Yet another resistance decade box

[johnmx]

Fortran, in order to prevent shorts during soldering I recommend you to make tented vias next time (no solder mask opening).

ez24, if you have a short circuit you can desolder the resistor (keep heating both sides 1s at a time until the resistor gets loose), remove the excessive solder on the board with solder wick and solder the resistor again.

[ez24]

ez24, if you have a short circuit you can desolder the resistor (keep heating both sides 1s at a time until the resistor gets loose), remove the excessive solder on the board with solder wick and solder the resistor again.

I will try this if I run out of boards. 

Did another one today successfully but ugly. The problem I have is leaving "whiskers" when I lift the iron.  I always have to go back and try and level them.  Sometimes I can and sometimes I cannot.

I have a question: what do people do with the standoffs?  When I started, I trimmed off all three, then I tried just the center, then I tried not to trim any.  Without trimming any I got the board out ok but I could not get the new one in.  In fact I destroyed the switch trying to get it in.  So I went back to just trimming the middle one BUT it seems the middle one is the most important to keep the switch wipers touching the board.  Just curious on what others are doing.

When I am done and before I assemble them, I think I will take a hot needle and press down in the center of the ones that I cut to make them spread out a little.

Vias
It seems to me, with a 10x glass, that the vias at 2,7, and 9 are actually touching the pads, whereas in the picture they do not.  I am afraid to test with a meter because if they are not touching, the probe would probably make it contact (it is that close). I try very hard to keep solder away from the via and it seems to work.  Comments ?

[Fortran]

Whiskers can have a few reasons.
Heating too long burns away the "wetness" and solder clings instead of flows.
Is your tip clean?  It should be silvery and shiny.
If it is..  have you tried adding flux?
If it still won't cooperate.. try a different/better solder. The cheap stuff is usually a nightmare to work with.
What's the dia on your solder? It might be too thick and that's no good either.


Standoffs:
You only need to cut the two. Use a scalpel or box-cutter to cut them flush to the board.

The vias on 2, 7 and 9 are connected to those pads, so a short there does nothing
It's only the one under 3 that's a potential risk of shorting.

[ez24]

Whiskers can have a few reasons.
Heating too long burns away the "wetness" and solder clings instead of flows.

--> I do not think this is the problem, I do not spend much time on the pad

Is your tip clean?  It should be silvery and shiny.

-->  Yes I clean it each time I use it


If it is..  have you tried adding flux?

--> I will order a flux pen, I do not have any


If it still won't cooperate.. try a different/better solder. The cheap stuff is usually a nightmare to work with.

--> I use Dutch Boy, I think it is good  (but very old maybe 50yo)   I will order some new solder - Kester
https://www.amazon.com/KESTER-SOLDER-24-6040-0027-Stand-Diameter/dp/B00068IJPO/ref=sr_1_7?s=hi&ie=UTF8&qid=1469859605&sr=1-7&keywords=rosin+core+solder

What's the dia on your solder?

--> Very small, my guess .5 mm  The Kester is .031", which sounds very small to me


It might be too thick and that's no good either.


Standoffs:
You only need to cut the two. Use a scalpel or box-cutter to cut them flush to the board.

--> now that I think of it, it is probably better to cut the pair and leave the center.  I will try that on the next one

The vias on 2, 7 and 9 are connected to those pads, so a short there does nothing
It's only the one under 3 that's a potential risk of shorting.

--->    this will help a lot. I was trying very hard not to get solder near the edge of the pad

So far I have done 3 good ones and 1 bad one     Not bad for an old fart.

thanks a lot - this will help

[Fortran]

Yeah that might be it.
Solder usually have an expiration date. It's probably fine a decade or so after that, but still. If it's 50 years old it wouldn't harm to try a fresh one.
I've never used Kester, but from what I've heard it's good stuff.
0.031" is about 0.78mm.  That's quite thick for SMD.
I'd go for 0.5mm or smaller just to have better control over the amount of solder you're putting on.

If you want to I can send you some 0.3mm, 0.5mm and 0.7mm to compare.

[sq9nje]

Hey Guys,

I just ordered 3 sets of boards with 1% resistors. The switches will probably take ages to arrive though...

Przemek

[Fortran]

Thanks Przemek.  It's been shipped.


Update:
The new resistors have arrived!
But the pre-orders grew during shipping so I'm already out of 0.1% kits.

So, ONLY 1% kits are available at this time, but I have plenty of them.

[johnmx]

Here is the finished decade box.
I used an old lithium battery box.
The overall size is rather small: 114 x 52 x 20 mm.
The banana connectors keep the box closed without using any screws.
The parasitic resistance is around 0.5 Ohm.

[Fortran]

Nice and compact 

[sq9nje]

Thanks Przemek.  It's been shipped.

Man, you're fast! Thanks Fortran! Will report back when I receive them.

[bitseeker]

That is excellent, johnmx! Looks good and is very compact.

[Blastcap]

Doing some last minute shopping, could anyone confirm that these will fit?
http://www.mouser.de/ProductDetail/CHERRY/PBC1-E015/

Its a 10 pack from "Cherry", they can't be too bad.

EDIT:
Don't buy these... they won't work!

[BFX]

Just got mine two sets   
Waiting for switches.

Thank you 

[Janne]

2 sets received today, very neatly packaged!! thanks 

[Fortran]

Great 

Happy to see that everyone seems pleased 

[ez24]

I got better at soldering, the main improvement was to hold the iron on the pad for about 2 seconds before adding solder (to prevent whiskers)   Now I have gone from 10% success to 90% i

I got a sample of the "big" switch and I like it.  It is easier for me to use.  I thought maybe I could wire up external caps and make a cap decade box BUT it is a BCD switch.  I never saw one of these.  I assume you need TTL logic to make it work, but I wonder if some sort of decade box could be made with it without TTL or MCU?   Maybe I should start a topic on it.  Does anyone have any ideas?  thanks

Again I want to say thanks Fortran for this project.  The professional quality was a surprise.

[Back2Volts]

...  I thought maybe I could wire up external caps and make a cap decade box BUT it is a BCD switch. ...

There are at least two variants of the switches I know of,   BCD and (straight) decimal.   Just because I was looking for different colors ones I ended up ordering some decimal and some BCD.     

[ez24]

There are at least two variants of the switches I know of,   BCD and (straight) decimal.   Just because I was looking for different colors ones I ended up ordering some decimal and some BCD.   

Thanks I will look for a large decimal switch.

[Narmaraktuk]

Just received a well-packaged set from Fortran. Many thanks!

[Alex Nikitin]

I've received the second packet as well - thank you!

Cheers

Alex

[gblades]

I got a sample of the "big" switch and I like it.  It is easier for me to use.  I thought maybe I could wire up external caps and make a cap decade box BUT it is a BCD switch.  I never saw one of these.  I assume you need TTL logic to make it work, but I wonder if some sort of decade box could be made with it without TTL or MCU?   Maybe I should start a topic on it.  Does anyone have any ideas?  thanks

I would have thought BCD might actually be better for a capacitor box due to the way you stack capacitors in parallel to combine the capacitance.
With a digital output you would need 1 of 1nf all the way through to 9nf. With a BCD output though you only need a 8nf, 4nf, 2nf and 1nf. The 1,2 and 4nf you can make up by stacking capacitors side by side or on top of each other of there is enough room. The 8nf then is a bit more awkward as 8 caps are a bit too many to stack but even so it does make it simpler and reduces the number of different value capacitors you need to purchase.

[Fortran]

Here's my box

They're both supposed to be short, but I broke my last M2 tap on the first hole 
Can't screw it together until I get a new one so I'm using an uncut box until then.

[Back2Volts]

Fortran, nice!     What are the dimensions of the box, 60x55x25 ?    Is the body just one tube piece?   How do you cut it?    I was thinking about running an aluminum box through my 10" table saw, but it kind of scares me

[Iwanushka]

Here's my box

They're both supposed to be short, but I broke my last M2 tap on the first hole 
Can't screw it together until I get a new one so I'm using an uncut box until then.

Nice boxes, do you mind sharing a link to them?

[Fortran]

It's 80x50x20
http://www.ebay.com/itm/172255252886

But I cut it down to 60x50x20 with a metal band saw.
Mine looks like this:

But a regular vertical one would work too. Just screw it together first so the pieces are aligned, and cut slow and carefully.

The endplates where cut with my CNC mill, because I'm too lazy to do it manually