Old NRI Tube Scope

[xratedpez]

Hello folks! I'm an active member on AK, and came into this old beauty as part of a trade. The folks there suggested I come over here to see what you think.

Here's the thread (with pictures).

It's an NRI Professional television oscilloscope, model 55

I'm in need for a good scope for my audio work, but some seem to think this won't cut the mustard and isn't worth restoring.

Any thoughts? Thanks in advance!

[Sandy G]

Well, yeah, they're right...And wrong. If you want a super-reliable, top-notch scope for measuring the last hair on Gnat's @zz, this prolly AIN'T it. But if you want a scope that you can pull out on a rainy day, & futz around w/yr old stuff, maybe "Wow!" the neighborhood kids & yr grankids, this may be what you're looking for. Honestly, I think this would be a very nice old scope to restore & show off every now & then, but for SERIOUS work ? Kinda doubt it. But I most certainly wouldn't condemn it to having its tubes robbed & then junked just 'cause its old...

[xratedpez]

Thanks, Sandy. It probably doesn't need to be super-reliable, but I would just like to use it occasionally to trace distortion, clipping, etc.

Assuming all the tubes work, maybe replacing the caps would be a decent idea? Although hi-voltage caps like that aren't the cheapest... and if a new(ish) scope can be had for $60, maybe that's a better option.

[Sandy G]

Yeah. Cap replacement is pretty much a given in something that age-60 years, +/-.

[snelson903]

oh yeah thats worth restoring i like the looks of those older scopes i think im up to 7 of the vintage tube type, my favorite is my dc wide band eico last yr i took the time to update everything in it new caps made sure everything was within or better than factory recomended tolerances calibrated everthing , its probley better now than when the first onwer built it new. you can make some cool add on's to the old scopes too.

[xratedpez]

Cool- that's encouraging. How would I know the calibration points, procedures, etc. without any type of documentation, though? I literally can't find anything on this unit.

[xratedpez]

Should I bring this up on the variac to see how she handles current? I don't have any probes, but I can probably scare some up.

[xratedpez]

Don't even know if they should be x10 probes...

[snelson903]

i would just recap it the paper one's if the can's look like they been leaking ,if it was me i would replace the lydics. cans, i never trust multiside caps, check over everthing for condition like trans see if anything been hot check all tubes, i try to even check as many resister's as i can without unsoldering then power it up then see if needs anything else. im sure you need to clean and inspec all contact switches / clean pots to .

[Phil Nelson]

Don't plug it in and don't try to bring it up on a variac. The electrolytic capacitors are just about guaranteed to be leaky, if not completely shot. Same deal with the tubular paper capacitors. Why bother powering it up to find that it works poorly, if at all, when you already know that the old caps are junk.

I can testify from experience that it's possible to fry a power transformer while bringing up an old tube device on an unmetered variac

Ask yourself the question, what do I want? If a workaday tool, then get an inexpensive used solid state scope. I got a sorta-newish BK Precision scope for $15 at a garage sale, never needed a bit of work and I have used it happily for about years.

I also own a vintage RCA scope, roughly the same age as your NRI. I have gotten it to work, but it's just a display toy, something I haul out once every year or two to show to somebody for a few minutes.

Just my $0.02.

Phil Nelson

[Sandy G]

Yeah, old scopes are Tres Kewl...And NEVER forget the mantra-"There is NOTHING wrong with Your Television Set..."

[jbivy]

Well i openly admit i know nothing about these, but DANG!, that is one good looking old o-scope. Anything with that much style deserves to have some work put into it.