Crossing a KOA RK73H Resistor from Japan to Walsin: RK73H2BTTD1003F Decodes to 1206, 100 Kilohm, 1%, and 27 Walsin Part Numbers in 5 Series Groups Answer It, 1 on the Hong Kong Shelf

A KOA RK73H cross reference for Japan starts with one string. KOA’s own ordering example decodes to a 1206, 100 kilohm, plus or minus 1% chip resistor, and we counted 27 Walsin part numbers that answer it, in 5 series groups. One of the 27 is on our Hong Kong shelf.

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Venatech Limited, an authorised Walsin distributor in Hong Kong, holds the Walsin Technology (Walsin) chip resistor export of 234,815 rows, 234,401 of them distinct part numbers once embedded spaces are removed. This post is for a procurement or design engineer in Japan who has a KOA RK73H line on a bill of materials and wants a second source, bought in small lots from Hong Kong. We name one KOA ordering string, decode it from KOA’s own sheet, and set it against Walsin’s export field by field. The market figure is sourced and dated, and every Walsin part number is real.

Why does Japan’s passive component output matter to a resistor buyer?

Because the official numbers show a flat segment, not a booming one. JEITA’s June 2026 production page reports passive components at 138,212 million yen for the month, 103.2% of June 2025, and 750,219 million yen for January to June, 97.3% of the same period a year earlier. We read that page on 23 October 2026.

The same page shows electronic devices up strongly and integrated circuits far ahead of a year earlier, so Japan’s electronics output is not weak overall. The page gives no breakdown of resistors, capacitors or inductors, and carries no release date, so we draw no conclusion about any one line. Our view, labelled as ours: a segment that is down by 2.7% for the half year is a segment where a buyer can reasonably want a second source on the common parts, and a resistor like the one below is common. Nothing in the JEITA page says any KOA part is short, and we do not say it.

What does a KOA RK73H number say, field by field?

Seven fields, and five of them cross cleanly. KOA’s RK73H sheet, whose last footer is dated 27 January 2026, shows the boxed example 2B T TD 1003 F under the type RK73H; joined, that is RK73H2BTTD1003F, a number we assembled from the boxes and have not checked against KOA’s own lookup. It is not in the Walsin export, and it is not a Walsin number.

KOA field	Code in the sheet	Meaning (KOA’s sheet)	Walsin side	Match / mismatch
Type	RK73H	Precision thick film chip resistor, 0.5% and 1%	Walsin series group, set by the class letters and a characteristic letter	Mismatch: no one-to-one series; you choose a group
Size	2B	1206	Characters 3 and 4: 12	Match on 1206, but see the size-code section below
Termination	T	Sn, lead-free	T in the tail; export says Sn base (lead free)	Match
Packaging	TD	KOA tape code	Last tail letter, L or R; export says 7-inch reel taping	Not comparable: the export carries no tape pitch, so confirm the tape
Resistance	1003	100 x 10^3 ohm, 100 kilohm	1003	Match, same digits
Tolerance	F	plus or minus 1%	F	Match
TCR and power	not in the number	Read from KOA’s ratings table	Export TCR 24 at 100 ppm and 3 at 50 ppm; power 1/4, 1/2 or 3/4 W	Open: enter your own values

KOA’s ordering text has no TCR code, so the number alone cannot say whether your design leans on the TCR. It also has no rated power field. Both are read from the ratings table in the KOA sheet, and both differ across the Walsin candidates.

How many Walsin parts answer a 1206, 100 kilohm, 1% line?

Twenty-seven, from five groups, and they are not interchangeable. We parsed the 37,566 distinct 1206 part numbers in the Walsin chip resistor export and found 27 at 100 kilohm and plus or minus 1%: 10 general purpose, 8 high power, 5 high voltage, 3 high precision and 1 anti-surge. Of the 27, 15 sit in series the export labels automotive and 12 do not; 18 are rated 1/4 W, 6 are 1/2 W and 3 are 3/4 W.

Walsin part	Group (export)	Power	TCR (ppm/°C)	Hong Kong shelf, 23 September 2026	Match / mismatch against the KOA string
WR12X1003FTL	General purpose	1/4 W	100	Yes	Match on case, value, tolerance, termination; TCR and power to check
WR12X1003FTR	General purpose, LF 100 ppm	1/4 W	100	No	Match on the same fields; mismatch on the packaging letter
WF12K1003FTL	High precision thick film	1/4 W	50	No	Match on value and case; mismatch on group and TCR, a tighter 50 ppm
WF12P1003FTL	High power	1/2 W	100	No	Match on value and case; mismatch on power, a higher rating
WF12A1003FTL	High power	3/4 W	100	No	Match on value and case; mismatch on power
WF12V1003FTL	High voltage	1/4 W	100	No	Match on value and case; mismatch on group, a high-voltage part
MF12E1003FTL	Anti-surge, series labelled automotive	3/4 W	100	No	Mismatch on group and power
WR12X1003FTLJ	General purpose, series labelled automotive	1/4 W	100	No	Match on all fields above; mismatch on the series label

KOA’s sheet carries a line reading “AEC-Q200 Qualified” followed by a size list that includes 1206 (2B). That is KOA’s wording for its own parts, and we do not translate it into a Walsin claim. Walsin labels some of its series automotive, and we do not say a Walsin part is certified to anything; whether the commercial or the automotive-labelled part belongs on your board is a qualification decision that stays with you.

Why does a two-digit size code pick the wrong case?

Because in the Walsin export three of the nine size codes you would map from KOA are shared by two different case sizes. Of 209,468 distinct part numbers with the prefixes WR, MR, SR, WF, MF, SF and WK, the code 12 marks 35,343 parts at 1206 and 1,660 at 0612, 20 marks 19,712 at 2010 and 830 at 1020, and 25 marks 20,037 at 2512 and 1,660 at 1225. We have not seen this counted anywhere.

KOA size code	Case	Walsin code	Distinct parts with that code	Match / mismatch
1F	01005	01	755	Match, one case
1H	0201	02	17,801	Match, one case
1E	0402	04	22,960	Match, one case
1J	0603	06	34,177 at 0603, 3 labelled 0805	Match; 3 anti-surge rows carry a different case label
2A	0805	08	34,684	Match, one case
2E	1210	10	16,939	Match, but not 12
2B	1206	12	35,343 at 1206, 1,660 at 0612	Mismatch risk: two cases
2H	2010	20	19,712 at 2010, 830 at 1020	Mismatch risk: two cases
3A	2512	25	20,037 at 2512, 1,660 at 1225	Mismatch risk: two cases

Every one of the 0612, 1020 and 1225 parts sits in the wide-terminal power group, where the characteristic letter after the size code is L, as in WK12L1R00FTL. A filter on the code 12 alone returns both shapes, so the characteristic letter has to be read as well. The trap that catches buyers is 2E: KOA’s 1210 maps to Walsin’s 10, so truncating “1210” to its first two digits, 12, lands on 1206. We counted the three odd labels at code 06 ourselves, and we have not resolved with Walsin which label is intended.

What do we hold in stock, and what do we not hold?

One of the 27, and no datasheet for most of the family. As at 23 September 2026 our list holds 1,125 part numbers, 254 of them chip resistors, and WR12X1003FTL is the only 1206, 100 kilohm, plus or minus 1% part among them. The other 26 are a factory order.

The stock list is a dated snapshot, and we quote part-number counts, never piece counts. The ready stock page shows what we hold. We hold two chip resistor datasheets, the general purpose WR and MR series, and none for the high power, high voltage or anti-surge groups that supply 14 of the 27 candidates. The WR sheet we hold is ASC_WR_V24, dated September 2016, so we say plainly that it is ten years old. The 28 Walsin datasheets we hold run to 451 pages, and none names a production site.

How can Venatech help a Japanese buyer cross a KOA resistor?

By stating the differences instead of hiding them, in small lots. Venatech Limited is an authorised Walsin distributor in Hong Kong. Walsin is our only authorised line, and the other lines we supply are Stackpole and Viking.

• Cross-reference. Paste your KOA number into the free cross-reference tool, which decodes 18 manufacturers’ part numbers across 800,000+ crossable parts, and read each Walsin candidate with match and mismatch stated field by field.
• BOM check. Upload a bill of materials to /bom/ and have each line checked against the same engine.
• Ready stock. The ready stock list is a Hong Kong snapshot dated 23 September 2026, never live-synced.
• Service. Hong Kong-based, small lots, cross-referencing help, and a quote requested through the site. Our address is Unit 207, 2/F, Sun Ling Plaza, 30 On Kui Street, Fanling, N.T., Hong Kong, telephone (852) 2628 4777.

A worked example from our own export: a KOA line that reads 1206, 100 kilohm, 1% maps first to WR12X1003FTL, the stocked general purpose part, and then outward to the 1/2 W and 3/4 W high power parts if your design wants more rating. Our chip resistor range lists the families. For the method behind other makers, see crossing Panasonic and ROHM chip resistor families to Walsin, and for the pasting trap see why Walsin part numbers do not paste into your BOM. Confirm against both datasheets and qualify in your own circuit. Ask your compliance team about any import or product rule; we give no legal advice.

The short version

JEITA’s June 2026 page puts Japan’s passive component production at 97.3% of last year for the half. For a KOA RK73H line the useful number is 27: the Walsin part numbers that answer a 1206, 100 kilohm, 1% string, with 4 other groups behind the general purpose part, and 1 on the shelf. Three of the nine size codes you would map are shared by two cases, so read the characteristic letter as well.

Send us one KOA line from your bill of materials and we will return the Walsin candidates with every difference stated. When your sheet says 2B, are you certain which of two cases your filter just returned?

Sources

Fetched 23 October 2026. The market statements are taken from the JEITA page and the ordering information from the KOA sheet; the Walsin counts come from our own export and stock list.

• JEITA, production by the Japanese electronics industry, June 2026 (English statistics page, no release date shown): https://cdn.jeita.or.jp/english/stat/electronic/2026/product_06.html
• KOA, RK73H precision thick film chip resistor sheet (last footer 01/27/26): https://www.koaspeer.com/pdfs/RK73H.pdf

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Frequently asked questions

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