Reviving a rusty Sharp WF-939Z

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stragulus

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Another fun project! Ever since knowing about this model's existence, which is actually only since a couple of months :-D I wanted one. They seem to be pretty rare, but a month ago or so there was one on ebay which I snagged.

It was relatively cheap, but it certainly has suffered a great deal. First of all it was completely dead. It also must have been stored for many years in a damp cellar as it was very rusty on several metal parts, and all openings were covered with some white film. This turned out to be spider silk, and there were several dead spiders and a whole bunch of spider eggs in the box!

The rust didn't seem so bad at first, just some surface rust of non-important parts at first glance and some green oxidation here and there. Most parts I could easily take off and soak in a vinegar bath to get the rust off. I couldn't save the chrome keys from the tape decks though; while trying to polish those, the chrome came off in several parts. also, while all the components leads are rust free, *ALL* the leds' legs in the box have rusted! That doesn't seem so bad, but this also applies for the matrix of leds that make up the graphical analyzer. Oof, that will be a fun job replacing all of those. They do still work, but they will have to be replaced.

All connector sockets are also rusted, and I have to replace all of those with something else. The antenna broke off (my own stupid fault trying to straighten it). Both tape decks are also up for a good cleaning, lubing and rebelting. Didn't try the radio yet.

But..at least, after a couple of weeks sporadically attending to it, I have brought it back to life! I'm super impressed with its sound. Its highs sound very clear, and it has more punch than the giant Conion. Plus, of course, the awesome graphical equalizer!

You can see it in action here, although it's still in pieces and will be for some time to come:

https://www.youtube.com/watch?v=f1j7F9H0GFI&feature=youtu.be
 

stragulus

Member (SA)
Replaced all the leds today. Wasn't quite as painful as I thought it would be. The old leds broke off at the slightest touch, so good riddance :cool:

IMAG4115.jpgIMAG4116.jpgIMAG4118.jpgIMAG4120.jpgIMAG4121.jpgIMAG4122 replacing leds - after.jpg
 

oldskool69

Moderator
Staff member
I have one of these and as great as they are they are temperamental to repair as they are prone to cold joints and traces. I actually farmed mine out for major repair work as at the time I was too busy. But when running, it's sooooo good.

Keep it going. You are well on your way. :yes:
 

stragulus

Member (SA)
Thanks!

So far at least the amp seems to work great. I'm now replacing all the ribbon cable connectors. They look like they were designed to be connected exactly once. Though in my case it didn't help that rust got to every uncoated metal surface, like in those connectors. All the pcb components, except for the leds, are rust free though.

It does sound great indeed! The highs especially sound fantastic, but it also has a good punch even on low volume. They were getting really good at making decent smaller punchy speakers around that time. I think it's the foam?
 

devol-toni

Member (SA)
I also have a 939 and it is a very nice sounding box, I can not take my eyes from those enchanting led graphic when bouncing :yes:
Good luck with the resto :-)
 

stragulus

Member (SA)
I've spent a lot of time on the sharp in the past weeks. Removed surface rust here and there, replaced all the ribbon cable connectors and sockets, and also reflowed many solder joints for all connectors, cables, pcb interconnects and switches. After all that work at least the amp, spectrum analyzer and radio work great!

Cosmetically it looks good, but the chrome painted tape deck buttons all need to be repainted somehow. There was green spotty oxidation on all of the keys, and sadly that was not just superficial. Now I know my way around the technical issues, but I have absolutely zero experience doing any body work whatsoever. Soo.. I could really use some noob-friendly advice here :-D

How can I get these back in a nice state? The buttons appear to be plastic with chrome paint. The paint also seems different..like the square on the stop key is shiny, while most of the rest of the key is diffuse. Let's say for simplicity's sake that I'd just paint them in 1 style.. how do I go about doing that? What tools do I use? What paint? I have a dremel with polish and sanding accessories. I have no paint or paint tools whatsoever. Will chrome paint spray cans work? Do I need a primer layer? Clear coating on top of the chrome paint? Do I need a paint gun of some sorts? So many questions! I don't know where to start..help!

IMAG4279 spectrum analyzer in action.jpgIMAG4282.jpg
 

Superduper

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Staff member
They aren't painted. They are real chrome that has corroded and pitted. You can polish then to look better but the damage is permanent. It's also possible to paint them with a metallic silver (auto paint). In my opinion, that's the best compromise. There are chrome paint but the results never look professional in my opinion. It's never really "chrome" shiny and can't be clear coated as that will dull the finish before you even release the paint can button. And without clear coating, chrome or aluminum paint isn't durable. As much pressure as it takes to depress those keys, you may find yourself suffering from silver fingertip syndrome! However, if you have deep pockets, there are solutions. You can contract them out to professional plastic rechromers. There is more than one method so choose wisely and budget accordingly. BTW, one company uses a process that was also used to chrome the "Gravedigger" monster car crusher. Those familiar with this sport will know which vehicle I'm talking about.
 

stragulus

Member (SA)
Thanks Superduper :) Yeah, metallic paint sounds like the right way to go then. It just has to look good enough, not too concerned with them looking exactly like originals. So, how would this work? I'll have to sand/smoothen the current layer I guess, somehow without destroying the imprints. What would be a good method there? And then what layers of paint? Sorry for all the dumb questions, but I'm really unfamiliar with this stuff!
 

MrMcBlaster

Member (SA)
I got a quote in Australia to re-chrome all switches/knobs/tape buttons on a C-100 for AUD$100. It's not dirt cheap but not that expensive either in my opinion to get a valuable box looking really nice once again, I mean nice chrome really sets a box off. I wouldn't use paint.
 

stragulus

Member (SA)
Meanwhile I've not done much on this box, but I did clean off all the chrome from the corroded tape keys using household bleach. Now I have a little pile of very clean plastic parts. I also have spazstix ultimate mirror chrome spray paint, but still not sure if I'll use that or have them chromes. Will have to see if the rest of the box cleans up better and works 100% before I make the final decision.

2015-03-21 15.19.42.jpg
 

stragulus

Member (SA)
hradf9.jpg


Lolwut, just found this on ebay. Does anyone know the story behind it!? It s a very close match, but also plenty of subtle differences (the most notable of course the lack of graphic equalizer).
 

oldskool69

Moderator
Staff member
There's tons of AKA's lookalikes out there. Don't trust them for spare parts...you'll likely be disappointed. :-)
 

stragulus

Member (SA)
Yeah, it looked great at first sight, but all the dimensions are off and the build quality is probably cringe-worthy.
 
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