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Re: Sampling head extender missing coax connectors

snapdiode <snapdiode@...>
 

PM me


Re: Very Inexpensive 7623A, but Problems

 

Thanks for the explanation. That's kind of what I was expecting for the NS7348s, that they were matched and thermally coupled. My real problem is that I can't seem to find any information on NS7348, and what I've found in the Common Design Parts Catalog (for Tek part # 151-0232-00) has only confused me further.

The service manual calls the part out as

151-0232-00 TRANSISTOR,SILICON,NPN,DUAL NS7348

but the CDPC (1982) lists 151-0232-00 as a 2N2484, and gives some specs, but does not indicate a saturation voltage (see pages 6-10 and 6-14).

If I look up the 2N2484 online, it is NOT a TO-78 package and does not appear to be a dual NPN transistor (it only has three leads).

Further down (in the Transistor Cross Reference Index, on page 9-11, there are several iterations of part 151-0232:

-01 = 2N2919
-02 = 2N2919
-03 = 2N2918
-04 = ITS1276

If I look up 2N2919 online I find what do appear to be dual NPN transistors in a TO-78 package, just like the transistors I have in hand. Same for the 2N2918. My searches for ITS1276 have been essentially fruitless.

Is the 2N2919 a substitute for the NS7348?

I'm surprised that I can't seem to find any information on the NS7348, not online, not in Tek's reference books, and not even in Nat Semi's Transistors Databook (1982). It doesn't help that the parts themselves only have the tektronix part number on them, so I am left wondering if there ever existed such a part as the NS7348.

I know too well that you should always work your way forward from the wall socket when diagnosing problems, but the temptation to start in the middle is often overwhelming, especially when starting from the wall socket requires more effort (I didn't realize until after I had blown a transistor that removing the power supply was easier than it appears). I'd say "live and learn" but I'm in my 50s and I just seem to be getting better at making the same mistakes.

-- Jeff Dutky


Re: Sampling head extender missing coax connectors

 

If you have a male and a female (since I need one for each end of the extender) ;) I'd happily pay postage.

D-sub coax contacts can be had, for example:
https://www.digikey.com/en/products/filter/d-sub-d-shaped-connectors-contacts/332?s=N4IgjCBcoLQdIDGUBmBDANgZwKYBoQB7KAbXDAFYQBdAgBwBcoQQBfVggJlJACUBxOAHYALAAJEhNAA8arIA

For almost $16 for just one pair. Plus postage!
I'm going to check my cable bin, maybe there are some coax contacts as mentioned...


Re: Sampling head extender missing coax connectors

snapdiode <snapdiode@...>
 

Meh, I creatively destroyed my connectors to get the contacts inside. Why not, I don't even know how or why I have a 7W2 in my box of shiny things. If they fit, I can ship them to you for the price of postage.


Re: Sampling head extender missing coax connectors

-
 

"They could be dsub coaxial contacts, as used in 13W3 connectors. I'd have
to measure it.

...beats me."

If they are then those same contacts were used in some of the old Sun
and SGI monitors and you might be able to get one of the video cables and
rob the connectors out of it. HP also used the same contacts in various
extender and unit interconnect cables.

On Sun, Feb 14, 2021 at 7:27 PM snapdiode via groups.io <snapdiode=
yahoo.com@groups.io> wrote:

Whoever did that did a pretty despicable thing... This connector kind of
looks like a SMB but isn't. The manual seems to suggest it is built of
parts intended for other things.

The inner female conductor is a DM53740-5001 which still exists today

https://www.mouser.ca/ProductDetail/ITT-Cannon/DM53740-5001/?qs=qCxwlXJ4fnyo0PCCdeMbuA==

...which says it's meant for RG187 or RG188 coax, which leads to these
connectors

http://www.coax-connectors.com/products/cables/ab/rg187.aspx
http://www.coax-connectors.com/products/cables/ad/rg188.aspx

They could be dsub coaxial contacts, as used in 13W3 connectors. I'd have
to measure it.

...beats me.






Re: Sampling head extender missing coax connectors

 

I'll look for your album, thanks.

The NorComp contacts are proving elusive (DigiKey lists them as "obsolete" and no price. Of course).

However, it appears that other manufacturers also make similar coaxial contacts, for example:
https://www.mouser.com/datasheet/2/18/amphenol_d-sub_inserts-1157297.pdf

I might as well chase this mirage while I'm waiting on Schottky (and tunnel) diodes ;)


2 photos uploaded #photo-notice

TekScopes@groups.io Notification <noreply@...>
 

The following photos have been uploaded to the D-sub coaxial connectors used in 012-0124-00 extender album of the TekScopes@groups.io group.

By: snapdiode <snapdiode@...>


Re: Sampling head extender missing coax connectors

snapdiode <snapdiode@...>
 

I think that will be the bigger problem, naturally the connectors need to be mounted at the right distance to work... Check out my exciting photo album.


Added album D-sub coaxial connectors used in 012-0124-00 extender #photo-notice

TekScopes@groups.io Notification <noreply@...>
 

snapdiode <snapdiode@...> added the album D-sub coaxial connectors used in 012-0124-00 extender: Looks like these fit


Re: Sampling head extender missing coax connectors

 

Those look good, but I wonder how the contacts were originally mounted in the extender cable. There is no mark where a nut or clip would have been, and no separate bracket. Perhaps it's a push-in lock (as it works in the D-sub connector body)?


Re: Sampling head extender missing coax connectors

snapdiode <snapdiode@...>
 

Forgot to link

https://www.norcomp.net/series/682m-series-solder-cup

sort of looks right. Don't know.


Re: Sampling head extender missing coax connectors

 

Thanks! Please post if you find out more details or measurements :)
The extender is still partially useful to start debugging the S-1 once I get the Schottky diodes from Digikey, assuming that doesn't fix it right away.
Meanwhile I can just leave the sampling heads in the scope and run a GR-874 cable to whatever I'm playing with. I've got a bunch of those cables in various lengths/delays and a variety of 874 adapters too.


Re: Sampling head extender missing coax connectors

snapdiode <snapdiode@...>
 

Whoever did that did a pretty despicable thing... This connector kind of looks like a SMB but isn't. The manual seems to suggest it is built of parts intended for other things.

The inner female conductor is a DM53740-5001 which still exists today https://www.mouser.ca/ProductDetail/ITT-Cannon/DM53740-5001/?qs=qCxwlXJ4fnyo0PCCdeMbuA==

...which says it's meant for RG187 or RG188 coax, which leads to these connectors

http://www.coax-connectors.com/products/cables/ab/rg187.aspx http://www.coax-connectors.com/products/cables/ad/rg188.aspx

They could be dsub coaxial contacts, as used in 13W3 connectors. I'd have to measure it.

...beats me.


Re: EIP 101B Spectrum Analyzer Plug-In - MPC "Panoramic Rx P/I"

Alain Mionnet
 

If it is a plug-in for Tek Scopes with Plug-in as 1Lxx you may create an album for the MPC.
I have tested the 101A. Video output seems not correct for the sensitivity.
I have the bandpass filter but the CF resolution is not enough fine with the potmeter definition.(because wire-wound)
I wrote many lines , must be read again.

Alain

France


Re: Sampling head extender missing coax connectors

 

After searching through the TekWiki connector page, I think it might be an SMB?


Sampling head extender missing coax connectors

 

When I bought my 3S2 sampling plug-in, it came with a 012-0124-00 Sampling Head Extender (3 ft). Thought that was a nice bonus. Unfortunately some genius seems to have removed the push-on coax connectors from each end (the trigger pickoff). No idea why. But that means I can't use the extender for normal operation! (Although the 3S2 doesn't have internal triggering, that's an easy work-around by connecting a short cable from the 3S2 trig out to the 3T77A ext trig in. Still need to run the trigger from the sampling head to the 3S2, though).

I took the scope-end and the cable hood apart, and the coax is there - someone cut it off, and inside the scope-end it was taped into a half loop with scotch tape. No way was that Tek factory original.

So, any idea what kind of push-on connectors those are, and where I can get one male and one female? If they're crimp style the remaining coax won't be long enough, so I'll have to run another piece of coax alongside the cable, too.
thanks.


Re: Very Inexpensive 7623A, but Problems

Dave Hills
 

The 2.1v of ripple on -15v is your clue. C811 is your prime suspect, likely very low to no capacitance. This "was" probably
your only problem. Have you checked the ripple across C811? (Hint: Before digging into circuitry, always check rectifier
filter capacitor ripple first.)

Q964 is your current limiter, separate, Beta matched NPNs will probably work OK. Not so for Q943.
A pair of NPNs here need to be matched for Beta AND thermally coupled as well, or else you will have a drifty -15v supply.
You might get away with a Beta matched pair of TO92 cased parts epoxied together face to face for Q943.
In the old days there were aluminum clip heatsinks made for this purpose. (i.e. for TO-5 and TO-18 cased parts and some of the weird
epoxy parts made by GE)

Dave

On Sun, Feb 14, 2021 at 12:39 PM, Jeff Dutky wrote:


I pulled all the transistors (except for Q958, on the back of the board) from
the -15V regulator and measured the voltages at each of their pins. Everything
looks good except for the following:

The voltages on the base and emitter of Q958 (the big power transistor) is a
bit low, meaning that the -18V rail may be bad. I will need to pull the power
supply (I think) in order to check the components of the -18V rectifier path
(C811, CR811, and R811).

The voltage at the base of Q943A is about half what it should be (-7.8V rather
than -14.9V), but that's driven by the -15V sense, which should be registering
maximum feedback in this case (so probably okay?).

I haven't tested the two canned NPN pairs yet (because it's hard to hook them
up to the component tester). I have ordered some from an eBay seller, so I
should have spares, in case either of these are bad, but I would be interested
in modern substitutes for the NS7348. Could I simply pop two discrete NPN
transistors (with suitable specs) in the socket and expect that to work?

-- Jeff Dutky


Re: 465B strange ripple

Michael W. Lynch
 

On Sun, Feb 14, 2021 at 12:12 AM, Chuck Harris wrote:


One tiny note:

When doing ripple tests, it is important that you make a
cable connection between the ground on the scope making the
test, and the scope being tested.
Chuck,

Would you say that it would be good general practice to connect the Test scope chassis and DUT chassis when making other measurements as well, in addition to these for power supply ripple?

--
Michael Lynch
Dardanelle, AR


Re: 2235 Repair having no power

satbeginner
 

Hi Roy,

it's been a while, was busy with other stuff.
As far as I can see it was from one of the support structures for the deflection plates.
The lower half of the screen was perfect, both horizontal linearity and amplitude, but the top half had the distortion.

It also looked like one small particle was stuck at the phosphor, causing the little optical deforming when I put the trace on that spot, the other pieces are loose inside the CRT...


But I was able to find a replacement, so I am happy.

Leo


Re: Help needed calculating trace impedance for SG503 Peak-to-Peak detector.

snapdiode <snapdiode@...>
 

Good enough for this I think. Rogers is a needless expense here. There are materials better suited to RF work without going to Rogers, such as Nelco or Panasonic Megtron. Rogers is what I use on Ka radios...

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