Author Topic: Mystery tin resistor box  (Read 6082 times)

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Offline enut11Topic starter

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Mystery tin resistor box
« on: May 22, 2020, 10:24:30 pm »
What is this tin 'resistor' box and what equipment may it have been part of?

It has 13 terminals and marked 13071.

Size is 9 x 3.5 x 3.5cm
« Last Edit: May 31, 2020, 10:51:17 pm by enut11 »
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Offline enut11Topic starter

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Re: Mystery tin resistor box
« Reply #1 on: May 22, 2020, 10:31:13 pm »
All the connection points appear to be connected by resistors mainly.

Measuring connector-to-connector:
1-2  3809 ohms
2-3  2999 ohms
3-4  short
4-5  9 ohms
5-6  short
6-7  1060 ohms
7-8  4062 ohms
8-9  1903 ohms
9-10  4060 ohms
10-11  1132 ohms
11-12  75 ohms
12-13 75.5 ohms
« Last Edit: May 23, 2020, 06:40:03 am by enut11 »
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Offline ChristofferB

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Re: Mystery tin resistor box
« Reply #2 on: May 23, 2020, 10:16:57 am »
Interesting! Well my first guess would be a resistance standard from some high-end test gear.

But that assumes that it litterally IS just a resistance box. Just because there are some measurable resistances doesn't necessarily mean it's only resistors inside.

The values seems strange for a meter reference, one would expect a larger range, from milliohms (or short) to multi-megaohms.

Can you measure capacitance? It could be RC networks for timing.

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Offline coromonadalix

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Re: Mystery tin resistor box
« Reply #3 on: May 23, 2020, 10:37:52 am »
Maybe a resistor network for some instrument ... like a frequency generator ?

Can you shoot some photos  from the bottom, is it completly sealed off ?

Stranges values indeed
 

Offline Gyro

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Re: Mystery tin resistor box
« Reply #4 on: May 23, 2020, 11:15:26 am »
You're missing quite a lot of measurements there, you've only measured between adjacent pins. Don't necessarily assume that it is internally wired as just resistors between adjacent pins, you might be measuring combinations. For instance, the pairs reading short might be common connections for a bunch of resistors to other pins. Try a some more probing combinations and the values might suddenly make more sense.

Edit: Or 3+4 and 5+6 might be kelvin sensed connections to the 9R resistor.
« Last Edit: May 23, 2020, 11:18:29 am by Gyro »
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Offline Tom45

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Re: Mystery tin resistor box
« Reply #5 on: May 23, 2020, 05:09:35 pm »
You're missing quite a lot of measurements there, you've only measured between adjacent pins.

Exactly.

There are N*(N-1)/2 measurements (78) but he only did 12 measurements.
 

Offline pardo-bsso

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Re: Mystery tin resistor box
« Reply #6 on: May 24, 2020, 02:15:10 am »
Make a hole and peek inside?
 

Offline mikerj

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Re: Mystery tin resistor box
« Reply #7 on: May 24, 2020, 09:56:45 am »
Have you tried measuring between the pins and the case?  There looks to be some kind of connection on the side of the case, though it's not clear enough to tell from the photos.
 

Offline Vovk_Z

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Re: Mystery tin resistor box
« Reply #8 on: May 24, 2020, 10:40:12 am »
]
There are N*(N-1)/2 measurements (78) but he only did 12 measurements.
/off
Good that it isn't N!  :)
 

Offline gbaddeley

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Re: Mystery tin resistor box
« Reply #9 on: May 24, 2020, 01:25:27 pm »
Could it be a transformer? Resistances seem like taps along a winding.
Glenn
 

Offline enut11Topic starter

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Re: Mystery tin resistor box
« Reply #10 on: May 24, 2020, 07:49:56 pm »
Maybe a resistor network for some instrument ... like a frequency generator ?

Can you shoot some photos  from the bottom, is it completly sealed off ?

Stranges values indeed

It is completely sealed.

More resistance checks, this time referenced to pin #1.
2:  3809 ohms
3:  809 ohms
4:  809 ohms
5:  804 ohms
6:  804 ohms
7:  521 ohms
8: 3810 ohms
9:  3808 ohms
10:  521 ohms
11:  877 ohms
12:  806 ohms
13:  877 ohms

None are connected to the metal can.
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Offline ratio

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Re: Mystery tin resistor box
« Reply #11 on: May 24, 2020, 10:47:57 pm »
Draw a picture looking down from above, measure the resistance between all of the terminals that had wires connected, & show them on the pic.
Also, do you have a CLR meter of some kind?
 

Offline enut11Topic starter

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Re: Mystery tin resistor box
« Reply #12 on: May 25, 2020, 05:41:44 am »
I have a simple CR/Trans tester.

The picture below shows the resistances that I measured between the previously soldered terminals. This is part 1 as interaction between upper and lower rows is not shown here but will be in a follow-up.
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Offline enut11Topic starter

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Re: Mystery tin resistor box
« Reply #13 on: May 25, 2020, 07:40:43 am »
This is the second part - Resistance measurements between the upper and lower rows.

Actually, I am not sure if these diagrams help. Just a rats-nest of resistances.
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Online Ian.M

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Re: Mystery tin resistor box
« Reply #14 on: May 25, 2020, 08:13:21 am »
Don't do a diagram, do a spreadsheet.   Terminal numbers as (text) column headers and row values, then a grid of measurements at each row/column intersection.  Obviously the diagonal where row=column will be blank.  Enter shorts as 0 and leave opens blank.
Always put the positive probe on the row label terminal so the results will meaningfully show the presence of any diode junctions, i.e if resistance(col,row)<>resistance(row,col)

Also, *HOW* is the box sealed?  some good photos of the sides may lead to suggestions for opening it non-destructively.   
What does it weigh, and what are its dimensions?
What does it sound like if you tap it with a hard object?  e.g. does it click, clank or ring.
Estimate where its center of gravity (C.G.) is by rolling it across a round toothpick, and marking the position of the toothpick when it tips.  Do this in both directions across a long side, and both directions across the base.

If its heavy and the C.G. is fairly central, perhaps biased a bit towards the base, it would make gbaddeley's transformer suggestion more likely.
 

Offline enut11Topic starter

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Re: Mystery tin resistor box
« Reply #15 on: May 25, 2020, 09:25:11 pm »
@Ian.M
The sketches were uploaded due to a query from another member and they do help somewhat. I will also look into your spreadsheet idea.

Some more pix attached showing the box is solder-sealed.

Box weighs 97g and size is 9 x 3.5 x 3.5cm

Noise? sounds like a click

CG is approx central on all planes.

There are no diodes in the box
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Offline Gyro

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Re: Mystery tin resistor box
« Reply #16 on: May 25, 2020, 09:35:15 pm »
It looks as if that box has already been opened - there is no continuous solder fillet (unless it is just the photo angle), maybe just tack-soldered in a few places.
« Last Edit: May 25, 2020, 09:36:47 pm by Gyro »
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Online Ian.M

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Re: Mystery tin resistor box
« Reply #17 on: May 25, 2020, 09:54:10 pm »
The weight means its unlikely to contain a transformer or to be potted.

As Gyro points out, that looks like it could be desoldered reasonably easily using a high enough wattage soldering iron.  Remove as much solder as possible using solder-wick, then work round it prying the joint open slightly while heating it, so residual solder doesn't bridge across the joint.  It will  probably remain in contact at the corners so you'll have to clamp it in a vice and work round reheating them and prying between the top of the vice jaws and the edge of the lid to gain a small movement at each corner in turn till the lid comes off.

Opening it will probably be less tedious than taking a full matrix of measurements (aka: the spreadsheet), and you'll also gain a reusable screening box, and if you are lucky some  precision resistors.
 

Offline M4trix

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Re: Mystery tin resistor box
« Reply #18 on: May 25, 2020, 10:20:29 pm »
Well, you could end the debate by grabbing a hacksaw and....  :popcorn:
 

Online Ian.M

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Re: Mystery tin resistor box
« Reply #19 on: May 25, 2020, 10:49:18 pm »
I would only take a hacksaw to it as a last resort as the enclosure is probably of greater use than the contents.   If its too difficult to get the lid off by ordinary desoldering, it would be less destructive to slit the corners of the lid with a Dremel cutting disk so the lid sides can be bent out slightly to ease desoldering them.   It could still be reconstructed if anyone has need of it, with the corner slits filled with solder, wiped to original profile.
 

Offline enut11Topic starter

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Re: Mystery tin resistor box
« Reply #20 on: May 26, 2020, 12:16:40 am »
It looks as if that box has already been opened - there is no continuous solder fillet (unless it is just the photo angle), maybe just tack-soldered in a few places.

Nope, there is continuous solder around the lid with no evidence of tampering
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Offline bob91343

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Re: Mystery tin resistor box
« Reply #21 on: May 26, 2020, 04:08:30 am »
I would try my hot air desoldering station on small areas.  I have opened boxes like this by heating with a big iron and forcing a screwdriver into the solder.  Once you get purchase you can try to bend it, as the solder is softer than the can.
 

Offline exe

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Re: Mystery tin resistor box
« Reply #22 on: May 26, 2020, 08:00:55 am »
Drill a hole and use a borescope  :horse:  :popcorn:
 

Offline enut11Topic starter

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Re: Mystery tin resistor box
« Reply #23 on: May 27, 2020, 12:58:07 am »
That would be too easy. Where is the challenge?
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Online bdunham7

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Re: Mystery tin resistor box
« Reply #24 on: May 27, 2020, 01:17:57 am »
Can you measure 11-13 and 7-10? And maybe 2-8 and 2-9?
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 


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