AF11x trannies - UK Vintage Radio Repair and Restoration Discussion Forum

val33vo · 14th Jun 2018, 6:05 pm

Wonder why they had a screen ? they are definately a fault waiting to happen re internal whisker growth , I also suspect they made a small fortune for radio repair shops back in the days when radios were actually sent for repair rather than thrown in the bin

Nuvistor · 14th Jun 2018, 6:13 pm

We didn’t make that much money repairing them, had to keep repair costs as low as possible or even then they would have been scrapped, but yes I did repair quite a few.

Has for the screening, some were designed for use at VHF, probably as cheap to keep the whole line the same encapsulation. It’s also possible that they were graded when they came off production line for use at different frequencies so the encapsulation would need to be the same.

AC/HL · 14th Jun 2018, 8:12 pm

Hindsight's a wonderful thing. Had they known about whiskering (or for that matter synthetic rubber formulation ageing) in advance...

Graham G3ZVT · 15th Jun 2018, 1:28 pm

Received wisdom for most of us, is that these new-fangled solid-state devices would last indefinitely, and that has, by and large, proved to be so.

Even if you don't earth the "screen" wire, and leave the metal can floating, the whiskers can still take their toll by growing out from the can to two parts of the crystal, or their internal connections.

14th Jun 2018, 6:05 pm	#1
val33vo Retired Dormant Member Join Date: Apr 2008 Location: Banffshire, Scotland, UK. Posts: 191	AF11x trannies Wonder why they had a screen ? they are definately a fault waiting to happen re internal whisker growth , I also suspect they made a small fortune for radio repair shops back in the days when radios were actually sent for repair rather than thrown in the bin

14th Jun 2018, 6:13 pm	#2
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,431	Re: AF11x trannies We didn’t make that much money repairing them, had to keep repair costs as low as possible or even then they would have been scrapped, but yes I did repair quite a few. Has for the screening, some were designed for use at VHF, probably as cheap to keep the whole line the same encapsulation. It’s also possible that they were graded when they came off production line for use at different frequencies so the encapsulation would need to be the same. __________________ Frank

14th Jun 2018, 8:12 pm	#3
AC/HL Dekatron Join Date: Nov 2003 Location: Heckmondwike, West Yorkshire, UK. Posts: 9,642	Re: AF11x trannies Hindsight's a wonderful thing. Had they known about whiskering (or for that matter synthetic rubber formulation ageing) in advance...

15th Jun 2018, 1:28 pm	#4
Graham G3ZVT Dekatron Join Date: May 2010 Location: Greater Manchester, UK. Posts: 18,711	Re: AF11x trannies Received wisdom for most of us, is that these new-fangled solid-state devices would last indefinitely, and that has, by and large, proved to be so. Even if you don't earth the "screen" wire, and leave the metal can floating, the whiskers can still take their toll by growing out from the can to two parts of the crystal, or their internal connections. __________________ -- Graham. G3ZVT