Re: 475A with High +110 rail

Harvey White

On Wed, 01 May 2019 08:31:39 -0700, you wrote:


That is another critical factor, one that I took into serious consideration. I used carbon comp resistors only as a temporary measure, simply to test the rest of the system, a "proof of concept" if you will. The ones I used were 5% accuracy, so way too little precision for the job. This was evidenced by the pair having a "calculated value" of 60K and an actual resistance measured at 58.8K, so still a ways off from the desired 60.4K (+/-1%).
Once you find a carbon comp resistor of the exact value, well, it's
still the exact value until it drifts.

It was simply not worth the time to try to come up with 2,3 or 4 carbon comps that theoretically could have been grouped to give the 60.4k that was specified. Much easier to just buy the right parts and fix it permanently and correctly.
Agreed. Worth the time and effort to do it right.

The repair also looks more professional as a major benefit. I have been buying Metal film resistors, whenever possible, since they do not cost that much more, they are more stable and more reliable. Thanks for your comment.
Glad to help. I use metal film for precision, and frankly, have not
replaced all that many carbon comp resistors. They generally get
replaced by film resistors since that's what I normally bought.


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