Product Overview
One Brown Devil, Marked On Both Faces, 4.0 Kilohm At 12 Watts
Condition
New old stock, unused. The photographed piece is the single unit in stock. Both faces carry legible white markings: OHMITE, B12J4K0 and 4K ohm on the front, 12W 8737 on the reverse, which by the usual year-week convention reads as 1987 week 37 (an interpretation, not a decode against a published Ohmite key). The brown vitreous enamel body is glossy and intact in these photos, with the normal casting seam running the length of each side. A flat welded flag lug sits at each end with a straight wire lead attached to it; the leads are bright and unbent, and no solder, cut marks or board residue are visible in these photos. Nothing here has been measured on a meter, and no packaging appears in frame.
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Product Overview
This is an Ohmite B12J4K0, a wirewound power resistor from the Brown Devil 200 Series, rated 4.0 kilohm at 12 watts with a tolerance of plus or minus 5 percent. The part number is its own spec sheet: B is the Brown Devil 200 Series, 12 is the 12.0 W rating, J is the 5 percent tolerance, and 4K0 places the kilohm multiplier where the decimal point goes, so the value is 4.0 kohm. There is no E suffix, which is the older non-RoHS spelling of the number and is consistent with the 1987 marking; Ohmite still publishes the Brown Devil line today, with current equivalents carrying the E. Per Ohmite's B12 series data the body measures 1.750 in / 44.45 mm long by 0.313 in / 7.94 mm in diameter on 18 AWG leads, built all-welded under a flame-resistant conformal vitreous enamel coating, with a maximum working voltage of 625 V for the 12 W size. At full rating into 4 kohm the part carries roughly 55 mA and drops about 219 V, so this value is power limited rather than voltage limited. The unit in the photos is the lug-with-lead build: a flat welded flag lug at each end, wire lead attached, rather than the plain embedded-axial-wire construction the series is sold with now. Whether Ohmite assigned a separate catalogue suffix to that terminal style is not confirmed, so treat the phrase as a description of the hardware in front of you. There is no N in the part number, so this is the standard inductively wound version, not a non-inductive one.
Key Features
- Ohmite Brown Devil 200 Series wirewound power resistor, 4.0 kohm, 12 W, plus or minus 5 percent
- Marked OHMITE / B12J4K0 / 4K ohm on the front face and 12W 8737 on the reverse
- Body 1.750 in / 44.45 mm long by 0.313 in / 7.94 mm diameter on 18 AWG leads, per Ohmite's B12 series data
- All-welded construction under a flame-resistant conformal vitreous enamel coating (Ohmite 200 Series datasheet)
- 625 V maximum working voltage for the 12 W size; temperature coefficient plus or minus 260 ppm/degC above 5 ohm
- Derates linearly from 100 percent of rating at 25 degC to zero at 350 degC
- Flat welded flag lug at each end with a wire lead attached, as photographed
- Standard inductively wound build; no N in the part number, so no non-inductive claim is made
Applications
- Restoring a tube amplifier or vintage power supply where the original bleeder or dropping resistor is a 4 kohm, 12 W wirewound and a modern film part would not fit the chassis or the heat budget
- Maintaining 1980s industrial or lab equipment that lists a Brown Devil by number in its parts list and needs the period-correct terminal hardware
- Building a bench load or a bleeder network where you want a part that dissipates in open air, mounts by its lugs, and does not care about being warm
- Collectors and repair shops matching an Ohmite marking exactly, where the date code and the original non-RoHS number are part of what makes the repair correct
Frequently Asked Questions
What does B12J4K0 actually decode to?
B is the Brown Devil 200 Series, 12 is the 12.0 W rating, J is plus or minus 5 percent tolerance, and 4K0 is 4.0 kilohm with the K standing in for the decimal point. The absence of an E on the end marks it as the older, pre-RoHS spelling of the number.
Has the resistance been measured?
No. The 5 percent figure is the factory tolerance printed into the part number, not a reading taken here. If your application needs a verified value, meter it on arrival.
Are the leads lead-free solder?
Not confirmed, and we would not assume so. Ohmite's current datasheet specifies a RoHS tinned finish, but this part carries no E suffix and a marking that reads as 1987, so expect a tin-lead era part and verify against the datasheet before use if that matters to your process.
Why buy this one piece instead of hunting a surplus lot?
Because there is exactly one of these on the shelf and you can see it before you buy it: both faces photographed, the full marking legible, the lug-with-lead terminals visible, no crate of unknowns to sort through and no minimum quantity attached. Shipping is $8 flat rate and free once your order passes $28, and orders leave our Idaho warehouse the same or next business day.
The reverse face reads 12W 8737, which by the usual convention puts it at week 37 of 1987, and it has been sitting still ever since, waiting to do the one job it knows. Give it air on both sides and it will turn watts into heat for you exactly the way it would have then.
