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 photo I just took follows.
Was the unit stored in a basement or a humid environment where condensation may have occurred? Although it should have no influence on the sound, these would bother me and I would replace them as it would probably cost you less than 3 dollars total for all of them. I would also do a thorough internal inspection to rule out similar problems on a more critical component.
-admin Home Theater in Member Gallery Main stereo: ART Amplifier and ET7s2. 2nd stereo: PV-14L and MV-55. Previously Owned: PF2 preamp, Evolution 2000 Amp, PV-12AL preamp, D/A-2b Vacuum-Tube Digital Processor.
Since I only bought the amp around 10 days ago, I don't know everything about how it was stored. I picked it up at the seller's house. He had it in a wooden cabinet in his living room, but he said he bought it as a demo from Spearit Sound when they had their final sale a few years ago.
I'd like to change the rusty screws for new ones and the price is no problem. I just want to make sure that I don't loosen something inside the amp that I may not tighten correctly. There are quite a few of the rusted screws on both sides, so several components may be fastened by them.
I noticed something else unusual. One of the screw holes was empty with only threads showing, but the very same position had a missing screw on both sides of the amp at the identical position, on the 15th cooling fin, counting from the front. So, this may be intentional. I'd like to check all this out with the company or the Music Technology shop in Fairfax, that seems to specialize in Conrad-Johnson.
Since this has zero effect on the amp and it sounds exactly as it should, I'll also try to get the official CJ advice about how to proceed. I.e. maybe just leave it alone until a real problem occurs with the operation.
I'm still left with the question of why they could not use some sort of stainless, non-rusting metal for the Allen screws. Why create a situation where the owner has to deal with replacing the screws? The Philips screws have no rust problem, so why couldn't the same metal have been used for all the screws, I wonder.
Thanks to everyone for letting me know more about the problem.
rff000 wrote: ↑Sat Apr 10, 2021 11:55 pm
I'm still left with the question of why they could not use some sort of stainless, non-rusting metal for the Allen screws. Why create a situation where the owner has to deal with replacing the screws? The Philips screws have no rust problem, so why couldn't the same metal have been used for all the screws, I wonder.
I don’t think that’s the question at all. I’ve never seen this before, and the two missing screws sounds “screwy” too.
You say it sounds like it’s supposed to ... but have you ever spent a month or two listening to one?
Pull the cover and take a look. It may have been flooded, possibly from a broken pipe, or doused in putting out a fire.
Unless a unit has been in the 80% humidity tropics, or has suffered from being doused with water, I’ve never seen screws in the condition you show.
Something isn’t right.
It’s just stuff. I like mine. I hope you like yours. I probably like yours too.
I can only say that it sounds much better than my previous amp. I don't have experience with this amp. The seller posted a picture of the inside of the amp in his ad and everything looked normal. I think it can only be resolved if I contact a knowledgeable person at the company, which is only 12 miles away from where I live.
I have also never seen rust anything like this on a CJ unit before either. I have seen very quick rusting on metal stored in humid shipping containers before. That is why I asked about previous storage conditions. Even a week spent in a storage container in the summer time could cause massive condensation (like dripping water off the metal) and corrosion. Since we really don't know the history of the unit I would really do two things:
1) Remove the rusted screws, clean the threads really well (may need to use a rust removal gel/spray), and replace all of them with new screws. Be careful not to break the screws when removing it if has locked on you as if you break the tops off it will be a nightmare to get the threaded part out.
2) Pop the cover off and do a really thorough inspection of the inside components. If you don't see any similar issues, I think you are good to go. Make sure you look at the transformer as that is a big hunk of iron, and if you are going to more rust, that's probably where it would be most prominent.
Good luck and let us know how it goes.
-admin Home Theater in Member Gallery Main stereo: ART Amplifier and ET7s2. 2nd stereo: PV-14L and MV-55. Previously Owned: PF2 preamp, Evolution 2000 Amp, PV-12AL preamp, D/A-2b Vacuum-Tube Digital Processor.
The reason I would pull the cover first is that those allen head screws could be holding transistors to the heat sinks.
Pull the cover and take a look, but do not touch anything inside, even if the unit is unplugged, unless you are familiar with draining charged capacitors by means other than providing a ground path through your body. There are lethal voltages inside.
If you’re only 12 miles from CJ, it would be easy to wag it over there.
But I probably wouldn’t until I’d taken a look under the hood.
If the only issue is rusty Allen head screws, I think I’d leave it alone.
But there’s something funny that’s gone on here.
FWIW, Spearit Sound was a GREAT reliable seller. Ralph Spears’ decision to retire is understood, but it was a blow to the CJ community. He still has some NOS gear that he offers on-line through eBay and AudioMart. He trades under the name Oconee Audio in South Carolina.
I would be surprised if the rust were part of Spears dealership ownership. I’ve bought several items from Spear, including from the South Carolina based Oconee, and never seen rusty CJ screws. The more I think about it, the more I wonder if these are the stock screws, and if they’re not, what’s the back story?
What can the seller tell you?
It’s just stuff. I like mine. I hope you like yours. I probably like yours too.
In the vicinity of that left screw, there is further evidence that something happened to this unit.
Look at the fin discoloration. I’ve never seen this before either. Occasionally you will see one that was dropped and a fin will be deformed, but this looks like more surface finish damage that has been cleaned up.
The big question seems to me to be “if they cleaned up the fins, why didn’t they replace the rusty screws?” Are they literally rust locked? If they are, and if they are holding transistors to the heat sinks, I would want the seller to take it back. This would be especially true if the inside does not look like his advertising photos. Normally, these cosmetic defects would be clearly shown in the advertising photos.
It’s just stuff. I like mine. I hope you like yours. I probably like yours too.
The more we talk about this and look at the picture, the more I am thinking that something happened with this unit beyond regular aging. Those "cleaned up fins" are definitely not normal aging. They were aggressively scrubbed or damaged/repaired.
As AnotherJohnson recommended, I would take the cover off first and do a thorough examination of the inside prior to removing any screws.
I don't think we necessarily have to get too pessimistic at this point, these just all may be cosmetic issues that can be fixed for a few dollars and little time investment. But my priority would be to make sure that the internal components do not show any similar signs of mistreatment.
-admin Home Theater in Member Gallery Main stereo: ART Amplifier and ET7s2. 2nd stereo: PV-14L and MV-55. Previously Owned: PF2 preamp, Evolution 2000 Amp, PV-12AL preamp, D/A-2b Vacuum-Tube Digital Processor.
After reading your last message I felt I had to take a look inside. It looked clean to me, with no evidence of water or other damage. The screws look pretty clean too, with a tiny amount of rust on one or two. I also took these two photos, in case anyone has a comment about what's there.
If the inside looks good you probably got lucky and everything is ok. I would replace the rusty screws so they don't lock on you and for simple cosmetic purposes. Clean the thread out as much as possible and put the new screws in. You should be all set. Maybe the outside got splashed with water and that's what caused the corrosion? Who knows?
Living so close to CJ you want it to drive down and get inspected but if it sounds fine,... not sure if it's worth it.
It's a great sounding amp which should give you lots of enjoyment. Don't let a few rusty screws damper your mood!
-admin Home Theater in Member Gallery Main stereo: ART Amplifier and ET7s2. 2nd stereo: PV-14L and MV-55. Previously Owned: PF2 preamp, Evolution 2000 Amp, PV-12AL preamp, D/A-2b Vacuum-Tube Digital Processor.
After struggling to put the amp back on the shelf and re-connecting all the wires, I'm just enjoying the audio for now. If it stays like this, it doesn't need service. And if it does need service, the pros can easily take care of the screws. I'm just glad it's working and it sounds better than any amp I ever had up to now.
rff000 wrote: ↑Sun Apr 11, 2021 1:16 pm
After struggling to put the amp back on the shelf and re-connecting all the wires, I'm just enjoying the audio for now. If it stays like this, it doesn't need service. And if it does need service, the pros can easily take care of the screws. I'm just glad it's working and it sounds better than any amp I ever had up to now.
I think you’ve chosen the best course of action.
Good job.
Enjoy the music!
It’s just stuff. I like mine. I hope you like yours. I probably like yours too.
Since the screws are connected to amp components like transistors, I'd rather leave them to the pros. I'm following the rule about not fixing something that "ain't broke." This amp handles high-pitched tenor and soprano voices much better than my old amp. I also hear individual instruments better.
I did go ahead and ask the seller if he knew what was going on. He answered and said that it was in his cabinet the whole time and he never knew about the rust. I only saw it by accident. Maybe it was in an environment near the ocean with salty air and that led to the rusting.
