GT322B Transistor - UK Vintage Radio Repair and Restoration Discussion Forum

ukcol · 17th Dec 2015, 4:24 pm

The AF11x series of transistors are well known for their tin whisker problem and the suitability of various substitutes has been discussed here.

My preferred substitute has always been the AF12x series but these are in short supply now and expensive.

Some time ago Chris (Herald1360) flagged up the GT322B which is available from a Russian supplier on Ebay and are not expensive. Like the AF11x and AF12x the GT322B is a germanium transistor and it uses the same package as the AF12x series. See the attached picture for the pin layout.

I replaced the three AF117s in a Bush TR130 with GT322Bs. Although the performance of the Bush was not terrible replacing the AF117s transformed it and it was very lively indeed. Fitting the GT322Bs was a fit fiddly because they have much shorter leeds than the original transistor.

I also did a similar transplant job on a Decca 1125 Intercontinental. This is a large high-specification set that employs an AF114, an AF115 and two AF117s in the pre-detector stages. The Decca was very deaf indeed just about picking up a couple of strong local stations. After the work the Decca's performed very well indeed which is what was to be expected given its specification.

Both sets performed well with the GT322Bs in terms of sensitivity, signal to noise ratio and the effectiveness of the AGC. These were all judged subjectively.

BTW if you're interested, the circuit for the Decca 1125 is on Paul Stenning's service data DVD but it is listed under "Intercontinental" and not under "Decca".

turretslug · 17th Dec 2015, 6:23 pm

Does this mean that "GT332B" needs amending to "GT322B" in the following thread title;

https://www.vintage-radio.net/forum/...d.php?t=121020

in order to assist with related AFxxx substitution-type searching?

ukcol · 17th Dec 2015, 6:40 pm

Yes it is quite possible a typo by the O.P. I am not aware of a GT332B. I typed GT332B once whilst writing for this post, so it's easily done.

AC/HL · 17th Dec 2015, 6:48 pm

It probably does, although there is an unanswered offer in the thread.

60 oldjohn · 17th Dec 2015, 6:55 pm

OP in post above quotes GT322B in first title then changes to GT332B the rest of the posts! HOW.

John.

AC/HL · 17th Dec 2015, 9:09 pm

I have corrected the title on advice, although it's a bit late now. It was 332 originally.

John_BS · 20th Dec 2015, 9:25 pm

I bought a batch of these Russian transistors some time ago, then made a test-jig to compare them to several alternatives at 10.7MHz.

They are very similar in performance to the AF117.

John

17th Dec 2015, 4:24 pm	#1
ukcol Rest in Peace Join Date: May 2003 Location: Harlaxton, Lincolnshire, UK. Posts: 3,944	GT322B Transistor The AF11x series of transistors are well known for their tin whisker problem and the suitability of various substitutes has been discussed here. My preferred substitute has always been the AF12x series but these are in short supply now and expensive. Some time ago Chris (Herald1360) flagged up the GT322B which is available from a Russian supplier on Ebay and are not expensive. Like the AF11x and AF12x the GT322B is a germanium transistor and it uses the same package as the AF12x series. See the attached picture for the pin layout. I replaced the three AF117s in a Bush TR130 with GT322Bs. Although the performance of the Bush was not terrible replacing the AF117s transformed it and it was very lively indeed. Fitting the GT322Bs was a fit fiddly because they have much shorter leeds than the original transistor. I also did a similar transplant job on a Decca 1125 Intercontinental. This is a large high-specification set that employs an AF114, an AF115 and two AF117s in the pre-detector stages. The Decca was very deaf indeed just about picking up a couple of strong local stations. After the work the Decca's performed very well indeed which is what was to be expected given its specification. Both sets performed well with the GT322Bs in terms of sensitivity, signal to noise ratio and the effectiveness of the AGC. These were all judged subjectively. BTW if you're interested, the circuit for the Decca 1125 is on Paul Stenning's service data DVD but it is listed under "Intercontinental" and not under "Decca". Attached Thumbnails

17th Dec 2015, 6:23 pm	#2
turretslug Dekatron Join Date: Nov 2011 Location: Surrey, UK. Posts: 4,400	Re: GT322B Transistor Does this mean that "GT332B" needs amending to "GT322B" in the following thread title; https://www.vintage-radio.net/forum/...d.php?t=121020 in order to assist with related AFxxx substitution-type searching?

17th Dec 2015, 6:40 pm	#3
ukcol Rest in Peace Join Date: May 2003 Location: Harlaxton, Lincolnshire, UK. Posts: 3,944	Re: GT322B Transistor Yes it is quite possible a typo by the O.P. I am not aware of a GT332B. I typed GT332B once whilst writing for this post, so it's easily done.

17th Dec 2015, 6:48 pm	#4
AC/HL Dekatron Join Date: Nov 2003 Location: Heckmondwike, West Yorkshire, UK. Posts: 9,642	Re: GT322B Transistor It probably does, although there is an unanswered offer in the thread.

17th Dec 2015, 6:55 pm	#5
60 oldjohn Dekatron Join Date: Dec 2004 Location: East Yorkshire, UK. Posts: 3,988	Re: GT322B Transistor OP in post above quotes GT322B in first title then changes to GT332B the rest of the posts! HOW. John.

17th Dec 2015, 9:09 pm	#6
AC/HL Dekatron Join Date: Nov 2003 Location: Heckmondwike, West Yorkshire, UK. Posts: 9,642	Re: GT322B Transistor I have corrected the title on advice, although it's a bit late now. It was 332 originally.