STC

What STC does

STC, Incorporated, doing business as Sun Transformer, is a privately held custom magnetics manufacturer and electronics manufacturing services (EMS) provider headquartered in McLeansboro, Illinois. Founded in 1986 after Brad Cross and a group acquired engineering files and select assets from National Transformer, the company designs and builds small to mid-size custom electronic transformers, inductors, chokes, coils, and toroids with power ratings up to 10 KVA, plus complementary printed-circuit assemblies, custom cable assemblies, and wire harnesses. Manufacturing is 100% domestic at a single ISO 9001:2015-certified and ITAR-registered facility (Registration M38782), with in-house SMT assembly, environmental testing (NEMA TS2 chamber), and 3D printing for prototype tooling. The product portfolio spans 18+ transformer types (custom, power, three-phase, high-voltage, isolation, autotransformer, ferroresonant, control, switching, instrument, high-frequency, encapsulated, inverter, PC-mount, toroids, inductors/chokes, coils) targeting eight primary verticals: aerospace/avionics, medical, defense/military, marine, broadcast, industrial, renewable energy, and commercial.

STC's customer base is concentrated in safety- and mission-critical applications, including Boeing (transformers for the KC-46 aerial refueling tanker), Honeywell (quality partnership with onsite Six Sigma process reviews), Garmin (avionics and navigation), Gates Air (broadcast), and industrial accounts such as SPX Corp, DORMA, and CO-AX Technology. The company is ITAR registered, JCP certified, IPC-A-610 (J-STD-001) compliant, and Dodd-Frank Section 1502 conflict-minerals compliant, with approximately 30% of the workforce holding 15+ years of tenure. The go-to-market is direct enterprise field sales with quote-based custom pricing and multi-year contract cadence; the company does not publish prices and customers submit specifications through a website quote-request form or direct sales contact. Revenue is not publicly disclosed, and STC remains founder/management-owned with no external funding rounds, parent company, subsidiaries, or M&A activity on record.

Name

STC

Legal name

STC, Incorporated

Website

https://suntransformer.com

Company type

Private

Founded year

1986

Operating status

Operating

Headcount range

11–50 employees

Short description

STC (Sun Transformer) is a privately held, ITAR-registered custom magnetics manufacturer in McLeansboro, Illinois, producing transformers up to 10 KVA, inductors, coils, and integrated PCB assemblies for aerospace, defense, medical, and industrial customers including Boeing and Honeywell.

Ownership category

akta.pro rank

Product category

Custom Electronic Transformers and Magnetics Manufacturing

NAICS

Power, Distribution, and Specialty Transformer Manufacturing (335311)

SIC

Power, Distribution & Specialty Transformers (3612), Electronic Coils, Transformers & Other Inductors (3677), Electronic & Other Electrical Equipment (No Computer Equip) (3600)

akta.pro industry

PRIMARYIMAGAAAA

Transformers (Power, Distribution, Instrument, Specialty)

Industrials, Manufacturing & Construction/Electrical Equipment & Industrial Electronics/Power Generation & Grid Equipment (Transformers, Switchgear, Substations)

SECONDARYEUADACAG

Instrument Transformers (CTs/VTs) & Sensors (Conventional/Optical)

Energy, Utilities & Environment/Electric Transmission & Distribution (T&D)/Substations, Switchgear & Protection Systems

Keywords

• Custom electronic transformers
• Magnetics manufacturing
• Aerospace magnetics
• Defense electronics manufacturing
• Electronic manufacturing services

Headquarters

HQ city

Mcleansboro

HQ country

United States

HQ region

North America

Offices1 record

Markets served

GTM type

B2B

Offering type

Hardware or Manufacturing

Cost components

Personnel, Operations, Technology or R&D, Supply Chain, Infrastructure, Others

Revenue model

1. Custom Transformer Sales: Design and manufacture of custom electronic transformers, inductors, coils, and toroids for aerospace, medical, defense, marine, broadcast, commercial, and industrial applications. Revenue generated through one-time product sales based on custom specifications.
2. Printed Circuit Assembly (EMS): Electronic manufacturing services including PCB assembly, custom cable assemblies, and wire harnesses for customers requiring complete electronics assembly solutions.
3. New Product Development Services: Engineering support during new product development phase, including design assistance, prototype building and testing, and custom magnetics integration.

Pricing tiers

Go-to-market motion1 record

Distribution channels1 record

Marketing channels5 records

Core offering

STC (Sun Transformer) is an ITAR-registered US manufacturer that designs and builds custom electronic transformers, inductors, coils, toroids, and related magnetic components up to 10 KVA, along with complementary printed circuit board assemblies, custom cable assemblies, and wire harnesses. Its products serve high-reliability applications in aerospace, defense, medical, marine, broadcast, industrial, and renewable energy markets, with 100% domestic manufacturing in McLeansboro, Illinois.

Product overview

STC Sun Transformer operates as a custom electronic transformer manufacturer and electronic manufacturing services (EMS) provider. The core product portfolio centers on custom magnetic components including transformers (custom, power, control, high-frequency, high-voltage, inverter, isolation, toroidal, and encapsulated types) and inductors/chokes, with power ratings ranging from small PC-mount units to 10 KVA three-phase transformers. The company provides complementary EMS offerings including printed circuit assemblies (PCB), custom cable assemblies, wire harnesses, and 3D printing prototyping services. This integrated approach allows customers to receive transformers already mounted to circuit boards, reducing shipping damage and inventory imbalance. The company holds ITAR registration and serves regulated industries including aerospace, defense, medical, and marine where source traceability and quality certifications are critical.

Differentiator

Problem solved

Functional benefit

Quantifiable outcome

• Customer return rate reduced from 25 RMAs in 2002 to 2 RMAs in 2021
• +2 more outcomes

Named customers7 records

Segments8 records

Ideal customer profiles5 records

API detail

Has API

No

API docs

API detail

Core technology

AI maturity

App detail

Feature5 records

Partnerships

One partnership is on record.

• Honeywell InternationalcoreImplementation/ SI/ Consulting PartnerQuality partnership with Honeywell International including regular onsite visits from Warren Witmer, Supplier Development Project Manager and Six Sigma Black Belt. Partner conducts inspections, process reviews, first-article inspection, self-release audits, and provides supplier development education. STC Quality Manager Angie Calkin serves as the primary contact.

Scale indicators4 records

Recent moves9 records

Expansion highlights5 records

Direct peers

• Triad Magnetics: Triad Magnetics designs and manufactures custom and standard transformers, inductors, and power magnetics for industrial, medical, aerospace, and military applications — directly overlapping STC's core magnetics product line and target verticals.
• Prem Magnetics: Prem Magnetics designs custom and catalog transformers, inductors, and chokes for industrial, medical, and audio applications — overlapping STC's transformer portfolio.
• Abbott Technologies: Abbott Technologies builds custom and standard transformers for aerospace, military, and industrial applications, with comparable ITAR-registered, military-spec capabilities.
• Coilcraft: Coilcraft produces inductors, transformers, and other magnetics for aerospace, defense, medical, and industrial customers, including high-reliability and custom-wound products comparable to STC's portfolio.
• Butler Winding: Butler Winding manufactures custom transformers, coils, and toroidal inductors for aerospace, military, and industrial customers, directly competing with STC in low-to-mid volume custom magnetics.
• Payton Magnetics: Payton Magnetics manufactures custom transformers, inductors, and chokes for industrial, military, and aerospace customers — a comparable mid-sized custom magnetics manufacturer.
• MPS Industries: MPS Industries designs and builds custom magnetics including transformers, inductors, and chokes for medical, military, aerospace, and industrial applications — closely overlapping STC's product mix and customer verticals.
• Standex Electronics (Magnet Group): Standex Electronics designs custom magnetics, reed switches, and sensors for aerospace, defense, medical, and industrial markets — a comparable custom magnetics specialist serving overlapping high-reliability verticals.

Broad incumbents

• Eaton: Eaton is a large multi-national power management company producing transformers, power supplies, and electrical components for aerospace, defense, and industrial markets — a scaled incumbent with adjacent but broader offerings.
• Hubbell (Transformer Solutions): Hubbell is a diversified electrical equipment manufacturer with significant transformer and magnetics product lines serving utility and industrial customers — a larger, broader incumbent in STC's product category.

Market position

Strengths4 records

Weaknesses4 records

Competitive moat6 records

Key risks5 records

Key highlights6 records

Customer concentration

• Xlinkedin.com/company/stc-inc.
• Facebookfacebook.com/stcincorporated
• LinkedInlinkedin.com/company/stc-inc.

Compliance5 records

Revenue estimate

Valuation estimate

Number of profiles

Profiles5 records

Funding overview

Funding rounds

Investors

Funding detail is available on the Subscription and Enterprise plan.Contact sales →

M&A

Investments

M&A and investment is available on the Subscription and Enterprise plan.Contact sales →

Frequently asked questions about STC