a few half-burned resistors in circuit. how bad is it?

[izarf]

Dear Fellow members,
Just started out with microelectronics. Verified the resistance of the resistances and 3 of ~40 indicated damage upon solding. Resistance is ~23 kOhm instead of the original 45.0 kOhm. How bad is it? What potential disasters could one expect from this?
Velleman k8055 board. Device is not yet started.

 

[Harald Kapp]

Welcome to our forum.
We can't say how bad it is without knowing the circuit (schematic diagram) and the position of the resistors. Anyway, as they show only half the nominal resistance, chances are that more damage than visible has been done to them. Remove these resistors and insert new ones. These should be easy to get at any electronic components store.
I hope you used sockets for the ICs? The ICs are even more sensitive to overheating than simple resistors.

Take care when soldering. The damage reported points to massive overheating. You should use a low power (<= 30W) soldering iron, preferably temperature controlled. Only heat the solder joint as long as required to melt the solder. Here's a tutorial on soldering.

 

[izarf]

R28 and R30 and R32 are the ones damaged.
http://www.velleman.eu/downloads/0/illustrated/illustrated_assembly_manual_k8055_uk_rev3.pdf

Thank you for your reply! Luckily I use socketed ICs yes. From now on I will use better suited equipment for this kind of work.

 

[Harald Kapp]

These resistors are not critical. Even 23kΩ should work. I recommend replacing them anyway - one never knows what else happened. They surely will not be reliable due to the damage.

 

[Colin Mitchell]

You cannot damage a 47k resistor and it never goes to 23k.

 

[(*steve*)]

Well, yes, you can damage resistors, but it's rare for them to do anything other than go high in resistance.

It's more likely that the resistors have been measured in circuit and you;re getting the effect of parallel resistance reducing the resistance measured across the resistor.

 

[KMoffett]

If you measure the resistances of the 47K resistors (R28,29,30,31,32) with the ICs removed, there should be no parallel resistance paths.

Ken

Also R33 and R34 with the address jumpers out.