Test Equipment: Oscillocopes

[Brian516]

You'll find plenty of tutorials for adapting certain surplus LCDs to the Arduino. The disadvantage is that they will need six or seven data lines to work, taking up output pins on the 'duino. That's why I like the Parallax brand serial LCDs, they only need one data line, and the two power leads, to give full functionality including the built in piezo speaker and backlight control.
I'm glad you find the Inductometer interesting! You can also make a capacitance meter with essentially the same circuit simply by using a known inductance instead of the known capacitance standard, and changing the sketch math a little bit. You don't actually need the LCD display; if you keep the Arduino plugged into your computer with the USB cable you can use the serial monitor in the Arduino IDE and put Serial.print statements in your sketch to give you the readout on your computer in real-time.

Good to know, I will aim to just buy a Parallax LCD, and in the meantime just use the serial monitor.  And if for some reason I run across a situation where I need it away from my PC, then I will spend the time turning one of my lcd's into a screen.

You can always use a direct connection with a patch cord from your signal generator to the scope channel. This will be equivalent to using a 1x probe. Strictly speaking I suppose you should use a 50 ohm impedance BNC patchcord with a T-fitting and a 50 ohm terminator at the scope input, but just a straight patchcord will work fine for low frequencies and casual testing.  That's good, maybe it's just a trigger problem or even just dirty switch contacts. The fact that you get a trace at all on CH2 is really good news! 

I don't have any of that stuff on hand, so if I need to hook anything up to the scope before I have a working probe I would have to just do the straight patch cord method you mentioned.  I'd rather just wait for a probe, though.   As for the BNC cord, T-fitting, and terminator.... I won't need any of that stuff when I have probes, will I? or would it come in handy to have it anyway?  It seems that it's extremely inexpensive stuff to get, like $10 with shipping and I'll have 2 of each.  For now I'm just going to put my money towards probes, though. Maybe I'll run across some of that stuff in the piles of stuff in my basement... or get it from the Comcast guy if I see him around.

I love that old General Radio gear! There is nothing like it, their designers were truly geniuses in those days. I found a manual for your oscillator, attached below. It looks like it has those weird type 847 "bisexual" connectors,  you might like to look around for BNC adapters for those things. The tubes aren't too weird, you can probably find replacements on the market, although I haven't looked. Svetlana is a possible source for new tubes if you need them. 

Thanks for the manual!  I'll have to read it and learn what I can use it for before I mess with it.  The guy I got it off of told me that it used to be used to push a signal thru the radio comm gear as a way to diagnose problems with it. All the tubes are good, and we took the case off... the thing is SPARKLINGLY, squeaky clean inside!! MINT condition!   I'll definitely see what I can find as for adapters for the 847 connectors. The pics I've seen of these things for sale just showed gator clips as output connections.  It's too bad it didn't come with the cables!! I've never seen one thus far that had them, though.

The missing GND REF button should not be a problem as long as it isn't stuck in "grounded" mode!

It doesn't appear to be. I'm going to attach a pic below of a close up of the switch contacts with a couple questions.

I don't know if you have the spring clip tip adapter... this is almost a necessity so that you can clip the probe in place and then free up your hands. New probes will have clip adapters included with the kit.  Almost every modern probe you will find will have a 1x/10x switch so there is no need to buy separate probes for that. Pool your money and just buy 2 higher-quality probes for the price of 4 lower-quality ones.

No, the 6062A does not come with the spring loaded part, but it does have the hook adapter. Maybe I can rig something up with a small piece of plastic tube from the pieces of the Fluke probe and put a little spring on it for the time being, until I can find that part online somewhere. Hopefully I can find a spring loaded hook tip adapter for this probe for cheap...
That's good to know, I will make sure I find a pair that has the switch, and I'll get the best ones that I can afford.

Yes, use the 10x setting on the scope and mentally multiply your graticule readings by 10. So the "20 v/div" range becomes 200 v/div with the 100x probe.
So if you have a 400 v input limit (as my Tek2213a does) then you are totally good to go with your 5 kV 100x probe because you'll reach the probe's limit far before you reach the scope's limit. 5 kV signal will mean only 50 V at the scope input, and a scope setting of 50 v/div (10x) will give you 500 v/div with the 100x probe and you'll run out of screen height before you hit either the probe or the scope limits.

So then since my scope has an 8 x 10 grid, and at 10X setting it's max setting will be 50v/div (500v/div), I won't be able to read anything over 4kV with the zero-plane at the very bottom (or top) of the screen, correct?   So with zero in the middle, I'll see 2kv pos and neg.
Since a lot of these devices that we mess with and test deal with HV spikes, I feel I should get a HV probe. But if I find a pair of standard probes that are a high jump in quality that I can afford if I don't get the HV probe, I will just get it later.  Not to mention I should hold onto some funds in case I have to buy something to repair channel 2.   While I consider what I should buy, I'm going to continue trying to rebuild this 6062A probe (which appears to be a $100 probe, so worth the effort).  Also, I would like to replace the cable on the 6065A probe.  Any suggestions on what the specs should be for a replacement coax cable?

I attached the pic of the probe switch I mentioned before.  My questions:

The GRD REF button appears to break the connection from PT3 to PT2 and connect to PT 5 when pressed. is this correct?
Probe tip to PT 1 has a direct connection. very little resistance.
Probe tip to PT 3 has a connection reading 9.06MegOhm resistance.
From the leftover solder/residual flux, it appears there was a connection to PT 6 of the switch.
From the residual flux, it appears there may have also been a connection to PT 1 of the switch.
When I opened the cover of the connector that goes to the scope, it appears that, in addition to the ground (shielding, which appears to be soldered directly to the metal housing) there are two wires. ( I will have to dissect the probe end and find the second wire... probably just a matter of cutting back the insulation and ground shielding far enough)
Inside the housing, the main super-fine wire in the middle goes to what I'm assuming to be a capacitor, though it is in the shape of a resistor. My meter doesn't read any resistance, and the capacitance it shows is about 0.015nF.  So there's my 10X wire.
The other wire, which is outside the shielding for the middle (in the case)  goes to a tiny resistor which reads 11.56Kohm.
There is also a 95.3ohm 1% resistor with a tiny, tiny capacitor across it, which on one end connects to the post for the center output pin (also connected to the capacitor for the 10X wire) which connect on the opposite end to the adjuster pot(?) which has a connection to ground.

I now know what you mean by how much of a PITA it is to rebuild these probes.....  but I'm going to do it anyway.  I just need to know where to connect what....
I am also missing one screw in addition to the grd ref button. I'm sure I can find a replacement in my container filled with screws from things I took apart, and cut it down to the proper length.  If the button would be useful, I'll widdle a new one out of some scrap plastic....

TK - do you have a link to that info you were referencing about the probe?  A diagram of the connections would be extremely useful....! hahaha
Sorry for all the questions on this... I just want to make sure I do it right the first time around, so I don't have to take it all back apart and try again, and again.

Thanks!!
Brian

[TinselKoala]

@Brian:
The GND switch is supposed to break the scope's connection to the probe tip and connect it to the cable's ground conductor instead, but without connecting the probe tip to ground so you don't short out your circuit under test.  This is so that you can easily identify which trace is which on a multi-trace display, by temporarily grounding the probe while it is in position for a measurement. I can't tell you what connects to what on the switch from here, though. And I haven't been able to find a "free" copy of the probe's manual, although it's easy to find them for sale.
Some of these better probes don't use a regular coax cable. Instead they have a shielded cable that has a very thin nichrome wire as the center conductor and it is practically impossible to work with this wire, as it can't easily be soldered due to the alloy, and it is so thin it is hard to handle physically as well, for crimps and such. I don't know if your probe has this type of coax or not.

It's always a good idea to have a few BNC patch cables around, plus adapters (BNC to GR874, BNC to the CB-type connectors SO-239 or PL-259, BNC to RCA phono jack) and a 50 ohm BNC terminator and a T or two. You will eventually want to connect your GenRad oscillator to the scope, and doing it with a probe is clumsy. For example you may want to use the GenRad to trigger the scope thru the scope's Ext Trig input as well as feeding the same signal to a circuit, and use both probes on the circuit for traces at some point. So you'll need a patch cable, a T, the 874 adapter, and another cable with BNC on one end and clips on the other end for that hookup.

http://www.ebay.com/itm/BNC-to-mini-grabber-test-clips-Pomona-2-sets-80cm-lead-/290533726392

Hopefully you can find the GR874 adapter cheaper than this somewhere:
http://www.ebay.com/itm/like/351136777620?lpid=82&chn=ps
http://en.wikipedia.org/wiki/GR_connector

Yes, you've got the scope vertical scaling issue correct.

I'd suggest you to get two decent 1x/10x probes and one 100x probe, plus at least one 6 foot BNC 50-ohm patch cable, an adapter for the GR connector, a few BNC adapters and fittings, like one that you can use to connect a probe to the patch cable (this is double-female I think, I am always confused about BNC gender assignments), a T fitting, and a BNC 50 ohm terminator that will fit on the T fitting. These things are available in assorted gender combinations, so try to get some that are compatible so you can string them together as needed.

Here's a pic of most of my adapter stash (others are fairly permanently connected to my RM503 scope which has the SO-239 panel connectors) :

[Brian516]

yeah, I think you're right on that... It probably is nichrome wire. Especially since it's so fine. I looked up "nichrome soldering" and apparently it can be done fairly easily with acid flux and silver solder. there were a few other people who said HCl based flux or Zinc Chloride flux. 
Other than the probe issues, I really hope that all this scope needs is a good cleaning/deoxing.... I really don't want to get into replacing parts on it, but obviously will if I must.

Thanks for all the help TK, and I will definitely do my best to get all of the BNC adapters and the 874 adapters.  I'm going to check around with some places/people I know of that deal in antiques and antique electronics stuff around town before I order anything. Also going to check with the RF engineer that I met when I was out playing pool a few months back. Hopefully he can hook me up!  That is definitely quite a taxing for only one fitting..
Another thing about the connections, other than the two 874 outs (one for audio one for RF) there are also two banana plug females that double as the screw posts. I'm not sure if these are meant as some sort of ground or are an alternate out, so I'll have to look into that in the pdf you sent me. Rob, the guy I got it from, also sent me the same PDF plus a PDF of "the general radio experimenter" magazine/pamphlet from 1950!!

I really appreciate you taking the time to help me with all this. In the future if there's anything I can do to help you out, let me know.

Brian

[Brian516]

I'm an idiot.  I had the manual for the 6062A this whole time.  right inside the front cover of the service manual.  If only I would have bothered to open it........... A day worth of headache could have been entirely avoided.

[Brian516]

It appears that the "Modify" button has disappeared, so I can't just edit my last post.
Sorry for my own stupidity in not checking the materials that I already have to see if I had the info that I needed before going and asking a bunch of unnecessary questions and taking up people's valuable time to read/reply to them.
When I'm to a point where I know what I am doing, I will pay it forward and teach the next guy since you all are taking your time to teach me.  That's only fair.  Then when I am incorrect about something or leave out important info, you will only then have to take the time to add a little info.

Brian

[edit] - ahh I see now, apparently after a certain amount of time has passed, you are unable to edit your posts anymore... [end-edit]

-  I am looing at probes to order, and from what I gather, the lower the model number, the higher the quality??

Here are my options for the standard 1x/10x probes:
---T5100 - http://www.ebay.com/itm/HQRP-100MHz-Oscilloscope-Probes-fits-Tektronix-HP-T5100-X1-X10-New-/221690519344?pt=LH_DefaultDomain_0&hash=item339dc8df30

---P6100   - http://www.ebay.com/itm/Two-x1-x10-100MHZ-Oscilloscope-clip-probes-HP-Tektronix-/290374567712?pt=LH_DefaultDomain_0&hash=item439bac4720

---TP6100 - http://www.ebay.com/itm/Two-Oscilloscope-Scope-analyzer-Clip-Probe-x1-x10-100MHz-Kit-For-Tektronix-HP/291177486377?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D29170%26meid%3D8ad8e434a92c4ee9afad4dbc3106985a%26pid%3D100005%26rk%3D6%26rkt%3D6%26sd%3D220375454020&rt=nc

All of them are 6Mhz/100Mhz except for the P6100's, which are 4Mhz/100Mhz.
All of them are X1 = 150VDC peak; X10 = 300VDC peak, except for the TP6100 which are 300VDC/600VDC.
My scope's Max Input Voltage is (dc coupled) 250V(DC + peak AC) or 500V p-p ac at 1khz or less;  (ac coupled) 500V (dc + peak ac) or 500V p-p ac at 1khz or less.
So, if I am correct here, If I want to be able to take advantage of the full ability of my scope with the 1X probe, I would want to choose the TP6100 probes?

Also, as for a HV probe -
http://www.ebay.com/itm/100MHz-High-Voltage-Oscilloscope-Clip-Probe-4000V-Alligator-Clip-Passive-P5100-/111586099163?pt=LH_DefaultDomain_0&hash=item19fb0cbfdb
http://www.ebay.com/itm/Tektronix-013-0290-02-Oscilloscope-Probe-Screw-On-Hook-Clip-Set-P5100-P5120-/321462078021?pt=LH_DefaultDomain_0&hash=item4ad8a20a45

Should I wait til I can afford that one and the spring loaded hook tip, or just get one along the lines of a $30 2kV probe with all the accessories?
I also noticed that none of those probes come with the spring point ground fitting. Is that just something more for HV applications?

Brian


heres a laugh..... a 1,000X  40kV probe....http://www.ebay.com/itm/1000X-P5104High-Voltage-40KV-40000V-20MHz-Oscilloscope-Passive-Probe-Clip-/291119549732?pt=LH_DefaultDomain_0&hash=item43c813cd24