Powering up a Tektronics 2440 scope after 8 years

The dim bulb tester is a better option. You just put a 1000 watt incandesce nt in series with the power line. It limits current so if something is shor ted it will not cause further damage. In fact on a scope you might want to use a 60 instead. The 100 watt is more suited for like audio amps in the 20

Tektronix scopes are not known for having deadly shorts. Their power supply design is like "interdependent" sometimes only using one Zener for one sou rce, like the -50 volts that has a very light load and using that as a refe rence for all the other sources. Also, since in a scope the current drain o n each source can be calculated quite accurately, it is designed only to pu t out the current necessary, making smoke alot less likely.

Problem with variacs is they do not limit current. At what voltage do you e xpect to see a trace ? Nobody knows really. With the DBT it should reach fu ll voltage fairly quickly.

Though unlikely with a Tek, it may be possible with a variac to cause a con dition where the CRT bias is not right and cause a screen burn. If there ar e no shorts, the DBT should allow it to get full voltage and you won't have that problem.

All it takes is a standard light fixture, incandescent lamp, standard outle t and an AC power cord. Or, you could just pull the main fuse and clip lead the DBT there. On many units you can just leave the power switch off and j ump it with that but don't, don't because there are so many weird designs o ut there and Teks are full of them. They had some REAL engineers. So just u se the plug and cord method.

Only eight years ? I give it a 90 % chance of just firing up and working fi ne. Might need some filters but they probably won't be shorted, and that is really the only issue. Other things don't just short out from sitting unus ed. But there could be some that need to be replaced. We had to replace lik e ten of them in one to get the hash out of the trace, but none of them wer e shorted. What was that ? I think a 2225. A good scope but not one of my f avorites. I prefer a 465.

I am downloading the manual now from bama.

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OK, I see it is a digital scope. In that case I would say not to use a vari ac on it. It might damage the data/program. I got that problem in an HP spe ctrum analyzer and you just can't get a flash for it, and your scope being from 1988 if you ask Tek for anything about it the will tell you to pound s alt.

If the bulb does not dim in a few seconds, turn it off, take the cover off and then locate the power supply, plug it in directly and look for signs of heat. I mean take your finger and see what is getting hot. Don't let the t hing dangle at half voltage or whatever. The most valuable thing in there i s the data, as they cannot be replaced. Maybe in 1989, but not today.

Good luck.

Oops, of course I mean 100 watts.

The debounce on this laptop is terrible. And I can't see worth a shit, and it was scrolled off by the time I hit the button.

When in doubt, recap.

My 475A was frying its mains transformer from leaking supply caps. The (old) mains fuse thought all was OK, so I tossed it on the go.

Cheers!

well, I have another experience with it: I was troubleshooting around an old computer when the 475 suddendly flashed and shut down (only the indicator lights remained on, all else, including fan was off). I didn't shut the power down very quickly, I rocked some knobs then I finally powered it down. I had a look at the schematic and I saw that the fan was on the +15V line. I opened the case, and sure enough there was a dead short on +15V line, tracked quickly down to a drop orange tantalum capacitor, 0.14 ohms across it. I thought this kind of fault would fry all the power regulation, when it happened on a HP-5328A, I had to change also the +15V pass transistor for example (and the fuse that should have protected it). After replacing the tantalum capacitor, the scope revived as nothing ever happened. So the power regulation circuit looks really well protected. It coped with a dead and prolonged short without damaging itself. Just for the record.

Frank IZ8DWF