The sound has stopped working in my Buddy L loco, which is a shame because the sound was my favorite feature on this loco. To me, it sounded just as good as the expensive systems I’ve heard in other locos. I’ve checked all the likely things such as loose connections, making sure the volume is turned up, new batteries, etc. Nothing is visibly damaged.
Unfortunately I know squat about electronics. Is there any way I could test each component to figure out which one needs to be replaced?
Most likely not. To effectively troubleshoot todays electronics generally takes fairly sophisticated test equipment. Because of that, most electronics is designed to throw away and replace. It’s generally a lot cheaper that way. 
The only thing you can do is to look for physical damage, and if you are good at soldering, take an iron and touch up all the solder joints to make sure you don’t have a loose connection or cold joint. Beyond that, I would suggest looking on eBay for a used locomotive and cannibalize the sound system.
I would have to agree with Warren .
After you have looked for obvious faults–mechanical ones , like loose wires–it is largely down to test gear . If you have a continuity meter , it can help --just to check that the wire between a and b is actually there (it can be broken inside the insulation) .
Even professionals can find it hard going ,even they can also miss the most basic odf faults .
Like me , once , in my younger clever dick days .
Skipper of Air Sea Rescue boat pops his head down the hatch to ask “Going to be long with that then ?” .
Me , sweating in the tropical heat and hating radar in general and this one in particular "Bit of a funny fault , sir , can’t say yet "
Skipper disappears briefly then pops head down hatch again
"I suppose you’ve checked the fuses Haw haw haw , ho ho "
Oh , shit .
Mike
Not me! I would never forget to do that… :rolleyes:
My friend replaced everything electric on his motorcycle and then checked the “Kill Switch.” 
madwolf
That ones has gotten me too but I was able to recover before I had replaced other parts!
ANdre’
Might as well tell you about the other pet fault finding hate —this happened to me . Why can people not be honest when they have been tinkering ?
Polishing the beautiful pipework on my 4and a Half Bentley (sob , sob , ) I was approached by a chap from up the road . I had feared that he would , ‘cos I could hear the “wa wa , wa , wowo, wowooo wooo…” of a starter flattening a battery .
"Er , got a minute ? Got a funny one on the car "
ME --"Wotcher bin doin’? "
Him -“Nuffin "
ME --“Yer 'aven’t touched anything?”
Him–“Nah , just been cleanin’ it . "
ME --” You’re sure ?”
Him --“Yes”
ME (looking at top of his radiator ) “Where is this rotor arm from then ?”
"Ah "
AND .
My son , working part time in car spares shop whilst at High School
“Yes madam , what can I do for you ?”
"I want a fan belt "
"Yes madam , we need to know what sort of car it’s for "
"Oh , a little red one "
Mike . Cynic . Wonder why ?
EDIT PS Ray , don’t be put off , just make a note of what you touch , move or whatever . We all make mistakes . That is how we learn .
"Mike" said:Ummm.....at least some do.... :/
We all make mistakes . That is how we learn .
You happen to know who made the sound?
I have a Paul Lousy system just delivered in a loco DOA yesterday, the battery is T/U.
Reads 5v on a 6v battery, won’t charge.
Some of these lousy systems need FULL voltage to function.
TOC