[Milsurplus] Electrolytics

[Dave Merrill]

I never knew the RETMA electrolytic values progressed in a logarithmic
manner. Makes sense. Thanks, Google.

--... ...-- Dave N9ZC

On Wed, Aug 20, 2025, 10:05 AM Nick England <navy.radio at gmail.com> wrote:

> For many many years resistors and most capacitors have followed the RETMA
> standard values
> 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82 or
> 10, 15, 22, 33, 47, 68
>
> But electrolytics didn’t, for some reason. Until we started seeing
> tantalums and the Japanese electrolytic invasion. I wonder why? Maybe
> because of the lopsided -20/+80% tolerance?
> But we commonly saw 20 and 40 uF values when they could have been 22 and
> 47 just as easily. Mysteries.
>
> Nick England K4NYW
> www.navy-radio.com
>
>
> On Wed, Aug 20, 2025 at 11:15 AM Charlie L. <mjcal79 at gmail.com> wrote:
>
>> Thanks Jim and David for the comments.  One thing about electrolytics is
>> that our old units seem to have a tolerance rating of -20/+80% of indicated
>> value. Most folks want to replace, say a 40uf at 450VDC, with the same
>> thing, and end up paying $10 or more for a name brand, while you can find
>> the 39uf at 450V and higher for just a few dollars.  A lot of the smaller
>> caps are also abundant  with a 630VDC rating at an inexpensive cost,
>> compared to being a purist and wanting .1 at 600 for $5 where the .1 at 630V
>> can be in the 50 cent range.  When you use Newark or Mouser, a big giveaway
>> when you are putting in the part value in the filter window and you see
>> three 40uf listed and 72 39uf listed, you know the 39's will be cheaper
>> with a greater voltage range selection.  The 20uf cap was ubiquitous in
>> just about any gear years ago, Newark has 3 choices for a 20uf and 28 for
>> an18uf, well within the acceptable  tolerance.  I thought when Newark
>> started selling leaded resistors for a fraction of a cent each, that they
>> were dumping stock,  as everything seemed to be going to SMD style, but
>> maybe that is not the case.
>>
>> Charlie in NC
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