[Coco] Re: Old radios

[jdaggett at gate.net]

Neil 

I was checking on the net and correct the #80 is a rectifier and if I 
remember correctlythe tube that was bad was the first IF amp tube. 
Dead filament. 

That is one way of reforming caps. Another is to remove them and 
slowly work the voltage up across the cap while limiting the current. 
Once you get them up to full working voltage then you can leave 
them at that voltage for a while.The one thing that is death to those 
capsis to hit it with to much current when the dielectric is not well 
formed between the plates. 

One can test the capacitance by using a know high value series 
precision resistor and a scope with a constant voltage source. 
Measure the time it takes to reach one sigma (63% max voltage) 
and then plug and chug into an equation. 

james

  

On 10 Mar 2004 at 18:09, Neil Morrison wrote:

From:           	"Neil Morrison" <neilsmorr at hotpop.com>
To:             	"CoCoList for Color Computer Enthusiasts" 
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Date sent:      	Wed, 10 Mar 2004 18:09:11 -0800
Subject:        	[Coco] Re: Old radios
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> 
> ----- Original Message ----- 
> From: <jdaggett at gate.net>
> 
> 
> > Eric
> >
> > I think the tube that is bad is a #80 or 83 something like that.
> They
> > are available but kind of costly.
> 
> An 80 is a rectifier isn't it? You could always wire silicons across
> the base.
> 
> > More so than the tubes is the condensors that will need replacing.
> > back then they used paper dielectric caps and they are almost bad by
> > now. Might be able to recharge them with a variac. Slowly bring up
> > the voltage and maybe the diaelctric will reform properly.
> 
> Or get an old style cap checker (Heath off eBay) and use it to reform
> and test the caps.
> 
> > What I do want to get is exact replacement caps if necessary and
> > restore it back to full tube use.
> >
> > james
> 
> 
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