Grey insulating cardboard
 

Ahoy,

In my Uhers there are rather fine pieces of thin, stiff, grey cardboard used between circuit boards and covers. Perhaps they aren't anything special, but they have nice pressed, smooth, shiny surfaces.

If I wanted to use anything similiar in my own projects, or replace something in an old piece of equipment, does anyone know the name of this cardboard equivalent, or if it's something one can still buy today? Does it have ratings or did they just use bits of cereal packet?

Re: Grey insulating cardboard
 

I dismantled so old battery drill batteries for cell renewal. They had similar card under and around the cells. I replaced it with card cut from a "hanger" out of a filing cabinet. The sort which slide in and out with the files sitting in the "cradle".
try that.
Les.

Re: Grey insulating cardboard
 

Is this a corrugated plastic material? If so, the brand name is Correx and sheets are widely available in different sizes. Probably something different.

Alan

Re: Grey insulating cardboard
 

This is the card I always use for those applications & more:

https://www.jaycar.com.au/pressboard...erial/p/HG9985

It is around 1mm thick and for cardboard it has an amazing dielectric strength. It also looks very good varnished.Have a look at the battery case made out of it on page 12-13 of this article:

http://worldphaco.com/uploads/USING_...CILLOSCOPE.pdf

PS: the original card Jaycar supplied was a redish color, like that in the article, of late it has changed to a pale brownish color but it is electrically identical.

Re: Grey insulating cardboard
 

The thin grey cardboard is called FISH PAPER.

It is used on a lot of stereo high power amplifiers, where the two amplifier channel boards have to be insulated from the metal cabinet.

If you have a local Pro Audio power amp repair company, they may well have some.

I had 20 sheets in stock in my department, before I was made redundant. I doubt it is still there, the new management who took over sent many thousands of pounds worth of parts to the tip.

Kevin

Re: Grey insulating cardboard
 

Sounds like what I knew as "Elephantide"- a stiff grey-blue card like sheet material.

Try this: RS Stock No. 775-7790

Re: Grey insulating cardboard
 

Yes, "Elephantide"

The use of ordinary cardboard is fraught with danger.

In damp/humid climes, it can absorb moisture and not only become conductive but it also promotes corrosion when in contact with metallic surfaces.

If you really, absolutely, must use cardboard, soak it in varnish or shellac and let it dry thoroughly before use.

Re: Grey insulating cardboard
 

Once again, the hive mind comes up trumps! Looking at listings for 'fish paper' and the RS link, I think we've found it.

As so often with the Infobahn the crucial thing is discovering the right search terms. I'll get some of this and compare it what I have. It's certainly more like cardboard than plasticard.

Thanks all - don't worry Terry_VK5TM, I don't think I'll be desperate to put any projects in cardboard boxes! Shellac, however, is a lovely material with many uses...

Re: Grey insulating cardboard
 

Transformer winding firms are likely to stock fish paper in some of the thinner grades.

I've always wondered just what fish have to do with it.

David

Re: Grey insulating cardboard
 

And just so you can be spoilt for choice:

RS 775-7794 PET, Press Paper Elephantide Laminated Presspaper

Re: Grey insulating cardboard
 

Wasn't there some story about it originally being used to wrap wet fish? Probably an old fishmonger's tale!

Alan

Re: Grey insulating cardboard
 

Fish paper comes in various colors and thicknesses.
When I need any, I go to my local electrical wholesale shop and they sell me some.
Other sources might be motor rewinders & transformer mfgr's.

Re: Grey insulating cardboard
 

Elephantide or Presspahn is still available. I restored a VHF81 and the service sheet said ‘slide the Presspahn heat deflector out’ but it was missing, I was pleasantly surprised to find they were still going and I ordered direct from them.

https://secure.presspahn.com/Cart/in...2g8li0aihgugg0

John

Re: Grey insulating cardboard
 

When I was looking for some on the web, it seemed much more readily available in the US than in Europe or UK. Can't think why...

Re: Grey insulating cardboard
 

Thanks for the tip, stitch1. Unfortunately Presspahn only sell brown (I happen to like the blue!) so it wouldn't match the Uhers, but the site looks an excellent source for all those materials I'm never quite sure where to get.

ajgriff - I hope they just used newspaper as this stuff seems rather too heavy-duty for real fish! Unless they needed the insulation for the stingray tails...

FrankB - this is where the US has some advantages over the UK. Here it's very rare to find such a shop, and they'll only sell lowest common denominator parts anyway. A real nadir was when I couldn't find anywhere in Brighton to buy good quality mains flex, an in-line switch and a good plug. I was reduced to Homebase with plastic packets of cheap and nasty pieces sold at outrageous prices.

Re: Grey insulating cardboard
 

I'd guess that old fish wives would have sourced extra thin paper from the US. :)

Alan

Re: Grey insulating cardboard
 

I got some of the RS Elephantide. It looks the part except one side has a very shiny plastic film on. I'm not sure if I'm supposed to leave this on or take it off - it doesn't peel off easily, and leaves a torn surface behind so it's not an adhesive protector.

The datasheet says '100% cotton' so is this some part of the process? The stuff already in the Uher is matt both sides, so I don't know if one side or the other is supposed to be 'hot'.

As it's just a shield so the broken main board doesn't touch the bottom cover it won't matter, but it might if I'm supposed to use it the right way round in a valve situation!

Re: Grey insulating cardboard
 

Even the manufacturers don't specify which side is "up", so I guess it doesn't matter.

Re: Grey insulating cardboard
 

Dad ( master rewinder and design engineer) always said shiny side to hi volts. I didnt ask, and he never said why.

Joe

Re: Grey insulating cardboard
 

Thanks both. It looks like for this application, aesthetics wins out and it's shiny side down to match the rest.

Why I mind I don't know - who else is going to look inside the bottom of an old cassette desk and notice it?

Perhaps it's like Gaudi and the Sagrada Familia in Barcelona - on being asked by a bishop why he'd designed golden angels right up on the top of the spires where no-one could see them, he replied 'God will see them'.