Testing Power Adaptor Correctly.

[ToddB66]

Need advice to confirm I am testing a power adaptor correctly, to see if it is working. Please advise what test or tests to do, the mode to use and where to connect the common and positive tester leads. Also what test results to expect.

I did Concentricity, Volt & Amp tests, but the results were questionable.

Test Meter: My tester is a RadioShack, Cat. No. 22-805, 24-Range Digital Multimeter, powered by a 9 Volt battery.

Power Adaptor Specs.: Brand: YHI, Made in China, Model: YS-1015-U12, Input: 100-120VAC, 60Hz, 0.45 Amps., Output: +12VDC, 1.25 Amps., S/N: 01725948, Symbol beginning left to right: Circle with dash in center connected by short horizontal line to half-circle (like letter C) with dot in the center, connected by short horizontal line to circle with plus mark in center.

Thanks much !

Todd :)

[bklein]

You need to test the adapter with a load to see how well it regulates. With any load up to the 1.25A it should keep its output at 12V within 10 percent or so. Beyond this load it may handle the higher load for a short period then shut down. Some cheap older adapters have poor regulation with no load - higher than rated voltage. You should toss it if it does this and get a better one.
If you send paypal me shipping I can send you one I know works well, at higher wattage too. I have a ton of em at work. I test em as part of my job. Barrel connector, center positive.

Barry

[ToddB66]

You need to test the adapter with a load to see how well it regulates. With any load up to the 1.25A it should keep its output at 12V within 10 percent or so. Beyond this load it may handle the higher load for a short period then shut down. Some cheap older adapters have poor regulation with no load - higher than rated voltage. You should toss it if it does this and get a better one.
If you send paypal me shipping I can send you one I know works well, at higher wattage too. I have a ton of em at work. I test em as part of my job. Barrel connector, center positive.

Barry

Barry......Thanks for your reply ! :thumb:

On the volt tolerance, by "within" do you mean 10% total spread, i.e. +/-5%, or 20% total spread, i.e. +/-10% ? In my past life as a machinist, "within" was used to mean 10% total spread, i.e. +/-5%, but I just want to be sure before going ahead with the test.

Based on a total spread of 10% (12V +/-5%) the meter reading could vary from 12.6 to 11.4 Volts.
Based on a total spread of 20% (12V +/-10%) the meter reading could vary from 13.2 to 10.8 Volts.

If my power adaptor turns out to be bad, I'll probably take you up on your kind offer of a free replacement adaptor and I pay the S&H only, thru Paypal.

Todd

[bklein]

The tolerance depends on what it specs are but the ones that I look at maintain +/-5%. Depends on what you are doing with it. Your circuit may be very tolerant or it may not be.... I have seen some really bad ones - like they say they are a 6V adapter but put out more than 10V with no load and maybe 7V with the expected load... Just place your meter in Amp mode/configuration and experiment with loads that approach 1.25A. Then take the meter out of circuit and configure in voltage mode and see what the voltage is.

If you paypal me for the cost of a flat rate priority mail box I will fill it with 12V supplies you can play with....

Anyone else for that matter. I have a bunch.

Barry

[ToddB66]

The tolerance depends on what it specs are but the ones that I look at maintain +/-5%. Depends on what you are doing with it. Your circuit may be very tolerant or it may not be.... I have seen some really bad ones - like they say they are a 6V adapter but put out more than 10V with no load and maybe 7V with the expected load... Just place your meter in Amp mode/configuration and experiment with loads that approach 1.25A. Then take the meter out of circuit and configure in voltage mode and see what the voltage is.

If you paypal me for the cost of a flat rate priority mail box I will fill it with 12V supplies you can play with....

Anyone else for that matter. I have a bunch.

Barry


Thanks again Barry ! Very interesting indeed. :thumb:

I'm expecting a phone call today from a computer techy, who will check my computer to see if the problem is with the software, etc..

I could have taken the approach that my adaptor is good, at least until after the computer diagnosis was completed, but with the scanner problem "on the table", I wanted to spend time learning how to test my transformer correctly. I'm all for gaining knowledge that can be used to solve future problems. Electrical work has always intrigued me.

I'll get back to you with a full report after completing tests on my power adaptor, regardless of whether results are Good or Bad.

Hope I'm not abusing your generosity.

Best Regards,

Todd :)

[ToddB66]

The tolerance depends on what it specs are but the ones that I look at maintain +/-5%. Depends on what you are doing with it. Your circuit may be very tolerant or it may not be.... I have seen some really bad ones - like they say they are a 6V adapter but put out more than 10V with no load and maybe 7V with the expected load... Just place your meter in Amp mode/configuration and experiment with loads that approach 1.25A. Then take the meter out of circuit and configure in voltage mode and see what the voltage is.

If you paypal me for the cost of a flat rate priority mail box I will fill it with 12V supplies you can play with....

Anyone else for that matter. I have a bunch.

Barry

Hi Barry !,

What kind of "12V supplies" would you be sending ? I would need a good adaptor of course (specs. below) and whatever else (components) is needed to make a test set-up. I have a good collection of wire left-overs and would be using my Radio Shack model 22-805, 24-Range Digital Multimeter (powered by 9V battery).

I will also need instructions on how to arrange everything for the test set-up, either text or diagram.

The specs. on the Power Adaptor I want to test are as follows:
Make: YHI, Model: ys-1015-U12, S/N: 01725948, Input: 100-120ACV, 60Hz, 0.45A, Output: +12DCV, 1.25Amps, Made in China.

The above adaptor came with an Hp ScanJet 3400C (flatbed) Scanner, that I bought new about 8 yrs. ago. The label on the bottom of the Scanner shows 12VDC, 1.25Amps and a symbol for positive polarity.

Let me know how much $ to PayPal you.

I'll be sending you a private message with my FAX, phone number, and e-mail, in case you would like to communicate that way, also my address.

Thanks a bunch :thumb:,

Todd