[Heath] Replacement Caps

[Glen Zook]

Remember, "modern" capacitance values are not always the same, exact, values as the original values.  Modern values follow the same tolerance system as resistors.  For example, 2 mfd are now 2.2 mfd, 3 mfd are now 3.3 mfd, 5 mfd are now 4.7 mfd, and so forth.  It is the same with the smaller values.


You can get the old "exact" values but you will have to pay a VERY premium price for them in most cases.  Frankly, with tolerances, the new values are usually closer in actual value to the indicated value on the schematic, are much smaller in size, and last a lot longer.
 Glen, K9STH 
Website: http://k9sth.net

      From: Kenneth G. Gordon <kgordon2006 at frontier.com>
 To: Doug & Kathy Davies <dkdavies3 at gmail.com> 
Cc: Heath at puck.nether.net
 Sent: Wednesday, January 31, 2018 7:14 PM
 Subject: Re: [Heath] Replacement Caps
   
On 31 Jan 2018 at 16:34, Doug & Kathy Davies wrote:

> I have some caps in an HR-10B receiver that are going to need replacement and I know that they 
> are no longer manufactured.  I need to know what to replace them with.  They are: 
> 
> Molded Mica and Tubular.

Depending on the value, molded mica can be replaced directly with epoxy coated silvered 
mica caps. Values are usually in the pfd range.

However, some caps LABLED mica in a molded plastic case are actually paper. 

Most of those were made by Micamold and are usually a dark-brown color. ALL of those are 
always bad. Those should be replaced with modern metalized film caps, usually rated at 
630 V, or disk ceramic caps, of the same capacitance value. I don't know if Heathkit ever 
used those, but some receivers are full of them. I replaced 13 of them in a National NC-57 
recently.

Tubular capacitors, if they are NOT electrolytic, are all paper, and should be replaced with 
modern metalized film caps, or disk ceramics, of the same value. Working voltage is not 
important as long as it is at least equal to the original value. Anything rated higher than that 
will be quite satisfactory.

Electrolytic caps should be replaced with modern, much smaller, ones of the same 
capacitance value and equal or somewhat higher working voltage.

All of the above caps are available from Mouser or Digikey or Jameco. Some are available 
from Allelectronics.

   
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://puck.nether.net/pipermail/heath/attachments/20180201/872e28c0/attachment.html>