Quothe William Donzelli, from writings of Mon, Nov 25, 2002 at 05:48:56PM -0500: Is transformer failure a rare occurance in a Tek 'scope, and is it usually caused by some unusual catastrophic failure in the power supply? I've noticed the the fuse in my "new" 585 is blown, but haven't had a chance to check the 'scope out yet. BTW, does anyone know if the transformers in the 531 and 585 are interchangeable? Alas, Tektronix doesn't honor its lifetime guarantee on the power transformers. Sounds like fraud to me, but they probably have some high-priced lawyers protecting them from false advertising lawsuits. Blasted biz'droids... [mumble, grumble] -- Copyright (C) 2002 R. D. Davis The difference between humans & other animals: All Rights Reserved an unnatural belief that we're above Nature & rdd(a)rddavis.org 410-744-4900 her other creatures, using dogma to justify such http://www.rddavis.org beliefs and to justify much human cruelty.

A manual for your oscilloscope can be found at: www.w7fg.com for $25 bux. I also second Tony Duell that it is unlikely the power transformer would have failed, especially in such a small and lightly-loaded device. But locating and removing the B+ secondary leads from the rectifier components (probably selenum in that vintage of a scope) will begin to isolate the problem. Also be very aware that shorted and/or arcing selenium rectifiers produce copious amounts of deadly (and stinky) hydrogen sulfide gas. (The same gas that makes rotten eggs so odiferous) Be thankful that it's a catasrophic, fuse-blowing-instantly type of fault - which will have a definite unmistakable cause and a hopefully easy remedy. But isolate the HV leads first, then the filament leads if the fuse still blows. Also verify that the proper value fuse is installed. I chased my tail all over the workbench trying to find the 'problem' in a Hewlett Packard VHF signal generator, only to realize that the fuse holder was clearly marked "4A" and someone had put a 1-1/2A fuse in it, which, of course, blew as soon as the voltage hit the tubes - and which I dutifully kept replacing with one of the same value as the blown one as I methodically and carefully 'troubleshot' the damn thing. D'OH!!!! Cheers John

This is marked "1.6A MDL" and I have no clue what MDL is. If it's marginal are you reccomending 2A? I perhaps could go even higher and use a circuitbreaker as backup. No Variac here, now I know why I want to buy one next time I see it. John A.

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John Allain wrote: MDL is a slow-blo fuse, designed to take the "shock" of the inrush current without blowing.

Not too rare. It happens enough that there is a small market for Tek replacement transformers. I can't really say if they fail because of the "usually" part, but I suspect that most Tek transformers can't tolerate catastrophic failures. William Donzelli aw288(a)osfn.org

I'd check the diodes for shorts too. What might work here is a variac with a 100W lightbulb in series. Ease up on the voltage, and the lightbulb will limit the current to a safe value and give you a visual warning. If all else fails, you might have a heater-cathode short across one of the tubes putting a load on the B+. They loved to have all sorts of positive and negative voltages to make those tubes work as DC amps. A book here would be invaluable, and some serious head-scratching time. Gary Hildebrand St. Joseph, MO John Allain wrote: