Different (lower) resistor values on PCB?

[Kobok]

Dear Alls,
For sure it id a stupid question, but help me to understand. I am in a Dell 2007WFP revitalizing project - searching reason why not starting. Some resistors needed to replaced is is obvious. When I have soldered some resistors the measured (with multimeter) values were sometimes rather different written on them. I supposed these are wrong units so I desoldered and made a checking measurement and voilá the values is the same is written on. This happens only in case of a few resistors, most have the same values (+/- 10%) are written on it. "strange" SMD resistors =>103 10k in hand, but 3.5k on the PCB, 183 18k in hand, but 8.25k and 9.27 on the PCB.
Is it normal? Or do other parts need to check/replace?
OTHER
2202 resistor shows increasing values when I measure on the PCB (starts from 4.1k upto 20.1k. In all cases the board is power off, of course.
Any tip, lesson to learn? Because of the strange values I do not want to switch the board onto 230V.

[petehall347]

Re: Different (lower) resistor values on PCB?

so you discovered you cant reliably test resistor values in circuit because other things change the results . the reading increasing in value is a capacitor charging up ..swap your probes over and it will drop rather than go up .

[Kobok]

Re: Different (lower) resistor values on PCB?

Thank you! So if I understand well, the phenomena is normal in both cases, isn't it? If the resistor shows normal values out-of-circuit measures, will work as must after soldering.

[Kobok]

Re: Different (lower) resistor values on PCB?

so you discovered you cant reliably test resistor values in circuit because other things change the results . the reading increasing in value is a capacitor charging up ..swap your probes over and it will drop rather than go up .

One more question: some diodes show the similar phenomena above, which is weird for me. In hand the diode shows polarity if I check with a multimeter (value in case of right polarity and nothing vice versa) BUT if I solder in the multimeter measure minimal value in both polarity direction. Is it acceptable or I have to seek a bad element somewhere in the circuit?

[petehall347]

Re: Different (lower) resistor values on PCB?

all depends on the circuit and what is affecting the reading .

[Kobok]

Re: Different (lower) resistor values on PCB?

So might it be a "normal" phenomena or a/some false other elements? If some error, what should I look for in the circuit? Any suggestion?