Chrome Plating

[skippy_ps]

Just got a semi-nasty MC-2205 that has a medium amount of ferric oxide on the top, around the caps and 'sinks. I tried a little to get it off, around the +/- 3/8" top edge of the sides and back. Used 3 different types of chrome cleaner and all did about the same. That is, some pits and bumps are left that can be felt with your finger. Not good. :worried: Doesn't look awful, but getting very close.

This a.m. I phoned a client here in town that is a commercial plater (and a casual friend) and asked him about it. He said that no matter what you do, the rust is still there, on the surface of the steel and there's no practical way to stop it other than stripping off the various layers of plating, polishing and re-plating. He offered to re-chrome the chassis and I'm considering it now. I asked if he was familiar with anyone that could do the silk screening and he was not.

I spent about 1/2 hour staring at the bottom wiring of the 2205, all the while being on guard that it didn't fall over (I had it on its side) and sever my hand or crash through the floor. Actually, it doesn't look impossible as a lot of the wiring is plug-in and it looks like not a lot of unsolder/solder would be required. And, yes, I've got the correct semi-tubular rivets and an appropriate rivet smasher.

The only thing I'm concerned about, other than a lot of work putting it back together, is the loss of the lettering on the back. It would also give me the opportunity to re-paint the transformers and the sheet metal - after I figure out a way to get the "decals" off and back on again without damaging them.

It seems to me that this would be a fun project and not too expensive as I can probably get the plating done for free. I'm not a very good painter and may get soemone to do this for me as I'm sure the results would be a lot better.

Any thoughts on this? Suggestions?

 

[Soundfitter]

www.micromark.com is a small tool modelmaking distributor..they offer a kit for making your own decals..it looks like you scan or copy your original to your computer and then print onto their clear decal paper. Page 52 of their catalog,if that helps...I've used some of their other tools, they are a great company...

 

[skippy_ps]

Interesting

Hmmm. Looks like most of the printing on the back could be done with an inkjet printer. White ink on a clear decal. Would have to do a little research to figure out the font for the McIntosh logo.

Typing the various info onto a silk screen seems to be the way to go, however. Much more difficult, tho.

 

[dewickt]

Pull the transformer labels by heating with a heat gun, hair dryer may get hot enough, heat, slip a thin blade under a corner, and lift off. I have used a thin sharp edge putty knife to remove (after heating) and then put back on with double sided carpet tape.

 

[skippy_ps]

Thanks Terry. I'm listening to FM on the MR-73 right now.

Murray

 

[skippy_ps]

Slight Pitting

It took about an hour to get this far - about 1/2 of that used up by getting the Panloc buttons off the front of the rod.

Anyway, the path is clear. I'm going to strip the chassis and have it plated.

Murray

 

[mech986]

Hi Skippy PS,

Good luck with your project, let us see what it will look like after its done.

Do you think your friend might be able to give a good discount for chroming a Dynaco ST-70 chassis that is sorta in the same condition? What would need to be done ahead of time for prep or would he do the rust stripping?

I'm in La Habra, where would you or he be located?

Thanks.

Bart

 

[Sandy G]

Skippy- A bit late now, but I hope you took pics of the underside, maybe made some diagrams, etc. Sure will be easier when you put it back together. Is yr plater gonna do copper, nickel, & then chrome ? That would probly be better than how they came from the factory.-Sandy G.

 

[skippy_ps]

I'm watching the end of the Daytona 500. Big crash with 19 laps to go.

Bart: I really don't have any idea of what the cost of doing this would be. And, sorry, I really can't ask the guy for a discount. We do business with his company (nothing to do with plating) and it would be improper for me to ask. He primarily does specialty plating (like antique bronze) of high-end bathroom and kitchen faucets and the like. It's a relatively small shop here in Palm Springs as I am. Next time I talk to him, I'll ask - but this probably won't be until I take my piece over there which will be at least week after next. Or so. It just depends on how far I get over the next few days.

As far as stripping, you'll have to remove literally everything that isn't the chassis. Rivets, screws, everything. The only thing that can be left is something that is welded to the chassis. No solder.

I'm not trying to sound like an expert on plating as I'm anything but.

More later.

 

[skippy_ps]

Lotsa Pics

Sandy,

Took beaucoup pics of the bottom while I was taking it apart. Have the right side autoformer and the small right side pcb off too.

I think that's called "triple chrome plating" - copper/nickel/chrome. I know very little about this but it's interesting that the process to replate something is to first un-chrome (the chrome goes back into the bath by changing the polarity) then un-nickel and so on.

I'm trying to figure out how to get some screws out that pass through the top of the chassis - they look like a flush rivet on top. Can't figure out if they're pressed in or threaded in. Maybe I need a bigger hammer.

Murray

 

[skippy_ps]

Nudes

Well, this is it. Interesting that all the rivets on the chassis apparently are brass. Must be zinc plated. Had to cut off the rca input jacks so they'll have to be replaced. Also had to clip off a few ceramic disc caps as I couldn't get to them to un-solder.

There's 10 studs with a #6 screw thread that seem to be pressed into the chassis from the top. Tried to hammer one out and it didn't budge. This is not good.

I may have to leave these in - will check with the plater but I think the answer is going to be "no can do." If anyone has a clue as to how to get these out without damaging the chassis, give a holler. Please.

 

[dewickt]

The studs are pressed in, past experience tells me he will plate them treating them as part of the chassis, this will build up the threads and you will have to chase them with a #6 die to get the nuts back on. Do you want a pair of original RCA's to put back when you are done, grind down to clean steel on the inside and solder them in.....

 

[skippy_ps]

The studs are pressed in, past experience tells me he will plate them treating them as part of the chassis, this will build up the threads and you will have to chase them with a #6 die to get the nuts back on. Do you want a pair of original RCA's to put back when you are done, grind down to clean steel on the inside and solder them in.....

Thanks for letting me know - whew.

One of the studs that is on the edge of the front cap was heavily rusted and I was concerned that it had rust underneath it. I got that one out and cleaned the rust off. Most of it, anyway.

It looks like Coke or Pepsi (can't tell which one) was spilled down the inside of the left heat sink and this may have caused some of the rusting on the left side of the chassis. The bottom sheet metal is gooey and rusted on the inside as well.

Thanks for the info re: solder in rca jacks.

No one said that it would be easy!

Murray