M4 RF patch DIY clean...

[daveywaugh]

My newly acquired M4 is in great condition but there is, what appears to be a big spot of dust, in the patch. I've owned a couple of Ms previously with rf issues, but this doesn't seem to be the usual issues... It literally looks like a piece of crap has Dropped into the rf window.

I've successfully cleaned my M2 viewfinder before, and have all the tools but am certainly no Sherry 🙂 I guess my question is: do you think it's worth removing the top and using a blower, or is it most likely something more sinister?

Thanks in advance for your help and advice.

 

[froyd]

The proble you describe sounds similar to what I had on my camera. It looked like large flecks of paint landed on the RF mirror.

Interestingly, it was not an easy fix. Youxin, who did a CLA said he did not have the ability to clean the RF patch, and recommended contacting Don Goldberg. DAG thought he could clean the RF unit, but ended up having to replace the RF assembly (I believe the cost was around $350). Don actually advised against the work because the camera was fully operational as it was, and the expense would only correct a cosmetic issue... but I went ahead any way.

Here is a picture of what the RF on my M4 used to look like (ignore the spot in the right side of the VF, it's a pushpin in the wall)

Dust 2 by kafe-pic, on Flickr

 

[daveywaugh]

Thanks for that - I hope it's not the case though 🙂 I just bought it and the seller said it had a "tiny speck of dust in the patch"... mmmm... Anyway, this is what it looks like. The seller also said it appeared suddenly about a month ago which is why I thought it might be a small bit of 'something' that has dropped into the chamber.

 

[jonmanjiro]

If it appeared suddenly just a month ago, it probably really is just a speck of dust or crud that can easily be removed. Since its showing in the focus patch (assuming it stays in the patch as you focus), I'd look at the secondary rangefinder patch prism and optical components leading up to the main prism first.

 

[daveywaugh]

Thank you jonmanjiro. Would you know how far I need to go inside? I've only ever gone as far as cleaning the VF. Would I have to completely disassemble the RF mechanism? I just can't remember if that is completely sealed or if I will be able to get to blow some air with just the top off. I guess there's only one way to find out 🙂

 

[jonmanjiro]

Yep, there's only one way to find out 🙂

But I suspect that it'll be as simple as popping the top and blowing some air in the right spot. I wouldn't want to mess with the RF mechanism as it comes out as a single unit anyway. Good luck!

Edit: photo removed. Sorry Gus. I found the image via a random Google search. It served its purpose so I removed it.

 

[daveywaugh]

Thanks very much jonmanjiro and froyd. Really appreciate it. I'll report back tomorrow and let you know how I went.

 

[daveywaugh]

All done 🙂 It just needed a quick blow and it was good. Took ages to get the top off. Everything was really, really tight... I found out why when I saw an L-seal... gulp... the camera is in almost mint so I'd say it has sat on a shelf for a while. So much for the "recent CLA". I think some people think a Leica CLA is taking it to a shop and have a salesperson say "yeah it's all good" 🙂

Thanks for all your help.

 

[daveywaugh]

Hi Gus - oops 🙂 Ah well - I got another Leica maintenance lesson. I must say it was an experience. I don't plan on selling my camera so to be honest, the seal means nothing to me. I wish I had waited a day or so and got your advice though. Thanks very much and I'll remember that for next time.