Electronics > Beginners

Vintage decade resistor box, are they really still good enough ?

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BravoV:
I'm talking about those used old decade resistor box like ESI, General Radio or Leeds Northrup brand.

Assuming its not abused like running current higher than allowed, or physically tampered inside, will they still have good enough accuracy after all this years ? I wonder if those precision wire wound resistors inside really drifted very far from the original value ?

If you have any of those, does it drifted really far after all this years ?

SoftwareSamurai:
Sure! Just make sure you get it "calibrated" every year or so!  ::)

:evil laugh:

amspire:
The old decade boxes are perfect useable, but they can be a bit large.

Don't expect them to be something they are not - the majority are 1% or perhaps 0.1% accurate. If you look at the pre-WW2 vintage decade boxes, the valve circuits at the time usually used 10% and 20% resistors. A 1% decade box for use as a resistor substitution box was more then adequate.

A 0.01% decade box would probably be rare. It is much easier to make a precision divider then it is to make a precision decade box as the divider only needs parts to match accurately - they don't need parts to have a high absolute accuracy.

Richard

BravoV:

--- Quote from: SoftwareSamurai on December 13, 2011, 09:34:06 pm ---Sure! Just make sure you get it "calibrated" every year or so!  ::)

:evil laugh:

--- End quote ---

Geez.. is that really that bad ? How much the typical drift you've experienced with yours ?



--- Quote from: amspire on December 13, 2011, 10:23:45 pm ---The old decade boxes are perfect useable, but they can be a bit large.

Don't expect them to be something they are not - the majority are 1% or perhaps 0.1% accurate. If you look at the pre-WW2 vintage decade boxes, the valve circuits at the time usually used 10% and 20% resistors. A 1% decade box for use as a resistor substitution box was more then adequate.

A 0.01% decade box would probably be rare. It is much easier to make a precision divider then it is to make a precision decade box as the divider only needs parts to match accurately - they don't need parts to have a high absolute accuracy.

Richard

--- End quote ---

Richard, glad to know, cause I've been offered an ESI 5 decades for about 30 us bucks and looks I better skip it, what do you think ?

Btw, how are those tube shaped KVD with stacked rotary switches on top like the one made by ESI ? Does it suffer the same problem ?

amspire:
I think an ESI 5 decade for $30 is an absolute bargain. I doubt you would regret it, unless it was physically too big to be if use to you. I do not know the model, but ESI boxes are usually very accurate.

I think it will have excellent quality resistors and switches.

Those rotary KVD's are extremely expensive devices with hand made and matched resistors.  That is why the new price is more then ten Rigol DS1052E scopes. A KVD though is a totally different thing to a decade resistor. A KVD is something that is useful only for checking or measuring ratios and usually need something much better then a handheld DMM to check for voltage nulls. The KVD is only dragged out very occasionally when you need accuracy. A decade box is something that can be used very regularly for all sorts of practical uses.

If you had a decade box mounted in a convenient place on your bench, you would find yourself using it all the time.  Good quality resistors means that when you see something drifting in the circuit under test, you know it is probably not the decade resistor.

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