Anyone have pictures of the 'guts' of a resistor decade box? - Page 1
Forum section: electronics / testgear

author: Pasky
author_rank: Regular Contributor
timestamp: January 24, 2014, 01:44:40 am
content: I'm curious how these are built. I see some on ebay for $150+ and wondering what the hell is in them for it to cost so much.

author: c4757p
author_rank: Super Contributor
timestamp: January 24, 2014, 01:45:49 am
content: Very good quality switches and good quality resistors. It adds up fast for low-volume items. The voodoo doesn't start until a much higher cost.

author: EEVblog
author_rank: Unknown
timestamp: January 24, 2014, 01:48:34 am
content: Plus:

author: EEVblog
author_rank: Unknown
timestamp: January 24, 2014, 01:48:54 am
content: Plus:

author: Pasky
author_rank: Regular Contributor
timestamp: January 24, 2014, 01:55:34 am
content: Thank you so much for your fast responses. And sorry I missed those videos sir.

author: iloveelectronics
author_rank: Frequent Contributor
timestamp: January 24, 2014, 02:23:54 am
content: https://www.eevblog.com/forum/reviews/chinese-decade-resistance-box-teardown-photos/msg225512

author: don.r
author_rank: Frequent Contributor
timestamp: January 24, 2014, 02:50:59 am
content: When it comes to seeing the guts of a decade resistance box, Gerry's is hard to beat...https://www.tindie.com/products/gerrysweeney/seven-decade-programmable-resistor-1r-9999999r-1-500mw-gerrysweeneycom/

author: BravoV
author_rank: Super Contributor
timestamp: January 24, 2014, 02:55:05 am
content: Another reference, photo from this thread ->Sperry Ratio Potentiometer Teardown

author: linux-works
author_rank: Super Contributor
timestamp: January 24, 2014, 05:48:15 am
content: dekabox unit (from local surplus store)general radio KV divider:

author: zapta
author_rank: Super Contributor
timestamp: January 24, 2014, 06:04:44 am
content: What is the usage of a resistor boxes in a lab? Design by trial and error? Having special values that are hard to find? Testing?

author: Rerouter
author_rank: Super Contributor
timestamp: January 24, 2014, 06:14:55 am
content: external sensors.... PT100's for a single example

author: Pasky
author_rank: Regular Contributor
timestamp: January 24, 2014, 02:32:22 pm
content: Awesome thanks for the all info, I saw the Gary Sweeny video and he mentioned the hack a day article, so I'm gonna build myself a couple of these.http://www.digitalunderpants.com/diy-resistor-substitution-decade-box/Thanks again!

author: linux-works
author_rank: Super Contributor
timestamp: January 24, 2014, 03:19:01 pm
content: one use I had was to pick a series R for led brightness. just turn the dials until you get the brightness you like, then subs. that value in the circuit.another use: we had to do some low current load testing on a psu and our 'power meter' was showing values we did not trust. so we added some series load R (via an old heathkit decade box) and put a current meter in series to compare to the power meter's view of things. with a set of meas1,meas2 points, we could create a calibration curve to fix-up the power meter's readings with our proper dmm's values.

author: don.r
author_rank: Frequent Contributor
timestamp: January 24, 2014, 03:31:34 pm
content: Quote from: zapta on January 24, 2014, 06:04:44 amI recently used mine to confirm my son's physics homework. They had a circuit where they had to calculate an unknown resistance value. I built the circuit and tweaked the box until all the other parameters were the same as the question's and voila, his answer matched the value on the resistance box.

author: zapta
author_rank: Super Contributor
timestamp: January 24, 2014, 04:17:20 pm
content: Quote from: linux-works on January 24, 2014, 03:19:01 pmThat's a good idea. I did it a week ago the hard way, started with 470ohm and ended at 10k, didn't expect to go that high with 5V.

author: linux-works
author_rank: Super Contributor
timestamp: January 24, 2014, 06:11:08 pm
content: just an outside shot, but still a nice oldie that still does its job well:it dates to 1950, approx. not saying its a precision unit, but its a strong unit and it gets extra points for being in a nice wooden box (that I refinished, as best I could). the bakelite original chickenhead knobs are impossible to find, today, in that style, and those are all original. later on (not in this photo) I replaced those ugly screws with nicer/new ones.

author: ben_r_
author_rank: Frequent Contributor
timestamp: January 28, 2014, 08:07:47 pm
content: Quote from: Pasky on January 24, 2014, 02:32:22 pmThat is awesome! Im going to do the same!

author: PA4TIM
author_rank: Super Contributor
timestamp: January 28, 2014, 10:52:08 pm
content: Danbridge 3 decade box. 0.1% ( 0.1 Ohm, 1 Ohm and 10 Ohm stepsGR-602M, 0.1% decade box. 1, 10, 100, 1000, 10000 stepsThis one is made somewhere in the 1930's and stil spot on.Homemade one for non-precision use. Same steps as the GRESI RV-722 Kelvin Varley devider, 7 decades.Detail of a Fluke 720, 7 decade KV. the grand dame of KV deviders, a class on its own.Fluke 750 dividerAnritsu, looks like a resistor decade but is a decade attenuator

author: echen1024
author_rank: Super Contributor
timestamp: January 29, 2014, 01:44:07 am
content: I wonder if you can do this with mainly 1206 SMDs and just the occasional through hole for the bridging. Much cheaper, no?

author: Pasky
author_rank: Regular Contributor
timestamp: January 29, 2014, 01:49:55 am
content: I made one using 805's, used a piece of wire to bridge the end ones.

author: echen1024
author_rank: Super Contributor
timestamp: January 29, 2014, 02:13:51 am
content: Quote from: Pasky on January 29, 2014, 01:49:55 amhuh. I would like it if you could take a picture for me. Thanks

author: TerraHertz
author_rank: Super Contributor
timestamp: January 29, 2014, 03:10:36 am
content: How did nobody mention this site?http://www.pbase.com/brixton_morris/resistance_boxes&page=allFound that while looking for info on a Muirhead A-25-L that I restored recently.Which still didn't tell me anything about where and when this one was made. I'd like to know.The Hundreds range had a strange error - every setting after zero was about 98 ohms too high. That seemed hard to understand, given the resistors were all wire wound types. How could a wire resistor become nearly double its correct value?Turned out the resistors were all wound with two separate wires in parallel. On the first resistor of the hundreds range, one of the wires was open circuit, with a single small spot of corrosion.With a bit of microsurgery I was able to bridge the break, losing only about 3mm of wire length. So the Hundreds range is all a tiny bit low now; about an ohm. If I cared I could insert an SMD resistor to compensate. But I don't.The fascia was in horrible condition - very grimy, Bakelite gone matte, legends almost invisible. It cleaned up OK, and I used white nail-hole touchup wax stick to get the lettering white again. Didn't do anything to the wooden box, I prefer it to look well used.Interestingly despite being in a wooden box the unit is well shielded. The front has a grounded metal backing sheet, and the inside of the wooden box is painted with some copper flake paint that actually measures as a dead short from any points you try with multimeter probes. It's just like a sheet of metal. The front plate spring contacts the metallic paint along the joint edges. Impressive.The first pic answers the question 'What are resistance decade boxes good for?'A: You can use them to check if your multimeter can count.(Spot the meter lead resistance value.)

author: PA4TIM
author_rank: Super Contributor
timestamp: January 29, 2014, 06:50:09 am
content: Could it be your Muirhead is a relabeld General Radio decade box ? (or GR is a relabeld Muirhead)Mine misses the Original wooden box. I know it is shielded like my GR-1800 VTVM and GR-605B generator, but those have coppersheet in side, no paint. Both are from the 30-40's periode so it is possible they switched to copper flake paint later (I did not know there was this sort of paint)

author: Pasky
author_rank: Regular Contributor
timestamp: January 29, 2014, 06:53:20 am
content: Quote from: echen1024 on January 29, 2014, 02:13:51 amhttps://www.tindie.com/products/gerrysweeney/seven-decade-programmable-resistor-1r-9999999r-1-500mw-gerrysweeneycom/Check out 9:20. Same idea. I've got mine sealed and don't feel like cracking it open.

author: Vgkid
author_rank: Super Contributor
timestamp: January 29, 2014, 07:02:08 am
content: PA4TIM, I know that they make a copper paint for helping to seal metal exhaust gaskets. Im not sure of the copper content.

author: Pasky
author_rank: Regular Contributor
timestamp: February 08, 2014, 09:14:19 pm
content: So, I want to make a Capacitance decade box now. But, I'm some what stumped as capacitors lose capacitance when in series unlike resistors. So I'm unsure if I can use these 0-9 Chinese switches:http://www.ebay.com/itm/321165234242?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649Or if there is another way I need to go about it. I was thinking of making 2 of them. One for the pF range, and one for the uF range, both 0-10,000. Any advice?Thanks.