Michael, In some Tek power supplies, I have observed that a degrading opto-coupler demands more and more current from a TL431A, eventually causing the TL431A to fail. --John Gord

Fantastic! As a fellow TDS 460A owner, I am quite impressed and pleased you got it going again. Once again the list collects an important repair story for posterity... --Toby >

After 6 months of on and off searching, I may have found the issue with my SMPS for my TDS460A. No schematics are available, so it comes down to trying to understand what goes on in one of these

It might be bought for a reasonable price except for shipping. Bob

Edward, I am going to ask what may seem a stupid question. Have you cleaned the "Beam Finder" switch? I have a 465 that was doing something similar. It had a dirty beam finder switch. The switch

Roger that, Roger!  At least somebody is on the ball these days.Thanks for the correction. JimSent from my Verizon, Samsung Galaxy smartphone

My new to me 466 2nd version has a strange issue. I see a background image related to the display. Hard to describe so there is a picture in photos under Edward Prest. It may be a blanking issue or a

True, but the period of the 50kHz oscillation is 20 microseconds not 20 milliseconds so the recovery time is indeed 200 x Trr. Roger

Indeed, but the period of a 50kHz is oscillation is 20us not 20ms so Ernesto's times 200 was actually correct. Roger

I see they also have a Tek 7854 in the previous picture, lot 19 in the catalog here: https://bid.tmcauction.com/auctions/catalog/id/23165/ I wish I was a bit closer to Sacramento. - Bob Headrick

Wonderful! I just wanted to be sure that you and others were aware of the issue. Also, many of these HV diodes are designed to be used in old color TV's, and CRT type monitors, so they need to be

Thank you Jim! I need to be more careful with my postings and avoid dumb mistakes! I try not to think that it is the years... The period of a 50 kHz wave is 20 uS, not 20mS. So this period is

Hi, Ernesto. Actually, 20 ms is 200,000 times longer than 100 ns. Just sayin'. Jim Ford

Hi Chuck, You are very right about the importance of the diode recovery time. The specification on Amazon for this cheapy diode is Trr = 100 nS maximum. Other "fast" HV diodes specify 60 or 70 nS,

BTW, I downloaded KiCAD 5.1.5-3 and was able to completely browse the design files from the EEVBlog converter. Very nice for the price (free). --Victor

I like the Glitchworks option better. I seems to fit in the same footprint as the original DS1742W. The board in the EEVBLOG link above is much bigger and requires an area next to the DS1742W to be

Indeed, which is why I said a 9V battery, or two... The diodes in these supplies are a little special in that they need to be fast recovery diodes. They are working at about 50KHz. A common

Hi Victor, I would be interested in a few bare boards. Tom Bryan N3AJA

Hi Chuck, Some HV diodes may need more than 9V to turn on. The ones I used in my HV supply need about 17V for a 2mA forwards current. they are some Chinese 20KV diodes used in microwaves (an