Today's hamfest wasn't as interesting as before; the only "interesting" items were some tasty switches - that I don't need.
Now, what should I do with them?
QUITE tasty.
Capacitor substitution boxes. One for electrolytics, one for ceramic disc and one for MLCCs. Make 'em all in shielded enclosure/enclosures.
Interesting, there's plenty of happy users on YouTube and other forums, even ours and I don't think if I went for one that I'm ever likely to be firing up any TX close by let alone a 50 Watt one.
Its just that I could actually get a new one for not too much to replace the Hitachi (freeing up some space) and I'd get the benefit of a warranty in the UK and Amazon have them on prime.
It's worth saving up a little more and getting a DS1054Z if you're going to do that IMHO.
Also don't forget that Amazon's Prime warranty is virtually non existent if it is just "fulfilled by amazon"
I saw someone exiting with what might have been a Philips EE "toy" set from the 1960s. I still have the manual, some of the springs, and a few transistors (AF116 etc).
The contact resistance is <1mOhm, which is right on the limit of any of my instruments and measurement technique.
Those EE sets were pretty good. AF116 is probably dead now. Damn tin whiskers ate a lot of them.
That is exactly what I learned when I went reasearching cheap DSOs a couple years ago; that while these were all cheap-ass 'scopes, there were distinct levels of "cheap-ass" and the DS1054Z was about as low as you could go and still be a usable tool for anything more than AF. At that level, it is considerably more bang for the buck than the Hantek offerings; hands-down.![](http://forums.parallax.com/discussion/download/78567/160_Electronics_Kit.jpg)
I grew up with the 160-in-1; I was 12-ish or so and my mother and I saved up together for it (this was my childhood in McKeesport; we were very poor, and it was for reals a big "discretionary expenditure"); I remember building the "crystal" radio (okay, ge AM detector and crystal earphone) and all I could receive was evangelist radio and Howard Stern between ball games. Even at that tender age, I knew he was a putz.
But I learned a lot from that box; like how easy it was to kill LEDs and transistors, and that resistors are our friends.
![Face Palm :palm:](https://www.eevblog.com/forum/Smileys/default/facepalm.gif)
I later found a 75-in-1 (not a lot of difference between the two, really) at a neighbor's yard sale; spent two whole week's allowance on it and happily ignored the Px with its penny candy aisle for most of the next month replacing the missing bits. I later hacked the crystal earphones from both kits into a stereo set with RCA plugs so I could listen to mom's old 8-track deck in bed...
![](https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=486296;image)
Interesting that our conversation should go here at just this time; as I just uncovered a very special box from a protected spot under my motorcycle... *Cue flashiebackie sound effect*
Fast forward 30 years to when my wife was pregnant with our son; I stumbled across 2 of the later "Electronics Learning Lab" kits at a church sale. These were the last kit Forrest Mims had a hand in; and it was obvious that he had a bug up his arse to do something of value with that legacy. It's a much more capable kit in every way; with a proper (if small) breadboard and actual digital logic study work as well. They have been carefully stored away in a box through 3 moves, and I've "augmented" them with several randomly acquired "grab bags" and "learning kits" from Jameco and Acme. I'm hoping to add my collection of Mims' Engineer Notebooks and several random "Build-It" kits I know are in "the Mountains of JENGA" somewhere...
He is ALMOST old enough... ALMOST. *wibble*
Comparative analysis is a valid troubleshooting technique; one I've been guilty of more than a few times. As long as substitution doesn't become your only repair method, there's no shame in using it as a diagnostic tool.
Just because I'm capable of component-level repair doesn't make me feel obligated to do it that way every time; my time IS worth something, after all. If I can buy a working XYZ board on fleabay for $20, how much diag time can I afford to spend on the original? Sure... figuring out the fault to repair and stow the original board for a spare is a good idea... if you have discretionary time; but I have a bin full of such boards from the Plasma Screen years that are little more than donors for heat sink material and Tesla coil projects now.
I'd definitely replace all 4 at once to be sure your rectifier array all have similar forward voltage drop. Or better yet, replace all 4 with a modern high-current rectifier in a TO-3PJ package.
But first, look for the flaky cap that probably caused the failure.
Here's a thread on this power supply; it links to a hand-drawn schematic which I've attached below.
Hope that helps.
mnem
*tzzzt*
the diodes all checked out ok.
started pulling the caps and the 4 out front looked ok and measured ok.
pulled the 4 in the back and oooooops! now that there is the problem.
the black goo eating away at the traces cleaned up with isopropyl and the short went away.
surprised me that the leakers still tested ok with a one button chinese component tester. guess they did not need as much electrolyte as was originally in 'em?
new caps are on order.
thanks nmem!
without your push i'da been tempted to say "well if the easy ones to get out are ok, the harder ones to reach must be ok too."
Glad I could help! Good that it wasn't the diode array at all; means your repair should be relatively painless. Just gonna say... since you have the PSU out replace 'em all, not just the ones that test bad. The ones that test good will follow suit sooner rather than later.
![ThumbsUp :-+](https://www.eevblog.com/forum/Smileys/default/icon_smile_thumbsup.gif)
Years of lurking on the BadCaps forums taught me one thing:
Electrolytic caps are the devil's footsoldiers, and they WILL hide their fallen from you. 10 caps in a row will test good; the last possible one, no 11, will be the one that brought it all crashing down in a hail of sparks and smoke. It's like they're the electronic manifestation of Murphy's Law.
![Shocked :o](https://www.eevblog.com/forum/Smileys/default/shocked.gif)
Trust NO CAPACITOR. EVER.
![Laughing :-DD](https://www.eevblog.com/forum/Smileys/default/smiley_laughing.gif)
mnem
"Murphy's a bitch; and she has puppies." - grand-dad