Change Line Voltage On IEC Connector - Page 1
Forum section: electronics / projects

author: bostonman
author_rank: Super Contributor
timestamp: April 17, 2022, 03:15:07 pm
content: I grabbed a Caltek CA8020a 20MHz oscilloscope someone was throwing away (not anything great and I may not even bother keeping it - but it was part of other items). It has an IEC connector as many pieces of test equipment (see attached picture), the sticker shows 220V, but the frequency is 50-60Hz.I've looked for the manual online and found one for a BK (I'm uncertain if Caltek is now BK), but it shows the same IEC connector with a caption that reads: line voltage selector. Looking on other sites, I found the input voltage to be 220V.My confusion is: Do 220V powered devices get the same IEC connector or could the sticker be wrong?I removed the fuse cover and didn't see a way of converting it to 120V, and also removed the cover and didn't see a switch on the PCB (the schematics are online too and didn't show a voltage selector switch).Without realizing it, I powered it with a standard 120V and it seemed to power normally except the horizontal line wasn't flat.

author: madires
author_rank: Super Contributor
timestamp: April 17, 2022, 04:00:15 pm
content: The IEC connector is the same for all mains voltages. If the scope runs fine with 120V then it should have an SMPSU with a wide input voltage range. Or someone has modified the SMPSU (remember the voltage selector in old PC PSUs?). Please post the PSU section of the schematic.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: April 17, 2022, 04:01:22 pm
content: AFAIK, the same IEC connector is used everywhere. The fact that it only shows fuse info for 220 makes me think it's 220 only. I can't tell from the photo, but some of those connectors have a pull-out circuit board below the opening that can be inserted for 120 or 220. The fuse should also be in there.

author: bostonman
author_rank: Super Contributor
timestamp: April 17, 2022, 04:14:18 pm
content: QuoteI've seen those and this doesn't have it. The plastic fuse holder only fits in one way with one spot for the fuse and a square hollow section for a spare fuse which is also included, and only two metal tabs inside (i.e. not two additional tabs that may indicate a separate 120 connection).Seeing the frequency range between 50-60Hz made me question whether it's American and European, but the sticker obviously indicates otherwise. The IEC connector I wasn't sure if a 220V would have a different plug, however, this question was answered.Attached is the picture and page 4 shows the input section. Nothing to me indicates this is also 120V, however, as mentioned, a BA manual (I don't believe it's for this scope) I found online shows the identical IEC connector with a caption that reads 'voltage selector' (see pages 9 and 12 of attached manual)

author: pigrew
author_rank: Frequent Contributor
timestamp: April 17, 2022, 04:39:39 pm
content: Taking a quick look at the schematic, the transformer's primary has two windings, allowing it to be reconfigured for 120V or 240. The windings should be in series for 240V, or in parallel for 120V.It uses linear regulators (well, except for the high voltages...), which do not auto-adjust between the line voltages.I expect that you will need to rewire your transformer, and also increase the fuse rating (likely double to be double the current value).The obligatory warning is that this contains a CRT, which will act as a capacitor, storing many kV. Be careful.

author: madires
author_rank: Super Contributor
timestamp: April 17, 2022, 07:02:36 pm
content: Yep, the next step is to check the wiring of the transformer's primary windings, i.e. if they are in series (240V) or in parallel (120V).

author: hli
author_rank: Frequent Contributor
timestamp: April 17, 2022, 09:25:14 pm
content: Hmm, Canada seems to be one of the countries using 240V and 60Hz, so it seems sensible to have the PSU run with that as well.

author: bostonman
author_rank: Super Contributor
timestamp: April 18, 2022, 03:20:09 am
content: It's probably not worth doing much to this scope because it's only 20MHz.I'll see about setting aside some time, but, the more I read the responses, the more I realized it will take much more tinkering than it's probably worth.

author: ledtester
author_rank: Super Contributor
timestamp: April 18, 2022, 04:08:47 am
content: You might try a "travel converter" which is simply a 120<->240 transformer. They are usually good for around 70W. I've seen them pop up at thrift stores now and then.

author: james_s
author_rank: Super Contributor
timestamp: April 18, 2022, 04:21:47 am
content: Quote from: hli on April 17, 2022, 09:25:14 pmCanada is identical to the USA as far as electrical goes. They have the same split phase 120-0-120 60Hz system as the US, large appliances are 240V while lighting and small appliances are 120V. I'm not aware of anywhere in the world that is 240V 60Hz without the split phase.

author: tooki
author_rank: Super Contributor
timestamp: April 18, 2022, 05:13:10 pm
content: Quote from: james_s on April 18, 2022, 04:21:47 amNot 240V specifically, but there are numerous countries with 220-230V/60Hz mains.

author: TimFox
author_rank: Super Contributor
timestamp: April 18, 2022, 05:51:20 pm
content: Quote from: tooki on April 18, 2022, 05:13:10 pmAccording to this listhttps://www.school-for-champions.com/science/ac_world_volt_freq_list.htmthere are four places listed that use 220 to 240 V at 60 Hz, disregarding the countries such as USA and Canada that use 120/240 or similar split voltages:Antigua, Montserrat Island, Peru, and South KoreaOf course, there are many countries with 220 or 240 V, 50 Hz power. Since Montserrat is a member of the British Commonwealth, I wonder if its inclusion was a typo.Wikipedia adds Saint Martin (French territory) and states Saudi Arabia is 220 V (only) at 60 Hz.

author: tooki
author_rank: Super Contributor
timestamp: April 18, 2022, 06:00:30 pm
content: Quote from: TimFox on April 18, 2022, 05:51:20 pmHuh? The page you linked confirms exactly what I said: 220V or 230V at 60Hz for all of those countries (and St. Kitts & Nevis Islands, which you missed), but not a single example of 240V/60Hz.

author: james_s
author_rank: Super Contributor
timestamp: April 18, 2022, 06:26:37 pm
content: Quote from: tooki on April 18, 2022, 06:00:30 pmI tend to lump 220/230/240V together, they are more or less compatible. I was not aware of those four countries that are 60Hz, learned something new.

author: TimFox
author_rank: Super Contributor
timestamp: April 18, 2022, 07:02:54 pm
content: Tooki: approximately 45 seconds before your post, I edited mine to read "220 to 240 V".What is the threshold for "numerous"?