Dansette Gem output transistors? - UK Vintage Radio Repair and Restoration Discussion Forum

Stylo N M · 2nd Nov 2016, 2:32 pm

Hi,

well all this talking about these dansette radio's, and the fact that i have managed to more or less get my red one working again, i thought i would have a look at my other one (that i had actually forgot about) and in any case i didn't want to rob that of parts just to get the other one working.
Now it is clean and in good order, except one of the output transistors is dead and the other one has a broken lead, now i have read the sticky thread on transistors, and i know i have some AC128 transistors that are good but i've got to dig them out, so can i replace the original 0C81 with two AC128 will this be ok and will it work?
thank you,

paul.

paulsherwin · 2nd Nov 2016, 2:34 pm

Should be fine.

60 oldjohn · 2nd Nov 2016, 3:02 pm

Check them first for tin whiskers shorting to case if used on a common heatsink.

John.

Stylo N M · 2nd Nov 2016, 3:21 pm

Hi,

thank you paul, just wanted to be certain, thanks john yes i saw somethng about that in the sticky, umm i sure the transistors i have are all new stock but i will certainly keep it in mind

Thank you,

paul.

DangerMan · 2nd Nov 2016, 4:02 pm

Unfortunately, new (old) stock is no guarantee that they will be free from tin whiskers so it's worth checking first to avoid disappointment... just the same as for AF117 etc..

Pete

60 oldjohn · 2nd Nov 2016, 6:06 pm

Yes Pete, when I checked my stock NOS of AC127s around half were affected by tin whiskers.

John.

Stylo N M · 2nd Nov 2016, 6:28 pm

Oo-er, I didn''t think that the tin whisker problem was that exstensive in the ACXXX ranges, I thought it was more those AF117 types

Paul.

60 oldjohn · 3rd Nov 2016, 10:45 am

Unfortunately not, even potentiometers can be affected in rare cases, there are photos on this forum.

John.

paulsherwin · 3rd Nov 2016, 11:43 am

The wider whisker problem with ACxxx transistors has only emerged in the last few years. I now test for shorts as well as general functionality before using any metal cased Ge transistor. I may experiment with Si replacement next time I have a radio with a failed AC128, as this issue will only get worse with time.

2nd Nov 2016, 2:32 pm	#1
Stylo N M Heptode Join Date: Jul 2012 Location: Derby DE1, Derbyshire, UK. Posts: 626	Dansette Gem output transistors? Hi, well all this talking about these dansette radio's, and the fact that i have managed to more or less get my red one working again, i thought i would have a look at my other one (that i had actually forgot about) and in any case i didn't want to rob that of parts just to get the other one working. Now it is clean and in good order, except one of the output transistors is dead and the other one has a broken lead, now i have read the sticky thread on transistors, and i know i have some AC128 transistors that are good but i've got to dig them out, so can i replace the original 0C81 with two AC128 will this be ok and will it work? thank you, paul.

2nd Nov 2016, 2:34 pm	#2
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,966	Re: Dansette Gem output transistors? Should be fine.

2nd Nov 2016, 3:02 pm	#3
60 oldjohn Dekatron Join Date: Dec 2004 Location: East Yorkshire, UK. Posts: 3,988	Re: Dansette Gem output transistors? Check them first for tin whiskers shorting to case if used on a common heatsink. John.

2nd Nov 2016, 3:21 pm	#4
Stylo N M Heptode Join Date: Jul 2012 Location: Derby DE1, Derbyshire, UK. Posts: 626	Re: Dansette Gem output transistors? Hi, thank you paul, just wanted to be certain, thanks john yes i saw somethng about that in the sticky, umm i sure the transistors i have are all new stock but i will certainly keep it in mind Thank you, paul.

2nd Nov 2016, 4:02 pm	#5
DangerMan Heptode Join Date: Jul 2009 Location: Stoke-on-Trent, Staffordshire, UK. Posts: 719	Re: Dansette Gem output transistors? Unfortunately, new (old) stock is no guarantee that they will be free from tin whiskers so it's worth checking first to avoid disappointment... just the same as for AF117 etc.. Pete

2nd Nov 2016, 6:06 pm	#6
60 oldjohn Dekatron Join Date: Dec 2004 Location: East Yorkshire, UK. Posts: 3,988	Re: Dansette Gem output transistors? Yes Pete, when I checked my stock NOS of AC127s around half were affected by tin whiskers. John. Last edited by 60 oldjohn; 2nd Nov 2016 at 6:12 pm.

2nd Nov 2016, 6:28 pm	#7
Stylo N M Heptode Join Date: Jul 2012 Location: Derby DE1, Derbyshire, UK. Posts: 626	Re: Dansette Gem output transistors? Oo-er, I didn''t think that the tin whisker problem was that exstensive in the ACXXX ranges, I thought it was more those AF117 types Paul.

3rd Nov 2016, 10:45 am	#8
60 oldjohn Dekatron Join Date: Dec 2004 Location: East Yorkshire, UK. Posts: 3,988	Re: Dansette Gem output transistors? Unfortunately not, even potentiometers can be affected in rare cases, there are photos on this forum. John.

3rd Nov 2016, 11:43 am	#9
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,966	Re: Dansette Gem output transistors? The wider whisker problem with ACxxx transistors has only emerged in the last few years. I now test for shorts as well as general functionality before using any metal cased Ge transistor. I may experiment with Si replacement next time I have a radio with a failed AC128, as this issue will only get worse with time.