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Cabinet and Chassis Restoration and Refinishing For help with cabinet or chassis restoration (non-electrical), please leave a message here. |
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17th Sep 2017, 1:18 pm | #1 |
Pentode
Join Date: Aug 2005
Location: Shrewsbury, Shropshire, UK.
Posts: 149
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Radford amplifier chassis refinishing?
Not being at all well versed in the art of metalwork, I’d greatly value the wisdom of the forum in respect of the chassis of a Radford amplifier currently under restoration.
It seems to be steel judging by its weight although it’s been plated or passivated. There’s rather a lot of staining and discolouration and also what appears to be pitting. Viewed through an 8x loupe the latter looks almost like tiny rust spots. My best guess is that something has been spilt inside the amp at some stage. Hopefully the photos give some idea of the problem. None of the stains respond to any solvent on my shelf including AVGAS (which can be very effective on metal staining) and common household cleaners don’t touch it either. It would seem that the only solution is going to be refinishing of some sort but can anyone suggest the best way to go about it? A colleague recommended powder coating but this isn’t something I’m familiar with. Any advice very gratefully received and I'll happily send more detailed pics if it helps. |
17th Sep 2017, 1:46 pm | #2 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,903
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Re: Radford amplifier chassis refinishing?
Some of the steel treatments of the period you won't be able to get redone, like passivated cadmium plating which was quite common
There seems to have been some sort of corrosion which you want to be sure is gone before adding any coating. So I think I'd start with bead-blasting to get to clean metal. You could go for painting them yourself, starting with a steel compatible primer. You could send them off for nickel or chrome plating You probably have a powder coater near you.Done properly, powder coating comes out like a durable but softish paint. Some powder coating comes out almost like dipping in PVC. If it was metal finish before, I'd probably go for nickel plating. A recent thread mentioned a firm in Manchester doing anodising (for aluminium) who may be worth asking. You may want a conductive treatment rather than powder coat or paint from the point of view of screening. David
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17th Sep 2017, 2:49 pm | #3 |
Dekatron
Join Date: Apr 2009
Location: Oxfordshire, UK.
Posts: 4,935
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Re: Radford amplifier chassis refinishing?
It's hard to tell from the pictures just what the original finish was and, as Wrangler says, it may well be some obsolete process. Powder coating involves firing tiny plastic particles from a gun on the surface and then cooking at ~200'C. Tends to produce a layer thay could be mistaken for thick paint. OK for garden machinery, perhaps even modern radio equipment, but suspect it will not look right on vintage equipment.
Maybe the way to go would be a zinc plater who can tint his plate. B
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17th Sep 2017, 3:27 pm | #4 | |
Pentode
Join Date: Aug 2005
Location: Shrewsbury, Shropshire, UK.
Posts: 149
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Re: Radford amplifier chassis refinishing?
Quote:
From what's been said so far it doesn't sound as though powder coating would be a good move. The thread about re-anodising heatsinks was mine (it's the same amplifier) and I'll ask whether they can also do bead-blasting and plating. |
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17th Sep 2017, 5:37 pm | #5 |
Nonode
Join Date: Jun 2014
Location: Bristol, UK.
Posts: 2,074
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Re: Radford amplifier chassis refinishing?
Radford Revival might know - http://www.radfordrevival.co.uk/ - they are very helpful chaps.
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17th Sep 2017, 5:58 pm | #6 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 14,009
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Re: Radford amplifier chassis refinishing?
Powder-coating could be problematic: the resultant coating is insulating so you'd need to scrape the coating away anywhere there's a need for a bolt-through earth tag.
I'd get it bead-blasted as a first approach, then perhaps an acid-pickle (chromate) to clean out any deep-seated pitting. Then a very-fine misting with etch-primer [you still want to be able to see the underlying metal through the misting]. These guys: http://www.arc-rite.co.uk/aluminium-...y-sizes-1564-p are worth consulting. Then spray the topside of the chassis with whatever topcoat colour floats your boat, but leave the underside unpainted for better contact where you need to bolt-down tags/valve-bases etc. |
18th Sep 2017, 5:53 pm | #7 | |
Pentode
Join Date: Aug 2005
Location: Shrewsbury, Shropshire, UK.
Posts: 149
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Re: Radford amplifier chassis refinishing?
Quote:
Must say it's very tempting to get it chrome-plated |
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18th Sep 2017, 8:19 pm | #8 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
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Re: Radford amplifier chassis refinishing?
Zinc takes time to age and settle to the point where anything will stick to it. Chrome shows every blemish. A matt Nickel finish may be preferable.
David
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Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done |
19th Sep 2017, 3:17 pm | #9 | |
Pentode
Join Date: Aug 2005
Location: Shrewsbury, Shropshire, UK.
Posts: 149
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Re: Radford amplifier chassis refinishing?
Quote:
Does anyone know of a company who could do this work without it requiring a second mortgage? |
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19th Sep 2017, 4:43 pm | #10 |
Retired Dormant Member
Join Date: Dec 2007
Location: Shropshire, UK.
Posts: 3,051
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Re: Radford amplifier chassis refinishing?
There's a fair bit of information on the Web about DIY Zn plating. Might be worth reviewing.
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19th Sep 2017, 4:55 pm | #11 |
Heptode
Join Date: Jul 2014
Location: Boston, Lincolnshire, UK.
Posts: 995
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Re: Radford amplifier chassis refinishing?
I've not used any for years, but if you Google "vintage motorcycle plating" you should find plenty of companies active in re-plating vintage m'cycle parts (e.g., frequently small order quantities & sizes). It might be worth calling a couple. £385+ certainly seems outrageous / just a price from someone not wanting the job.
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