What type of capacitors was used in early marshall amps?

ELS

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I'm interested in the type of the capacitors used in old marshall amps, the grey ones, yellow ones, etc.
wheather they're PIO, paper-wax, or film caps.
 

william vogel

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Pretty certain they are film. The mustard caps are and I’d think the grey molded ones are too.
 

ELS

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actually I found what those mallory mustard caps are, they're polyester caps. but I didn't find anything about the grey molded ones
 

playloud

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Yep, those grey RS (Dubilier?) ones are polyester film too I think. As well as the green Hunts and yellow/blue Dubiliers.

What about these ones in the JTM prototype? They look different to the Dubilier ones.

iu
 

ELS

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Yep, those grey RS (Dubilier?) ones are polyester film too I think. As well as the green Hunts and yellow/blue Dubiliers.

What about these ones in the JTM prototype? They look different to the Dubilier ones.

iu
yes I meant the ones in the prototype and really early offset amps!
 

Pete Farrington

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From what I can make out, RS were still selling caps that looked like that in the 80s, described as polypropylene film.

The casing can be white, gray, blue, or a ‘half and half’ combo, with one half one of those colours, the other another colour.

I’ve never found them to be leaky.

I’ve seen reports that they’re sometimes branded Dubilier.

Polypropylene caps are typically described as being bulkier, but having better properties than polyester, eg lower losses and temperature coefficient.

Due to the latter, Aiken reports that polypropylene are his preferred type.
 
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TAZIN

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For the Dubilier caps the blue, blue & white, and blue & yellow were paper & foil construction. Their gray and gray & white ones were metallized paper.
 

TAZIN

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The Dubilier caps had a polypropylene case with an impregnated polystyrene coil made of either paper and foil or metallized paper.
 

stickyfinger

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The Dubilier caps had a polypropylene case with an impregnated polystyrene coil made of either paper and foil or metallized paper.
That would explain why all the NOS ones I've bought measured 30-40+% more than value. Stopped buying them after 10 or so bad ones.
 

Seanxk

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Fair enough! Here's a zoomed-in view of the caps:



Original version here: https://www.fuzzfaced.net/jtm45-origin.html
These are earlier RS cap's, they are similar in construction to the notorious Hunts, basically if there's a crack or slight damage they de-laminate, a bit like when you bight into a chocolate ice cream and a great chunk of the chocolate cover comes away and lands in your lap, not advisable whilst driving ( which I was ).
 

StuC

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Further to Tazin's post, my 1965 RS catalogue describes them as "Tubular Paper Capacitors". "Wax impregnated plain foil and paper units moulded into a tough protective case".
 

TAZIN

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Further to Tazin's post, my 1965 RS catalogue describes them as "Tubular Paper Capacitors". "Wax impregnated plain foil and paper units moulded into a tough protective case".
Would those be like the ones that Pete Farrington posted?
 

playloud

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No
y2x7ijw.jpg

PaOQ062.jpg

Wax paper and foil

Science!

These are earlier RS cap's, they are similar in construction to the notorious Hunts, basically if there's a crack or slight damage they de-laminate, a bit like when you bight into a chocolate ice cream and a great chunk of the chocolate cover comes away and lands in your lap, not advisable whilst driving ( which I was ).

Literally happened to me yesterday (the ice cream not the caps). Devastating
 

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