Before you begin. This procedure is general reference information, not professional advice. Equipment varies by manufacturer, model, and year. Always follow the documentation supplied with your equipment — where it differs from this page, follow the manufacturer. Verify that you have the tools, the working conditions, and the ability to do this task safely. If anything is unclear, if the equipment is damaged, or if the task exceeds your experience, stop and use a qualified professional. You are responsible for your own safety and for the outcome. This site accepts no liability for any loss, damage, or injury arising from the use of this information.
Specifications marked unverified could not be traced to a manufacturer source. Do not rely on them — obtain the value from your equipment documentation.
Summary
Your equipment carries a label with its power requirement. The label lists four things: the output voltage, the current capability, the polarity (whether centre pin is positive or negative), and the connector type. Find the label, read these four items, then search for an adapter that matches all four.
Necessary equipment
| Item | Note |
|---|---|
| Magnifying glass | Optional. Use to read small or worn markings on the equipment. |
Locate the power specification label
The marking on the equipment may be small or worn.
Use a magnifying glass to read it.
- Locate the power input connector on the rear or underside of the equipment.Report a problem with step 1, Locate the power specification label
- Find the label with the power specification marked on the equipment case near the connector.Report a problem with step 2, Locate the power specification label
- Open the user manual if the marking on the case is not readable.Report a problem with step 3, Locate the power specification label
Read the specification data
- Read the output voltage from the label (marked as V or Vdc).Report a problem with step 1, Read the specification data
- Read the maximum current from the label (marked as A or mA).Report a problem with step 2, Read the specification data
- Find the polarity symbol on the label: a circle with a dot or circle reversed.Report a problem with step 3, Read the specification data
- Write down the connector type: the barrel diameter and pin size.Report a problem with step 4, Read the specification data
Match the adapter to the specification
Do not connect a power adapter with reversed polarity.
Reversed polarity can damage or destroy the equipment.
- Select an adapter with output voltage that matches the marked voltage exactly.Report a problem with step 1, Match the adapter to the specification
- Make sure the adapter current rating is greater than or equal to the marked current.Report a problem with step 2, Match the adapter to the specification
- Match the polarity symbol on the adapter to the equipment marking.Report a problem with step 3, Match the adapter to the specification
- Make sure the adapter connector size fits the equipment socket.Report a problem with step 4, Match the adapter to the specification
- Insert the plug into the socket and apply light tension to the connection.Report a problem with step 5, Match the adapter to the specification
Terminology
This page uses one term for each item and holds it throughout, as ASD-STE100 requires. Equipment sellers and other guides use the names below for the same parts.
- power adapter
- Also called: no common alternatives
- output voltage
- Also called: no common alternatives
- current
- Also called: no common alternatives
- polarity
- Also called: no common alternatives
- barrel connector
- Also called: no common alternatives
When to use a professional
Contact the equipment manufacturer if the marking on the equipment case is not readable and the manual is not available.
Common questions
What if the label is worn off or illegible?
Check the user manual or manufacturer website for your equipment model. Many manufacturers provide downloadable documentation. If the manual is unavailable, contact the manufacturer's support line with your equipment model number.
Do I have to match the current exactly?
No. A higher current rating is safe. For example, if your equipment requires 2 amps, a 3-amp adapter is fine. The device only draws what it needs. However, the voltage and polarity must match exactly.
What happens if I connect the wrong polarity?
Reversed polarity can damage or destroy the equipment. Modern devices often have protection circuits that prevent damage, but older equipment typically does not. Never guess about polarity; verify it before connecting.
Are there universal power adapters?
Universal adapters exist, but they require careful selection. A true universal adapter must include swappable connector tips and voltage/polarity switches. Even then, you must verify every setting matches your equipment marking before use.
How do I know if a connector is 2.1mm or 2.5mm?
A 2.5mm connector is slightly thicker and will fit loosely in a 2.1mm socket. A 2.1mm plug will not fit in a 2.5mm socket. If unsure, measure the connector with a caliper or take a photo to a local electronics retailer for comparison.
Can I use an adapter from a different brand if the voltage and current match?
Yes, as long as the voltage, current, polarity and connector type all match. The adapter does not have to come from the original manufacturer.
Related procedures
Sources
Every specification on this page is traced to one of these sources. Tier 1 is a manufacturer document, a published standard, or a government safety authority. See Standards for the full tiering rule.
Revision history
Current version 1 · updated 2026-08-03 · next review due 2027-08-03
- v1 · 2026-08-03First publication.
Corrections to this page are listed in the public corrections log. Reports that are credible and not yet verified are listed in the public errata register, and an open one renders above the step it concerns.
Comments and corrections
Found an error? A correction with a manufacturer source is applied and logged publicly. You can also write to corrections@fixchecklist.com.
Every step above carries its own report control, which tags the report with that step so a correction reaches the right place. For anything about the procedure as a whole — the order of the sections, a step that is missing, something that did not match your equipment — use this: report something about this whole procedure.