Building MS- Q14 and Q15? - Miata Turbo Forum -Boost cars, acquire cats.

Welcome to   Members

MEGAsquirt A place to collectively sort out this megasquirt gizmo

LinkBack Thread Tools
Old 03-25-2008, 11:51 PM   #1
Senior Member
Thread Starter
iTrader: (4)
Join Date: Jan 2008
Location: Falls Church, VA
Posts: 1,367
Total Cats: 16
Default Building MS- Q14 and Q15?

I'm building the MS and want to make sure I'm not crazy here. I have just installed Q14 and Q15, which is right after installing R37 and R38 for the driver FET current limiting circuit. Whenever I have soldered closely spaced parts like these transistor legs, I've checked continuity with my meter to make sure I haven't bridged any connections, and I haven't messed up any yet but these have me wondering.

I'm showing continuity between two of the three legs, on both Q14 and Q15, and they sure don't appear to be bridged by mere visual inspection. The thing is, it might be because the only thing between those two legs (verified with the schematic) is R37 or R38, which are only 0.5 ohms. My meter reads continuity across R37 or R38 alone, and I believe lacks the precision to consistently measure anything below 1 ohm and just sounds the continuity beep.

I wouldn't wonder at all if I hadn't just replaced the soldering iron tip, and I had to hold it on the components a bit longer to get the solder to flow. If you get the transistor too hot, can it be internally shorted? If that happened, would there even be any significant consequences given that it's only bypassing a 0.5-ohm resistor in a circuit that is supposedly optional to install? Or should I quit worrying and assume everything's fine until the magic smoke leaks out?

EDIT: Well spank my *** and call me Charlie, a more thorough search reveals that I'm not the only one who had this problem.
Guess I was worrying over nothing.

Last edited by ScottFW; 03-26-2008 at 12:07 AM.
ScottFW is offline   Reply With Quote
Old 03-26-2008, 12:05 AM   #2
Elite Member
iTrader: (24)
Join Date: Jul 2007
Location: Cypress, TX
Posts: 3,778
Total Cats: 35

You can kill a transistor with too much heat IIRC from tech class in 6th grade.

2 legs of Q15 were jumped for me on a premade MS. It didn't cause any permanent damage. It only caused injectors 1 and 3 not to fire. That took me 2 weeks to figure out.
Bryce is offline   Reply With Quote
Old 03-26-2008, 12:11 AM   #3
Senior Member
Thread Starter
iTrader: (4)
Join Date: Jan 2008
Location: Falls Church, VA
Posts: 1,367
Total Cats: 16

I was editing while you were replying. I think I'll assume it's okay and was just the low resistance reading as continuity. But I will put it in my little miscellaneous notes file as a possible culprit in case I have injector problems when it's installed.
ScottFW is offline   Reply With Quote
Old 03-26-2008, 12:20 AM   #4
Elite Member
iTrader: (13)
cjernigan's Avatar
Join Date: Oct 2006
Location: Atlanta, GA
Posts: 8,147
Total Cats: 5

I wouldn't worry to much about it. Normally you shouldn't have continuity but I have seen some weird results from testing installed transistors like that.

Sand the tip of your iron, then re-tin it and keep it clean this time.
cjernigan is offline   Reply With Quote

Related Topics
Thread Thread Starter Forum Replies Last Post
LucaCarMods's Boosted Dutch Miata Build! LucaCarMods Build Threads 11 02-14-2016 06:13 AM
WTB MP62 (Hotside) (NB2) Rick02R WTB 3 01-03-2016 07:18 PM
Is my swirl pot design okay? FrankB Race Prep 10 10-02-2015 09:00 PM
Bad head gasket or ? shooterschmidty Engine Performance 8 09-30-2015 10:28 PM
Image resizer concealer404 Front Desk 3 09-29-2015 12:41 PM

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

All times are GMT -4. The time now is 03:14 AM.