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Posted

the paint was perfectly fine before that. I sanded away the little dust that got on there when the paint was drying. I really could have lived with what i had but decided to go with one last light coat. no paint remover was involved at this stage. took it to home depot and the guy told me to go with separate primer and paint this time and suggested there might have been something wrong with the paint. which would make sense if it happened right away but this was maybe 10 coats in (5 prior to the removal).

stripped it all down again to bare aluminum. will primer it saturday morning if i get time. bleh.

Posted

When you use any kind of paint stripper you have to clean the surface extremely well. Even a little residue will eventually cause bubbles and cracks. It generally happens relatively slowly.

Posted

What paint did you use? Rustoleum? How long did you wait between coats?

I am not sure water, while a universal solvent, will do much to remove the chemical residual from the stripper without some help from a soap or solvent. Before I paint my cases, I wipe them down with 91% isopropyl alcohol and let them dry completely. This removes a lot of the oils and whatnot that can accumulate. I am then VERY careful not to directly touch the visible surfaces to be painted until that first coat is on.

I must admit, I have never seen that happen. But, I have not used stripper either. I also generally stop between 4 and 6 coats, applied in pairs.

Posted

First place I called with good reviews on google quoted me 20 bucks for the whole thing to be powder coated. I dropped it off this morning and told the guy specifically not to coat parts of the case (grounding hole, insides of the bottom half and the edges which go into each other on the sides of the case). Guy calls me at 2 pm saying everything is done. I go to pick it up and the top plate is scratched to hell. They anodized the insides too so I don't know if the pcb will slide in anymore as it barely fit earlier. The powder coating has made the mating parts too thick to where they don't fit into each other. Everything aside the guy looked pissed when I asked him if the scratches could be fixed by sanding or some filler compound. I mean sure it was 20 bucks but does that really mean it can be done with no regard for a final product?

When I brought up the fact that he had disregarded everything I told him to watch out for he threw the case on the table scratching it further and told me to get it wet painted instead. Gf was with me. She agreed I couldn't have been more polite. So wtf. Really. Wtf.

Posted

You can't really pick and choose what gets powder coated. You just have to grind off the bits you don't want after the fact. It's just a feature of the finish.

Posted

If you don't mind sharing could you post the hints anyways? If this doesn't get resolved I will probably have to get another case unless there is a way to get the powder coating off. The whole thing is useless if the sides don't mate. If there is a way to get the coating Off I'll try to do it correctly. Would be much appreciated.

Posted

Hard to believe that the anodizing could build up so much as to make the sides no longer mate, or the PCB not fit. I think the best bet is to probably sand it down -- use a dremmel on the built up parts.

These anodizing and powder coating shops are largely slop shops. They work on volume, and don't care so much about quality. I ran into the same issue when building my prototypes. Most places I called said they wouldn't do runs of under 100,000 parts. I eventually found a friendly local anodizer who said he's be happy to drop my stuff in with another run for a small fee. I spent hours sanding the aluminum only to have him smack it around, and then deny he'd done it (and get really nasty when I suggested he be more gentle). Fortunately, I got it back before it went in the bath so the scratches and dings were not permamently etched in. But, in the end I have discovered that to get case parts finished the way I want that they need to go to a specialist metal finisher who understands "high end audio" and who will work with small volumes. Such places are few and far between, and their work on this case would likely cost as much as the whole kit.

As for a replacement -- it might not be as easy as you'd hope. It would leave us with an extra pcb and transfomer set. However, you could order a blank one from Context (not sure of the cost, or I have a blank from a different manufacturer that will work -- IIRC it was about $40) and send it to FPE to have it machined. Probably run about $50-60 for the machining. Not sure the one-off cost at Context to do that.

Posted

It may be worth it for some of you to do your own powder coating. It's not that difficult. You'll need a dedicated oven (it's not safe for food after powder coating), but ovens with bad stove burners are easy to find dirt cheap. And Eastwood makes a nice kit, and sells the powder as well...

http://www.eastwood.com/hotcoat-elite-powder-coat-kit.html

Relatively inexpensive, if doing multiple cases or items.

Posted

It may be worth it for some of you to do your own powder coating. It's not that difficult. You'll need a dedicated oven (it's not safe for food after powder coating), but ovens with bad stove burners are easy to find dirt cheap. And Eastwood makes a nice kit, and sells the powder as well...

http://www.eastwood....r-coat-kit.html

Relatively inexpensive, if doing multiple cases or items.

Oh wow, didn't know it was that cheap. Do want.

Posted

I guess I'm very lucky to have a place that powder coats even one amplifier lid for me and does it well enough for my crazy standards. :)

As for removing the old paint, just have the case sandblasted.

Posted

If you don't mind sharing could you post the hints anyways? If this doesn't get resolved I will probably have to get another case unless there is a way to get the powder coating off. The whole thing is useless if the sides don't mate. If there is a way to get the coating Off I'll try to do it correctly. Would be much appreciated.

Sorry to hear of your trouble.

Depending on how deep the scratches are in the powder coat, you could wet-sand with progressive grades of sandpaper, then use rubbing compound to bring back the shine. Some old-school finishes were done this way on purpose. As for the thickness around the mating joint, you could try to cut through it with an X-acto knife (or screwdriver blade, more likely).

I'm just guessing, though. I've not worked with powder-coat in the past - just two-part epoxies and other standard paints.

  • 4 weeks later...
Posted

I picked up the case today. No scratches this time but the holes for the screws for the mounting plate are completely filled in. The two halves don't mate due to the thick coating. Is there any chemical process via which everything can be returned to the way it was before? I'd rather take a chance again with painting it myself. Actually got better results with that.

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