"The Crocodile"

[Shaq888]

This design could easily be put on a 10cm x 10cm board using thru-hole components including the LM6172s,

There is a photo in the first post that shows how it started -

So if you seriously want to go through-hole, you don't even need a PCB as such

Although the small variant also includes SMPS on board. You don't really want to make that one trough-hole. Once one half is SMD, it does not makes sense to keep the other one old-school.

 

[ammel68]

Yes, I saw that first post photo.

When I first saw it, I remember saying to myself "that's the worst bird's nest of point-to-point construction I've ever seen"...LOL...

But in all seriousness, I'm sure it took you quite a bit of time to assemble that old crocodile and work out any bugs.

 

[Shaq888]

I'm sure it took you quite a bit of time to assemble that old crocodile and work out any bugs.

It wasn't that bad at all. It took something like one and a half hours of soldering. There wasn't much of debugging either, more like a bit of a final tuning.

BTW, after I got I running on the small board, I made a new PCB design, where I ditched unused components etc, and it was under 40x40mm. Never sent to to production though

 

[adydula]

I got a YIHUA 898D+ hot air gun station for less than $50, a genuine YIHUA model and it works well with the SMD parts, and this was my first time using these really small OPA1622's etc...with another DIY's design.

I was intimidated at first, worrying about damaging and getting the parts on the board soldered without shorting stuff out underneath the 2mm x 2mm parts....but it was a lot easier than I thought....

The hard part is getting the dang things placed on the board correctly .....just have to be careful and take your time...the solder paste makes the parts stick to the pcb rather nicely, then just make sure you dont turn up the air too high and move the parts around!! lol..

I hope to start this crocodile later this week and will post pictures etc..

Alex

 

[adydula]

I asked this question back in post #36.

The coils in the schematic call for 4.7uh coils...the coilcraft ones.
But the part number in the BOM is for 10uh coil??

So is this acceptable or not? The coils AGDR sent me are the 10uf ones/

Help!
Alex

 

[Shaq888]

4u7H <=> 10uH - it was an optimization for a specific input voltage, AFAIR, but it will not make a big difference. Solder whichever you have. Will need to update the BOM some day

Placing of SMD components on the solder paste does not have to be very accurate too - surface tension will align them properly. If this does not happen it means that something is wrong - temp is too low, surface is oxidized, bad solder paste etc.

 

[adydula]

Great!!

Then I shall I continue! I am an anal person ....Mr. Exact....and thanks for holding my hand!!

:>)

 

[adydula]

Sergey, in post #24, you state that c2, R381 need tweaking for start?
In the schematic C2 is shown as "NF' and R381 is not listed in the BOM, but shows 150K on the schematic?

Alex

 

[Shaq888]

C2 and R381 are to flip Q3-Q4 trigger into "on" position on power up. Start with R381 around 150-220k, if there is a problem you can add a small cap.

 

[adydula]

ok, so install c2 or not? its a NF in the list?

 

[Shaq888]

Try without C2 (NF - not fitted). Most likely you will not need it.

 

[adydula]

I found some zero ohm links!! So I can use these for L4, L5, L6 and L7

Alex

 

[adydula]

Ok we have started!

 

[adydula]

Ok I was just going to put C1 on the pcb, its a 0603 part 100nf (.1uf) part.
AGDR sent me his parts and when I pulled them out of the bag here is what I saw:

The cap is soooo small it makes the 805 4.7uf cap look like a giant!!
There is no way I can tack this one down!! Ha! LOL!

I will order a 805 part....must be a error in the BOM Sergey.

Alex

 

[OlegSh]

I guess the smaller one is actually 0603 metric code or 0201 imperial... Don't breathe while looking at it

 

[adydula]

I am not good at the numbers, but the 0603 smaller part is indeed VERY SMALL!!

I am good, but not that good!!

 

[Shaq888]

Sizes of footprints are pulled out automatically by the CAD, so that the only part I'm sure in this BOM 0603 parts can soldered on 0805 footprints easily. I would say don't stress, solder whatever you have got.

 

[adydula]

Sergey, this C1 part doesnt even span the 805 pads.....I could bridge it with solder but the part is really too small for the way the pads are layed out...these parts are the size of a pin head...

Here is a pix of the part we have...it may be incorrect in the order??

 

[adydula]

Other than that I have all the parts in the U1300 circuit installed, the only two issues are this C1 part and C66 which should be 470pf...which AGDR sent me (2) .47uf or 47,000pf caps...size is ok just value probably due to the BOM being incorrect a year back or so.

NP. I will order and get the 470pf caps from Mouser.

So far its looking good...

Alex

 

[Shaq888]

It is 0402 if not smaller on the photo. Those footprints are 0603, afair. I didn't go that small Definitely a wrong part.