Aqualisa Aquastream Mk1 shower

[bayard1music]

Can anybody help me identify the transistor fitted to the Printed Circuit Board on my Aqualisa shower. I've got a broken device (the lead has corroded) and I can no longer read the part ID. There are only two other electronic components are relay and capacitor and sorry resistor these are all fine and the shower works in all other respects so don't want to scrap. I'm an electronics eng. but a bit puzzled as I dropped a common NPN transistor in expecting it to work but it worked back to front i.e. motor on with the dial turned off. So guess it's an PNP but which type? A photo would do as long as I can see the part number. Thanks in advance. (Aqualisa offer no help with this enquirey)

 

[bayard1music]

Can anybody help me identify the transistor fitted to the Printed Circuit Board on my Aqualisa shower. I've got a broken device (the lead has corroded) and I can no longer read the part ID. There are only two other electronic components are relay and capacitor and sorry resistor these are all fine and the shower works in all other respects so don't want to scrap. I'm an electronics eng. but a bit puzzled as I dropped a common NPN transistor in expecting it to work but it worked back to front i.e. motor on with the dial turned off. So guess it's an PNP but which type? A photo would do as long as I can see the part number. Thanks in advance. (Aqualisa offer no help with this enquirey)

Well I think I can answer this myself! After buzzing out the circuit and conferring with a colleague I've concluded and validated that it's a NPN darlington transistor with an internal protection diode. I've purchased a BD139 from Maplin on the high street. Not the original form factor but with data sheet you can arrange the leads. The lead out on the PCB is E, B,C. Where the collector is nearest the TR1 silk screen symbol. Only time will tell if this proves reliable but see no reason it won't . But no guarantees. What a pity the values weren't on the board or provided by Aqualisa. Much time has been wasted.