No 1% resistors available

Thread Starter

atferrari

Joined Jan 6, 2004
3,388
Working currently with active filters I am facing again the problem of getting 1% resistors (rarely available locally or with a 5 weeks delay - yes, what you read - to have them on the counter). Simulation is nice but I want to build things.

The gymnastics of assembling 3 or even 4 resistors (series/parallel combinations) to reach each value used to be fun but it is time consuming.

Many times I've read pejorative comments about this and, honestly, I tend to feel a little like that.

What to do? How much could I round values?

Suggestions welcome.
 

Thread Starter

atferrari

Joined Jan 6, 2004
3,388
Gracias for repyling, Bertus.

THe first PDF, while quite interesting did not help me much since it seems more oriented to those thinking of buying a stock for future needs.

My problem, still unsolved is the lack of enough values to avoid composing the right (accurate ones) required.

Mybe I should consider buying a kit (a huge one!) once for all.

Last night I built an active filter just by repeating the series/parallel game.

Learning to live with that.
 

Wendy

Joined Mar 24, 2008
21,840
There was a statement (I'm not sure if I totally believe it) that modern 5% are actually 1%, it is more trouble than it is worth to create a separate production line for a process that already produces precision components cheaply.

Easy enough to verify. In the early days resistors drifted, so the 1% were needed. I believe that problem has been solved. Add to that the values are automatically trimmed with lasers and you can see where the first paragraph is coming from.

I think a production line I worked on way back when where the resistors were fabricated on the ceramic PCB were being trimmed to ±5%. It appears the laser trimming stopped when the resistors +4.9%. They wound up redefining it as +0.1%/-5%.

The older process, which is why the tolerance existed, used chemicals. They used a acid on a Q-Tip to etch the resistive material away on the PCB, as soon as the tolerance was met with the ohm meter they applied a neutralizer with another Q-Tip. They really did need the full tolerance range both ways.
 

Lundwall_Paul

Joined Oct 18, 2011
226
Tell me the values/wattage/package needed and I will build a mil-spec part number that you can purchase from Newark.

Call me sick I have been dealing with Mil-Specs way too long and I enjoy them.
 

Thread Starter

atferrari

Joined Jan 6, 2004
3,388
Tell me the values/wattage/package needed and I will build a mil-spec part number that you can purchase from Newark. Call me sick I have been dealing with Mil-Specs way too long and I enjoy them.
Hola Paul (and all others)

Thanks for replying.

Hard to buy from that people living here. This country is a more and more complicated place to live.

Reading the preceding responses plus several in other two forums I realized that I was approaching this in the wrong way trying to stick to the E96 series (and wrongly expecting that I could avoid the need of composing specific values).

I concluded, based on what has been told plus my (VERY) limited experience: I have to expect the need to compose specific values using parallel/series, sooner or later.

I could do that with resistors of any tolerance as long as I measure them one by one putting them in series / parallel as needed.

For that, the Excel calculation and the program will be put in good use. Gracias for that!!!

My designs are not commercial, so, as long as I accept the cost (time spent), it is OK to do that.

Do I have it right, now?
 

MrChips

Joined Oct 2, 2009
19,160
Maybe a couple of little spreadsheets would help, one for parallel and one for series:

What a great idea. I'm surprised that I had never thought of this before. But then I grew up before spread sheets were invented!
 
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