M1AYM Posted January 9, 2011 Share Posted January 9, 2011 Hello, Ive been on the ESU forums to no avail here and wonder if anyone can help. Ive recently been working on a repair to a freinds Class 20 sound chip. I need a circuit diagram in order to work out what should be connected to what and complete the repair. [unfortunately Loksound do not seem to want to help. Understandable as they dont want to give their design away or the synic in me says they want me to spend another £100 on a new module !] Anyway - The original problem is that the amplifier IC blew as a result of a short circuit solder joint across the speaker which blew the amplifier IC apart and blew a header pin out of the PCB leaving a crater in the board. I have sourced the amplifier IC from RS and replaced it. The audio now seems to work but there was more damage to the PCB which has left a motor control problem in one direction. Link to post Share on other sites More sharing options...
spud Posted January 11, 2011 Share Posted January 11, 2011 hi, ive never repaired a decoder ( yet!!) but i am an electronics engineer and specialise in drives and automation. if you are familiar, and it sounds like you are, then you should be able to see the output stage for the motor which is normally four FETs arranged in a standard H-bridge configuration. bet anything that you've either lost one of these, or one of the interconnecting tracks when the fault first occured. Hat well and truly off to you for replacing the amp, nice one! Link to post Share on other sites More sharing options...
M1AYM Posted February 6, 2011 Author Share Posted February 6, 2011 Thanks for the response – haven’t been on here for a while but just noticed the reply. Good answer your probably right. Had plenty of trouble with FETs in the past. Not repaired at board level for a number of years and lost touch with what’s what numbers wise (also been overtaken by SMD stuff as well to a certain extent). Am quite used to finding older larger FETs in stuff but would have trouble identifying SMD types. Do I just look for all 3 legged transistor devices or would I be looking for an IC package? If so any pointers in the right direction ? Regards Bob Link to post Share on other sites More sharing options...
spud Posted March 11, 2011 Share Posted March 11, 2011 hi bob, sorry been away from Rm for a short while!!! funny you ask, because ive just repaired a loksound v3.5 ( my first!!!) the drivers are the two small 8 pin ic's next to the audio amp! Link to post Share on other sites More sharing options...
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