Beauty of old electrical and measuring things, etc.

[sysprog]

About 25 years ago I gave an old RCA meter to a friend who likes to do electronics work $-$ he just sent me a link to a video regarding his rebalancing of the meter:

 

[Tom.G]

I have that same RCA VTVM. A minor quirk is that the "D" size flashlight battery used for Ohms measurement MUST be a Carbon-Zinc cell. The slightly lower open circuit voltage of an Alkaline cell is just low enough that the you can not Zero the Ohms scale.

As mentioned in the video at 19:30, electrical calibration and zeroing should always be done with the meter laying on its back. (I wondered when he was going to get to that.) That way the balancing has no effect on the reading.

Then the balancing is done with no power applied and checking that the needle does not move off of zero regardless of meter orientation.

With the meter on its back, adjust the mechanical zero for a Zero reading.
Then position the meter with the face vertical.
Start with the main counterbalance weight that is in-line with the needle. Adjust (move) the main counterbalance weight to get a Zero reading.

If there are existing compensating weights (mounted at right angles to the needle), they are usually 'close enough.' Check them by rotating the meter in the same plane with the face vertical (that is: rotate the meter in the plane that the needle moves; about 6:30 in the video).

If the compensating weights do need adjusting, be aware that they interact with each other and with the main counterbalance weight. Ideally the two compensating weights should be the same weight in the same position on their arms.

If the Zero shifts by different amounts depending on which side edge the meter is on (the direction may be the same or different), adjust each of the two compensating weights by HALF the amount needed to cancel the movement.

When done, re-check that the meter is still Zeroed when on its back.

And if you want to be really paranoid, check the electrical calibration with the meter lying down on its back and with the face vertical. If the linearity changes, probably the two compensating weights are slightly mis-adjusted or the meter needle or one of the weight arms is bent.

Have Fun!

p.s. the above was learned the hard way after fighting about four attempts on various meter movements!

p.p.s. be sure there are no metal filings or drill chips in the area. They are almost impossible to remove from the meter innards without damage.

 

[Oldman too]

Here are the arrow heads after they were attached with silicone sealant:
View attachment 290343

Do I see several Clovis points in there?
Edit note: I seem to have jumped to this thread replying to another thread,
https://www.physicsforums.com/threa...please-any-info-welcome.1012894/#post-6606447

Hmm. this does look like an interesting thread though.

 

[dlgoff]

Here's an old TV that I had put away:

edit: It's diagonal screen width is 12 inches.

 

[jedishrfu]

Not old enough, it must be a B&W to qualify for retirement.

 

[dlgoff]

Not old enough, it must be a B&W to qualify for retirement.

I think you're right. When I turn it on, I get a noisy B&W raster. I haven't tried it with my regular TV's outside antenna yet. I'll do that when I get a chance. Too many other things going on right now.

 

[collinsmark]

I think you're right. When I turn it on, I get a noisy B&W raster. I haven't tried it with my regular TV's outside antenna yet. I'll do that when I get a chance. Too many other things going on right now.

I'm guessing it won't do much good, if connected directly to the antenna. I don't think TV stations still broadcast in analog anymore, in the middle of the US.
https://www.fcc.gov/consumers/guides/dtv-and-over-air-viewers-along-us-borders

You could still test it in conjunction with VCR, DVD player, DTV converter, or cable box that has the appropriate connectors though. Just don't expect it to receive a signal directly through the air anymore. Not without some sort of digital TV converter box.

 

[dlgoff]

I'm guessing it won't do much good, if connected directly to the antenna. I don't think TV stations still broadcast in analog anymore, in the middle of the US.
https://www.fcc.gov/consumers/guides/dtv-and-over-air-viewers-along-us-borders

You could still test it in conjunction with VCR, DVD player, DTV converter, or cable box that has the appropriate connectors though. Just don't expect it to receive a signal directly through the air anymore. Not without some sort of digital TV converter box.

I'll look into that. But it's probably more trouble than it's worth. I'll just keep the thing and not worry about it.

 

[jedishrfu]

You can always do a Second City comedy skit with it. I remember their opening credits where TVs were thrown out the windows of an apartment building.

 

[anorlunda]

Try it with a pair of panty hose stretched over the screen.

Spoiler

https://content.time.com/time/specials/packages/article/0,28804,1888721_1888719_1888699,00.html

 

[gmax137]

... it's probably more trouble than it's worth. I'll just keep the thing and not worry about it.

Maybe you can find a Betamax to pair with it.

 

[dlgoff]

Maybe you can find a Betamax to pair with it.

I have a friend that use to have one, but he's probably gotten rid of it by now.

 

[jedishrfu]

How about a sony camcorder? I remember they had cables to connect to old tvs. Alternatively, an old game console would be cool too like an Atari 2600 or vintage Nintendo.

 

[dlgoff]

How about a sony camcorder? I remember they had cables to connect to old tvs. Alternatively, an old game console would be cool too like an Atari 2600 or vintage Nintendo.

I don't have access to either. I'm just going to hang on to it and not try to make it work.

 

[dlgoff]

Okay. Enough of that old TV. Here are a couple photos of something that's electrical and measures:

 

[anorlunda]

Okay. Enough of that old TV. Here are a couple photos of something that's electrical and measures:

That could be a prop from any 50s SF movie. A Geiger counter. Every movie scanned the monsters using one of those.

 

[jedishrfu]

Nice, Gieger Counter. Have you noticed any temporary shrinking on anyone tested with it?

A lead-in to a funny story: While an undergrad student of physics, I and my classmates overheard our instructor answer a call from a frantic mother. She was concerned that her son was shrinking after exposure to a Gieger Counter as school. Our prof told her not to worry that it was a temporary effect that would go away in a week.

We couldn't contain our laughter upon hearing his response. After the call, he said she would never have responded well if he had said you're imagining it so instead he allayed her fears by telling her it was temporary. We learned a great lesson in compassion that day.

 

[dlgoff]

I may have posted this Ludlum counter before. It works better than the others as I have a Radium check test sample that I've used:

 

[Janus]

Okay. Enough of that old TV. Here are a couple photos of something that's electrical and measures:
View attachment 303908
View attachment 303907

I've actually used one of these, on myself.
20+ yrs ago, I was diagnosed with a renal carcinoma. They sent me to get a bone scan just to make sure it hadn't metastasized. This involves being injected with a radioisotope tracer, and then they scan you looking for "hot spots" that would indicate something unusual. (they only detected the aforementioned tumor.)
The technician who gave me the injection mentioned that I would be "radioactive" for a day or so.
My place of employment at the time was not too far from a nuclear power plant, and so we had a Gieger counter just like this in our emergency supplies. So, of course, the next day when I was back at work, I had to test it out. I switched it on, held it out, and got click...click...click. I brought it in and ran it over my body. When I got to the area of the effected kidney, I started getting click..click..click..click.

 

[gmax137]

Okay. Enough of that old TV. Here are a couple photos of something that's electrical and measures:
View attachment 303908
View attachment 303907

Do those still work? I'd like to get one, maybe an ebay search is in order...

 

[dlgoff]

Do those still work? I'd like to get one, maybe an ebay search is in order...

I just put a battery in one and checked it out on this old x-ray tube:

and it didn't work. But the Ludlum counter worked just fine.

 

[berkeman]

So, of course, the next day when I was back at work, I had to test it out. I switched it on, held it out, and got click...click...click. I brought it in and ran it over my body. When I got to the area of the effected kidney, I started getting click..click..click..click.

You missed a golden opportunity to play a play a practical joke on your fellow workers there...

 

[dlgoff]

Before Radio Shack went out of business in 2015, I bought this Digital Meter:

It still works well.

 

[Opera]

I have the first HP desk calculator with a CRT and delay line for memory. It has this interesting feature; the keyboard mechanically locks up while it is doing a calculation. Odd that this was easier done mechanically than with electronics. I'm away so will picture some stuff later.

 

[berkeman]

I have the first HP desk calculator with a CRT and delay line for memory. It has this interesting feature; the keyboard mechanically locks up while it is doing a calculation. Odd that this was easier done mechanically than with electronics. I'm away so will picture some stuff later.

Wowie, what is the HP model number?

 

[Opera]

I'm a thousand miles away for the summer. Several other items. Posted to bookmark the thread.

 

[jedishrfu]

Wow that's quite collectible. So you said it had a CRT and not nixie tube digits.

Is it an HP 9100?

https://history-computer.com/hewlett-packard-9100a-guide/

 

[dlgoff]

Wow that's quite collectible. So you said it had a CRT and not nixie tube digits.

Is it an HP 9100?

https://history-computer.com/hewlett-packard-9100a-guide/

I'm not sure what part of this thread you are referring to. Can you post the page you are asking about?
@berkeman
Since you liked the post, maybe you know?

 

[berkeman]

I'm not sure what part of this thread you are referring to. Can you post the page you are asking about?

I think they are referring to this post by new member @Opera:

I have the first HP desk calculator with a CRT and delay line for memory. It has this interesting feature; the keyboard mechanically locks up while it is doing a calculation. Odd that this was easier done mechanically than with electronics. I'm away so will picture some stuff later.

 

[dlgoff]

I think they are referring to this post by new member @Opera:

Oh. Now I understand. Forget the request in my previous post.

Thank you.