Icom IC-R7100 RF Shield Oxidation?

[spongella]

Am in the process of realigning and changing the memory batteries on an Icom IC- R7100 VHF/UHF receiver and noticed what appears to be heavy discoloration on some of the RF shields as seen in the attached photo. At first I thought it might be due to overheating, but it appears more like oxidation. Has anyone seen this before on a radio? The radio works fine except for the dead memory batteries. There's no burnt smell and I am not the original owner so I don't know the radio's history.

Tnx and 73's.

 

[ve3ext]

I too replaced the batteries this week and noticed the same thing.
I attributed it to heat over the years., now running on 13.9vdc., no more heat!
This is a great radio., even though the various scanning types is a learning curve!

Jerry VE3EXT

 

[kruser]

I've worked on many of the older Icom's from that era and many had the same discoloration also on the RF shields like in your picture.

It's not from heat as many of the rigs were run from external power sources only plus those stages of a radio usually produce no or very little heat. If something became hot enough to discolor the metal like that, there would be other issues as well. Likely major issues.

It's probably just something with the particular metal used for the shield cans. Or maybe manufacturing oils left on some of the metal that was not rinsed after manufacture. Regardless of the discoloration, they have always shown to be perfect both mechanically and electrically and do their shielding job just fine.
My R9000 also has shields that look the same.

I've never seen it continue into other areas of any of the radios I've worked on. Just seen on the shield cans and covers and not always all of them even though they appear to be made from the same material.
I agree that it does appear to be a form of oxidation.

 

[ra7850]

I've worked on many of the older Icom's from that era and many had the same discoloration also on the RF shields like in your picture.

It's not from heat as many of the rigs were run from external power sources only plus those stages of a radio usually produce no or very little heat. If something became hot enough to discolor the metal like that, there would be other issues as well. Likely major issues.

It's probably just something with the particular metal used for the shield cans. Or maybe manufacturing oils left on some of the metal that was not rinsed after manufacture. Regardless of the discoloration, they have always shown to be perfect both mechanically and electrically and do their shielding job just fine.
My R9000 also has shields that look the same.

I've never seen it continue into other areas of any of the radios I've worked on. Just seen on the shield cans and covers and not always all of them even though they appear to be made from the same material.
I agree that it does appear to be a form of oxidation.

kruser,

Any chance you still work on the Icom IC- R7100 receivers? I have one that needs a keypad. I'm also looking for parts if you know of anyone.

Thanks
Robert

 

[kruser]

kruser,

Any chance you still work on the Icom IC- R7100 receivers? I have one that needs a keypad. I'm also looking for parts if you know of anyone.

Thanks
Robert

Sorry, I've pretty much stopped working on all but my own personal radios. My eyesight is nothing like it used to be so I sure don't want to be responsible for making someone else's radio worse than it was when sent my way!
I don't have a source for parts for the older Icom's. For the keypads, several models used tactile type switches mounted on a small board.
The switches should be able to be found at places like Mouser or Digikey. They are usually simple little thru hole mounted mechanical switches.
Finding an unused keypad is not likely so replacing the actual switches was the next best thing. A bit more work but not really all that hard if you are good at working on old thru hole mounted components.

Good luck on your 7100. These older Icom's are usually well worth repairing as long as you can find someone competent to do the work along with reasonable labor rates. I really enjoyed working on them all when my eyesight was still near perfect. Nothing like bringing a dead one back to life!

 

[majoco]

It's been a while since I had the lids off my R7000 but I recall that I had some of the screening cans discoloured just like yours. IMHO the heat is actually generated by the components inside rather than from some external source. I'm wondering what the plating is on those cans - if it's something with a silver content then it will tarnish reasonably quickly. It does seem strange that it's the side of the can nearest to the front panel that is marked - I would have expected that to be cooler.

But seeing as the radios have been in use for 20+ years and were left on 24/7/365 by the military then I suspect that there's nothing to worry about!

 

[spongella]

Thanks for all the helpful comments. While I have the radio open, figured I'd try some silver cleaner on those oxidized shields, see before and after pics. Keeps my sense of aesthetics in balance hi hi.

 

[majoco]

It will be interesting to see if they get discoloured again. If it's the components inside that are getting hot, I would have thought that matt black paint would have been applied.