No 1% resistors available

Discussion in 'General Electronics Chat' started by atferrari, Feb 24, 2012.

  1. atferrari

    Thread Starter AAC Fanatic!

    Jan 6, 2004
    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.
  2. bertus


    Apr 5, 2008

    Have a look at the attached PDFs.
    The tiltes will say enough.

    Last edited: Feb 24, 2012
  3. atferrari

    Thread Starter AAC Fanatic!

    Jan 6, 2004
    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.
  4. luvv


    May 26, 2011
  5. Markd77

    Senior Member

    Sep 7, 2009
    Maybe a couple of little spreadsheets would help, one for parallel and one for series:

  6. bertus


    Apr 5, 2008
  7. Wendy


    Mar 24, 2008
    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.
  8. Lundwall_Paul

    Active Member

    Oct 18, 2011
    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.
  9. atferrari

    Thread Starter AAC Fanatic!

    Jan 6, 2004
    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?
  10. MrChips


    Oct 2, 2009
    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!