Hi All,
I have just picked up one of these as I do have a use for it albeit I cannot find any information, use guide, schematic - can anyone help at all?
Best Regards
A photo would help. I presume it's a decade resistance box. The only things you might need to know are tolerance and power rating.
Yes,
Its a decade box. I have been looking for one for a while as I plan to use it for finding the correct value bias resistors when working on my valve amps.
I have no info on this whatsoever.
Best Regards
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The current ratings for each decade are on the labels. The tolerance is likely to be better than you need and can be checked with a decent DMM. No other info needed.
Just beware that the long leads comapred to a resistor in circuit can give unwanted effects. Less likely in audio amps but valves (and transistors) don't know they are only meant to be doing audio. Given a chance to oscillate at some outlandishly high frequency they can and do.
Nice decade box Rob, still got relatively recent calibration stickers on too. Looks like you use the bottom two terminals, as Jeffrey says, check with your DMM to make sure. The top terminal - "screen" for most work can be left alone.
Andy.
A small point. I don't know if the switched are break before make or otherwise. If they are break before make then you will get momentary open circuit when changing settings. If this will harm your circuit then make sure there's a fixed resistor in parallel with the box. You can check with a meter to see if you get an open circuit when slowly switching between steps.
The greatest errors are likely to be when you get a "carry". So from 999R to 1000R, 99.9k to 100k etc. You can check with a DMM if this is a worry.
Personally, I'm not keen on decade boxes and have found little use for them. This is partly because I've often worked with circuits where the stray L and C from a decade box are unacceptable. I've tended to stick in a pot, adjust on test and measure the result. Often with a series or parallel resistor to get close to the result because this makes the pot easier to adjust and gives less scope for harm. The pot can be anything from a tiny preset (often multiturn) to a hulking great rheostat depending on what I'm doing.