aernschd

The IC in the 138/139 unit is an ASIC, so it is very probably not replaceable... So I do hope that only a transistor is gone. I'll try and check them using some standard transistors and add the missing flywheel diodes. Those missing diodes are surely a weak point of the original cirquit. By the way - I wonder why the whistle for the 138/139 set is tunable, as the 138/139 control unit does not seem to distinguish between two different frequencies but between a short and a long signal. High tolerances within the cirquitry? Anyway, the older whistle does the trick, too (as well as clapping hands).

Hi there! Anyone still interested in reverse-engineering the 138 cirquit? I've dismantled one that only works forward/stop. I've made a sketch of the cirquit. There are three transistors 0N114, which must be PNP type, and two 0N115, which should be NPN, all in TO-1 casings. I could not really identify these type numbers, but they might be something like AC114/AC115, these would be similar to ECG102A and ECG103A. The integrated cirquit is housed in a DIL-14 package and is marked 211 0M. No idea what it is...