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Old 3rd August 2011, 01:06 PM   #1
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Default Rattle can a power transformer

I scored a magnavox 93 series chassis on the curb this week. Its power transformer was covered in pitch or some type of potting. I got the power transformer stripped down to the almost metal with a metal brush and i got the paint stripped off the end bells (still alittle surface rust).

How can i paint the transformer with a spray can? I dont think i can get the endbells off without snapping the heads off the bolts. I have a spray can of black vynal dye thats super thin and meant for dash boards. My concern was putting too thick of a paint layer on to the point that the transformer wont be able to radiate heat well.

Really i want to spray the thing down with truck bed liner but i think that will really insulate it.
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Old 3rd August 2011, 01:25 PM   #2
TheGimp is offline TheGimp  United States
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I wouldn't worry about it too much. I've worked with a similar Magnavox amp with a similar potted transformer. I believe it is typical for Magnavox.

Mask off the leads and hang it up in the air and wipe it off with paint thinner. Let it dry good and spray it with a good black enamel paint in two or three thin coats.

With the potting and construction they used, a couple thin coats of paint won't do anything to heat loss.
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Old 10th August 2011, 09:46 PM   #3
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Any tips on painting the aluminum chassis? Ive taking a brillo pad to it, tryed hammered metal paint, that didnt stick, tryed stock flat black primer, that didnt stick. I got a feeling im going to have to just brillo pad in one direction and call it brushed aluminum since nothing sticks to it unless i spend $50-100 to paint 1 square foot.
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Old 10th August 2011, 09:54 PM   #4
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Have you tried a self etching primer
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Old 10th August 2011, 10:10 PM   #5
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Question Painting aluminum plus Magnavox use

I have had luck with first using some 220 grit papar on the aluminum and then using rustoleum hammered. The note by someone else concerning self etching primor works well too but it doesn't seem to like the hammered paint.

I have been playing with a Magnavox mono amp with 4 6V6's, 2-5Y3's and 1 12AX7. I replaced the 12AX7 with a preamp driver phase inverter system based on the Pilot 410 amp. 6C4 as a triode preamp, then 1\2 the 12AU7 as a voltage amplifier and the other half as a phase inverter. It alsways has worked perfectly with these types of amps and is very easy to work with. This time I have an issue with the scope trace. Just after the peak I get "fuzz" (sorry best description) I can post a picture of this trace if someone can tell me how to do it.

I traced my way through the circuit and have a perfect sine wave at the plate of the phase inverter and the fuzz at the cathode. Amp doesn't sound bad, it just doesn't sound as goood as I expect it to. Voltages all close to what they should be. Power supply completely rebuilt
Bruce
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Old 11th August 2011, 12:03 AM   #6
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found this at home depot:
RustOleum.com

the etching primer im having trouble finding in less then 1 gallon sizes.


Ive also heard good things about plain appliance epoxy:
http://www.rustoleum.com/CBGProduct.asp?pid=101


i can write my name in with my fingernail with strait hammered 1 week after cure, after taking a brillo pad to rough it up.





UPDATE: There is hope for a cheap solution if i can find it at autozone or advanced

http://www.rustoleum.com/CBGProduct.asp?pid=397

Last edited by nightanole; 11th August 2011 at 12:29 AM.
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Old 11th August 2011, 12:46 AM   #7
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I bought it in a rattle can at menards.
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Old 11th August 2011, 11:03 AM   #8
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Default Rattle can

I use automotive engine enamel for transformers. It is shiny, black and tough. Lays down nice. I use a lot of the hammered paints and have never had them be soft like yo are saying it is. Strange

Bruce
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Old 11th August 2011, 01:02 PM   #9
TheGimp is offline TheGimp  United States
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Rattlecan self etching primer is available at most automotive supply stores. Automotive paint supply stores also carry it.

Just watch for enamel/laquer incompatibility. Use the same family primer as you use top coat.
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Old 11th August 2011, 01:56 PM   #10
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I have had no problem painting aluminum chassis. The finish seems solid with the only chips coming from removing the transformers after they were bolted down for several months. Some of the paint was stuck to the transformer legs. It won't be visible once I put it back together.

Aluminum oxidizes very quickly. The oxide coating will easilly scratch off taking the paine with it. Clean and rough up the finish as you described. I use a Scotch Brite pad. Wipe down the surface with a paper towel soaked in lacquer thinner and paint it as soon as the surface dries (a few seconds). I use Rustoleum rattle can paint (usually flat black) for the first coat. The coat should be thin enough to barely cover the metal. I put down several more coats as each one dries, which is maybe 10 minutes in the hot Florida sun.

I let that dry for a few days in a hot environment. I use a closed car that I won't be driving for a few days. Then wipe again with lacquer thinner and apply the final color coat.

This one was done in "Stone" paint from Home Depot. The OPT end bells were ugly grey rusted power transformer covers rescued from scrapped HP audio oscillators that were left outside in the Florida rain. I used the same method except the final coat was Rustoleum glossy black.
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Last edited by tubelab.com; 11th August 2011 at 01:58 PM.
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