Author Topic: Dekabox score from Local Recycler!  (Read 7049 times)

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Offline staze

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Dekabox score from Local Recycler!
« on: July 07, 2013, 05:12:18 am »
Check out what I just found for $8 at a local Electronics recycler!

A Dekabox DB-655. 1R to 2MR (-1R) in 1R increments! Even has a calibration sticker on it from a General Dynamics Aerospace Standards Lab on it from February of 1965! Though, can't say I know what you'd calibrate on something like this...

Seems like it's in great shape. Anyone have one of these? Know if I should open it up and clean it out or anything? I'm actually curious how they're set up... I'm guessing they're set up as a Kelvin-Varley, but I can't say for sure.

Still, pretty sweet for $8!
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Offline rexxar

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Re: Dekabox score from Local Recycler!
« Reply #1 on: July 07, 2013, 05:20:13 am »
Now that's some knob porn right there
 

Offline staze

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Re: Dekabox score from Local Recycler!
« Reply #2 on: July 07, 2013, 05:22:00 am »
Now that's some knob porn right there

LOL! yeah, I figured even if the thing was toast on the inside (since I forgot I had a pocket multimeter in the car), just the casing and knobs would have been useful for SOMETHING!

The fact it was made in my hometown didn't hurt either.

Funny thing, the guy at the counter was like "so, figure out what that thing is, because we have no idea". LOL!
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Offline c4757p

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Re: Dekabox score from Local Recycler!
« Reply #3 on: July 07, 2013, 05:24:30 am »
"Calibrate" here means verifying that everything is still within spec.

Nice find :-+
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Offline staze

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Re: Dekabox score from Local Recycler!
« Reply #4 on: July 07, 2013, 05:25:52 am »
"Calibrate" here means verifying that everything is still within spec.

Nice find :-+

Yeah, figured as much. And thanks!
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Online amyk

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Re: Dekabox score from Local Recycler!
« Reply #5 on: July 08, 2013, 05:23:06 am »
Let's see the inside! :-/O
 

Offline Vgkid

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Re: Dekabox score from Local Recycler!
« Reply #6 on: July 08, 2013, 05:10:56 pm »
Very cool, and you got it for a good price.  I was bidding on a 8 decade version(non working), and it shot past $70 really fast.
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Offline staze

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Re: Dekabox score from Local Recycler!
« Reply #7 on: July 08, 2013, 05:25:16 pm »
Let's see the inside! :-/O

If I can figure out how to open it up easily enough, sure! Guessing it could use to be cleaned.
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Offline PedroDaGr8

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Re: Dekabox score from Local Recycler!
« Reply #8 on: July 08, 2013, 06:52:11 pm »
And I thought I got a good score recently.

I got an Autonetics rack mount device that had 4 Dekastat 1643's in it for $40. It appears it was an internal device because it lists schematic numbre on the back instead of part number. I took apart one of the Dekastats i'll see if I have some pictures around.
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Offline staze

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Re: Dekabox score from Local Recycler!
« Reply #9 on: July 10, 2013, 08:10:55 pm »
Actually found this via a google search!

http://www.flickr.com/photos/linux-works/7315472468/#

So I guess that's what the insides look like. =)

oh, nevermind... that's a voltage divider. ugh. maybe I'll try to pull mine apart this weekend.
« Last Edit: July 10, 2013, 08:12:44 pm by staze »
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Offline komet

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Re: Dekabox score from Local Recycler!
« Reply #10 on: July 10, 2013, 08:22:07 pm »
I wish I lived in a country with a military-industrial complex. The only defence hardware I've ever found was an analog multimeter.
 

Offline staze

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Re: Dekabox score from Local Recycler!
« Reply #11 on: July 10, 2013, 08:34:27 pm »
I wish I lived in a country with a military-industrial complex. The only defence hardware I've ever found was an analog multimeter.

Oh god, careful what you wish for. The amount of money this country spends on defense.... sure, the cast offs are great, and sure, they do stuff like invent GPS and the internet... but crap, to think what we could be like if we used that money for education, healthcare, feeding the poor, etc.

But, I digress.

I just emailed IET labs asking if they had a service manual for this DB655... we'll see what they say!
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Offline staze

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Re: Dekabox score from Local Recycler!
« Reply #12 on: July 10, 2013, 08:40:05 pm »
Actually, guessing it does look pretty similar to that other post.

Here's someone that posted the internals of a DB655A on an eBay listing.

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Offline saturation

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Re: Dekabox score from Local Recycler!
« Reply #13 on: July 11, 2013, 03:30:18 pm »
Those are great resistance boxes compared to what's available today.  The lower ohm resistors tend to burn out in those units.  Check the 1k outer scales.  Its easy to replace the worn custom wire-wound resistors on the "n" step rotary switch, if any are off.  But, if the low end range is continuously variable its more difficult to fix as it acts like a potentiometer wiper arm on a precision wire wound resistor.  You can get a precision pot to replace it [ like a Bourns pot], but it isn't easy to fit into the chassis design.
« Last Edit: July 11, 2013, 03:36:10 pm by saturation »
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Offline staze

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Re: Dekabox score from Local Recycler!
« Reply #14 on: July 12, 2013, 05:39:19 am »
Those are great resistance boxes compared to what's available today.  The lower ohm resistors tend to burn out in those units.  Check the 1k outer scales.  Its easy to replace the worn custom wire-wound resistors on the "n" step rotary switch, if any are off.  But, if the low end range is continuously variable its more difficult to fix as it acts like a potentiometer wiper arm on a precision wire wound resistor.  You can get a precision pot to replace it [ like a Bourns pot], but it isn't easy to fit into the chassis design.

Everything seems to work well resistor wise. The selector for at least the single ohm range is a finicky and requires a bit of "jiggle" to get it to settle into the range properly. Guess that could be a bit of grime on the contacts? otherwise, all the ones I've checked have worked great. With my 4.5 digit fluke, things seem pretty good. Once I get my 5.5 digit bench meter working (if), I'll be able to really see if those lower ranges meet their 0.05% stated accuracy.

One question though... they seemingly list a maximum current through each range (like, the 1R range is 710ma)... am I reading that right? Is this before they published any kind of drift? or is this some other way of stating accuracy?
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Offline casinada

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Re: Dekabox score from Local Recycler!
« Reply #15 on: July 12, 2013, 06:23:47 am »
Now you can build your own laboratory precision voltage source :)

 

Offline TerraHertz

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Re: Dekabox score from Local Recycler!
« Reply #16 on: July 12, 2013, 09:42:50 am »
One question though... they seemingly list a maximum current through each range (like, the 1R range is 710ma)... am I reading that right? Is this before they published any kind of drift? or is this some other way of stating accuracy?

I'd expect that to be the safe current limit, that won't damage the resistors.
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