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Broken resistor and fuse in lab shaker's control panel

PhilipAG

Nov 30, 2023
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Hi everyone,

I'm a complete newbie when it comes to PCBs but I'm trying my best of luck.
In the lab, one of our shakers (photo 1) no longer functions and I could vaguely smell something burning inside the control panel (photo 2).

I opened up the control panel and at the front of the PCB (photo 3) I detected two burned spots, which are a resistor and fuse.
- The SMD resistor (photo 4) had the value 1000 written on it before, so I assume it is a 100 ohm resistor? I'm in doubt whether the size is 0603 or 0805.
- The SMD fuse (photo 5) had "Pc" written on it. For the size I think it is 1206.

Photo 6 & 7 show the intact resistor and fuse from the other shakers we have in the lab.

Based on the photos and info I supplied, does anyone know if I can replace the resistor with for instance 101 or 01A resistors?
How can I determine the fuse rating or does "Pc" stand for a certain value?

Once I know what to get I will try to remove to old parts and solder new parts to the PCB. Anything I should be cautious about?

I hope you can help me out.
 

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Delta Prime

Jul 29, 2020
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Is this a medical laboratory?
Those look like culture bags! They're usually flasks... anyway this is highly regulated; if you're in USA by the (NIH).
National institute of health.
You must contact the original manufacturer for repairs documentation is critical.
 

PhilipAG

Nov 30, 2023
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These are erlenmeyers which are still in a bag.
We're an academic research lab, so no worries, we don't make anything for human treatment or likewise.

How do you think I could replace the resistor and fuse?
 

Bluejets

Oct 5, 2014
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Resistors don't "just burn up" for no reason so there must be more to it.
No idea what photo 4 is all about.
However, your resistor in photo 7 from a good board shows the value to be 1K ohm, (1001) not 100.
Simple to measure the good resistor for size.
Fuse value, no idea but could expect maybe 500mA, depends what the display board is driving.
If only a display and signal out, perhaps 500mA would be sufficient.

To be quite blunt though, don't think you stand a chance of actually fixing it.
Time for a new one.
 

Harald Kapp

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Nov 17, 2011
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However, your resistor in photo 7 from a good board shows the value to be 1K ohm, (1001) not 100.
The resistor is question is R92 which shows 1000
1701410353012.png
The size is probably 0805, not easy to judge from the photos. Take measurements and check against this table.

Resistors don't "just burn up" for no reason so there must be more to it.
Usually this is the case: a fault somewhere else on the board. It may, however unlikely this is, be one of the rare cases where a component fails for no obvious reasons (repeat: happens rarely). Replacing the resistor is inexpensive so this is a repair that can be tried at next to no effort.

Fuse value, no idea but could expect maybe 500mA, depends what the display board is driving.
I agree. Unless you find documentation on the fuse it is next to impossible to find the value from the pictures alone.
Just to check the current: When replacing the resistor, remove the fuse. Put an ammeter between the two solder pads where the fuse was mounted. Assuming the board spins up on power on, measure the current though the fuse aka ammeter. Do not operate the board for any long time, switch it off once hyou ave the current measurement. Then mount a suitable fuse.
 

Bluejets

Oct 5, 2014
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The resistor is question is R92 which shows 1000
Photo 6 & 7 show the intact resistor and fuse from the other shakers we have in the lab.
So which is it...totally confused now.
Usually this is the case: a fault somewhere else on the board. It may, however unlikely this is, be one of the rare cases where a component fails for no obvious reasons (repeat: happens rarely). Replacing the resistor is inexpensive so this is a repair that can be tried at next to no effort.
Perhaps but the thing is all burnt up including the tracks.....one with a fair amount of experience would find it a task to replace a "good" one let alone be a beginner ...and ...burnt to a crisp into the bargain.
 
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