Crowbars

If you do something stupid with an electronic power supply, sometimes they are equipped to sense it and throw a crowbar across the output to protect the insides. Picture a Jacob's Ladder running, an evil scientist cackling maniacally, and a hero sneaking through the shadows carrying a crowbar--he then poises to cast his payload into the crackling storm of electricity--

If you're reading my blog, you probably know by now that something rather technical shows up once in a while. This is one of those posts.

I'm checking out a Con Avionics HS26-13.5 analog power supply. It weighs a good 30 lbs. and is rated at 24-28 VDC at 13.5 A. This particular unit has been dropped on its head. The front right top corner has been displaced a good inch into the volume of the machine.

I could tell the case would short a couple of contacts inside if it were powered up, so I resolved to get the cover off. Well, first thing to do is take an odd silver (matte aluminum) box off the back. It's a -Con Avionics OVH26-13.5. Google says "con avionics ovh26-13.5" doesn't exist. At the moment I think it's merely a sophisticated external overvoltage crowbar circuit.

It's connected across the output. It has large bolt-mounted diodes or SCRs of some kind and an MCR648-2 mounted on the outside on a moderate heat sink. The supply is "HS26-13.5" while the attachment is "OVH26-13.5," so it seems to me we have Over Voltage Handler or somesuch with a common voltage-current pair with the supply proper.

Eratron PPC 8200 and family

Howdy!

You're no doubt tearing your hair out looking for some tidbit of technical data on a piece of Eratron equipment. Me too. I've found a few things that might help you:

Eratron is another name for ERA, or Energy Research Associates that was based in or near San Francisco some time ago. (Source) The patent application mentioned below indicates it was Campbell, California.

They patented their electron beam power supply design. It's rather brilliant compared to the more conventional design the Mideast Industries PR-40 uses, but its brilliance shows up mostly in electron beam applications where output arcing is not uncommon.

The patent number is 4,314,324. If you use the USPTO site, you'll want to go to http://www.uspto.gov/. In the left column under Patents click Search. Scroll down to the heading "USPTO Patent Full-Text and Image Database (PatFT)" and click on either Patent Number Search (if you want just the text) or View Patent Full-Page Images (if you want the partial schematics). Enter the patent number on either page and it'll zap you right to the patent.

Now if you're like me, the computer will be grumpy and not show the TIFF image the image viewer embeds. If this is the case, right click on the side of the page, select View Source, scroll down in the new window to the bottom and start looking for:

<embed src="/.DImg?Docid=04314324&PageNum=1&IDKey=219CCF24E627
&ImgFormat=tif" width="570" height="840" type=image/tiff></embed>

Now for a bit of surgery. Take the URL you've found for the image viewer. For me it was:
http://patimg1.uspto.gov/.piw?Docid=4314324&idkey=NONE

Snip up and paste together a Frankenstein URL using the first half of the image viewer URL and the embed tag's data:
http://patimg1.uspto.gov/.DImg?Docid=04314324&PageNum=1&IDKey=219CCF24E627
&ImgFormat=tif

Paste that into your address bar and the image should come up after thinking a bit. Now, see that PageNum=1 bit stuck in the middle? You can use your original page viewer to see how many pages there were and what sections they were divided into to navigate simply by changing that one number.

Cool, eh? :) I thought so anyway. It's a simple hack. If you want to actually read the images or keep them, you can use a tool like wget with the Frankenstein URL to pull the TIFFs straight off the server.

Have a nice day!

...and remember, 3-phase can kill you. :)