Changing A-BFastiron SS-305MP Binding Posts

I needed a cheap power supply for a project and it was easy to find a nice one in A-BFastiron SS-305MP. It was small enough, looked good, and had shiny display. What could man want more?

Well, how about proper binding posts?

And no, I am not only talking about quality albeit one coming with it are quite flimsy and it already arrived with one cracked. I am talking about spacing. I simply hate when binding posts don’t observe standard ¾" distance between them.

And this power supply almost had it right. I measured spacing to be a smidgen over 20 mm while standard would call for 19.05 mm. With such a small difference, there was literally no reason to go non-standard. But non-standard they went.

If you open the power supply, you’ll see that binding posts are held by the PCB in the back. Thick wires are soldered onto it and nuts are used to connect to posts themselves. So the whole operation can be done with a simple PCB update with correct spacing. Only thing needed extra is a bit of filing action and you can reassemble it all.

However, since my binding post was already cracked, I decided to swap them for Pomona 3760 (black and red) set. But that brought another issue - panel cutout for them is completely different. And yes, a patient man might shape it enough, but for those with 3D printer there’s an easier solution.

To mount it all, I used some nice red MH Build PLA to print really tight mounting base and spacer for posts.

After filing plastic a bit to expand holes toward each other, I placed binding posts into the printed base, pushed it through the hole, used another 3D printed spacer on inside and added some more height to set using spacers that came with binding posts themselves. Then in goes the custom PCB and finally all can be fastened using lock washer and nut that cane with posts.

Result are nice binding posts at proper spacing. :)

On GitHub you’ll find source files and releases with gerbers and part list. 3D model can be found on TinkerCAD.

PS: The only downside of Pomona is that it uses ¼" imperial nuts while the power supply originally had 7 mm nuts. So, in addition to metric socket set you already have, you’ll need a witchcraft-sized set too.

Prepping Image for ESXi

I like using vboxmanage for disk conversions. When dealing with major formats it often can do everything I need. For example, if I wanted to convert raw disk image to .vmdk, it’s easy:

vboxmanage convertdd in.raw --format VMDK out.vmdk

However, sometime this simple tool is too simple. For example, using that image with ESXi, any modern version will just give you “Not a supported disk format (sparse VMDK version too old)”.

But it’s not like vboxmanage is the only game in town. For example one can use qemu-img.

qemu-img convert -f raw -O vmdk in.raw out.vmdk

Different tool, same error.

For ESXi to work, we need to tweak options a bit.

qemu-img convert -f raw -O vmdk \\ -o adapter\_type=lsilogic,subformat=streamOptimized,compat6 \\ in.raw out.vmdk

And this one does the trick.

Well Grounded

Playing with electronics as a hobby has its advantages. Most notably, I don’t need to deal with high-speed signals or EMC most of the time. However, in the days of faster and faster I/O, high-frequency content “sneaks in” whether you want it or not. Just because your microcontroller works at 48 MHz, that doesn’t mean your I/O edge is not (much) faster. And sorting out those issues is hard.

Fortunately, there are many “rule-of-the-thumb” guides out there, but I found none better than Rick Hartley’s. Well worth the watch.

Attending Conference in the Time of Covid

Working from home is saving a lot of time. No commute, no lunch break, no interruptions. So it seemed like a good idea to attend an online conference - especially since I got one ticket for free. While signing up it asked for my work email and phone. As often before I gave my real information. I always did so for many conferences without any issues. Topic didn’t interest me much but I saw no downside in “attending” it. Worse case scenario, I’ll just have it on in background while doing some work.

But it’s like universe wanted to teach me a lesson…

As soon as conference has finished, I started getting emails from vendors. And phone calls. Many phone calls. During “physical” conference times I occasionally did get into touch with interesting people. However, it was only when I found their product interesting and of my own volition. Never before I had conference share my phone number with sponsors. I guess this is a new normal.

I pretty much had every company present at the conference give me a call by now. I must say that most of them were pleasant and understanding when I told them I was not interested / had no use for their product, but surprising number of them were as close as you can get to a spam call.

Companies we never worked with claimed to be calling from “our” account team. There was a lot of persuasion to connect them to somebody higher up. And a lot of trouble hanging up. You see, I am used to “no” meaning no. And I expect the other person to accept it so we can end the conversation on a pleasant note. I’m old fashioned that way.

Pretty much each unpleasant caller had the same tactic. Ignore “no” and pepper me with questions about company I work for. As I refuse to answer a question, ask why and immediately pop another. Damn it, I had spammers that were more pleasant callers than these.

Well, lesson learned…

DKRed

While I use OSH Park most of the time, I always like to look at different services, especially if they’re US-based. So, of course I took a note of DigiKey’s DKRed. Unfortunately, review will be really short as I didn’t end up using it.

On surface it looks good. Board requirements are reasonable. If you want to use DKRed service you need to have your design fit 5/5 mil minimum - more than sufficient for all I do. While more detailed specifications are available for other PCB vendors on their platform (albeit Royal Circuits has a bad link), there’s nothing about DKRed itself. Yes, I know DKRed might use any of manufacturer’s behind the scene but I would think collating minimum requirements acros all of them should be done by DigiKey and not left to a customer.

And not all limitations are even listed on that page - for example, fact that internal cutouts are not supported is visible only in FAQ and whether slots are supported is left as a complete secret. Compare this to OSH Park’s specification and you’ll see what I mean.

But ok, I went to upload one small board just to test it. And I was greeted by error that length is shorter than 1 inch. As I love making mini boards smaller than 1", I guess I’m out of luck. But specification page did correctly state that fact so I cannot be (too) angry. Never mind - I’ll try a slightly bigger board. Nope - it has to be more than 4 square inches in area. Something that I didn’t find listed anywhere.

Well, I had need for one board 65x72 mm in size - that one would work. And yes, DKRed finds that board OK. But cost is $43.52. OSH Park charges $36.25 for the same board. And yes, DKRed gives 4 boards ($10.88 per board) while OSH Park only provides 3 ($12.08 per board) so it’s slightly cheaper if you really need all 4 boards. If you’re hobbyist requiring only 1 board like me, you’re gonna pay more.

And this is where I stopped my attempts. Breaking deal for me was the minimum size as this makes it a no-go for most of my boards. And cost for just a prototyping is just too high. Mind you, it might be a good deal for people regularly working with bigger boards at a small quantity. But it’s not for me.