AF117 is there a definitive answer! - UK Vintage Radio Repair and Restoration Discussion Forum

markhardy · 26th Sep 2010, 4:37 pm

Just about to start a major restore on another old sailor, sorry that should be Sailor (the lower case S could easily be mis-interpreted!)

It's very rough and has been battered about a fair bit, and the cracked glass could be the big stumbling block, bad news is its full of AF117's. Interestingly I've got several early sailors, oops I mean Sailors!, all late 50's early 60's, all with AF 117's and all are still going great, wonder if the marine environment somehow inhibits whiskering a bit?

It did crackle into life for a very short while, prior to smoke billowing out of a resistor!

Not bothered particularly about totally authenticity, as long as it works as well as it was intended.

So is there a definitive replacement to the AF117, or a near as damn it shove it in and it'll perform virtually the same?

There's 4 AF117's, 1 AF101, a couple of OC604 and a couple of AC106 doing the audio bit. having looked at the schematic I suspect the AF101 is kerputt as well

Have searched and read through a few threads on here on this subject, but still none the wiser!

paulsherwin · 26th Sep 2010, 4:54 pm

The AF124 is the definitive AF117 replacement, though AF125-7s appear to be identical. My Towers suggests an AF124 as a sub for an AF102 too.

A large number of other transistors will also work including some silicon types, depending on the circuit, but the AF124 is your safest bet. They crop up on eBay now and then.

An AC128 is the best bet for the AC106s and OC604s, but again a large number of types are likely to work. There's no particular reason to think these will be bad though.

markhardy · 26th Sep 2010, 6:31 pm

cheers paul. off on a mission...

seen someone selling 10 sets of tested match pairs of 128's cheaper than some folks want for one, same with the 124's so going to buy a pile, use what i need, any leftovers I'll post on here at cost

just spent 3 hours on that radio - managed to remove the grub screws from 3 knobs - but not the knobs and only stabbed myself twice!

this one might take a while!

paulsherwin · 26th Sep 2010, 6:34 pm

The prices for these sorts of parts do vary a lot. AF125s are often cheaper than AF124s for some reason. You should be able to buy them for less than £1 each if you buy 5 or 10.

peetleetech · 26th Sep 2010, 11:14 pm

Mark, be a bit careful when changing the AF117 for the AF124. As I remember they were used mainly in the IF stages, the AF102 and AF106 were front end amplifiers. When I was a lot younger I spent hours swapping transistors in Namibia trying for better sensitivity on SW. In the earlier sets the higher gain often resulted in instability. A useful trick on those transistors was to slowly warm them up with a soldering iron. They suddenly started working and then stopped as they cooled down. Pinpointed the fault exactly, I even had one that just continued to work, still does, I think.

Jonster · 26th Sep 2010, 11:40 pm

Quite often giving the offending AF11x device a good beating with a screwdriver or other implement will cause them to burst into life - this 'cure' is often short lived but useful nonetheless for identifying the culprits!

mark pirate · 27th Sep 2010, 8:22 am

Don't forget, cutting the screen wire will often bring the transistor back to life!

Mark

'LIVEWIRE?' · 27th Sep 2010, 7:29 pm

Personally, I replace AF117s on sight, usually with AF127s, especially in any radio in which they're hard to get at.

DAVEHALL · 27th Sep 2010, 10:43 pm

Quote:

Originally Posted by mark pirate

Don't forget, cutting the screen wire will often bring the transistor back to life!

Mark

Yonks ago - whilst in PO Telephones( forerunner to BT) , we were always behind the times in modern devices . But we had the advent of the AF devices- and a wonderful cure - ( but then we only went up to 552khz) - if a problem on a board with collector/screen s/c - cut the earth - we did ,it got stuff working ,and we never got any further problems .

AlanBeckett · 27th Sep 2010, 10:49 pm

Dave,
Didn't you use OC170s?
I don't suppose that it made any difference, and they were obsolete in my time (1968 onwards) for new designs, but the old codgers used to tell stories about them.
Alan

paulsherwin · 28th Sep 2010, 1:06 am

Cutting the screen wire of an AF117 isn't a permanent repair. The tin whiskers are still inside and still growing. At some stage other internal shorts will occur.

robjkmannering · 28th Sep 2010, 5:46 pm

Then of course there is the other old dodge mentioned a number of times elsewhwere of connecting E,B and C together and dischrging a fairly big cap charged to 50v between them and screen. Personally, had a lot of sucsess with this and transistors repaired in this way are still going strong after several years.
Of course it doesnt prevent the whiskers growing but someone mentioned the discharging action may carbonise the ends.
Dont know if that theory is correct, but seems to work in practise.
Regards,
Rob.

DAVEHALL · 28th Sep 2010, 8:46 pm

Quote:

Originally Posted by AlanBeckett

Dave,
Didn't you use OC170s?
I don't suppose that it made any difference, and they were obsolete in my time (1968 onwards) for new designs, but the old codgers used to tell stories about them.
Alan

Possibly - but I can only remember the AF solution, it stuck in my mind as a bodge . I got out to work on more modern radio kit in the late 70's . This was on 62 type -the only sort of fault we used to get on channel kit .(Apart from the dreaded plastic connecting loom) .

DAVEHALL · 28th Sep 2010, 8:50 pm

Quote:

Originally Posted by paulsherwin

Cutting the screen wire of an AF117 isn't a permanent repair. The tin whiskers are still inside and still growing. At some stage other internal shorts will occur.

Give you an idea of how mich of a technical backwater GPO were in in the 70's - AF types were new on the scene and this problem had only come to the technical advice section . When I left in the late 70's , no cure had been mentioned .Don't forget that some equipment in those days still used solder in CV2000 VALVES .

saxmaniac · 2nd Oct 2010, 11:21 am

Another bodge I have posted on previously is to heat the case with a soldering iron for as long as you dare, you'll kill it or cure it!

Billy T · 20th Nov 2010, 9:51 am

I consider that there is too much risk in the cap-flashing or soldering iron 'cures' and since AF117s and their ilk are an endangered species these day, it behoves us to protect them if we can.

I have had great success using two or three used mini-9volt batteries in series, joining ebc together (properly, by soldering if you can) and applying the voltage between them and the screen wire which connects to the can.

You are only trying to fuse tin-whiskers of microscopic thickness, and this method simple melts them, hopefully leaving a small ball on either end to inhibit regrowth. The cap-discharge method killed the transistors completely on several attempted cures and I think there is just too much energy floating around for comfort with that system.

You could probably even do this in-situ if access is good, just bridge ebc temporarily, nip the screen wire, apply the volts then reconnect the screen and remove the bridging. This has worked well for me on a number of used and NOS AF117s and I believe it is much safer and more reliable than bashing, heating or blasting!

Cheers

Billy

Don Collie jnr · 2nd Dec 2010, 9:53 am

Look, this may sound silly, but has anyone tried removing the AF117 [et al] can and manually removing the tin whiskers? The can could be separated using a dremel saw, carefully - you have nothing to lose.

Don.

Darren-UK · 2nd Dec 2010, 11:51 am

I've unsoldered the cans, removed all the grease (taking the whiskers with it), replaced with new grease and refitted the can. This can be done with the transistor in situ, providing it's accessible enough. I haven't always bothered to refill with new grease either and it seems to make no difference.

'LIVEWIRE?' · 2nd Dec 2010, 12:03 pm

I haven't tried any of the above, since, as stated in my post #8 above, I prefer to replace any AF11x transistors with the equivalent AF12x series in any 'case', although even those are getting scare now.

kalee20 · 2nd Dec 2010, 2:25 pm

Trouble with removing the can, is that you expose the insides.

Germanium corrodes in moist air - unlike silicon, which it if does anything just forms a tough thin oxide layer over itself.

That's why germanium devices are in hermetic packages. A few early ones were in plastic packages, but they did not last long before dying.

26th Sep 2010, 4:37 pm	#1
markhardy Retired Dormant Member Join Date: Aug 2010 Location: County Durham/Weardale. Posts: 69	AF117 is there a definitive answer! Just about to start a major restore on another old sailor, sorry that should be Sailor (the lower case S could easily be mis-interpreted!) It's very rough and has been battered about a fair bit, and the cracked glass could be the big stumbling block, bad news is its full of AF117's. Interestingly I've got several early sailors, oops I mean Sailors!, all late 50's early 60's, all with AF 117's and all are still going great, wonder if the marine environment somehow inhibits whiskering a bit? It did crackle into life for a very short while, prior to smoke billowing out of a resistor! Not bothered particularly about totally authenticity, as long as it works as well as it was intended. So is there a definitive replacement to the AF117, or a near as damn it shove it in and it'll perform virtually the same? There's 4 AF117's, 1 AF101, a couple of OC604 and a couple of AC106 doing the audio bit. having looked at the schematic I suspect the AF101 is kerputt as well Have searched and read through a few threads on here on this subject, but still none the wiser! Attached Thumbnails

26th Sep 2010, 4:54 pm	#2
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,947	Re: AF117 is there a definative answer! The AF124 is the definitive AF117 replacement, though AF125-7s appear to be identical. My Towers suggests an AF124 as a sub for an AF102 too. A large number of other transistors will also work including some silicon types, depending on the circuit, but the AF124 is your safest bet. They crop up on eBay now and then. An AC128 is the best bet for the AC106s and OC604s, but again a large number of types are likely to work. There's no particular reason to think these will be bad though.

26th Sep 2010, 6:31 pm	#3
markhardy Retired Dormant Member Join Date: Aug 2010 Location: County Durham/Weardale. Posts: 69	Re: AF117 is there a definitive answer! cheers paul. off on a mission... seen someone selling 10 sets of tested match pairs of 128's cheaper than some folks want for one, same with the 124's so going to buy a pile, use what i need, any leftovers I'll post on here at cost just spent 3 hours on that radio - managed to remove the grub screws from 3 knobs - but not the knobs and only stabbed myself twice! this one might take a while!

26th Sep 2010, 6:34 pm	#4
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,947	Re: AF117 is there a definitive answer! The prices for these sorts of parts do vary a lot. AF125s are often cheaper than AF124s for some reason. You should be able to buy them for less than £1 each if you buy 5 or 10.

26th Sep 2010, 11:14 pm	#5
peetleetech Retired Dormant Member Join Date: Sep 2010 Location: Kempton Park, Gauteng, South Africa. Posts: 84	Re: AF117 is there a definitive answer! Mark, be a bit careful when changing the AF117 for the AF124. As I remember they were used mainly in the IF stages, the AF102 and AF106 were front end amplifiers. When I was a lot younger I spent hours swapping transistors in Namibia trying for better sensitivity on SW. In the earlier sets the higher gain often resulted in instability. A useful trick on those transistors was to slowly warm them up with a soldering iron. They suddenly started working and then stopped as they cooled down. Pinpointed the fault exactly, I even had one that just continued to work, still does, I think.

26th Sep 2010, 11:40 pm	#6
Jonster Heptode Join Date: Apr 2008 Location: Eastbourne, East Sussex, UK. Posts: 671	Re: AF117 is there a definitive answer! Quite often giving the offending AF11x device a good beating with a screwdriver or other implement will cause them to burst into life - this 'cure' is often short lived but useful nonetheless for identifying the culprits!

27th Sep 2010, 8:22 am	#7
mark pirate Dekatron Join Date: Mar 2008 Location: Worthing, West Sussex, UK Posts: 5,185	Re: AF117 is there a definitive answer! Don't forget, cutting the screen wire will often bring the transistor back to life! Mark

27th Sep 2010, 7:29 pm	#8
'LIVEWIRE?' Rest in Peace Join Date: Mar 2006 Location: N.W. Oxfordshire(Chipping Norton) Posts: 7,306	Re: AF117 is there a definitive answer! Personally, I replace AF117s on sight, usually with AF127s, especially in any radio in which they're hard to get at.

27th Sep 2010, 10:49 pm	#10
AlanBeckett Rest in Peace Join Date: Dec 2008 Location: Burton upon Trent, East Staffordshire, UK. Posts: 1,686	Re: AF117 is there a definitive answer! Dave, Didn't you use OC170s? I don't suppose that it made any difference, and they were obsolete in my time (1968 onwards) for new designs, but the old codgers used to tell stories about them. Alan

28th Sep 2010, 1:06 am	#11
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,947	Re: AF117 is there a definitive answer! Cutting the screen wire of an AF117 isn't a permanent repair. The tin whiskers are still inside and still growing. At some stage other internal shorts will occur.

28th Sep 2010, 5:46 pm	#12
robjkmannering Retired Dormant Member Join Date: May 2009 Location: Norwich, Norfolk, UK. Posts: 717	Re: AF117 is there a definitive answer! Then of course there is the other old dodge mentioned a number of times elsewhwere of connecting E,B and C together and dischrging a fairly big cap charged to 50v between them and screen. Personally, had a lot of sucsess with this and transistors repaired in this way are still going strong after several years. Of course it doesnt prevent the whiskers growing but someone mentioned the discharging action may carbonise the ends. Dont know if that theory is correct, but seems to work in practise. Regards, Rob.

2nd Oct 2010, 11:21 am	#15
saxmaniac Heptode Join Date: Oct 2007 Location: Birmingham, West Midlands, UK. Posts: 618	Re: AF117 is there a definitive answer! Another bodge I have posted on previously is to heat the case with a soldering iron for as long as you dare, you'll kill it or cure it!

20th Nov 2010, 9:51 am	#16
Billy T Retired Dormant Member Join Date: Feb 2008 Location: Auckland, New Zealand Posts: 631	Re: AF117 is there a definitive answer! I consider that there is too much risk in the cap-flashing or soldering iron 'cures' and since AF117s and their ilk are an endangered species these day, it behoves us to protect them if we can. I have had great success using two or three used mini-9volt batteries in series, joining ebc together (properly, by soldering if you can) and applying the voltage between them and the screen wire which connects to the can. You are only trying to fuse tin-whiskers of microscopic thickness, and this method simple melts them, hopefully leaving a small ball on either end to inhibit regrowth. The cap-discharge method killed the transistors completely on several attempted cures and I think there is just too much energy floating around for comfort with that system. You could probably even do this in-situ if access is good, just bridge ebc temporarily, nip the screen wire, apply the volts then reconnect the screen and remove the bridging. This has worked well for me on a number of used and NOS AF117s and I believe it is much safer and more reliable than bashing, heating or blasting! Cheers Billy

2nd Dec 2010, 9:53 am	#17
Don Collie jnr Retired Dormant Member Join Date: Jul 2008 Location: Invercargill, New Zealand Posts: 51	Re: AF117 is there a definitive answer! Look, this may sound silly, but has anyone tried removing the AF117 [et al] can and manually removing the tin whiskers? The can could be separated using a dremel saw, carefully - you have nothing to lose. Don.

2nd Dec 2010, 11:51 am	#18
Darren-UK Retired Dormant Member Join Date: Apr 2003 Location: Blackpool, Lancashire, UK. Posts: 4,061	Re: AF117 is there a definitive answer! I've unsoldered the cans, removed all the grease (taking the whiskers with it), replaced with new grease and refitted the can. This can be done with the transistor in situ, providing it's accessible enough. I haven't always bothered to refill with new grease either and it seems to make no difference.

2nd Dec 2010, 12:03 pm	#19
'LIVEWIRE?' Rest in Peace Join Date: Mar 2006 Location: N.W. Oxfordshire(Chipping Norton) Posts: 7,306	Re: AF117 is there a definitive answer! I haven't tried any of the above, since, as stated in my post #8 above, I prefer to replace any AF11x transistors with the equivalent AF12x series in any 'case', although even those are getting scare now.

2nd Dec 2010, 2:25 pm	#20
kalee20 Dekatron Join Date: Feb 2007 Location: Lynton, N. Devon, UK. Posts: 7,082	Re: AF117 is there a definitive answer! Trouble with removing the can, is that you expose the insides. Germanium corrodes in moist air - unlike silicon, which it if does anything just forms a tough thin oxide layer over itself. That's why germanium devices are in hermetic packages. A few early ones were in plastic packages, but they did not last long before dying.