AF 121 Replacement? - UK Vintage Radio Repair and Restoration Discussion Forum

TimothyStuart · 15th Dec 2021, 2:23 pm

I am new to the forum and wonder if somebody can advise on the best replacement for an AF 121 transistor. Looking at my 1st edition of Towers I cannot see an obvious match. Thanks for the help.

paulsherwin · 15th Dec 2021, 2:44 pm

It's a VHF transistor - my Towers suggests an AF239 as a replacement. Other HF types may also work, even silicon, depending on the circuit.

Why do you want to replace the AF121 though?

HamishBoxer · 15th Dec 2021, 2:48 pm

Af127 ?

paulsherwin · 15th Dec 2021, 3:05 pm

The AF124-7 series have a significantly lower Ft. This may or may not matter, depending on the circuit.

Cruisin Marine · 15th Dec 2021, 7:21 pm

These appear to be equivalents
AF102, AF106, 2N2495, 2N3588, AF178, AF200U

paulsherwin · 15th Dec 2021, 9:16 pm

Don't use an AF102 or AF106. They have the dreaded tin whisker problems.

TimothyStuart · 17th Dec 2021, 9:48 am

Thank you everyone. The reason for the replacement is a lack of FM signal and the AF121 has tested bad. There are 2 other trs in the IF stage that are also suspect but these are AF116s. Thank you for the replacement suggestions.

15th Dec 2021, 2:23 pm	#1
TimothyStuart Triode Join Date: Jan 2021 Location: Hove, East Sussex, UK. Posts: 20	AF 121 Replacement? I am new to the forum and wonder if somebody can advise on the best replacement for an AF 121 transistor. Looking at my 1st edition of Towers I cannot see an obvious match. Thanks for the help.

15th Dec 2021, 2:44 pm	#2
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,966	Re: AF 121 Replacement? It's a VHF transistor - my Towers suggests an AF239 as a replacement. Other HF types may also work, even silicon, depending on the circuit. Why do you want to replace the AF121 though?

15th Dec 2021, 2:48 pm	#3
HamishBoxer Dekatron Join Date: Aug 2007 Location: W.Butterwick, near Doncaster UK. Posts: 8,935	Re: AF 121 Replacement? Af127 ? __________________ G8JET BVWS Archivist and Member V.M.A.R.S

15th Dec 2021, 3:05 pm	#4
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,966	Re: AF 121 Replacement? The AF124-7 series have a significantly lower Ft. This may or may not matter, depending on the circuit.

15th Dec 2021, 7:21 pm	#5
Cruisin Marine Octode Join Date: Jul 2018 Location: Worthing, West Sussex, UK. Posts: 1,002	Re: AF 121 Replacement? These appear to be equivalents AF102, AF106, 2N2495, 2N3588, AF178, AF200U

15th Dec 2021, 9:16 pm	#6
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,966	Re: AF 121 Replacement? Don't use an AF102 or AF106. They have the dreaded tin whisker problems.

17th Dec 2021, 9:48 am	#7
TimothyStuart Triode Join Date: Jan 2021 Location: Hove, East Sussex, UK. Posts: 20	Re: AF 121 Replacement? Thank you everyone. The reason for the replacement is a lack of FM signal and the AF121 has tested bad. There are 2 other trs in the IF stage that are also suspect but these are AF116s. Thank you for the replacement suggestions.