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voltage regulator part 7824

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mrwhitee

New Member
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.
 

Sceadwian

Banned
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

Active Member
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

New Member
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

New Member
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

New Member
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

New Member
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.
 
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