After making the rounds of my 'hood during my usual Sunday afternoon "Asset Recovery Sweep", I do a triage of the haul, lest my garage be overrun with stuff. The following tutorial is how I decide what electronics I keep and what goes into the strippit pile. The two subjects were obsolete video tape recorder/ players, whom I suspect suffered the usual end of life fate for this class of machine; malfunctioning tape transport and drives. In such cases, it is more than likely the electronic part of the item is still quite serviceable, it not being a mechanical apparatus. In particular the desirable transformer isolated power supplies seemed functional, and so I decided to retrieve them.
Step 1: First Operation
After making a determination of the circuitry site, dissection was performed. The motherboards are now put in the strippit bin and the supply sections are given closer inspection. I also note the board is single- sided phenolic, but then again this is a consumer grade item in what was once a very competitive sales arena, so I'm not put off by this as G10 epoxy board would have been overkill. Other observations will tell a fuller story.
Step 2: What Do We Have Here?
I see two sets of full- wave rectifiers, that's a good start, it indicates a bi- voltage supply. To the right is a high quality finned aluminum extrusion used for the heat sink, again another very favorable clue; lesser quality products will use a simple slab of aluminum or worse yet, sheet steel for this duty. The input of the transformer is fused at 3 amps, figuring a rule of thumb that a 100% safety margin is used, therefore at 120 volts A.C. and 1.5 amps. design maximum, it could likely supply up to 180 watts output, but that will need verification on the test bench.
Step 3: Semiconductors Tell the Story
The venerable 7805 regulator (5 volts) is on hand, and a 2SD1832 NPN switcher is there as well. I also see several TO92 transistors, Zeners, and clamping diodes too, so this is indicative of a dependable, full- feature supply.
Step 4: What Else We Got?
The main filter caps, 3300 microfarads, 25 volt, indicates a 12 volt supply with ample filtering, in addition to the 5.0 volt logic supply. This is further confirmed by the presence of a 13 volt relay coil. No burnt resistors, or puffy caps either, this treasure looks like a keeper to me.
Step 5: The Summary
That tells me all I need to know at this point. I'll remove extraneous stuff later, like the RCA jacks, Video input/ output connectors, etc. if and when I put it back in service, but for right now I can tag and shelve it for future projects.
Step 6: A Closing Bonus
Just wanted to show another use for that illuminating Instructable project "Portable Spotlight", being used to light up the subjects of this here Instructable.
Step 7: Parting Thoughts
The above was only an investment of less than 1/2 hour and renders an asset as compact as it needs to be, saving me shelf space yet being capable of a return to useful life in a minimum amount of time.
Now lemme see, I been itchin' to make me a make a video tape recorder/ player...