Circuit Broad Capacitor Replacement

[Mr.Monkeyface]

I need to replace this capacitor on a circuit board but I can not read the color code. If someone could tell me what type of capacitor it was it would help.

[mariushm]

It's not capacitor , it's a resistor

And it's possible it's 0 ohm, basically used as a flame-proof/ explosion safe fuse... either that or it got so hot the color rings are gone

 

a bigger pic (more area around this part) may help.

[mariushm]

it's more like just black which is zero, then optional 5th/6th ring as brown (some companies use that for fuse/flameproof/etc) and gold (+/-5% tolerance)

[Mr.Monkeyface]

I tested it on my multimeter and this is what I got.

[CodeNova]

3 minutes ago, Mr.Monkeyface said:

I tested it on my multimeter and this is what I got.

153.3ohm

must be a 150 ohm resistor then, with a tolerance of +- 0.05%. Sometimes companies remove part numbers and id markers to avoid repairs and reverse engineering. The thing you really need to figure out is the wattage rating. Side note, if your resistor tested fine, why do you need to replace it?

*note: your also not really suppose to measure components in circuit, other parts may affect your dmm reading. If your going to replace it, de-solder it carefully, then measure it again to confirm your original findings.

[CodeNova]

1 minute ago, CodeNova said:

must be a 150 ohm resistor.

I feel my assumption is wrong, Black, x, Brown, Gray. This could be 0Ohms - 90Ohms

[Unimportant]

11 hours ago, Mr.Monkeyface said:

I tested it on my multimeter and this is what I got.

You need to test it out of circuit (desolder 1 leg for example). Otherwise that 150 ohm reading could come from another circuit parallel to it.

Report what value you get then.

[rhyseyness]

13 hours ago, Mr.Monkeyface said:

I tested it on my multimeter and this is what I got.

-snip-

If this is a measurement out of circuit, looks like the resistor isn't dead.

Dead resistors will read open circuit (>2Mohm). Massively unusual for them to fail and read anything other than short or open.

 

As @Unimportant quite rightly says, you could be measuring something in parallel.

 

On 3/8/2019 at 1:11 AM, campy said:

But if it is a 0 ohm, you shouldnt need to replace it unless its physically damaged. Run a multimeter over it and see what it reads.

 

This is not true.

You'd definitely need to replace a 0 ohm resistor because it forms a connection in your circuit, just like a wire link.

If a wire link snapped in half, you wouldn't say "you shouldn't need to replace it," haha.

[Mr.Monkeyface]

I do not know if I need to replace it since it still has a reading. Under the resistor is black and looks burned. This resistor comes from a board in a soldering station with a built-in power supply. I open it up because I lost the ability to change the voltage on the power supply. It is the only part that looks broken. I should be able to remove it and test it once I find my old soldering iron. I will try to get you the reading as soon as possible. Thank you for your help so far.

[Mr.Monkeyface]

I removed the resistor from the board and under it was text that said "150/3W". Then I tested the resistor after I removed it from the board and got 156.5 ohms.

[Unimportant]

Looks like the resistor is fine then. 150 ohm as printed on the silkscreen.

[CodeNova]

On 3/9/2019 at 7:28 PM, Mr.Monkeyface said:

Under the resistor is black and looks burned.

yeah it dose! whats the pcb for? it kinda looks like a power supply to an audio amp. You should post some more pictures, top down, of both the front and back of the pcb.

[Mr.Monkeyface]

The PCB is from a soldering station with a built-in adjustable DC power supply. If the resistor is fine any idea what might cause the power supply to output a constant voltage. I added some more pictures of the PCBs and other parts if they help. Thank you for your help so far.

[mariushm]

I would replace that capacitor that is near the resistor.  Picture says C14 220uF 50v .

The reason for that is because the resistor was very hot for a reasonably long time, to cause the circuit board to go black under it.  That amount of heat was close enough to that big capacitor to heat it up either through its leads and by being so close to it, so the electrolyte inside was probably overheated and degraded by now and that capacitor may be out of spec.

 

I can't tell from the pictures what the resistor is used for.

 

If the output of the power supply is always some big value, then my guess is the pass transistor or whatever is used to adjust voltage is dead, shorted (input goes straight to output), or the opamp adjusting the smaller transistor controlling the big regulator (pass transistor etc) is faulty and keeps the transistor fully open all the time.

Go backwards from the jacks on the case, follow the wires, then follow traces, find what IC is producing the voltage that goes on the wires which go on the panel on those + and - jacks.

 

Even with this pictures, it's very hard for me to figure out what goes where... don't understand how some people can't take good pictures of anything.

 

Luckily that's just a rebranded Yihua 853d, and pictures are available from other people.

Also there's this thread on EEVBlog : https://www.eevblog.com/forum/reviews/yihua-853d-rework-station/msg210109/#msg210109

 

If you want, replace the 150 ohm resistor with a 150 ohm rated for higher wattage, like 5w, 7w or 10w ... and solder it with some space between the board and the body of the resistor.

 

 

[Mr.Monkeyface]

I ordered a new resistor after testing the voltage adjuster knob (or whatever it is called) and I will see if that does anything. Thanks for your help.

 

[Mr.Monkeyface]

I replaced the resistor and I can still not change the voltage. After I put in the new resistor in I tested the temperature of it and it got up to 200°f (93°c). Any ideas what might be causing this. I also noticed that when I hit the power switch to turn off the power supply it still outputs voltage but the screen that displays the voltage is off.

[Unimportant]

Without schematics this is just a stab in the dark.

[Mr.Monkeyface]

Yeah, I look for a schematic but since it is a rebranded and obscure soldering station it is almost impossible. Thanks anyway.