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Help Inductor Identification for an HD20

aplmak

Well-known member
Ok.. so I recapped a while back a HD20 (old 20MB version)... It was working just fine... I booted it up today and it whirled up and started booting.. All of a sudden the burning smell of components.. and the drive spun down... Found it was an inductor on the hard drive pcb.. Well I happened to have another HD20 and took a snapshot of the color codes.. But I need help finding a replacement... Any help would be greatly appreciated!!!

hd20inductor.jpg

 

aplmak

Well-known member
I think you read from the large silver band to the left (this pic is upside down) So I see green then maybe brown and then blue followed by gray/silver?

 

aplmak

Well-known member
Yeah I don't think the drive is seized.. It was running when it failed.. Strange why it failed.. The computer was booting normal and extensions were loading...

 

aplmak

Well-known member
Any idea why you think it may have failed?? I had put in new tantalum caps on the hd20 pcb... and that was a while back.. the drive was working fine.. All I could think is I had some whisker solder hanging around that could have shorted it..

 

360alaska

Well-known member
Well you can try the drive with another board... and toast that board... if it's popped that means too much current draw, and that could mean a seized motor...

 
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360alaska

Well-known member
Well you can try the drive with another board... and toast that board... if it's popped that means too much current draw, and that could mean a seized motor...

 
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aplmak

Well-known member
360alaska... You think this one is a suitable replacement?? Also does the orientation matter?? Is it polarity sensitive?? Sorry I sound like an idiot.. I don't think it matters from what I know about inductors.. It's hard to see these colors against a green case... I think it's black then blue then gold and gold.. My electronics guy gave me this..  I actually called him.. He thinks the first band is green... but again hard to tell on a green case.. what a pain!

IMG_4241.JPG

 
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techknight

Well-known member
Need to find out why it burned out. the inductors are used to help stabilize the output for feedback/regulation purposes, as they form a pi filter. 

If it started smoking, you have a short on that voltage rail. 

I have learned over the years in electronics repair, Dont chase the symptom, chase the cause which in this case requires extensive knowledge of electronic circuitry. 

Also the color bands in the picture arnt making any sense. Dont know if they are faded, or a potato cam, or something... I see a green brown blue. It would make sense if it was gold, but I just cannot tell if its gold. 

 
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aplmak

Well-known member
Well I replaced the inductor.. It still didn't work.. So I recapped it again and whala!! It works.. I think there was a bad cap that may have done something.. I tested it for a while and no issues now..

 

360alaska

Well-known member
Need to find out why it burned out. the inductors are used to help stabilize the output for feedback/regulation purposes, as they form a pi filter. 

If it started smoking, you have a short on that voltage rail. 

I have learned over the years in electronics repair, Dont chase the symptom, chase the cause which in this case requires extensive knowledge of electronic circuitry. 

Also the color bands in the picture arnt making any sense. Dont know if they are faded, or a potato cam, or something... I see a green brown blue. It would make sense if it was gold, but I just cannot tell if its gold. 
+1 on that, it's almost always a bad idea to just replace a burnt component. Imagine that the inductor was shorted with one side being 5v and the other being almost shorted to ground (1 ohm). 5 Volt/1 Ohms Resistance = 5amps (Assuming the 5v supply can supply that much.) See the problem? I'm guessing that inductor could probably only take 1/4-1/2 amp tops. Hard to know without a model number and a spec sheet but you can sorta guess based on it's size.

More info:

https://www.allaboutcircuits.com/textbook/alternating-current/chpt-3/ac-inductor-circuits/

 
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aplmak

Well-known member
I think there is a possibility that one of the replaced capacitors may have been crossing over to another trace or onto the rail of the board.. and that is what caused it.. Because after replacing the first recap it is working just fine.. no issues... So perhaps by me soldering in new caps I fixed where it was bridging to another circuit.. This is my thought.. I do agree that just replacing something shorted is not the best solution and finding the cause is the real solution...

 

360alaska

Well-known member
Also, consider that a cap installed backwards is essentially a short. That being said usually the cap blows...

 

aplmak

Well-known member
I considered that.... I double checked them all.. they were all installed with the right polarity.. strange.. It works just fine now..

 
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