first think to do when plugging in a very old 'scope

[mikepukmel]

Had lunch with a good friend I used to work with. He was cleaning out his closets and asked if I wanted his old 'scope. He worked at a lab in the 1990's, a division went out and they had a yard sale, literally everything on tables outside. he picked up a solid old Tektronix scope for 10 bucks, brought it home plugged it in, verified it worked, put it in the closet and there it sat for 20 years.

I have to get the model number, but I think its late 70's early '80's. Gave me a bunch of extra modules and probe set as well.

So, ok its not a guitar amp, but a significant attachment! My question: the scope worked 20 years ago, sat inside a house, not basement or attic. Looks to be in very good condition.

What should I do to it before plugging it in? Do these scopes have electrolytic power supply caps? Is there something cheap I should replace before giving it a shot of 120v and seeing if it works or goes pouf?

[olddawg]

Had lunch with a good friend I used to work with. He was cleaning out his closets and asked if I wanted his old 'scope. He worked at a lab in the 1990's, a division went out and they had a yard sale, literally everything on tables outside. he picked up a solid old Tektronix scope for 10 bucks, brought it home plugged it in, verified it worked, put it in the closet and there it sat for 20 years.

I have to get the model number, but I think its late 70's early '80's. Gave me a bunch of extra modules and probe set as well.

So, ok its not a guitar amp, but a significant attachment! My question: the scope worked 20 years ago, sat inside a house, not basement or attic. Looks to be in very good condition.

What should I do to it before plugging it in? Do these scopes have electrolytic power supply caps? Is there something cheap I should replace before giving it a shot of 120v and seeing if it works or goes pouf?

I hope it isn't a giant Apollo era tube scope on a giant caddy.. Probably wouldn't hurt to run it up slowly on a variac over a couple of days. In my experience they are pretty resilient. If you don't have a variac just plug it in, see if you have a trace, and see if it will trigger. It's not like it's worth a lot or you paid a lot for it. If it doesn't work and has a handle you can always attach it to a boat. My 2 cents anyway.

[mikepukmel]

Thanks Dawg. its not giant, but pretty big. I will get some photos. I don't have a variac, looking to buy a used one. Heh, yeah, man it would make a NICE boat anchor. Or hood ornament. No, you couldn't see the road.

[pdf64]

No need for a variac, ever really.
A light bulb limiter is way better for most every use a variac might be used for in our sector.
Perhaps start off with a fairly low power bulb that gives a bit of glow even after the initial power up, in order to help the ecaps reform.
Leave it for a while and then try a beefier bulb.

[mikepukmel]

Well, its a Tektronix 7613. Manual says October 1974. So, its practically new. Can't possibly be any bad caps in this unit. And it barely weighs 50 pounds. I could lift it with both arms.

Im giving it aroma therapy. Thought Id start with vanilla, then move on to raspberry. I'll wait till after dark to plug it in the first time (in well over 20 years). Maybe play a little light rock music in the background. How about Steely Dan Rikki Don't Lose That Number, that's '74.

Should I get the fire extinguisher ready when I plug it in?

[olddawg]

No need for a variac, ever really.
A light bulb limiter is way better for most every use a variac might be used for in our sector.
Perhaps start off with a fairly low power bulb that gives a bit of glow even after the initial power up, in order to help the ecaps reform.
Leave it for a while and then try a beefier bulb.

In nearly 30 years on the bench servicing thousands of units I never used a lightbulb limiter even once. They are nearly useless for SS equipment. Some of the old flakey TV techs used them working on flyback circuits but that's about it. Kind of like using a rock for a hammer imho.

[J M Fahey]

I have used nothing but light bulb limiters for over 40 years, go figure.
Variacs add one extra layer to take care for, and if I´m not fast enough I can end in an explosion; while lightbulbs are both *automatic* , they will limit current on their own if and only if there´s an overload or short, and even if I am not paying attention and looking elsewhere, the visual indicator is there to show me, like it or not, that something is wrong.

And way more useful in SS atuff than tubed one, because SS has very low idle consumption so I can use a quite small bulb, which increases sensitivity, while on tube gear filaments alone mean an important "base" consumption under which I can never go.

But of course, to each his own

[Mick Bailey]

I use a bulb limiter and/or variac, depending on what I'm doing. Have to say the limiter has saved me more times than I care to remember. We're on 240v nominally, though last week my mains was 252v. Sometimes a piece of gear will be fine at (say) 220v and then suddenly the current draw will avalanche when nudged up a little further. Things happen quickly - sometimes too quickly to catch. A bulb will light up much quicker than my DMM/eye/brain/hand response in turning the dial back on a variac.

Back to the scope - yes, the caps can age and fail, just like any other piece of gear and some form of current limiting is advisable at first turn-on. At least give it some kind of soft-start and have some means of observing current draw. Usually those 70s scopes are fine. The biggest problem you're likely to come across is the caps in the DC restorer failing. Easily fixable, but the caps are hard to find (some scopes even come with a coil of silver-alloy solder stashed inside especially for this job). The most annoying will be phosphor-burn.

[olddawg]

I have used nothing but light bulb limiters for over 40 years, go figure.
Variacs add one extra layer to take care for, and if I´m not fast enough I can end in an explosion; while lightbulbs are both *automatic* , they will limit current on their own if and only if there´s an overload or short, and even if I am not paying attention and looking elsewhere, the visual indicator is there to show me, like it or not, that something is wrong.

And way more useful in SS atuff than tubed one, because SS has very low idle consumption so I can use a quite small bulb, which increases sensitivity, while on tube gear filaments alone mean an important "base" consumption under which I can never go.

But of course, to each his own

Juan... the variac I always used had a current meter and you would watch that as your voltage came up. If there was a draw issue you would know immediately. When you are working with multiple protection circuits
circuits and PMPS I just can't see the advantage of a light bulb limiter. I've seen managers of large shops throw them out and when we had manufacturers (especially Yamaha) inspections they would pull your authorization if they saw one. That said.. there's a time and a place for everything. And as you said to each his own.

[mikepukmel]

Thanks everyone. Well, I don't have a variac, as mentioned have been looking for a reasonably priced used one. I do have a 250 watt light bulb limiter setup, though, could use that for the first "fire up". The scope has been stored inside a house anyway not in an unheated garage or damp basement. Will try the bulb thing and see what happens.


IF its advisable to replace filter caps, I could manage that if I knew which ones to replace. I imagine its pretty complicated in there.

[mozz]

Sometimes there are webpages on certain model scopes with cap replacement. I have a 2465a analog which worked when i fired it up after sitting many years, but next time i tried to use it i had all sorts of problems, caps are bad and it's a project for later this summer after i clear the bench of guitars and amps.

On the variac, that's all i ever used, along with a wattmeter, never used a light bulb limiter, but i watched and learned as my dad fixed tv's 50 years ago.

[g1]

If using the bulb limiter, start with a low wattage bulb (40 or 60) and work your way up to the 250.

P.S. I like the 'euro-talk' in the thread title.

[bob p]

I hope it isn't a giant Apollo era tube scope on a giant caddy..

If it is one of those giant Apollo era tubes scopes, with 100 tubes inside, I WANT IT!

[Justin Thomas]

First Think?

"Please don't explode, please don't explode, please don't explode, PLEASE don't explode!"

Justin

[loudthud]

IIRC the 7613 has a linear power supply with the exception of the High Voltage. At Tektronix every bench had a Variac on it, go figure. An oscilloscope has pretty much a class A load, it's drawing current all the time so a light bulb limiter will give a flash to start but then will hog too much Voltage. Make sure the correct fuse is installed. Then crank the Variac up slowly watching the current draw. The filter caps Tek used will be next to impossible to find exact replacements. You'll end up removing the old ones and improvising replacements into the circuit board holes.