Hey guys.
I've been replacing some resistors on my monitor PCB, from a 1981 sit down game. A lot of the resistors were toast. So, I ordered up some new ones. They came in, I tested them and begun soldering them into the board.
Once in, a lot of them are reading around half of what they are supposed to. Supposed to read: ( 2.7ohm - 1w +or-), but after putting them in I'm getting a reading of 1.2 to 1.8ohm.
Like I wrote above, I tested them all before soldering them in and they were fine.
Of course, I haven't tried plugging in the board yet.
So.... any idea on why the changes? The traces are all good.
I am reasonably new to all this. Not completely new, but nowhere near experienced. Haha.
Any thoughts would be great.
Cheers.
Lower than normal resistor readings.
- billyC
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- Asayuki
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Re: Lower than normal resistor readings.
the resistance you are measuring in-circuit is the Thevenin equivalent of the circuit itself. http://www.calvin.edu/~svleest/circuitE ... theory.htm
In other words, what is happening is that all components present in the rest of the circuit are contributing their own characteristic or parasitic resistance to your measurement in a complex series-parallel configuration.
If a measurement in-circuit is the way in which you have deteremined that they were broken then I'm afraid all those resistors you replaced were probably good to begin with.
My 15kHz cabinet Peplos will never power up, with any item, and I am quite proud of that.
- RMRM
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Re: Lower than normal resistor readings.
That is why you always have to test an IC out of the circuit when you suspect it is bad
- billyC
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Re: Lower than normal resistor readings.
Pffff. Doesn't that just figure. Haha.
Well... I guess I got some good soldering practice then. Half of them I replaced were bubbling, or the board itself was burned around them. I did still replace an extra 6 or 7 before stopping and writing this message.
Thanks guys. Good to know. I guess that means I only have another 2 to replace still (that were burned) instead of... well... lots.
Cheers and thanks for the help.
Well... I guess I got some good soldering practice then. Half of them I replaced were bubbling, or the board itself was burned around them. I did still replace an extra 6 or 7 before stopping and writing this message.
Thanks guys. Good to know. I guess that means I only have another 2 to replace still (that were burned) instead of... well... lots.
Cheers and thanks for the help.