UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Memories and other stories from Pye etc PMR engineers.

Jon_G4MDC · 16th Sep 2017, 10:28 am

Neosid F29 ferrite. Weller TCP Soldering Iron magnets could kill them. Generally only used in the VHF tuned ccts I think.
The cores in low freq coils in mutlipliers etc were not the same stuff and was why it never worked to pinch those from scrap boards as replacements.
A DC spike in the winding caused by accidentally grounding the collector/drain end could kill them too.

First time I have heard the magmount story - nice one.

Just found this - didn't know about shock, don't drop them on the floor!

Note: Perminvar ferrites undergo irreversible
changes of characteristics if subject to strong
magnetic fields or mechanical shock.

16th Sep 2017, 10:28 am	#49
Jon_G4MDC Nonode Join Date: Nov 2015 Location: Welwyn Garden City, Hertfordshire, UK. Posts: 2,015	Re: Memories and other stories from Pye etc PMR engineers. Neosid F29 ferrite. Weller TCP Soldering Iron magnets could kill them. Generally only used in the VHF tuned ccts I think. The cores in low freq coils in mutlipliers etc were not the same stuff and was why it never worked to pinch those from scrap boards as replacements. A DC spike in the winding caused by accidentally grounding the collector/drain end could kill them too. First time I have heard the magmount story - nice one. Just found this - didn't know about shock, don't drop them on the floor! Note: Perminvar ferrites undergo irreversible changes of characteristics if subject to strong magnetic fields or mechanical shock. Last edited by Jon_G4MDC; 16th Sep 2017 at 10:39 am.