Test eqpt & tantalums

I like good test equipment and when I started in the 1950s good was homebrew, war surplus and the local radio TV shop. Then in the RCAF it was a Tek 545 and later at university it was a Tek 545B. (I worked my way thru college as a TV repairman working 20 to 30 hrs per week!) After university and when I had spare cash I graduated from homebrew and surplus to kits. Then my first good bad scope was an HP 120. Nothing but problems with the HV supply. Now unwllingly retired at 63 one of my passions is to build a up a small lab for personal enjoyment by finding at good prices test equipment made by the best mfgs such as Tektronix , GR, HP, Fluke, Boonton, and others, but the others usually don't hold a candle to the top 4. Others include Wavetek, Racal, Philips, Systron Donner, etc. There's a third class that includes Heathkit, Eico, RCA, Sencore, Hickok, B&K and others who furnish radio and TV test bench eqpt and I have some that is very, very good. A fourth class is foreign like Marconi, Meguro, Siemens, Rohde & Schwarz, all excellent but that I generally shy away from them because information and parts are in the unobtanium category. Generally finding a very good deal at a swapmeet means there's something wrong with it, either unknown or undisclosed by the previous owner. Finding docs for the best is hard enough but an order of magnitude harder for the others and that goes another order of mag for parts. Sometimes one needs 2 or 3 junkers to succeed or give up. I don't like to leave a swapmeet without some good deal that I can take home and plug into the Variac to see what it does. Generally I'll look inside to see if it's complete with no obvious missing parts and no char babies. Then I turn the Variac up and watch the current and look and smell to see if all the smoke the the factory sealed-in is still there. If it is but it doesn't work I check power supply voltages. It never ceases to amaze me that very few of the mfgs have figured out how to build a reliable power supply. In my work, Telecom, most critical hicap stuff had dual supplies so it could still operate if one supply failed and to top that off they migrated to hot swapable supplies! (If you don't have good tires, carry 2 spares!) My own theory on power supply unreliability is that the companies assign newly graduated engineers to design power supplies and those guys don't have enough experience to understand the ravages of long term heat, continual cycling and the crazy stuff that can come down the AC power line! One exception today may be PC power supplies as I don't see boatloads at the meets like I used to but maybe it's because I'm not looking! First, I check the supply voltages and if they're down I check the rectifiers and capacitors. Many times I'm lucky and find the problem right away but other times if its a short it's an arduos process on a pcb. After much wasted time the bad cap is found, an Al electrolytic if there are no or few tantalums but if there's lot of tants there's a very good chance it's one of the tantalums with a dead short and not exploded. Partial shorts for high I^2*R are best because they smoke or end up as char babies! It would be nice to find a set of bath tub curves on some of the old tantalums. I don't have a clue as to how many mfgs there were and how many times they improved their designs as they experienced failures. I guess what we need to know is which one fail the most. I salvage many parts and haven't had any real bad experience re-using previously well-used tantanlums. Is an good old time tested tantalum better than a new one? If the fault isn't in the power supply or on a supply rail it soon becomes a waste of time without a schematic. To end this mild diatribe, obsolescence of test eqpt is a matter of economics for business and sadly me! I still like my Boonton 260 Q meter but I'd rather have an HP 4342A and I'd rather have an HP 8921A to replace my HP

141T, a newer Tektronix TDS to replace my Tek 465. Space, time, dollars, and performance all suffer in my lab but it's there for my enjoyment and entertainment, and most likely to be upgraded with smaller, higher performing, newer, less obsolete gadgets. I perceive that eqpt with surface mount, PICs and ASICs is generally impossible to repaiur at the componenet level and board swap is an alternative if you can find spares but then there are so many suffix updates! 73 hank wd5jfr
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Henry Kolesnik
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Henry Kolesnik: Yes, agreed. Good luck with your search, acquisition and repair mission.

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Best Regards,
Daniel Sofie
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Sofie

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