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Re:load Pro

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Re-load ProI have wanted a Programmable load for a while, and truly needed one since I purchased an unknown quality HP 6624 for $10 at Goodwill and needed a way to test it before re-selling. I’ve looked at the venerable BK Precision, as well as the “knockoff” (or OEM, depending on who you believe), Maynuo equivalent. But, I just couldn’t swallow the $300+ price tag. I also looked at building one, but it just never made it on my list. But then, Arachnid Labs came to the rescue, and created the Re:Load Pro, a programmable version of his inexpensive Re:Load that offered a simple DC load equivalent to Dave Jones’ venerable one from years ago.

Unfortunately, I somehow missed the Kickstarter for the Re:load Pro, so I had to order one off Tindie and wait for them to ship. Thankfully for my pocketbook, and my wife, I had some money in Paypal from an eBay sale that I used to buy the Re:Load Pro.

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“Book” Project

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pop_blank_book_coverAt the request of my wife, I’ve started playing with the idea of writing a “book” for the purpose of educating hobbyist’s and EE’s spouses (or significant other), as well as kids. It’s point is to be very simple, not delve into the math at all (except ohm’s law, of course), and instead just explain basics of what we’re working on, what’s on our bench and parts bins, etc. The hope being that they could read through some basic information, and be able to have a basic concept of what we spend all our time doing, or when we explain a repair, they have some basic knowledge to use for understanding our language.

From my looking around, there isn’t really a good example of a “book” like this. A book about electronics, but not for someone that’s looking to learn electronics, but rather to relate to someone that’s interested in the field (if that makes sense). I’m guessing you’d call this a primer, or compendium to your significant other/spouse?

Anyway, I hope to work on it for the next few months, then open it up for edits/comments. Wish me luck!

Rubidium Oscillator (Repair?)

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fe-5680aA seller on eBay recently listed some FE-5680A Rubidium Oscillators for $30 + $10 shipping for parts repair, and I couldn’t pass up the chance to pick one up, especially when there’s so much info out there, and the wonderful FAQ here.

The unit arrived in the mail after two weeks, so I set about wiring it up. Since I only have a single output bench PSU, I had to wire up a simple 5V regulator (just an LM7805CV with heatsink) to supply the 5V logic power needed for the unit ((As a note: if you forget/forgo to apply 5V to the unit, you’ll get no output at all from Pin 7 (and Pin 6 only outputs 1PPS once lock is achieved). I spent several minutes the other day trying to figure out why my counter was just picking up noise until I noticed the 5V lead had come unplugged from my breadboard)) and fed that with my PSU supplying 15V 2A to the whole circuit ((Note, you may want to JUST power the 5V circuitry and limit your power supply to 80mA or so to make sure you’re not going to fry anything. A lot of people note that there’s no protection on the 5V rail, and have accidentally supplied 15V to it and blown everything out)).

On first power up (on the messy breadboard), the unit warmed up, and BRIEFLY locked (pin 3 went low), then quickly fell out of lock, and dashed my hopes it would work out of the box (on the plus side, I got to do a repair!). The repair, of sorts, generally involves adjusting a trim-cap in the unit to make sure the PLL sweeps through 10Mhz. You can check if this is the issue by looking at the output (Pin 7) on a counter, and seeing if it goes above/below 10Mhz on its sweep. In my case, it did not, and went from about 9.99970Mhz to 9.99998Mhz, then back down (about a 280Khz sweep). The fix is to remove the top cover (more on that in a sec), move some foam aside, and adjust C217 ((If you’re interested, this fix appears to be necessary after time since the oscillator (VCXO) in the unit (not the Physics package) drifts due to long term heat exposure, and adjusting this cap corrects that drift)).

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