But for this simple purpose probably all four will work, but higher leakage could drain the battery quicker.Īn American replacement for the (European) AC125 could be 2N1176 or 2N406 (even same pin-outs), but I think, for the simple purpose it is used, any transistor that is a low power germanium PNP will do. I would take the most expensive type, with the highest hfe (amplification factor), and lowest leakage. Probably they come in the flavours of different amplification factor. You say to have found the AC125 transistor, but you don't know which to buy from the four offered. If it would help I can photograph my actual circuit (both sides) and draw the schematic but not sure what the internals of the transistor would be. I just want something to perform the job and I don't have enough knowledge to figure out what's suitable. I'm only basing that on the schematic I found. Replacement does not necessarily have to be the AC125 germanium. ( DIY Guitar Pedals has some germanium transistors for sale, but I'm not sure which would be suitable.) I did find a DIY guitar pedal site that seems to have AC125 gemaniums but 4 different sorts - but I don't know which of them would be suitable. The whole thing runs off a 1.5V C size battery.ĭoes anyone know of a suitable transistor that would perform the job? If the original is available, where could I get it in Australia? The working card, which has slightly different circuitry layout again - but still drives the movement, has a tall thin transistor (4.6 x 10mm) that has '13X' and a small red dot on it. It is 8mm round by 7mm high internal parts embeded in light green epoxy with 3 gold legs protruding and a small tag adjacent to one leg. There are no markings on it to say what it is. I'm pretty sure the coils are OK (measured for continuity) and I have even swapped the capacitor over and that is not the problem, which leaves the transistor. The two interwoven coils, sense and drive, work with the oscillating spring balance that has two plates (above and below) with two small permanent magnets. I have a similar clock with the same shape circuit card that I have swapped into the non-working unit and it works fine. I then believe I've found a schematic of the card - however the actual circuit I have differs slightly from this layout but still only the 4 parts (2 coils, capacitor, transistor).
Very simply, 2 coils, a capacitor and a transistor. Here's a picture of the whole thing (top right hand corner) and circuit cards shown below. Trying to find if there is a suitable commonly available replacement transistor for a small circuit card on a Junghans W.707 clock movement (about 50 years old.)
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