I'm tuning a bunch of control loops on breadboards so I figured a capacitor box would be handy. Amazon had the Elenco so I got one.
It was intermittent so I opened it up to see why. Amazing garbage.
Note the reference designators in that last pic!
I'm tuning a bunch of control loops on breadboards so I figured a capacitor box would be handy. Amazon had the Elenco so I got one.
It was intermittent so I opened it up to see why. Amazing garbage.
Note the reference designators in that last pic!
-- John Larkin Highland Technology, Inc lunatic fringe electronics
Amusingly-pointless exercise: build a box that uses a fast high-voltage ADC and DAC to emulate any two-wire component of any value, in the same undemanding conditions where you would use a cheap substitution box like this one.
-- john, KE5FX
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sure it is not a diy kit someone returned assembled? :P
I guess they use the same PCB for a resistor box
-Lasse
We make resistor simulators, and that's plenty hard enough.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
Elenco makes toys, educational kits, and test equipment: I can't determine which classification the CS440 falls into.
If you're having difficulties, the documentation at: suggests: "If you are a student, and any parts are missing or damaged, please see instructor or bookstore."
Ah, I think I found the problem. See page 3: "Use only rosin core solder of 63/37 alloy." Looking at the dull solder connections in your photo, it appears that someone has used RoHS solder.
The documentation also has a troubleshooting section, which consists primarily of mechanical and soldering defects. It would appear that troubleshooting bad soldering is common and part of the OOB (out of box) experience.
The schematic on Pg 6, shows that all the capacitors have resistor reference designators. It would seem that the PCB was originally designed as a resistance substitution box.
I think you could have done better by purchasing something that was not a "toy".
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com
Usually Amazon sells decent stuff.
What benefit is it to Elenco to sell trash? It takes no more effort to do it right.
I also got their resistance box, the one with rows of slide switches, and it seems fine. It's very accurate.
Can anyone recommend a reasonably priced small c-box? I'm tuning voltage regulators, switchers and homebrew LDOs mostly. I don't have trustworth Spice models for everything.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
Not so advanced, but a little USB box, full of small relays and resistors and caps, maybe even some inductors, would be cool. Some topological cleverness could keep the parasitics down.
Then a PC program could interface to an oscilloscope, be given some performance rules, and could optimize things. I sometimes get "lost in space" doing manual tuning.
OK, separate small R and C boxes for versatility. The minimal PC program would just have sliders, or solution-space scanners, so I can tune by hand or semi-automatically, and look at the scope until I see what I like. A 2D slider would be cool for adjusting, say, a series RC that compensates a switcher. This would run maybe 1000x faster than Spice, and would be a lot more realistic.
I really want that.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
It looks to me like the PCB does not have plated- through holes, leading to inferior soldering.
I can attest that they sell piles of counterfeit products, labeled as if they're the real thing. Most of these are imported from the Pacific rim, and put up on Amazon as "Other Sellers".
However, in this case the seller is Elenco, and it's a Prime item. So it's genuine crap.
-- Thanks, - Win
Agreed, but the Amazon name is no guarantee of quality. Caveat Emptor.
Well, since Elenco makes kits and educational products, I can image a situation where a skool might buy a few kits, have their students build them, and sell the results on eBay or Amazon. The proceeds from the sales would fund the next round of kit purchases. Of course, I have no proof this is what happens, but if true, it does help explain the general lack of soldering quality.
Probably a better class of student kit builders.
I made my own using a 10 position thumbwheel switch and some carefully selected capacitors. No packaging, just a switch and a tangle of caps. You could do the same with a 10 position rotary switch.
I did some Googling and found these: I'm not sure how long the dip switches will last. Manual:
This looks nice but costs more:
eBay perhaps:
Or maybe just buy an Elenco CS-440 kit, and build it yourself with better soldering technique?
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com
It says right there in black and white: The assembled "instrument" is the CS-440 and the corresponding "kit" is K-38.
It's not bad for an educational kit. Looks like that company is frozen in the 1970s or something, kinda pathetic offering.
Correct. However, every photo I could find of the K-38 kit shows that the front panel is labeled CS-440.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com
The Redrocket stuff looks nice. The c-box covers a nice range for loop compensation.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
The RCA WC-412A RC box is good for this sort of thing. A favourite of Bob Pease IIRC.
(the 4440B is very nice as well!).
And there's one on ebay just now for $30.
Nice idea, a programmable decade box. Are you sure it does not already exist ? seems like it should.
-- Regards, Adrian Jansen
We use these:
Good quality, but expensive
The same for resistance decade box:
But very expensive
Cheers
Klaus
Programmable Decade Box:
Lot's of hits
I would make it with a HP34907A, some resistors R2R style and a little prog ram
Cheers
Klaus
Intermitency is most likely from the rotary switch.
These can be cleaned and lubricated, but it the contacts aren't designed for small signal applications, the problem will only repeat.
RL
Here are a couple uncased circuit boards that use dip switches:
1nF-to-9999nF-Step-1nF-Four-Decade-Programmable-Capacitor-Board-- Never piss off an Engineer! They don't get mad.
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