topic Re: Canon 600EX-RT won't turn on at all in Speedlite Flashes

Canon 600EX-RT won't turn on at all

jimlopes — Tue, 09 Jan 2024 17:26:10 GMT

I own two 600EX-RT speedlite's. One of them hasn't been used much and is totally dead. I tried half a dozen different batteries and won't turn on.

My 2nd speedlite turns on, but sometimes it doesn't. The led screen sometimes is looks like it half on. So this flash is proving to be unreliable on a shoot.

Canon has stopped supporting this version so I can't even get these repaired. Is there a reset button on the device or anything else I can try to revive them? Thanks

Re: Canon 600EX-RT won't turn on at all

rs-eos — Tue, 09 Jan 2024 17:37:50 GMT

Were they stored with batteries in them? If so, shine a light in the battery compartment when empty to see if any corrossion exists on the terminals. Also inspect the terminals on the inside of the battery terminal.

It's sounding like either no power, or only partial power is getting to the circuitry.

Re: Canon 600EX-RT won't turn on at all

jimlopes — Tue, 09 Jan 2024 17:45:53 GMT

This flash was stored without batteries. I typically take them after after a shoot to prevent them from leaking. The contacts look clean to me. What do you think?

Re: Canon 600EX-RT won't turn on at all

jimlopes — Tue, 09 Jan 2024 17:53:51 GMT

I also tried cleaning the contacts with rubbing alchohol just in case, but didn't help. Any other way to revive this guy?

Re: Canon 600EX-RT won't turn on at all

normadel — Tue, 09 Jan 2024 18:27:10 GMT

About batteries.....a number of years ago I had a Canon 420EX flash (actually I still have it) that quit turning on. I checked the batteries and terminals and all looked clean. Sent it to a repair service to see if it was save-able. They sent it back working, with a note telling me that the batteries I was using, Duracells, were prone to causing a barely-visible film to form on terminals. All it took was cleaning the terminals, and a recommendation not to use Duracells but to use Energizers. I have used only Energizers ever since.

Re: Canon 600EX-RT won't turn on at all

jimlopes — Tue, 09 Jan 2024 18:39:36 GMT

I just tried cleaning the terminals with rubbing alchohol but that didn't help. Never knew about the duracells, so that's good to know, thanks for that.

Re: Canon 600EX-RT won't turn on at all

rs-eos — Tue, 09 Jan 2024 18:43:44 GMT

Bummer. Agreed they look clean and I didn't know about the Duracell batteries. The only batteries I used in them were Sanyo (and then Panasonic) Eneloop rechargables.

Re: Canon 600EX-RT won't turn on at all

normadel — Tue, 09 Jan 2024 18:55:39 GMT

I can't say that the Duracell thing is still valid, just relating what a repair shop's experience was then.

I too don't use alkalines at all in my flashes anymore. I have Energizer and Eneloop rechargeables.

I'll also use lithiums, even though Canon warns against them in their flashes because doing rapid flashes can cause dangerous overheating. So I don't do rapid-fire flash shooting. Here is a good article about powering flashes and AA batteries:

https://www.scantips.com/lights/flashbatteries.html

Re: Canon 600EX-RT won't turn on at all

wq9nsc — Tue, 09 Jan 2024 19:30:23 GMT

The terminals look OK to me also but try a little WD-40 sprayed on a cotton tip to wipe them down. WD-40 is primarily light distillates of petroleum with a little light lubricant thrown in and it makes an excellent contact cleaner and will cut through film that alcohol will not.

WD-40 also makes a product specifically labeled for contact cleaning that is effectively the same compound except it doesn't have any lubricating property but it is harder to find and more expensive. The lubricant used in WD-40 doesn't negatively impact contact conductivity, it became my cleaner of choice after test and measurement equipment maker Tektronix tested a number of specialized cleaners and recommended regular WD-40 especially for their extremely expensive precision 10 turn potentiometers used in their lab grade scopes which even in the 1970s cost well over $100 each to replace.

NOTE: Don't just spray WD-40 inside, spray it on something else to wipe the contacts. Although it won't hurt most plastics, don't chance it. And until it finishes vaporizing, it is highly flammable so don't use near open flame. When manufacturers started using light duty diesel engines in passenger vehicles in the 1970s, some of them recommended WD-40 as a safer alternative to ether for cold weather starting.

Rodger

Re: Canon 600EX-RT won't turn on at all

jimlopes — Tue, 09 Jan 2024 20:37:10 GMT

Thanks for that info. I actually have a WD40 precision pen which is great instead of the spray for door hinges, etc. and for this case of cleaning the speedlight contacts. I tried that but unfortunately it didn't do anything. This thing is dead as a door nail. It sat around for a couple of years during covid and its hasn't been used a lot since I bought it as its mostly my backup. So I'm surprised it doesnt turn on at all even though it hasn't had heavy use.

Re: Canon 600EX-RT won't turn on at all

jimlopes — Thu, 11 Jan 2024 14:33:03 GMT

So I was about to put this flash to bed after trying everthing suggested here and not being able to send in for repair. I decided to just hit the flash a couple of times of the side of my hand. Figuring the old school way of trying to getting something to work. Well, it actually worked and the flash fired right back up! I couldn't believe it... could there been a connection inside that was loose? What could explain just hitting it a couple of times for it to work again?

Re: Canon 600EX-RT won't turn on at all

normadel — Thu, 11 Jan 2024 17:53:50 GMT

Sure, could be a connection somewhere. Battery terminal connections that you can't see, for example. Don't know how you can tell without opening up the flash, though, which I'd be very cautious about doing.

Re: Canon 600EX-RT won't turn on at all

rlhdpcetc — Wed, 10 Sep 2025 16:28:07 GMT

Jim, you saved the day. I have two of Speedlite 600 EX-RT flash units and both were malfunctioning. A quick whack on the left side (if your looking at the screen) brought both back to life. I had already tried a whack on the right and it didn't work. A day later and they are functioning as expected. My battery terminals were clean, there was no corrosion in the housing, and I had fresh batteries. The ole whack technique worked like a charm. Thanks!

Re: Canon 600EX-RT won't turn on at all

dpastern — Tue, 11 Nov 2025 10:53:17 GMT

Having this issue myself. Purchased a used unit from keh.com in the first half of 2023. Tested it when I received it and it was working OK. Tested it again around a year ago and same. Haven't used it properly, just 2 tests. Went to use it today properly and it's as dead as a door nail. Contacts look clean, but I'll try the WD-40 option tomorrow. Was not stored with batteries. I tried the whack option just now, no go. Still dead as a door nail.

My utterly horrible 2025 continues to just get worse day by day (I've had a true annus horibilis).

I have emailed my contact at Canon, but reading in this thread that it's no longer serviced by Canon will mean it's probably dead for good and just rubbish now.

Dave