R15 getting hot

[jleilich]

I've assembled my MS3 and when I applied power to the Stim R15 smoked and burned. The solder was suspect so I replaced the resistor and re soldered. I turned on the stim and kept my finger on it and it got hot again pretty quick. I did however turn it of before I lost my resistor this time.

Where do I need to look? Whats going on that is making R15 get hot?

Thanks in advance

[slow_hemi6]

Solder bridges on Q14 or Q14 installed the wrong way? Sounds like something is pulling R15 hard to ground.

[jleilich]

Great thanks, Ill check it out. appreciate the help

[jleilich]

Q14 definitely has some extra solder on it. ill get the soldapult out and see if I can get that straightened out. No time last night.

[jleilich]

So I de-soldered Q14 and R15 is still getting hot. I'm going to replace Q14 all together and see if that fixes it.

any other suggestions?

[billr]

Is the "inj-1" output disconnected when R15 is getting hot? I'm thinking Q14 isn't the one to disconnect, try putting that back and remove Q1 and see what happens. The way I see it, any power to fry R15 has to come through the injector and Q1. (correct me, somebody, if I'm way off here...)

[slow_hemi6]

Well I usually don't just pull advice out of my rear end. In this instance you will find said advice, early in this troubleshooting guide. http://www.diyautotune.com/tech_article ... ooting.htm Perhaps this IS the easiest way for the OP to get it sorted anyways...... rather than me meter it out in steps.

[jleilich]

Slow_Hemi6
thanks for that link I've never seen that one. I'm a real noob at this so dont assume I know what the hell I'm talking about.

[jleilich]

Not sure if it matters, but I discovered R15 only gets hot when the MS3 daughterboard or CPU is attached. It's fine otherwise. I'm waiting on a a new Q14 to come in so I can just replace it all together.

[slow_hemi6]

Well without a cpu you wouldn't get any signal to the fet driver so you wouldn't get any supply to R15.

[jleilich]

ok thanks for the sanity check. Ill wait for my new Q14 to come in. I can't unsolder the current one without destroying it. Sitting too low on the board and I cant get my iron under it.

[billr]

"So I de-soldered Q14 and R15 is still getting hot."

I thought you had already removed Q14; not so???

[jleilich]

"So I de-soldered Q14 and R15 is still getting hot."

I thought you had already removed Q14; not so???

I didnt want to take it out until i had a new one. Good news, just replace Q14, powered up, R15 good to go.

Thanks ..

on to the next issue

[slow_hemi6]

Just for information. It is almost impossible due to the via's on the pcb to expect any component that is "de-soldered" but not removed to be isolated from the circuit. Most suspect components must be removed for testing.

[jleilich]

Just for information. It is almost impossible due to the via's on the pcb to expect any component that is "de-soldered" but not removed to be isolated from the circuit. Most suspect components must be removed for testing.

Good to know, thank you