10-04-2015, 03:44 PM
(10-04-2015, 08:57 AM)Old Sparky Wrote: Ah! The dreaded 'Tin Whisker' problem with AF117s and their ilk. BTW I always replace AF11x transistors, rather than fiddle about trying to cure them. Recently I have found, courtesy of a fellow meber of UKVRRR, that theree is a russian transistor, type no GT322, which can replace AF12x & AF11x types. It is a TO-72, presumably alloy-diffused, device like the AF126/127, etc, however it's base & emitter connections are reversed compared to those of the AF12x series -i.e. the same as tose of an AF139, 239 etc. Specification, however, is similar to that of an AF127. The GT322 is available from several eBay sellers at around £1 each in quantities of 15, so is a more economical buy that AF127s.
As to the problem with the overheating, I can only second the suggestions that smoothing capacitors may be the culprit(s), or possibly faulty output transistors, though it's just possible that the fault may have been caused by soldering connections to the earphone jack with the radio switched on. Incidentally, if i may mention it here, the service info. for the TR114 is available from 'Vintage radio Service Data' ( part of UKVRRR), but you have to register as a member before you can purchase this.
Sadly I stopped using E-Bay totally. They recently automated the whole system and I was finding you can't contact actual people if a problem arises. It got to the point I was wasting a lot of time chasing after customer service including by snail mail. I have bought stuff on E-Bay before such as driving belts and I didn't used to have problems. Pity really as it's a huge market but boils down to personal experience.
Yes, I think you are bang on - the overheating would have been a wiring fault around the ear socket. Perhaps I've been very lucky I didn't blow my audio stage. I wasn't aware the speaker had gotten so hot till I touched it and then realised. Actually I did test it for ohms last night and it's about 14 ohms so quite high. Then again the specific speaker was made with the higher ohms reading.
As to the point about AF117's, there are many ways to look at it. I think the main thing is to get it working again but, on the other hand, I like to think it's as close to the same radio as possible. I have quite a thing about sixties radios because I'm a big Beatles and Stones fan and I like to imagine someone was listening to Love Me Do on this set when it first came out. I have a 1965 Transwave and somehow I think of Rubber Soul.
I guess I like the technical learning process of this hobby but I'm very nostalgic.
