Golborne Vintage Radio

Full Version: Resistor prices and inflation
You're currently viewing a stripped down version of our content. View the full version with proper formatting.
Pages: 1 2 3
A poster on a Usenet forum who runs a lab at UEL posted that a lecturer had asked him to order some 10% tolerance resistors.

This intrigued me, so I did a little research and I found the results very interesting, so I'll share it here. See what you think. This was my answer:

Quote:Why does he want resistors with such a wide tolerance?

I haven't been responsible for ordering components regularly sine 1969 (!) and I didn't have a resistor with a tolerance worse than 5% in my entire stock even then.

Taking a quick look on-line to see what is available today:

https://cpc.farnell.com/c/electronic-ele...-resistors

I see lots of 0.25W 1% resistors for just over a penny each and 5% values for half that so it isn't going to be an economy measure!

I looked for 10% tolerance and only found 9 results - and they are all 2W at 8p ea!

Interestingly, in 1969 I was paying 16/- (80p) for 100 0.5W 5% resistors so a pretty comparable price despite all the rampant inflation in the intervening years!

Given that all my resistors were carbon film and the modern ones are superior metal film, today's prices are a bargain!
They certainly are. More accurate, cheaper, more stable and last much, much longer!

And capacitors. Paper types for 15 years? Or cheaper, smaller polyester types for hundreds?
Modern general purpose components are not worth ordering in less than quantities of 100.
Even TO220 power devices come by the 400mm tube quantity.
Modern components are just cheap.
"Modern components are just cheap. " To a point, start going up in voltage and prices shoot up. Also the better quality part, like a long hours 105 deg cap by a known decent manufacturer starts getting expensive if you need a few.

While were on the subject of caps etc, has anybody any experience with Kemet caps? I was under the impression that they were cheap cr*p, the name reminiscent of Kermit, a bit like Multicomp, but several posts on various forums has led me to think I might be wrong.

Andy.
I have had no bad experiences with Kemet capacitors. I tend to think of them in connection with surface-mount multilayer ceramic, but they bought Evox-Rifa some years ago so have film capacitors in their portfolio.

So on that basis, I'd avoid the metallised paper like the plague... but other types are good.
Perhaps the teach just wanted to demonstrate tolerance spread in components?
Back in the early 1980s, designing broadcast equipment at Michael Cox Electronics, we used Mullard MR25 2% metal film resistors as our standard. I measured a few once, using a good DMM and found very few worse than 0.5%. Within a batch they tended to cluster very tightly round a value that was within the tolerance range. For professional (as against consumer) purposes they were cheap even then. No point in stocking 5% or worse parts.

The main exception to the 2% parts were 0.1% resistors by Holsworthy. Fairly expensive and hence used only where needed. 75R for accurate video terminations and custom values for such things as RGB to YUV matrixing in PAL coders.
(09-10-2019, 08:21 AM)Amie Wrote: [ -> ]Perhaps the teach just wanted to demonstrate tolerance spread in components?

That could easily backfire! There is no guarantee that variation between samples from a single batch will cover anything like the maximum possible range. [EDIT: Just spotted that Jeffrey beat me to it while I was writing this!]

A calculator would be simpler!

Or even a chart, such as the one I posted for you in this post.

It was only when I produced that chart that I spotted an anomaly which had completely passed me by many years earlier. Virtually all postwar radio and TV production in the UK, up until the early 60s used large numbers of of Egen ½W resistors. These are quite bulky compared with more modern  counterparts because the resistive element was inside an off-white ceramic tube (which showed off the colour codes very well!) with a cement seal on each end.

They were virtually all ±20% tolerance. Now ±20% tolerance only needs 6 values (E6) to cover each decade, yet they were made and sold in the E12 values more suited to ±10% tolerance components!
Thanks Terry

Dad told me that when he was first interested in electronics and was building something that required say 2% components, he would (in ignorance) try to select values from a batch wider tolerance types, apart from other problems, he found that the values of 20% resistors for instance would be within 20% but outside 10%, he says probably because they were selected from production runs as 5%, 10%, 20%.

I believe that he referred to the resistors Terry described. I have some of dads stock of those ceramic bodied composition resistors, that I keep only for curiosity, most are +50% marked value now, being made by "Erie" (?) according to the packages in 1957!
I don't remember Egen resistors, just their pots, I remember the Erie ones though, in ceramic tubes with cemented ends, mainly +-10% jobs.

Lawrence.
Pages: 1 2 3