[morzh]

Yep, that's a handful.

[Arran]

Are you certain that the tuner chassis out of that Scott 16 was chrome plated? It looks pretty dull for chrome plate, as a matter of fact it looks more like cadmium plating or zinc possibly, chrome plate should look like that power supply/amp chassis before you started. Since the 16 was a sort of budget model maybe they skipped the chrome on the tuner chassis but left it on the power supply/amp since the latter was shared with other models? The good news is that if it was cadmium or zinc plated then it's much cheaper to redo since it's only one type of metal, most chrome plating such as for car bumpers is triple plated, copper, nickel, and then chrome. I have a suspicion that Scott performed what is known as "flash" plating, like what they used on cheap bicycle parts, they chrome plated the bare steel and skipped the other steps, otherwise why would the plating get spotted or rusty on something that spent it's life indoors when old car bumpers would not?
Regards
Arran

[rfeenstra]

Arran, it is chrome, no question. You may be correct about the "flash" plating. Perhaps someone on the EHScott website knows. I have yet to see any evidence of copper under the nickel and have wondered about that. if there were copper, there would probably be much less rust. anyway, the process has begun. the IF transformers, tuning cap, and other parts have been remove from the chassis. I will attempt to remove the tube sockets with wiring attached. It appears that much of the RF section can be removed as a single unit that includes the band switch and coils. Once everything is removed, it's off to the re-chrome shop. Fewer but larger parts this time. Hopefully the fewer parts will translate into lower cost. Still hundreds! Ouch. I'll never get the money I put into this thing out of it. but then, that's not why I'm doing it.

[Phlogiston]

Nickel can be plated directly onto steel. Actually acid-copper can not be plated directly onto steel, but there is another process for that. If I want to copper plat a chassis I have to nickel plat it first otherwise the acid in the copper bath dissolves the steel - and ruins the copper bath.

The nickel is polished very smooth and then chrome is applied. It is like a clear coat on a painted surface, but has lots of imperfections so it will not protect by itself.

[rfeenstra]

Interesting.  When the chrome shop redid my amp for the 16, they used a lot of copper to fill in the rust pits.  So, it may be nickel under the copper, then more nickel, then the chrome?  Quite a process.  I've done some brush plating of airplane parts - cadmium, no less.  Dangerous stuff that can't be found any more.  That was a lot simpler than the chrome process.  I've tried to protect the chrome on the redone amp and my Scott 16A with carnuba wax.  Russ, do you suggest something else?

[Phlogiston]

Like I said, there is a process to plate with copper - first, but it isn't necessary unless you are filling holes. Solder can also be used to fill holes.

Waxing a chrome chassis is a good idea. Carnuba (regular car wax) is what I use also.

If you are interested in the plating process, Caswell has a good book. It is included with most orders but can be purchased separately.

[rfeenstra]

Chassis is ready for re-chroming.  All of the tube sockets, terminal strips, and controls were remove with as much wiring intact as possible, hoping to make re-construction as easy as possible. Looks like a rat's nest to me!

All caps will be re-stuffed.  Most of the resistors are easily within specs so I'll leave them.  The power resistor has an open section so I'll have to strap on a wire wound - bummer.  Does anyone know how to rewind these things?

How about the dial face.  Everything is embossed.  However, I don't know how to clean it up without damaging the ink or whatever is in the embossed area for the numbers.  Any ideas or experience out there?

Thanks!

       

[Phlogiston]

I cleaned mine with a damp rag.

People - I for one - have tried to rebuild the candohm resistors. Opening the outer case is a real problem. The other issue is getting nichrome wire with a high enough resistance for sections with resistance above a couple of hundred ohms. (Nichrome with resistance of an ohm or 2 per foot is available but this would require close to 100 ohms - or more, per foot)

In several radios (2 Zenith Strats) I have used a knife to score the wire, opening all of the windings, so that there is no possibility of an intermittent, and then hid a 20W wirewound under the old candohm for originality/looks. Also got some blowback on ARF from the non-restoration know-it -alls.

The original is insulated with fish-paper (possibly asbestos). If it is not visibly burned or cracked, it should provide adequate insulation for the one-wind on each end of the candohm that is still connected to the circuit.

[Electrothaumaturgist]

What would be ARFs' beef with trying to retain a little originality??? I don't get it...

[rfeenstra]

Thanks Russ. That is about as clean as it gets with a damp rag. Even tried a bit of alcohol around the outer part but it didn't help. It may have to stay as is.

As far as the candohm is concerned only one section that ties to ground (end section) is open. Have you ever trusted the rest of the sections to hold up under actual use, or is it best to replace all sections with a WW resistor? If I were to do that, I'd probably install a terminal strip. Sure wouldn't look original, but one must do what one must do to make things work.

[Phlogiston]

What would be ARFs' beef with trying to retain a little originality??? I don't get it...

If they did not think of it or it makes what they did 2nd rate - they don't like it. You know - kill the message/messenger. This applies to finishes, colors, old wire, restuffing caps, molded resistors and on and on - - SEE: Who Looks Under A Chassis (COOL, it is the first two things to come up on Google)

INSERTED LATER: I think that this is mostly an outspoken minority, or newbies surprised by the extent that an old radio can be restored. In several posts "professional restorers" claim that they would never go to this extent for a customer. It might well eat into their profit. To quote a well known political figure "sad".

I put the Dale WW resistor below ( even if the original candohm is on the side of the chassis). I use the original connections with the original resistor element disabled as stated. The Dale resistors are compact and black color, so they are not obvious with the original candohm in place.

A razor knife easily slips between the fishpaper at the seam. You can feel the wire as it is cut. If the paper/insulation is degraded/burnt, don't do this. Test the unit when completed. This is to eliminate the possibility if an intermittent connection to the original (open) resistor.

This is a solution I arrived at while attempting to rebuild failed candohms. Still looking for the appropriate nichrome wire.

If I had to do one section, I would probably do them all.

[rfeenstra]

This candohm does not allow one to get to the windings without actually taking the unit apart.  Some major metal bending would need to be accomplished.  Since it is the end section that connects to a ground lug right next to the end, I could just not hook up the end terminal and let it float, preventing any intermittent issues.  I'll look into the Dale resistors.  I can mount it so that it is not too obtrusive.  Thanks for your help!

[Arran]

Russ;
  I got a little blowback the same way with regard to someone's brand Z console cabinet, the know it alls insisted that with "Cowards" restore a finish the party that owned it wouldn't need to strip and refinish it, the trouble was that probably 50-60% of the finish had flaked off and was down to the bare wood, the rest was lifting and about to flake off. They were all talking about it like they were preserving an original finish, the trouble being is that there was no original finish to save, so basically it was just a cover for laziness. Sure , it brings up the grain, then six months later (at the most) the oil dries out and it looks like a "chicken coop" special again, so why not do it right the first time? I honestly hate "Howards" almost as much as I hate the refinisher in a can stuff, too many sleazy antique dealers, fleabay sellers, and craigslist sellers used it on their cabinets just to make it look good for the photos, more then one guy on here has overpaid for a set because they thought it was a nice original when in reality they were paying for a bottle of "Cowards" to be rubbed on it.
Regards
Arran

[Arran]

That Candohm looks like one of the kind that you would have to open from the back, however it looks like they mounted the resistors, and the terminals in a strip of Bakelite or phenolic. It actually doesn't look like it would be too hard to get apart if you needed to, a thin flat blade looks like it should slip under where the front piece folds over the mounting plate, if the front piece is aluminum that would make it even easier. In answer to your second question, yes you could bypass the last section, if it's between the next section and ground, it won't do anything if that final terminal stays open circuit.
Regards
Arran

[Phlogiston]

Candohm - yes, the metal case is very tough. That is the first reason that rebuilding one could be difficult.

The concern regarding the use of the candohm contacts as a point to mount a new resistor arises from the prime reason most candohms fail, and that is an intermittent at the pressed-on contact/stud. If the connection is reestablished (it is intermittent) then the value of the resistor will be 1/2 of the desired value (old WW + paralell new = 1/2 assuming both are the same value).

Consider how they are assembled. A wire-wound resistor wound around an insulator/substrate is laid down on fishpaper which is laid down on a metal sheet. Then the sheat/fishpaper is folded around the resistor. In the process, taps were provided at points on the WW resistor. These taps are not soldered or connected except by mechanical means. These tap points are usually the problem. The connections become loose, probably because of heating and cooling AND it is likely that some oxidation also occurs between the tap and the resistive wire.

Now, when this whole mess is folded up there is still a seam on top. Both the contacts and some of the fishpaper emerge from the seam in the folded assembly. What I was doing was to push a razor knife in between the sheets of paper. The blade will contact the wirewound element. Dragging the blade along the element cuts the wire in many spots, making an intermittent connection very unlikely.

Again, if the candohm has been overheated then the insulation value if the fishpaper is compromised.