What have I broken...?

Edwardatherton · Post by **Edwardatherton** » Sun Aug 05, 2007 5:42 pm

I started sodlering the kit together and took it out to the garage to test for the correct voltages.

Everything checked fine, and I was so surprised that I started checking again! The multimeter probe slipped and sparked briefly on one of the diodes by the plug. After that I do not get any voltages (5 or 12) on the board.

I have changed the diodes (not the zener one because I couldn't find one) and capacitors without success - is it possible to get another voltage regulator from somewhere?

Post by **brentp** » Sun Aug 05, 2007 7:49 pm

Hi,

Once you replaced the diodes were you able to re-verify +12v? Trace back from your supply through the molex connector down to the +12v input on the voltage regulator.

If, you see 12v on the input to the voltage regulator but not +5v on the output then you may consider replacing it. However, since you shorted it out near the 12v section it may very well not be damaged. Again- make sure you see +12v on the input of the regulator before you consider replacing it.

However, if you do need to swap it out, suitable replacements are: LF50 (StMicro) LM2937-ET-5.0, or a standard 7805 should work OK.

Regards,

Edwardatherton · Post by **Edwardatherton** » Mon Aug 06, 2007 8:34 am

Thanks Brent. I had a good look this morning and found the problem - you might be able to see it in the picture...

The 'track' on the underneath of the board (just underneath where it says 'D2' appears broken). Is it simply a case of soldering a wire between the molex connector and the diode?

MartinM · Post by **MartinM** » Mon Aug 06, 2007 10:14 am

Interesting!

I would either:
- scrape away the green mask immediately either side of the gap and bridge the gap with solder
- essentially do the same as above but use a piece of wire (end of a resistor type thickness) to bridge between the two connection points

Edwardatherton · Post by **Edwardatherton** » Mon Aug 06, 2007 10:33 am

Thanks very much!

Top tip to anyone else starting the project...

When you get the kit, do not start soldering it together in the evening when you are extremely tired! I was quite excited when it arrived and couldn't wait to get started!

dr.occa · Post by **dr.occa** » Mon Aug 06, 2007 3:41 pm

good advice E but i still did so late at night (only opportunity - family took precedence). i just had coffee on the burner ready

Post by **brentp** » Mon Aug 06, 2007 3:51 pm

Looks like you found your problem. That trace acted like a fuse when your test probe slipped.

Tip #2: Use a current-limited power supply when testing, such as a 9v battery.

Edwardatherton · Post by **Edwardatherton** » Tue Aug 07, 2007 8:09 am

All finished for the moment - installed a new bit of wire to bridge the 'gap', installed the last bits and cased it this morning before work.
Then remembered that I need to install the twin map option switch!
Oh well! More work tonight...

dr.occa · Post by **dr.occa** » Tue Aug 07, 2007 4:06 pm

Edwardatherton wrote:All finished for the moment - installed a new bit of wire to bridge the 'gap', installed the last bits and cased it this morning before work.
Then remembered that I need to install the twin map option switch!
Oh well! More work tonight...

just love those times when you cleaned up and thought you were done...

i understand all too well.