exxos's Atari, Amiga & retro forum

Hey guys,

I need help identifying what type of component this blue square object is:


And I need to source a replacement coil, but knowing nothing of coils I need some help, I can barely make out M8.51 on the surface:


Thanks,

I have no idea, does not look like standard coding on the inductor..

Is the inductor open, you could always measure it with a inductance meter..

The blue box I assume is a resistor as it has R5 next to it. May well be a fusible resistor, or surge resistor type thing.

I agree with exxos the resistor is at the beginning of the power supply circuit so most like a thermal resistor. The coil is the stand part number printed on top and is working with the capacitor and voltage regulator beside it

Tom

Something like this for the blue part

@exxos I forgot I had a multifunction tester haha, well, I tested it and it gets:
0.02mH
R=0.21ohm

Which as far as I can tell means it is at fault? I did some reading online and apparently any inductor measuring under 1 ohm is basically shorted.

With the blue box - sorry I forgot to mention - it has 3 legs! I also think it is marked X1 on the pcb (not r5, thats referring to an smd resistor next to it) And when looking on-top of it, it is similar to a bussed resistor as it is drawn as such: [| ] ... So one leg then two pins.

@Tomswork What would I replace the coil with?

Steve wrote: 29 Jun 2021 21:03 @exxos I forgot I had a multifunction tester haha, well, I tested it and it gets:
0.02mH
R=0.21ohm

Which as far as I can tell means it is at fault? I did some reading online and apparently any inductor measuring under 1 ohm is basically shorted.

Thats just totally wrong though.. My big inductors on my PSU are so low resistance they are pretty much zero ohms. "Crap" inductors are 1R and above.. better ones are 0.1R and below. It depends on the current carrying capability.. more current = larger wire = less resistance. Similar lower values = less wire = less resistance.

So I think there is nothing wrong with that inductor IMO.

Steve wrote: 29 Jun 2021 21:03 With the blue box - sorry I forgot to mention - it has 3 legs! I also think it is marked X1 on the pcb (not r5, thats referring to an smd resistor next to it) And when looking on-top of it, it is similar to a bussed resistor as it is drawn as such: [| ] ... So one leg then two pins.

Probably a suppression choke like on most ST's. Assuming you get like the same resistance from the middle pin to each of the outside pins.. it's probably fine as well.

@Steve

My guess would be 175uh or 176uh the number is hard to read the other number should be the size

Tom

@exxos I checked the resistance across the middle pin to outside pins (in lots of different ways) and got absolutely nothing... (OL in all configs)

Tomswork wrote: 29 Jun 2021 21:24 @Steve

My guess would be 175uh or 176uh the number is hard to read the other number should be the size

Tom

Hey Tom did you see the readings I got when putting it on my tester?:
0.02mH
R=0.21ohm

@Steve

Yes I did its hard to tell without a frequency on the coil they all have the resistor range set at nominal frequency say 1khz so it can be a pain. Here is a sample spec of what I think you have there just its a surface mount

Edit the reading you have would make me replace it


Tom

Hey @Tomswork I luckily found a much better picture before I cleaned everything with IPA :) can actually read it now, looks to be 470 L? Or t? Would that make it 470uh? And do I need to be careful of how many amps it should be able to carry?

I did a bit of reading here: https://how-to.fandom.com/wiki/How_to_i ... r_markings
"Third digit is the multiplier (or number of zeros added to the value)"

So the third being '0' means 470 then right? But how do I know it is in 'uH'.