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Conrad-Johnson Discolored (rusty?) Allen screws on side of MF-2550.

I just bought a used CJ MF-2550 a short time ago and it's been working perfectly. Today I was just checking the routing of my cables with a flashlight and I accidentally noticed that there are Allen (hex) screws on either side of the amp, between the cooling fins. There are also regular Philips screws. The question is that the Philips screws all look completely normal, but some of the Allen screws are discolored and may be rusty.

Would you think I should just leave well enough alone since the amp is working OK or should the discolored Allen screws be replaced? I'd be hesitant to do the replacement myself, in case any of them broke off and left inner components unsupported. Any advice would be appreciated. A link to a photo I just took follows.

https://i.imgur.com/rJnfyZs.jpg
rff000
rff000 OP
23 posts
 
I'd be inclined to just get a bunch of rustproof screws and replace them but I want to first find out if they have to be a specific kind of metal and what they are fastened to. I'd hate to mess up the job of re-fastening new screws to components inside the amp since it's working fine now.

I also noticed something strange. At the exact same position on both right and left sides (the fifteenth cooling fin), there is an empty screw hole with threads showing. Since it's at the same position on both sides, it doesn't look like an accident. Maybe the case has the threads but they're not used for this amp design.

I hope I can get an answer from the company without having to bring it there for service.
oldhvymec
5,101 posts
 
OP a little dab will do you. Put a little light oil like 3 in one or lighter WD40 on a soft fiber or even brass bristle tooth brush size brush. Gently brush the heads of the cap bolts. Just get them wet.. Leave it alone. Let it set for 20 min or so.. Two or three swipes two or three times.. They will look like new AND be ready to remove it you want to do so..

It's not the space shuttle..

LOL BUT that is how you would work on it too :-)

Wipe off any excess with Isopropyl. Touch up the heads with a permanent marker, touch up paint or nail polish..

Regards
arcticdeth's avatar
arcticdeth
1,572 posts
 
If you use oil, no wd40 no regular oil.

   Mobil 1 synthetic. Just half a drop anywhere needed will be great.
1 quart willlast a lifetime. 
pehare's avatar
pehare
835 posts
 
For years I've use Ospho/phosporic acid all the time to neutralize rust on parts.  It won't harm surrounding finish and gets rid of the rust.  It doesn't burn your skin like you think it might.  I use a q-tip and dip it in the bottle then lightly dab on rusted bolts, screws and parts.  

https://www.acehardware.com/departments/home-and-decor/cleaning-and-disinfectants/rust-removers/1386...
corelli
977 posts
 
Had the same thing of a Bellari phono amp. 
Remove the screws.
Clean as above
Shove the threaded end into styrofoam and spray paint heads of the allen screws.  Make sure to let the paint harden for a week or so before replacing them.
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