JBC JTSE mains voltage conversion - Page 1
Forum section: electronics / general

author: MindBender
author_rank: Regular Contributor
timestamp: September 01, 2023, 08:09:56 pm
content: Hi,I don’t know if this is the proper topic to post this under, so @admin: Please feel free to move this to wherever is is more suitable.Recently, I have purchased a brand new JBC RMVE set, at a pretty good price. The catch was, that it is a 120 Volt version, while I live in a 230 Volt country. Now the DDE contains a big custom transformer, so the chances on converting that from 120 Volt to 230 Volt are pretty slim; I have read posts here of other member trying and failing to obtain a replacement transformer for the same purpose.But the JTSE has a switch-mode power supply, and at the input circuit a resistor footprint marked “Config 230/120”. On my 120 Volt JTSE, the resistor is missing. It seems to have been present, but cut out, as some residual leads are still present in the pads. Perhaps it is tested at 230 during production, perhaps this does not mean anything.Now I have found some photos of the 230 Volt version of this board in this post:https://www.eevblog.com/forum/reviews/jbc-jtse-2a-repair/msg4986466/#msg4986466And the top photo clearly shows a 0 Ohm resistor mounted at Config.So I mounted a wire bridge and connected my JTSE to a variac. When slowly increasing the voltage, the JSTE starts powering up at around 75 Volt. That was unexpectedly low, so I removed the wire bridge and repeated the experiment. Again it powered up at around 75 Volt. No difference, so it doesn’t seem to be wise to try 230 Volt, I think.Anybody here have an opinion on this? Does anybody know more, or perhaps has access to service documentation?Thanks a lot in advance!

author: thm_w
author_rank: Super Contributor
timestamp: September 01, 2023, 09:59:23 pm
content: A switch mode supply would normally run from ~75V all the way to 230V. Interesting the resistor was cut, would imply that the design is similar or the same.The issue here though is mostly going to be if the heater coil in the hot air handle is designed to run off of 120V or 230V. The resistance will likely be vastly different.The spec stated is: Peak Power (JT) 700W. Which would be around 20 ohms for 120V. You could measure this.Maybe you can add some photos of the 120 config resistor and the transformer windings.

author: MindBender
author_rank: Regular Contributor
timestamp: September 02, 2023, 09:51:31 am
content: Quote from: thm_w on September 01, 2023, 09:59:23 pmYes, that’s what I figured too.Quote from: thm_w on September 01, 2023, 09:59:23 pmThat is averygood catch! I did not realize that the different mains voltages versions also use different hand-piece versions. So that needs to be replaced as well, making this a problem not worth solving.Quote from: thm_w on September 01, 2023, 09:59:23 pmThere is no transformer, unless you mean the SMPS transformer. The Config resistor doesn’t seem to make much of a difference, input voltage wise. Perhaps it tells the firmware what version of hand-piece to look for.But I have come to the conclusion that it’s not worth solving; The DDE needs a step-down transformer anyway, because it has a custom transformer powering the hand-pieces with AC directly. A 2000VA toroidal step-down transformer, in a metal enclosure, costs 75 Euro, less that a new hand-piece, so I think that’s the way to go.Thank you for preventing me from blowing up my hand-piece!