AEI Gt41 Transistors - UK Vintage Radio Repair and Restoration Discussion Forum

jim_jobe · 12th Oct 2012, 10:40 am

Just to inform Vintage Transistor enthusiasts that Birketts in Lincoln have unearthed some boxes of 100 AEI Germanium GT41 transistors which they are selling at £15 for a sealed box of 100. I doubt if these will ever be available like this again.
Jim

Herald1360 · 12th Oct 2012, 12:34 pm

Are they any good for those "Fuzz" devices that seem to demand silly money for OC44/45 series transistors?

Maybe Birkett missed an opportunity here

peter_sol · 12th Oct 2012, 2:19 pm

They are equivalent to OC44N

Refugee · 12th Oct 2012, 4:41 pm

They have a lower Hfe than OC44N by quite a bit.

jim_jobe · 14th Oct 2012, 10:18 am

I've ordered some, so I'll let you know how thet test out; hFE is supposed to be about 30 and fT 4MHz. They were originally sold as IF amps and switching transistors.
Jim

jim_jobe · 16th Oct 2012, 10:56 am

The GT41Bs arrived this morning. They are packed in five layers of 20 (see photo) and I've tested the top layer for hFE using a DMM. Out of the twenty, one has a gain of 4, one of 74 and one of 102. One is a dud with very high leakage from C to E but all the others have gains between 30 and 54. I haven't time today but I'll check their fTs in a day or so. I reckon they're a bargain at 15p each!
Jim
(PS: I have no connection with Birkett's!).

jim_jobe · 17th Oct 2012, 5:13 pm

I've tried checking fT by connecting the transistors in common base and putting in an input from my sig gen and feeding the output to a CRO but this wasn't very successful (I;ve mentioned this before!).

paulsherwin · 17th Oct 2012, 5:21 pm

My Towers gives an fT of 2M so they will probably be OK as OC44 replacements, though the gain is indeed a bit low. Individual transistors may be better if you can hand select of course.

Be careful with voltage though - the Vce is only 9V

jim_jobe · 17th Oct 2012, 8:34 pm

Cheers Paul,
The gain in common base fell by 3db at about 3MHz but it did the same when I substituted an OC44 and an ASZ21 (!) so I think there was something wrong with my methodology somehow! I just used a very simple setup using common base set up for Ic of 1mA and connecting my CRO across the collector load. The input was from my Heathkit Sig. Gen.
Interestingly the "dud" (Icbo=0.5mA) worked just as well as also did the one with hFE of 4.

12th Oct 2012, 10:40 am	#1
jim_jobe Heptode Join Date: Nov 2004 Location: Ripon, N.Yorkshire, UK. Posts: 782	AEI Gt41 Transistors Just to inform Vintage Transistor enthusiasts that Birketts in Lincoln have unearthed some boxes of 100 AEI Germanium GT41 transistors which they are selling at £15 for a sealed box of 100. I doubt if these will ever be available like this again. Jim

12th Oct 2012, 12:34 pm	#2
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,536	Re: AEI Gt41 Transistors Are they any good for those "Fuzz" devices that seem to demand silly money for OC44/45 series transistors? Maybe Birkett missed an opportunity here __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

12th Oct 2012, 2:19 pm	#3
peter_sol Octode Join Date: Aug 2003 Location: Welwyn Garden City, Herts. UK. Posts: 1,906	Re: AEI Gt41 Transistors They are equivalent to OC44N

12th Oct 2012, 4:41 pm	#4
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,554	Re: AEI Gt41 Transistors They have a lower Hfe than OC44N by quite a bit.

14th Oct 2012, 10:18 am	#5
jim_jobe Heptode Join Date: Nov 2004 Location: Ripon, N.Yorkshire, UK. Posts: 782	Re: AEI Gt41 Transistors I've ordered some, so I'll let you know how thet test out; hFE is supposed to be about 30 and fT 4MHz. They were originally sold as IF amps and switching transistors. Jim

16th Oct 2012, 10:56 am	#6
jim_jobe Heptode Join Date: Nov 2004 Location: Ripon, N.Yorkshire, UK. Posts: 782	Re: AEI Gt41 Transistors The GT41Bs arrived this morning. They are packed in five layers of 20 (see photo) and I've tested the top layer for hFE using a DMM. Out of the twenty, one has a gain of 4, one of 74 and one of 102. One is a dud with very high leakage from C to E but all the others have gains between 30 and 54. I haven't time today but I'll check their fTs in a day or so. I reckon they're a bargain at 15p each! Jim (PS: I have no connection with Birkett's!). Attached Thumbnails

17th Oct 2012, 5:13 pm	#7
jim_jobe Heptode Join Date: Nov 2004 Location: Ripon, N.Yorkshire, UK. Posts: 782	Re: AEI Gt41 Transistors I've tried checking fT by connecting the transistors in common base and putting in an input from my sig gen and feeding the output to a CRO but this wasn't very successful (I;ve mentioned this before!).

17th Oct 2012, 5:21 pm	#8
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,970	Re: AEI Gt41 Transistors My Towers gives an fT of 2M so they will probably be OK as OC44 replacements, though the gain is indeed a bit low. Individual transistors may be better if you can hand select of course. Be careful with voltage though - the Vce is only 9V

17th Oct 2012, 8:34 pm	#9
jim_jobe Heptode Join Date: Nov 2004 Location: Ripon, N.Yorkshire, UK. Posts: 782	Re: AEI Gt41 Transistors Cheers Paul, The gain in common base fell by 3db at about 3MHz but it did the same when I substituted an OC44 and an ASZ21 (!) so I think there was something wrong with my methodology somehow! I just used a very simple setup using common base set up for Ic of 1mA and connecting my CRO across the collector load. The input was from my Heathkit Sig. Gen. Interestingly the "dud" (Icbo=0.5mA) worked just as well as also did the one with hFE of 4.