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I need help identifying an SMD capacitor and ordering 2 axial inductors

jacob varley

Mar 28, 2017
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So the cap died and took the inductors with it, so i need to replace the items. I borrowed the same item from a friend in order to read the values and took pictures but i have no idea how to ID the cap let alone where to find it to buy. I have ID'd the axial inductors but again I'm not sure where to get them. I got to mouser and digikey and I'm lost as what to put in. I was told the inductors are 2watts and i've been linked to smaller but want exact. See photos

thank you for your help
 

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davenn

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So the cap died and took the inductors with it, so i need to replace the items.

so pull out the board and observe what is written on the electro cap

those 2 yellow things in the second image are tantalum caps 4.7uF @ 25V ... NOT inductors

what makes you think any of the 3 items have died ? .... the tantalums look good ...
when tant's fail it is usually VERY obvious ... they blow themselves apart

. I borrowed the same item from a friend in order to read the values and took pictures but i have no idea how to ID the cap let alone where to find it to buy.

ohhh ok ... so what do your ones look like ?
 
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jacob varley

Mar 28, 2017
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Yeah I didn't show you the dead photos. The photos are from the working unit for reference. The inductors are FRIED, colorless but all brown, the cap is complete brown and crumbled to pieces. I've attached photos for you. Now I normally don't ask for people to do all the work for me, but is there any chance you can link me directly to replacement parts so I can order them? I tried looking at mouser and was very confused as it was asking for fields that I knew nothing about.
 

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davenn

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The inductors are FRIED,

well you didn't show that pic in the first post those 2 inductors .... I cannot read the values
your board is a bit different to the one you originally posted ..... what is the value on the one that isn't cooked ?

I've attached photos for you. Now I normally don't ask for people to do all the work for me, but is there any chance you can link me directly to replacement parts so I can order them?

the big electro cap value is 2200uF at 25V .... the temp making must be on the other side .... use a 105 deg one for better life
 

jacob varley

Mar 28, 2017
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we seem to be on two different pages here. here are photos of the broken and working. The boards are 100% identical with the exception of the SMD caps in the photo but they're damn close. I can only assume the value on both inductors (new and old) is the same since everything else is. The new inductors say 2.7 uH with a 10% tolerance but as for the SMD caps, I have no idea exactly how to read those.
 

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73's de Edd

Aug 21, 2015
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Sir jacob varle . . . . . . . .

Ahhhhhhhhh so . . . . . . this do be velly- velly intelesting . . . .

Rather than a further observational manner, instead lets move more of an analysis of what we currently have.

Figure on our DC power coming in from the shown VERY nearby power connector and then initially passing thru the parallel connected 2W power resistors / or / inductors and then the outgoing power flows over to the 2200 uf cap.
You then have a basic filtered power source, ready to distrubute around the board or with part of it to possibly be regulated down to sub voltage(s).
That is, until it then flows down its branches and then encounters that top right tantalum cap which breaks down and rapidlly plummets down to an almost zero ohm short across that supply.
The 2.7 resistors / 2.7 inductors then heat up as they were not designed for carring that level of power thru them.
Ole 2200 cap over there is watching the mayhem . . . . but its no load on him . . . since its strictly being THEIR problem.

If its being shown on your plug in power pack . . . . . give us its voltage and current specs + wattage if being available.
It took some POWER to fry those components to their currently damaged states.

To analyze, now take metering in hand and set up for its lowest range ohms and short out the meter probes to see what your then testing of an ALMOST 0 ohm short will display on your metering. ( Take mental ref of reading)
(That unknown variable anomoly, is being the intermediate lead and contact resistances )

With an unpowered unit . . . . . one then reads across the RED ARROW fried tantalum top and bottom tabs for its present resistance value. Close to 0 ohms ?

Then measuring from its top tab over to the 2200 elect + terminal should be close to the same.

Now for the mystery tandem pair, you need your GOOD board to measure across them to get their paired resistance.
See if it is reading close to 0 ohms or is it on up as high as ~1.3 ohms ?
ALSO take a like reading on the same parts on the burnt board., is it same low ohms or an open circuit ?
Should it happen to read 20 or 200 ohms, would be suggesting of your having had a carbon composition pair.

Elsewhere on the board I can partially see a modern day metal film 2 watt what looks to be either a 0.22 or 2.2 ohm resistor.
Which Is what you would expect to be finding on this board
BUT for those two parts , their axial lead bonding and caseis looking akin to 2 antiquated 2W carbon composition resistors, and they are also BURNING in the same manner and positions that they do, when they fail.

BUT the case color coding bands aresomewhat akin to inductor marking protocol.

The way the photographs color reproduction is showing up for me is SILVER end band RED band GOLD band VIOLET band and SILVER, other end band.

One other factor unavailable is their odor . . .the carbon compositions emit their distinct phenol odor on overheating . . . .akin to what you might relate to the odor of LYSOL, a readily available cleaning and disinfectant product.. A nearby nose sniff should still detect that odor.



I also have never seen as low of an inductance of 2.7uh heat up that much, unless you come up in the above reuested info, one hefty current level being available.

Wierd that there was no inline fuse nearby also.
Unless these units were carbon composition resistors being used as sacrificial fusible resistors.

BTW what is this mystery units brand and model number ?
Waiting to see which way the resistance suggests on the reading of the parallel pair on the GOOD board.


73s de Edd
 
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jacob varley

Mar 28, 2017
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Oh yeah, TONS of current available for this baby. It's rated for 12vdc but was given 16.8vdc from a Li Ion battery. This is for location sound recording and sending audio to directors, producers, and so on. This is technically a desk top device but many guys put it in their bag due to it's size, power consumption, and performance. We run 4 cell lithium ion batteries (NP1) into a distribution that's generally unregulated. I'm fairly certain the extra 25% more volts did it in. This NP1 batteries can supply enough current to cook no problem. I know the parts are inductors because I looked them up and measured the old to the new and the old actually had the same resistance value but I'm replacing anyway, 1.2ohms. I did the inductor test and removed them altogether, removed the destroyed cap, and the unit powered up fine. The power input on this device is right next to it's antenna and at 216mhz I can see why they wanted to filter their power. I could just bypass the inductors with wires (as some forums have said to do) but I'd rather be as close to original as possible. I contacted the company for help on this and they said no, send it in. It's far out of warranty and their service isn't fast. I honestly find it funny that they're so concerned about making sure their components are filtered on so many levels because honestly, these units sound like shit. They're super compressed, noisy, tons of hiss, RF interference up the ass, etc. They aren't cheap but there are so many better options out there.

I did remove the parts from the working device and swap them out and the unit works perfectly. I measured across and everything seemed fine, the inductors weren't getting even warm so again, I'm chalking this up to the extra voltage that's well above 10% tolerance. In my theory, when I removed the cap the unit "worked" (meaning it emitted RF and the old inductors didn't get hot) and the only use of that cap was for RF filtering - your thoughts?

http://comtek.com/bst-75/
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Inductors appear to be 2.7uH

Tantalum cap 4.7uF 25V

Any chance the power was connected up the wrong way? Different (wrong) power supply?
 

(*steve*)

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The other possibility is that the tantalum failed in their usual manner (short circuit) and it took out the two inductors.

It was with asking if something odd had happened to the power. That's more likely to happen again.

It might be worth replacing both of those caps. It may save you if the other one is preparing to kill itself.

How old are these units?
 

jacob varley

Mar 28, 2017
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4 years old, I ordered 4caps (actually found them easily thanks to the identifying) so I'll replace them.
 

(*steve*)

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Be careful with the orientation (they're polarised) and don't apply to much heat!
 

jacob varley

Mar 28, 2017
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I'm glad you said that, I forgot about polarization. On larger caps that's obvious, so thank you.
 

73's de Edd

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Sir jacob varley . . . . .


Just a ton of additional . . . . . . "NOW I know why it did that " . . . . . . facts now coming forth.


(meaning it emitted RF and the old inductors didn't get hot) and the only use of ((( that))) cap was for RF filtering - your thoughts?

Nope . . . . the best capacitive type of RF / RFI filtering is being provided by ceramic capacitors of .001-----.01 cap range
(lHigh or low end of the RF spectrum)

73s de Edd
 
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