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How do you test these? The 7 pS rise time is a pretty difficult spec if you want a 10x margin.

I'm contemplating a mercury wetted reed relay, but even that looks to be 2-3 pS at best.

I just received a couple of SD-22s and at 23 pS those are too fast for my pulser from Leo Bodnar. It's really all Leo's fault for sending plots from his CSA803 with the unit. I managed to get an 11801 with an E5622 error for $185 shipped and a pair of SD-22s for $150 shipped. The latter came today. The 11801 is supposed to arrive Friday.

I don't really need it, but an SD-30 or SD-32 would be kind of neat to have. I plan to get an SD-24 to augment the SD-22s.

Unfortunately no one in the US has fresh NVRAM and won't until June.

Reg

Hi Chuck:
Thanks for letting me know.
I saw that about the 308 does it (from Tekwiki).. page 1, and page 78, in the 308 operator guide/instruction manual.
Signature analysis is built into the 308... you don't need the word recognizer probe/module accessory, to do it (at least by the page 78 example.)
Does anyone know if the 318 or 338 do signature analysis (I didn't see that in their manuals)?
Will any of the later Tek LAs do signature analysis?
Best regards.

The common faults and solutions to the power supplies on ALL the 22xx scopes are in the archives of this group. seriously this group goes over the same stuff repetitively :)
The 2246 (applies to the 2247) power supply can be removed from the scope and using the fan as a load can be tested as a unit.(With care! this is a mains potential switching supply).
Common failure on these is C2210 4.7uF and in many cases that's all, but if you are unlucky then Q2209/10 which if I remember correctly are TIP32C, following on in the unlucky stakes the mosfet Q2214.
The secondary diodes are rarely at fault, mostly schottky so reading low on diode ranges. and in my opinion the secondary 3 leg caps are reliable.
If testing the board watch out for a bite from J2208 long after you power off! (Near the multiplier, drain it with a 100k resistor). Rarely T2204 fails, also I've had the multiplier fail, (Disconnect its input to confirm).

On Wed, Mar 13, 2019 at 08:59 PM, Nicholas Keller wrote:

So if I understand correctly, I
can connect the DUT to the isolation transformer using all three prongs.

That is correct.

Raymond

I see that possibly adding correction magnets to fix the problem has been mentioned here somewhat. Here's another idea, that may seem far-fetched, but not impossible: What if the 2467 CRTs originally did have small tweaking magnets attached, to assist in geometry. What if the adhesive or tape or whatever used became ineffective after many years, and let go, so the magnets would come loose and stick somewhere, like inside the mu shield? t wouldn't be obvious, because it wouldn't be rattling around loose inside the scope.

Has anyone seen any sign of magnetic assistance on these CRTs, or anything in the manuals, etc? Just wondering.

One other far-fetched one: Is there any possibility of the trace rotation coil popping out of place, putting it off-axis?

Ed

Is this being offered by you personally or by Astro Too?

If it’s for Astro Too I don’t think that it is appropriate to use this forum as a sales channel.

DaveD

Sent from a small flat thingy

On Tue, Mar 12, 2019 at 01:00 PM, Raymond Domp Frank wrote:

wading through an operator manual saves time in getting acquainted

Well, upon seeing the Operator's manual (Thanks for posting it to Tekwiki!)… I can see that manual has examples of how to set up the 318, that the Army service manual doesn't give. But I guess, and this is the just of my question, I think... I just didn't recon anyone was using them, to do logic analysis, or for servicing stuff anymore (the p.c. based L.A.s are so cheap and powerful)... so I was thinking, I'm missing some use for these old LAs...(other than for technical/design/parts interest... which the service guide covers much better).
I understand what you are saying... but, most of the older L.A.s, I run across, are being used to weigh down the basement floor. If people are doing something useful with them, I'd like to do it too.

Yes, it has full signature analysis.

-Chuck Harris

Roy Thistle wrote:

On Tue, Mar 12, 2019 at 11:49 AM, Harvey White wrote:

if you regard signature analysis as fun, then you can do that.

Hi Harvey:
Thanks for the reply. There's always a few old L.A.s keeping the concrete slab down, in someone's basement... and I'm thinking about that, whenever I see one. The 308 has a word recognition module, and the 318/338 have word recognition modes... but, if its signature analysis... aren't captured word(s), further processed, to generate the signature? Can you do that with a 308/318/338?

Greetings. I have this tektronix 7704 scope that i have been having a
difficult time finding a good home for. I am looking to sell it. It powers
on, however i lack the skills to properly test it. Attached are some photos
of the scope. Its on a cart. It powers up and displays some numbers on the
screen. I would be happy to answer any further questions you may have to
the best of my ability.

It has been here for a while, and is in the way, i am open to offers and
would like to get it out of here asap.

The device is in Melbourne Florida.

Here is a link to a gallery of photos of the scope.


--Devin D.

On Tue, Mar 12, 2019 at 12:52 PM, Raymond Domp Frank wrote:

1 mega-sample

sorry... typing too fast... that should be 100 mega-samples

I was simply using a hand held DMM (craftsman 82400) to test the voltage at
C2202. I do not own another bench scope. So if I understand correctly, I
can connect the DUT to the isolation transformer using all three prongs.

I will check the value at this capacitor this evening

Nick

Hi all I picked up a SG503 and a PG506 just recently for a very decent price. Haven't tested or used them yet as both have some issues broken knobs missing parts some cosmetic damage. Have checked with Sphere and Qservice and neither has what I need so will list here to see if anyone has some spare bits for one of them.
PG506 SR# B059635 later version
1 - 366-2082-00 Knob gray volts/Div.
1 - 378-2030-06 Lens Red LED Dspl Printed PG506
1 - 337-3039-00 Shield Elec Side complete w/latch
1 - 386-2843-00 Subpanel Front (optional)

SG503 SR# B068393
1 - 386-2848-00 Subpanel Front ( broken a lot)
1 - 366-1527-00 Knob Gray tuneing

Any subs that can be used recommended will be appreciated.
Also am planing to replace the Sprague 30D caps on the 506 and all the multi color tants on the 503. tants on the 506 all are tan color AVX type like the new ones from Mouser.

Any other recommendations offered?

Jim O

On Wed, Mar 13, 2019 at 03:17 PM, Nicholas Keller wrote:

Is this what you describe as “floating the 2247A”?

Hi Nicholas,
Glad you bought an isolation transformer!
My advice to "float your 2247A" actually was very badly formulated. I meant to say something like "float the hot (primary) circuits of your 2247A", meaning the circuits directly connected to the mains *and* I should have added *not* to float your testing equipment (like your testing 'scope).
Many people disconnect safety ground on their measuring 'scope but that's *very* bad and dangerous practice.

Always make sure all instrument chassis are connected to safety ground if at all possible.

Your 2247A is an example where you can get the protection of your isolation transformer and still connect the chassis of both your testing 'scope and the device under test (DUT) to safety ground. This is because T2204 takes care of isolation of all low-voltage circuits from the mains, *including* the 'scope's chassis, which is connected to low-voltage/ secondary ground.
The isolation transformer makes everything directly connected to the two mains input wires (the hot circuits) float i.e. galvanically disconnected from "the rest of the world".
Since the 2247A's chassis is isolated from the hot circuits, it's safe and actually a good idea (safe) to connect that chassis to safety earth. The ground connection on your isolation transformer always connects that transformer's housing to safety earth and the ground wire you're mentioning is supposed to connect that earth ground through to the 'scope's ground (3rd pin in 3-prong adapter).

If you connect things this way, your testing instruments will remain connected to ground, as will your 2247A's chassis.
Only the hot (primary) circuits of your 2247A will be isolated from mains via the isolation transformer on their input and from the 2247A's chassis through T2204 on their output.

Four final notes:

1. In most instruments, there are one or more capacitors between the mains connection(s) and chassis. These are there for EMC reasons but they may present a high-impedance voltage on the chassis (of Vmains/2) if safety ground is disconnected in that instrument.
2. Providing safety earth continuity to your DUT (where possible) provides protection in case of leaks or one of the capacitors as in 1. short-circuiting.
3. In most (older) instruments with linear supplies, like the 465 'scope, providing this earth continuity while using an isolation transformer won't do much good. In those instruments. By all means use an isolation transformer but skip the earth continuity.
4. Be aware that, though disconnected from mains, hazardous voltages still exist inside hot circuits connected via an isolation transformer!

Good luck with your repair!

Raymond

/g/TekScopes/album?id=86536

I tested a Toshiba A1962 PNP transistor to assess the overall condition of the step generator. It works as you can see from the link, however the trace becomes garbled with lower step sizes of the generator and higher vertical sensitivity. I am using 15 inch clip leads from the test fixture so that is probably not helping. Finally I have a strange reading when I set the step generator to 0.05 and 0.1V

Hi Tom,

Yep, and even under magnification it looks perfect.

No glass, no elements akimbo.

It doesn't look like it has been abused... except for
the trace, that is.

-Chuck Harris

Tom Miller wrote:

I just got my trusty 7904 and tried the same test with squarewave.

Same result as the 7104 , precisely rectilinear, no visible distortion.

Cheers,

Jon

I just paid $150 USD for one with several issues. Now that I fixed it I expect to get $200-250 pretty easily.

If you dont want it, I will take it.

Good idea, I have an oscilloscope, I will put it to good use

Have you worked through the adjustment procedure, checked the waveforms against the manual? I usually find any faults/oddities that way, The step generator waveforms should be very clean. Getting the sockets out is very time consuming, I avoid it if possible. Some Deoxit on the ic's and a couple of insertions cures almost all but the worst sockets. Also deoxit into the pushbutton switches cures a lot of problems.