2. amps-preamps
  3. 165850-46419

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
 
Thanks for your help.
arcticdeth's avatar
arcticdeth
1,549 posts
 
my first step is to have the factory do a serious inspection and replacement of any part(s) which is needed.  

    Congrats on the new CJ power amp, they are a great company. Enjoy.

 What speakers and other components are you using..



   
rff000 OP
23 posts
 
Speakers are NHT 2.5
Preamp is McCormack Micro Line Drive
DAC is Jolida FX Glass DAC III
CD Player is Rega Planet
Turntable is Thorens TD-203
Phono Stage is Rotel RQ-970BX
DVD and Hi-Res: Sony UBP-X700

Not real high end, but I used the system for many years with a smaller amp than I just got. I’m a little reluctant to spend a lot for a factory check when everything is working well but I may ask them how to handle the rusty screws.
mitch2
3,683 posts
 
Those appear to be socket head cap screws that are often made from black oxide alloy steel.   The black oxide process is used to add,
"mild corrosion resistance, for appearance, and to minimize light reflection. To achieve maximal corrosion resistance the black oxide must be impregnated with oil or wax."
Moisture in the air (humidity) can contribute to corrosion.  Humidity present in lower levels of conventional homes (i.e., in basements) can condense on cooler surfaces.  Increasing air flow, increasing temperature, and operating a dehumidifier all help reduce problems related to humidity and condensation.  However, even mild condensation over years could have contributed to the oxidation you see, it is not uncommon on those types of screws.

If you are concerned, open the top and look for any obvious evidence of corrosion inside (be safe - unplug the amp first and do not touch any large capacitors or other areas which could result in shock).  If you see significant evidence of corrosion inside, take a picture and send it to CJ for discussion. However, if everything looks fine then I wouldn't worry about it except to make sure you are operating the amplifier in a warm, dry place.   If you wish, you can replace the screws or clean and oil them as discussed by @russ69.
rff000 OP
23 posts
 
Thanks. I'll check it out.
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