Hello,
I'm not sure what these are and could use a bit of help.

The little orange one I believe is a capacitor. It only says 471 on it but 471 what? uF? mF?

The round black one I have no clue. An inductor maybe? It doesn't have ANY writing or markings on it. The 4.7k under it I believe refers to a nearby resistor and the color chart below identifies the resistor next to it as being 4.7k

I just replaced the MC34063A shown in the photo.
Thanks for your help!



The 4.7k would be Yellow / Violet / Red
and that's what this chart says

 

The 471 cap is 470 picoFarads ceramic. The black round thing is most likely an inductor. Both show no visible damage.

What is wrong with the unit?

 

The orange thing is a ceramic capacitor 471 = 470pF the 1 indicates the number of zeros. The black thing is an inductor but without any markings it is difficult to determine the value without measurement.

 

The 471 cap is 470 picoFarads ceramic. The black round thing is most likely an inductor. Both show no visible damage.

What is wrong with the unit?

Everything works EXCEPT the USB port. No power going to it.

 

The orange thing is a ceramic capacitor 471 = 470pF the 1 indicates the number of zeros. The black thing is an inductor but without any markings it is difficult to determine the value without measurement.

ok thanks. I'll Google up on how to test an inductor.

 

DodgyDave posted this schematic so I'm trying to use it to help identify and relate the components also. According to this, pin 2 does in fact connect to a conductor so that verifies it being an inductor. In fact, this diagram seems to VERY closely match the actual board on this device I'm working on.

 

DodgyDave posted this schematic so I'm trying to use it to help identify and relate the components also. According to this, pin 2 does in fact connect to a conductor so that verifies it being an inductor. In fact, this diagram seems to VERY closely match the actual board on this device I'm working on.

The Inductor will measure approx 1 to 3 ohms on a dvm, chances are the diode or the 0.33 ohm resistor is faulty, the 470pf capacitor is for the oscillator frequency, only way to check the oscillator is with a scope or frequency counter.

 

Everything works EXCEPT the USB port. No power going to it.

Is the chip getting that ≈25V in?

 

The Inductor will measure approx 1 to 3 ohms on a dvm, chances are the diode or the 0.33 ohm resistor is faulty, the 470pf capacitor is for the oscillator frequency, only way to check the oscillator is with a scope or frequency counter.

Thanks Dave. I'll check the diode and the .33 ohm resistor

The diode must be removed from the board to test correct?

 

Is the chip getting that ≈25V in?

Vin is actually 12v from the car battery. I can check that.

 

Vin is actually 12v from the car battery. I can check that.

Oh I see. I've never worked with that unit so my guess is that you would have to tweak the component values for a desired output (Before you do anything like that lets get more knowledgeable people in here.) . Are you measuring the Vout with a load or not?

 

The Diode is an 1N5810

It has a silver band on one end of the otherwise all black, round body.

With the VOM set to the Diode Check setting.....
When the positive lead of my VOM is connected to the end with the silver band I do not detect any continuity.
When I connect the negative lead to the end with silver band I read 138 something

Can anyone verify if these readings indicate the diode is good or bad?

 

Ok, according to a YouTube video I just watched, this diode is good so I'll solder it back into the PC board.

 

1N5810 Series Power Diodes - Schottky
Features: • Low forward voltage drop.

Sounds about right.

OP beat me to it...

 

1N5810 Series Power Diodes - Schottky
Features: • Low forward voltage drop.
Sounds about right.
OP beat me to it...

I really appreciate the reply nonetheless.

The video did say .2 - .6v
I got 138 (which I think means .138v ?)

 

Q1 inside the chip does all of the heavy lifting and is the first suspect. If your board does not have Rsc in place, then a very short duration overcurrent on the output can pop the chip. Since you've replaced it, the suspect pool is getting very small. Was the unit operating when the output failed, or did it die on startup?

ak

 

Q1 inside the chip does all of the heavy lifting and is the first suspect. If your board does not have Rsc in place, then a very short duration overcurrent on the output can pop the chip. Since you've replaced it, the suspect pool is getting very small. Was the unit operating when the output failed, or did it die on startup?

ak

I can never recall the USB port working on this device ever since I bought it. It either never worked or I have forgotten that it worked long ago.

I attempted to test voltages at the USB port and found that no voltage is getting to it. (Rules out a bad USB port?) There should be around 5v getting to the USB port.

 

Do I need to remove resistors from the PCB to get accurate readings?

 

Do I need to remove resistors from the PCB to get accurate readings?

Only to measure the resistance of the resistors. Other than that nah.

 

So I checked every resistor on the board. Below are the results.
The items marked in red are suspect.
But note that 7 of the resistors do not match the markings on the PCB.
It seems that 3.6k ohm resistors were used in slots where the PCB printing called for 1.5k
I do not understand this. Why would the people who put the board together use resistors that did not match what was printed on the PCB? Maybe the boards were all printed but it was later discovered that 3.6k resistors worked better?

Resistor #R3 and #R4 are the two most suspect resistors IMO. Agree?