Trying to understand why V is used instead of VDC or VAC - Page 1
Forum section: electronics / beginners

author: CrashTestMonkey
author_rank: Newbie
timestamp: September 05, 2024, 03:53:37 am
content: I'm relatively new to this so forgive what I'm sure is a really simplistic question, but I haven't had any luck finding the answer. I'm really interested in restoring and modding game consoles, and I really want to do things right. When I look to obtain an ac adapter for some of the older devices I like to try and find an OEM adapter that was originally shipped with them, but even those can be challenging simply because of the age of the 'wall wart', so I also look to get a quality alternative that meets the requirements it was designed for. This has brought me to my question...When looking at the details on the ac adapters I find some are labeled as having a 9V output (for example), while others have 9VDC or 9VAC. Older console adapters don't consistently have the best info, as you can imagine, but even new ones have information on them like this. I'm wondering why they wouldn't all use either VDC or VAC? Does the use of just "V" indicate VDC, or something else entirely?I figure some of the older consoles were designed to run off batteries (like the original Magnavox Odyssey) so they would use a VDC adapter, but I'm not sure. I want to avoid toasting a device with old circuitry by making an error, so this is one of the things I'm looking to learn to help me make the best choices.Apologies if this has been covered in previous posts... I looked but couldn't find anything.Thanks!

author: ataradov
author_rank: Super Contributor
timestamp: September 05, 2024, 04:22:45 am
content: No real reason. When people design a bespoke power supply that goes with a specific device, as was the case when AC power supplies were a thing, they simply did not think about accurately labeling them. There was no need, since the replacement would be the same exact supply.And for DC supplies, they could not even agree on the same center pin polarity. It was just arbitrary and whatever worked in a specific project.

author: IanB
author_rank: Super Contributor
timestamp: September 05, 2024, 04:29:46 am
content: Often, AC or DC is indicated with a symbol rather than with letters, like this:When it is DC, you also have to be aware of the polarity. If there is a barrel jack, sometimes it is center positive, sometimes center negative.

author: CrashTestMonkey
author_rank: Newbie
timestamp: September 05, 2024, 04:40:26 am
content: So it sounds like there's no definitive answer... I guess the only solution is to break out the multimeter if I have the adapter on hand. Otherwise look to see if I can find the schematics or other documentation. Sometimes it's like going on an archeological dig! LOL!Thanks for the answers!

author: ataradov
author_rank: Super Contributor
timestamp: September 05, 2024, 04:45:28 am
content: You can often tell by looking at the input circuitry of the powered device. In many cases there will be a bridge rectifier right on the input, so it will work with either AC or DC. And the voltage could be reasonably predicted by looking at the capacitor voltage ratings and voltage regulator input and output specifications.

author: J-R
author_rank: Super Contributor
timestamp: September 05, 2024, 05:14:56 am
content: I dug through my stash of approximately 50 wall warts going back maybe 40 years and I didn't find a single one where the output wasn't labelled as AC or DC. You got photos of these adapters you're running in to?