voltage regulator part 7824

[mrwhitee]

I have a circuit board that I need to repair if possible. It runs off 24 volts a/c. I noticed a 5.2 ohm resister ( green red gold) was burnt immediately after the 24 volt power coming in. I replaced the resister and it immediately got very hot and started to burn. Next part in line after the resister is a voltage regulator 7824. The area on the board around the regulator and resister has all overheated. I am wondering if a bad regulator can cause my resister to burn up. I would appreciate any help before I order the regulator for it. Its a $1500.00 board so thats why I am willing to try. Any other trouble shooting tips would be apreciated too. I have included a picture if it helps. You can see the upper left hand corner where the 24 volt wires come in and then the resister to the right and then a diode to the right and then the 7824.**broken link removed**

 

[Sceadwian]

A bad regulator could have permanently damaged the rest of the board too. It's worth a shot replacing the regulator but I wouldn't get your hopes up too much just in case.

 

[pfofit]

the foil trace connecting the cathode of the diode and the regulator also goes to the input filter cap and the 8 pin DIP. Either of which could be shorted. Other side of board I can't see..

Try lifting the input lead of the regulator to see in the resistor still cooks. Alternately you could remove it from the board and test it on its own.

 

[mrwhitee]

I lifted the input lead like you said and now the board has powered up and the resister is ok. I guess Ill try and replace the regulator and hope that works.

 

[Draco]

it may be worth it to replace a few of the caps or at test them with an ohm meter for an internal short or low resistance, i realy don't like that discolored trace that is at pin 3 of that 7824. that's just my 2 pennies

 

[Berserk87]

it may be worth it to replace a few of the caps or at test them with an ohm meter for an internal short or low resistance, i realy don't like that discolored trace that is at pin 3 of that 7824. that's just my 2 pennies

that was the first thing i saw.

the whole pad under the regulators is discolored as well.

 

[mrwhitee]

I just finished replacing the regulator and the capacitor and fired it up. So far its all working. I can connect to it with the software and energize all the cooling relays. I dont see anything overheating or smell anything burning. Thanks for all your help!

This is an HVAC controller board by the way.