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Old 30th Apr 2018, 2:00 am   #81
dseymo1
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Default Re: Very rusty ViewMaster TV

I recently de-rusted some heavily oxidised spanners by immersing them in a solution of citric acid for a few days. The results were better than I'd hoped for, with bright steel showing in places, and a dull grey finish everywhere else.
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Old 30th Apr 2018, 7:43 am   #82
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Default Re: Very rusty ViewMaster TV

Quote:
Originally Posted by julie_m View Post
Ah, yes, I did briefly also wonder about the other end of the pH scale. I was thinking acid because it would tend to attack the rust by itself;
Fe2O3 + 6HCl → 2FeCl3 + 3H2O.
But maybe that's not exactly what you want, because the acid can also react with the un-oxidised metal too?
2Fe + 6HCl → 2FeCl3 + 3H2.
The Fe-O bond is unlikely to be covalent; oxygen wants all the electrons to itself, and metals tend to treat electrons like toddlers treat shoes. If it's not ionic, it's polarised enough to ionise at the drop of a hat. At any rate, none of that's particularly interesting to Na+ or OH- ions. But when you start pushing some fast-moving electrons in from elsewhere, and insert an oppositely-charged electrode, there are going to be some O-- ions heading for it. So the current isn't merely helping the reaction, it's the only thing keeping it going -- the electrolyte leaves the un-energised workpiece alone. And even NaHCO3 will end up as NaOH after bubbling off some carbon dioxide .....
Is that more like how it works?
I think I need to sit down and take a tablet. It's only an old telly. John.
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Old 18th May 2018, 8:20 pm   #83
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Default Re: Very rusty ViewMaster TV

The timebase and power supply chassis is ready for testing.
Now comes the most difficult part of the restoration, I have to turn my attention to of the rusty RF unit.

DFWB.
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Old 19th May 2018, 7:04 am   #84
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Default Re: Very rusty ViewMaster TV

That looks brilliant so far. Are they 6K25's didn't know it used Mazda valves. Does the 14A86 still work?.

Peter
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Old 19th May 2018, 9:32 am   #85
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Default Re: Very rusty ViewMaster TV

Hi Peter,
The timebase valves are all Mazda and the valves in the receiver section are mainly Mullard except for the sound output valve which can be a Mullard EL33 or Mazda 6P25. The RF pentodes are EF50s.
The timebase valves are: two Mazda thyratrons type 6K25. Line output Mazda 6P28, frame output Mazda 6P25.
It should be possible to test the timebase without the receiver unit. Might try to do that later today. We'll then find out if the metal HT rectifier is any good.

DFWB.
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Old 20th May 2018, 9:52 am   #86
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Default Re: Very rusty ViewMaster TV

Hi David, plenty of EF50's here if you need them.

Ed
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Old 23rd May 2018, 8:36 am   #87
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Default Re: Very rusty ViewMaster TV

I love the look of it i wish you luck bringing this little beast back to life ! it is lucky it has a new master ~!
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Old 23rd May 2018, 8:51 am   #88
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Default Re: Very rusty ViewMaster TV

That looks really great David.

Just a thought but it looks like a bride in a white wedding dress waiting for her rather rough groom. It appears she has been left at the alter..

Just clean the top of the RF unit with a fibre pencil David. It might take an hour but at least you will retain some of the original builders good work.

My Viewmaster is a channel 3 version. Bit of a nuisance but lucky to have any version all these years on. Regards, John.
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Old 26th Jul 2018, 11:15 am   #89
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Default Re: Very rusty ViewMaster TV

Well here goes, the restoration of that horrible RF amplifier deck.
The first attempt wasn't successful so I'm going for broke and will completely disassemble the unit. So far I've removed all the sound components, as you can see from the second picture the valveholders and all the associated components have been removed. Today I will remove the vision RF amplifier components. The only components that can not be easily removed are those disc type decoupling capacitors, any attempt to unsolder these might result in damage and replacements are impossible to find.

High temperature paint will be used because a large number of components are soldered to the metal RF chassis.

DFWB.
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Old 26th Jul 2018, 5:47 pm   #90
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Default Re: Very rusty ViewMaster TV

Now all the components in the vision RF, detector and video output stage have been removed, see the first picture.
Also, It has proven possible to remove those disc decoupling capacitors so now the RF chassis is void of all components, second picture.
Next, paint it with high temperature paint, either grey or silver.

DFWB.
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Old 26th Jul 2018, 5:49 pm   #91
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Default Re: Very rusty ViewMaster TV

Stirling work so far David, I was just thinking Grey might be the best colour for a kit built chassis maybe ?

Marc.
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Old 26th Jul 2018, 6:12 pm   #92
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Default Re: Very rusty ViewMaster TV

Hi Marc,
Grey will be the best choice because then it will be same as main chassis. Did try silver and it looked silly.

DFWB.
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Old 26th Jul 2018, 6:22 pm   #93
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Default Re: Very rusty ViewMaster TV

I've dismantled chassises like this to paint or zinc plate and can say it's a very time consuming and labour intensive job.
Also there is more chance of introducing faults that previously were not there so great care must be taken on reassembly.
I think this was the right way to go David considering how rusty it is and now you have stripped all the parts off, you can paint the underneath as well.
Are you going to use a deruster first?
Looking forward to future posts.

Robin
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Old 26th Jul 2018, 6:31 pm   #94
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"Are you going to use a de ruster first?"

Hi Robin,
That might be a good idea because the metal is badly rusted. I'll remove as much rust as I can but if the hi temp paint is to adhere to the surfaces some chemical de-rusting agent will have to be used first.

DFWB.
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Old 27th Jul 2018, 7:11 am   #95
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Default Re: Very rusty ViewMaster TV

Hi David and friends Following the thread,
I know how much work it is to clean a chassis like that. I have to do it on very old radios that friends told me to put into garbage because it looked terrible..
Anyway in such operation, I would be careful about bad grounding connexions due to the paint or non conductive material when rebuilt. A lot of problem may arise because of that.
Roger
I still have the EF50's for you David. I will try another expedition hoping you will receive it that time.

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Old 27th Jul 2018, 9:00 am   #96
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Default Re: Very rusty ViewMaster TV

Hi David, plenty of EF50's here if you need them to save Roger the trouble.

Ed
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Old 27th Jul 2018, 10:04 am   #97
Peter.N.
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Default Re: Very rusty ViewMaster TV

Good idea to leave the components connected to the valve holders, that will eliminate some margin for error.

Peter
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Old 27th Jul 2018, 1:07 pm   #98
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Default Re: Very rusty ViewMaster TV

A good move for a chassis like this is to have it fine glass bead blasted to remove the rust, then have it electroplated with passivated zinc.

If the silver surface looks fairly respectable at that point, I would mask the holes (where earth connections are important) with 6mm diameter discs, you can ask your local sticker store to cut them out of adhesive backed vinyl sticker material, or you can make them yourself with adhesive tape applied to a plastic backing like mylar, and punch them out with a hole punch (the type used for making holes in A4 paper for binders)

A sticky disc is then applied to both sides of the chassis hole, where you require good earths, before you paint or lacquer it.

In short it is best to find or create a way to remove all attached chassis components without damage so they can be re-attached to the chassis later. It sometimes requires some creative engineering where things were previously soldered or riveted in place.

I would use high temp VHT clear paint or the Duco/Holts automotive lacquer.

If the surface after glass bead blasting and re-electroplating is respectable looking, it is best just to protect it with the clear coat. However, if it is very pitted where the rust crystals were, you could go for Holts silver automotive spray which gives a good finish.

If you do re-plate it with zinc, it must not be left bare or the finish will grey and degrade over time. With the zinc you can also go for blue or gold passivation whichever takes your fancy. If you can get access to an electroplater that uses electro-less nickel, that is better again as it plates down holes and into chassis internal corners as it does not depend on an electric field.

Most electroplaters now have the fine glass bead blasting in their shops, or if they don't can usually eliminate all the rust electro-chemically. Of course you can do the electrochemical rust removal yourself, but I can assure you that paint alone over bare steel, regardless of the proposed rust inhibiting properties of the paint, is nowhere near as good as electroplating and then painting or a coat of clear lacquer over that.

As a second best option, if the shortcut is taken to manually clean off the rust, and not take it to the electroplaters, the effect of the remaining rust crystals, in the pits in the metal, can be deactivated with Fertan organic rust converter. The black-blue residue (an organic derivative) leaves obvious marks, so it is definitely then necessary to use the fine metallic silver spray over that. This works, but it is not as long term effective as completely eliminating the chassis rust followed by electroplating, which is the method I have gone to after decades of restorations and seeing the long term results as the chassis again ages. However, there are some composite structures I have dealt with composed of steel and aluminium where electroplating is a not an option, so this is the way in those cases.
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Old 27th Jul 2018, 1:34 pm   #99
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Default Re: Very rusty ViewMaster TV

"I know how much work it is to clean a chassis like that. I have to do it on very old radios that friends told me to put into garbage because it looked terrible..
Anyway in such operation, I would be careful about bad grounding connexions due to the paint or non conductive material when rebuilt. A lot of problem may arise because of that"

Hi Roger,
That's why I'm not going to do anything with the underside of the RF chassis. There are many components which are soldered to the metalwork so any paint or plating will make the soldering process difficult. OK, the underside of the chassis doesn't look too pretty but does that matter much because it's not seen anyway? "Good idea to leave the components connected to the valve holders, that will eliminate some margin for error."
Hi Peter,
In fact that what I have done so when the metal chassis has been tidied up all the component should go back to their original positions.
Well, that the theory, we'll find out when reassembly begins.

Hi Ed, I might well need a few EF50s, it all depends how the originals perform.

DFWB.
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Old 27th Jul 2018, 11:28 pm   #100
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Default Re: Very rusty ViewMaster TV

DFWB,

My suggestions might not be wonderfully welcome, but anyway looking at that last attached photo of the two valve sockets, I doubt that any of the resistors there would be reliable, or the capacitors either. The wiring has hardened and cracked insulation. Also those wafer octal sockets are notoriously poor in that the pins, which are often corroded, have a low spring grip on the valve pins, though you could re-tension them, that helps for a while, but then after thermal cycling they loosen up again, or after plugging a valve in and out a few times.

The Tag strips though would be unique and should be cleaned up for re-use. I would go for nos sockets (there are many much better quality phenolic and ceramic ones about with better socket pins that won't give any trouble) new R's & C's and fresh wiring. The Silicon rubber covered wire from RS looks old fashioned and its insulation doesn't retract and melt when its soldered.

Still I appreciate the idea of trying to keep the restoration as original as possible, but there is that trade off with reliability with those very old R's and C's & sockets which might leave you chasing down a number of fixed (or intermittent faults)after the restoration. So it can work out better to avoid that in the first place. I have found with major restorations, that this works well and when the TV is re-powered, there are generally few if any faults to fix, or intermittent issues, merely adjustment issues (such as RF bandpass characteristics) and even those can be quite time consuming for something like a TV.
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