Carbon Composition Resistor Replacement

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Dear Freaks,

 

Carbon composition resistors litter all the old electronics and power controls equipment in facilities I service.    Carbon comp resistors are basically obsolete, what replaced them? 

I need % percent resistance tolerance, 1 Watt, and the ability that the old carbon composition resistors had to be able to hold up to pulse loading with minimal inductance.  Also they need to last the test of time.  

Any idea what kind of axial resistors would work well for an abusive application such as my resistors which I'm using on gate pulse transformers for DC drives?

 

Exactly, I want the best replacement money can buy, what kind of resistors would we recommend?  Wire wound resistors have inductance, please don't mention these nor carbon film which don't hold up and have changing resistance values over their service life.

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Ceramic perhaps?

 

 

You did not say what tolerance you needed, but you can search.

Jim

Click Link: Get Free Stock: Retire early! PM for strategy

share.robinhood.com/jamesc3274

 

 

 

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Thanks for the help Jim,

 

Lots of websites say that carbon comp is gonzo but no one says what to use, ceramics look great, i was about to buy metal film but this will rock.

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great, come back and let us know your experience with them after you try them out!

 

Jim

 

Click Link: Get Free Stock: Retire early! PM for strategy

share.robinhood.com/jamesc3274

 

 

 

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I wound up going for the OX82GKE Ceramic Comp 10% Surge....

I like how pricey they are too!  You know you are getting a good product when you pay almost two bucks for a single 1 watt resistor, great find.

 

There won't be any updates on this one, equipment goes into service and doesn't come back until it blows up again, if the new resistor fails like the last one did, I will post but otherwise, thanks again for the help. I miss having a job where I needed this forum every day =(

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Carbon film? Metal film?

#1 This forum helps those that help themselves

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#4 "If you think you need floating point to solve the problem then you don't understand the problem. If you really do need floating point then you have a problem you do not understand." - Heater's ex-boss

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All types of film resistors have a tendency to have significant inductance and/or capacitance, I think the OP doesn't want that.

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From what I'm reading, seems like the old carbon composition resistors were great.  No one product can do everything they can do unless I'm wrong. I ultimately went with the ceramic after reading online somewhere else that carbon film suffer from long term issues with drift.  Not sure how they stand up to surge currents either.  I assume they are non inductive as carbon composition were.   Too bad carbon comps are all but vanished now, they really did a lot of stuff for really cheap

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I just remember the smell.    It was horrible.

 

From memory,  a 2W was about 25mm long and 5mm diameter.    They would be warm at 1W.   Hot at 2W (and smell).    Anything over 2W would release all the wax as well as even worse smell.

 

David.

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smkipus wrote:
if the new resistor fails like the last one did

 

Just curious, was "the last one" the original carbon comp or a replacement that failed early?

If a replacement, what type?

 

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El Tangas wrote:

All types of film resistors have a tendency to have significant inductance...

 

Due to the way they are constructed.  A carbon film is applied to a cylindrical insulator and then a spiral cut is made in the film (similar to threads on a screw) to set the resistance.  So these devices are "wound" carbon resistors; the winding type of construction leads to the inductance.

Letting the smoke out since 1978

 

 

 

 

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Yeah I don’t know if the carbon comp failed or if the gate pulse transformer failed. Resistor was black in the middle and in two pieces, gate pulse transformer had a piece melted down near the resistor was soldered onto the xformer... not sure how to determine who killed who really. All I know is that mouser and digikey don’t carry one watt or two watt carbon comps so I’m glad the ceramic ones exist now even if they are expensive that’s fine.

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The mosfet probably failed and pushed the drain energy through to the gate as the silicon melted. I wouldn't have though surge capability was a critical parameter in the gate circuit - you pretty well know what the conditions are at design time.

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I have tons of those old carbon composition resistors in my collection.  I didn't know I had something so special.  I will remember to use them when I need low inductance.  I have a bunch of those great big ones too.  Somebody gave me a big box of resistors all jumbled together years ago, and I separated them out into little baggies by resistance, and learned the color codes at the same time.  Good to know they have special uses.

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You can easily have 5 amp or higher surge current in gate drive circuits for high power mosfets. Choosing a 1/4 watt (the actual average power is less) that can handle the surge can be a challenge.

Letting the smoke out since 1978

 

 

 

 

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Are we talking about a 'surge' which is an irregular overload event or a 'peak' which is expected? 

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No the composite are not obsolete and you will not replace easy.

you have RS & Farnell has a lot in stock. use for new design.

RS serie : 

  • RCC050 ( 0,5W)

or 

  • RCC025 (0,25W)

example:

  • RS-lagernummer 166-3937

 

 

 

 

Thierry Pottier

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Lately I've discovered there is 'service  life' and 'service life'.  I've been restoring a couple of old Hammond Organs.  I seems that after 60 years or so, some carbon comp resistors that spent a lot of time with DC across them just simply fade away, increasing dramatically in resistance or going open.  Mostly plate and screen dropping applications, apparently it happens enough that it is one of the first things you look at if an amp doesn't sound right.  The tubes are rarely an issue, all of mine are factory originals 8)

 

Tom Pappano
Tulsa, Oklahoma

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'Molded mud' was the affectionate term for these resistors. Not sure if electromigration would be the issue in the carbon resistors going high/open - this is an issue with metal film resistors so you need to choose wisely.

 

About the only time I worked with carbon comp resistors is with the electronics kits from radio shack. I'm showing my age! Pretty much when I got into electronics in the mid 70's, metal film resistors were the go.

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I need % percent resistance tolerance, 1 Watt,

Not sure what you mean by "need" 1W ...if your power is 1W, you need to double that & use 2W.... you can't run a 5W resistor at 5W, maybe 2 or 3W without burning it up.  You can run a 5W at 5W if you put it in liquid, blow a fan on it, etc. 

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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Carbon composition  has never make i % , best was 5% normal 10% 

if you need 1% , see another type but they will not take so much peak current. 

 

Thierry Pottier

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"Thick film resistor" might be a candidate:

http://www.resistorguide.com/thin-and-thick-film/

 

With wire wound resistors there are also "bifilair" wound resistors.

This means that the wire is fold double before winding it on some tube.

Because the current winds up and down the spiral the inductance of these half windings (alsmost completely) cancel each other out.

 

There are also lots of variations of resistors.

Quite enough to get easily lost...

Some of the power resistors are built in the same form factor as a TO220, or TO247, and those are often designed for low inductance.

 

Oops, TO220 is not an "axial resistor".

Doing magic with a USD 7 Logic Analyser: https://www.avrfreaks.net/comment/2421756#comment-2421756

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When I started my career in the early 70's, carbon comp resistors were being replaced by film. We found out the hard way that carbon comp withstood surges from lightning real well whilst the carbon film did NOT. Look for 'pulse withstanding' resistors. Digikey carries a lot of them.