AF11x transistors

[ppppenguin]

Many members will be familiar with AF114/5/6/7 transistors. Especially with their notorious tin whisker problems.

According to to my 1968 Mullard Data Book AF114/5/6/7 all have near enough identical specs though the 116 and 117 have slightly higher capacitances. I think they were all selected from the same production line. Does anyone know the basis of the selection?

AF114: RF amp in AM/FM receivers
AF115: Mixer/oscillator in AM/FM receivers
AF116: IF amp in FM receivers
AF117: IF amp in AM receivers

fT is 75MHz for all of them.

AF118 looks similar but is a totally different beast. It was an early video output transistor with impressive specs for a Ge device.
VCBO: 75V
Ic: 30mA
Ptot: 250mW
fT: 175MHz

I've not had to replace an AF118 but you'd need to choose with care. Later video output devices were all NPN. You might get away with a BC547. Only 60V rated but many will work at rather higher voltages.

[Mark Hennessy]

I've said pretty much all of that in my vintage transistor article, and yes, I also suspect that they were labelled upon test. Someone on UKVRRR said he'd be surprised if they were actually tested, and were labelled according to order books. In practice, both might have been true. It's the case for CPUs today, after all, else over-clocking wouldn't work

Hopefully Pat Pending will have some insider-information...

[ppppenguin]

The AF118 is a real oddity. I don't think much has been written about it. Possibly because it wasn't that widely used.

Make, test, sort into bins has been done for many parts. Carbon composition resistors were routinely done this way, hence the nice (almost) geometric series of preferred values. Hands up those who have use 2N2926 transistors. With about 5 different hFe ranges. ISTR green sport were the higheset gain, followed by yellow. Did anyone actually use the lowest grades? Or BC108A/B/C. Or the horrendous variability of 2N3819 FETs which weren't selected and binned. Or BF245A/B/C FETs which were and hence much easier to work with.

It's quite possible that BC107 was simply BC108 selected for high VCBO. And BC109 simply BC108 selected for low noise.

Then there's the 2N3055 where you've really no idea what's inside. The original spec was so wide you could put almost any reject power transistor die in the package and theoretically meet spec. Except the ones with high fT would sing like canaries in some circuits.

[Pat Pending]

"Hopefully Pat Pending will have some insider-information"

I'll make a note of the question and ask when I do the interview thing. Don't want to spoil the friendship or get a restraining order! There may be a good article in it, and the chap graciously agreed to do it  

All of Jeffreys comments are spot-on. General purpose small signal transistors should use the
Old ETI. Magazine method. TUP and TUN it would be more honest

Oh, and a Healthy, Happy and Prosperous new year to everyone. Regards. Andy.

[Terry]

 General purpose small signal transistors should use the Old ETI. Magazine method. TUP and TUN it would be more honest

I never read ETI so can't comment on whether they used this terminology or not but I remember it from the early issues of Elektor ...

For the benefit of anyone who hasn't encountered these terms before, they stand for Transistor, Universal, PNP (or NPN)

See www.sentex.ca/~mec1995/circ/tuptun/tuptun.htm  for more.

[Pat Pending]

 General purpose small signal transistors should use the Old ETI. Magazine method. TUP and TUN it would be more honest

I never read ETI so can't comment on whether they used this terminology or not but I remember it from the early issues of Elektor ...

For the benefit of anyone who hasn't encountered these terms before, they stand for Transistor, Universal, PNP (or NPN)

See www.sentex.ca/~mec1995/circ/tuptun/tuptun.htm  for more.

Quite correct terry, I can't even blame that one on a typo. 
Must engage brain before using keyboard. Regards. Andy.

[ppppenguin]

I've not had to replace an AF118 but you'd need to choose with care. Later video output devices were all NPN. You might get away with a BC547. Only 60V rated but many will work at rather higher voltages.

Re-reading an old thread. Surprised nobldy picked me up on the silly error. Should have said BC557 which is PNP, not BC547 which is NPN.

ZTX752 looks possible for AF118 replacement though the Mouser catalogue says it's obsolete: http://www.mouser.co.uk/ProductDetail/Di...9PeA%3d%3d

How on earth did they manage 2A collector current rating in an E-line package.

[Murphyv310]

Hi.
Funny thing is I have a Perdio Portarama and have had a couple to fix through the years and not one has had tin whisker troubles! I've had many transistor radio's of the same or similar age with countless tin whisker troubles, very odd!
The AF118 is a remarkable little transistor and a good Portarama gives a very good picture indeed, I'd rate it ahead of the Sony 9-90 especially on sensitivity!

[Herald1360]

How on earth did they manage 2A collector current rating in an E-line package.

Low VceSAT?

[AlanBeckett]

And very briefly.

Ala