like Weyrad design in which case be very careful not to crack the cores which will be very difficult to fix.
Assuming the core is not cracked the best approach I have found is first to apply heat, as much as you dare without causing collateral damage, then a couple of drops of white spirit and leave for a few hours in a warm place. A proper trim tool which fits accurately is a must. If they are the Weyrad design they sometimes have very small polystyrene caps inside the can which have been known to fail.
If the radios are very deaf it is unlikely that core adjustment is the only cause.

buggies · 21st Oct 2023, 7:24 pm

The transformers were made "in house". I think that in the PR7 they were only accessible from the top as the pcb covered the bottom. The slots go the length of the cores and require the correct (copper) tool. They are very fragile and virtually impossible to remove without damage once cracked.
I suggest that it might be wise to assume that they have not been tweaked by the phantom and are aligned exactly as they left the factory.

newlite4 · 21st Oct 2023, 9:16 pm

Dribbling a little bit of lighter fluid (naptha) into the threaded core generally works for me. It is enough to free off any stubborn wax and other forms of stiction and it dries off quickly with no residue.
Neil

FrankB · 7th Nov 2023, 9:23 am

I have had good luck heating a metal rod of the correct size and applying it to the core.
On the hex core types, I use a sacrificial metal hex wrench heated dull red inserted in the hole maybe 5 seconds, then use a correct size plastic or wooden adj tool.
I have also used a heat gun with the correct size tip as well as my new hot air desoldering station with the correct size tip. That takes a bit of practice though.

(Of course, if I screw up and break the core, I have a drawer full of cores I saved over the years from scrapped radios & TV sets as replacements. It seems to be perfectly fine to grind down a too long replacement core to the correct size also. At least I never had a problem with this).

20th Oct 2023, 11:42 am	#1
Tractionist Heptode Join Date: Apr 2016 Location: Cheltenham, Gloucestershire, UK. Posts: 853	Stuck IFT cores Hi All - I'm currently looking at a pair of Perdio 'Piccadilly' trannies - both of which seem to be pretty deaf. (I've been all the way through one and re-capped it etc.). The 'final touch' was going to be an alignment check but ....... the Toko style IFT cores [they aren't Toko by the way] in both sets seem to be pretty much 'stuck' - complete with perished rubber locking threads pretty much disintegrated too (but doubtless still inside the core tube etc.). So ..... my question is: what is your favoured method of freeing-off these cores without causing unnecessary damage?. __________________ Red to red, black to black. Throw the switch and stand well back!

20th Oct 2023, 5:08 pm	#2
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,433	Re: Stuck IFT cores When you say "Toko style" IFTs, do you mean the small quare stamped-brass cans with a hole in the top through which you can access a broad slot in the upper part of the ferrite pot-core? Usually with different colours on the cores [red, yellow, green] to distinguish the function? Have never seen these with rubber locking filaments, the adjustable locking was in my experience done with wax. Perhaps you could try gentle heat? __________________ TURN IT UP! [I can't hear the Guitar] - TMBG. Last edited by G6Tanuki; 20th Oct 2023 at 5:24 pm.

20th Oct 2023, 5:16 pm	#3
radiomobile Pentode Join Date: Nov 2020 Location: Bristol, UK. Posts: 107	Re: Stuck IFT cores I have never encountered Toko IF transformers with locking threads. The type in the Perdio Piccadilly look more like Weyrad design in which case be very careful not to crack the cores which will be very difficult to fix. Assuming the core is not cracked the best approach I have found is first to apply heat, as much as you dare without causing collateral damage, then a couple of drops of white spirit and leave for a few hours in a warm place. A proper trim tool which fits accurately is a must. If they are the Weyrad design they sometimes have very small polystyrene caps inside the can which have been known to fail. If the radios are very deaf it is unlikely that core adjustment is the only cause.

21st Oct 2023, 7:24 pm	#4
buggies Heptode Join Date: Jan 2009 Location: West Lothian, UK. Posts: 751	Re: Stuck IFT cores The transformers were made "in house". I think that in the PR7 they were only accessible from the top as the pcb covered the bottom. The slots go the length of the cores and require the correct (copper) tool. They are very fragile and virtually impossible to remove without damage once cracked. I suggest that it might be wise to assume that they have not been tweaked by the phantom and are aligned exactly as they left the factory. __________________ George

21st Oct 2023, 9:16 pm	#5
newlite4 Octode Join Date: Nov 2003 Location: Bath, Somerset, UK. Posts: 1,772	Re: Stuck IFT cores Dribbling a little bit of lighter fluid (naptha) into the threaded core generally works for me. It is enough to free off any stubborn wax and other forms of stiction and it dries off quickly with no residue. Neil __________________ preserving the recent past, for the distant future.

7th Nov 2023, 9:23 am	#6
FrankB Heptode Join Date: Oct 2005 Location: Olympia, Washington, USA. Posts: 653	Re: Stuck IFT cores I have had good luck heating a metal rod of the correct size and applying it to the core. On the hex core types, I use a sacrificial metal hex wrench heated dull red inserted in the hole maybe 5 seconds, then use a correct size plastic or wooden adj tool. I have also used a heat gun with the correct size tip as well as my new hot air desoldering station with the correct size tip. That takes a bit of practice though. (Of course, if I screw up and break the core, I have a drawer full of cores I saved over the years from scrapped radios & TV sets as replacements. It seems to be perfectly fine to grind down a too long replacement core to the correct size also. At least I never had a problem with this).