Romisen RC-T6 Teardown & Mod

Hello,

I just got a Romisen RC-T6 off ebay today, and I haven't found a really detailed tear-down or mod of it yet. So I thought I'd drop one, as this thing seems really cheap!

As a sidenote: if you are getting this off ebay, don't get the one with the charger included ("SINCE SE-H001"). The charger is absolute garbage.

I've tried to avoid duplicating anything that's in the other threads!!

Obviously do anything in here at your own risk - there's a very good chance of damaging your flashlight, or running your batteries at too high a drain current, which could cause fires.

Construction

The flashlight is constructed pretty well! As other people have mentioned, the wiring is pretty crappy...

I was interested in the o-rings, as I'm hoping to make this waterproof for a dive light.

There is double o-rings on the extension tube / battery end, with lots of grease:



However the two seals closer to the head have a single o-ring, but they do still have the o-ring at least!





And the glass does have an o-ring pushed against it:



Tear-Down

Taking the flashlight apart is a little tricky, you've got to do it in the right order! Don't just twist or you might rip all the wiring out (see other threads):



You MUST unscrew the very front part of the flashlight first. Wack it on the table if needed to break the seal...

With the front off, you should be able to twist at "3", make sure the six LEDs are twisting with the main body.

When you take the reflector out, you should see the heatsink the LEDs are mounted on. Note that when putting the reflector back in, it is NOT perfectly symmetrical. You'll have to rotate it until the LEDs line up perfectly, which they will.

Here's a picture of the heatsink:



And here's how it looks with the reflector out:



Finally you have to remove the LED driver. To do this use pliers, and unscrew the aluminum part carefully:



Then the driver should slide out. There you go, that's it!

LED Driver

The box on the Romisen said it would work from 6V to 16V input. The driver itself is based around a PT4105 (see http://www.zhaoming.com/bbs/u/2008/08/22/13021219393302.pdf), of which there are three exact copies. Each driver drives two LEDs.

The switch just mechanically selects if 1, 2, or 3 drivers are powered. There is no intelligence to it, no memory. The order is 1,2,3 driver for low/med/high.

The Mod

The feedback resistor can be adjusted to adjust current. Before the mod each LED had 0.389A* going through it. I only modified two of the drivers in the end, leaving two LEDs with 0.389 and four with 0.505A*. This was done for two reasons: (1) to have a "not suicidal bright" setting, and (2) to avoid having too high a drain on the battery (it's still pretty high!).

*measured with DC ammeter, won't capture peak.

I added a 1-ohm resistor in parallel with the on-board 0.27 ohm resistor:



In my case I only did that to two of the .27 ohm resistors. In fact in the final version the resistor shown in this picture isn't mounted, this is the only .27 ohm that wasn't modified!

The inductors for the driver are on the other side, they are 22 uH. I noticed some stability / start-up problems with the driver, since you are now running it will above the designed current! But it seemed to work most of the time!

Here's the unmodified one:



There's a snowstorm outside right now, so can't get any outdoor beam shots sorry.

Hope someone finds this useful / interesting!

Regards,

-Colin

I realize this is an older thread and that the OP only has this one post here, but I'd just like to say that I really appreciated finding this thread. I just got the Romisen RC-T6, and though I don't plan on trying to mod it anytime soon, I was glad to have directions on how to take it apart without suffering any of the solder-breaking or O-ring-trashing problems that have been reported in other threads about this light. So thanks to the OP even if s/he doesn't ever see this!

Only had the light a little less than 24 hours and have only used it to walk the mutt last night, but my first impressions are very positive. I'm really glad I didn't get a DOA model like others on the site have reported, as this light was a replacement for an Ultrafire WF-1000L that I bought from DX which was DOA. I ordered that light on 1/31/09 and just finally got a working flashlight out of the deal yesterday, so I'm not real impressed with DX, but then again, they were courteous and responsive to my communications, so the report card on them isn't all bad. Just slooooow.

Oh well, I'm a total dweeb when it comes to the technical reporting. I seriously doubt this light is 1500 lumens as advertised at some outlets, but DX did not advertise it that way. They just left out a lumen rating altogether! I based my pick of this light as a replacement for the UF on several reviews of the light on DX's site, some of which did include technical evaluations from people who obviously know more about this stuff than I do, but at least 90% were very positive overall in any case. So far, I concur with the positive feedback. This light is as bright as I can imagine myself ever needing. It has multiple battery configurations. Except as noted with other reviewers, the construction of mine is top-notch. The fit and finish is equal to or exceeds any light I've held in my hand since realizing that there might actually be legitimate need for something higher quality than a 2-C or 2-D Ra-O-Vac that costs under $5.00 at any hardware store! While that realization is still fairly fresh, I have done a lot of "looky-loo'ing" at lights ever since it hit me a year or so ago. The fit and finish of this light compared to the UF, even if it had worked, would be off the charts.

Anyhow, assuming the thing keeps working, I am very satisfied with this purchase. For under $59 bucks with free shipping, it's a pretty darned good deal just as you get it. Add the potential to use it as a platform for higher-end modding, and I'd say it would be a winner for many of the folks on this forum.

There seems to be a problem with the pictures. I'm going to get a Romison T6 in a few days and I'd like to know how to disassemble the torch and modify the LED driver.

I hope that it's possible to have a look on the pictures!