Date   

Re: OT 10Mhz references

J. L. Trantham
 

I 'second' Nigel's comments.



You can get a 'stand-alone' 10 MHz 'reference' such as an HP 10811 or any of
the oscillators you and others have mentioned and could be left on
permanently. However, you will eventually need a 'primary standard'
(Cesium, GPS disciplined oscillator, etc.) for comparison to be able to
'adjust' it back on frequency as time goes by.



A GPS disciplined oscillator, such as the Thunderbolt, could to be that
'primary standard' when needed and not need to be left on permanently.



Good luck.



Joe


Re: 7A13 Knob

 

Does this happen to be the knobby you seek?
Unfortunately, it isn't.

The correct knob does not have the black insert at the front. Instead, there's empty space in that area to allow the pull-out variable attenuation button with its white ring to "sink in" at least 5 mm, probably more like 7-8 mm.

The knob on Ebay looks like what's used on e.g. the 1481 Waveform Monitor's front, at the right side.

Raymond


Re: 7A13 Knob

Malcolm Hunter
 

On 11 March 2016 at 06:29, analogaddict013@... [TekScopes] <
TekScopes@...> wrote:

That sure looks like it. How did you find it? Searched "Tektronix knob"
and
waded through all the results? Thanks!
Nathan KK4REY

.........
I'm actually that guy that stalks the Tektronix listings religiously. It
came up in the "ending soonest" category. I hope it's the one you're
looking for!
‚ÄčThat's how I found a cheap 465 front cover - they only specified
"Tektronix cover" and gave its dimensions.

Malcolm ‚Äč


[Non-text portions of this message have been removed]


Re: 2465A focus

cmjones01
 

I've got four 24xx scopes, and on three of them the optimum focus point is
roughly in the middle of the focus knob's travel. One one of them (a 2465)
the best focus is with the focus knob turned all the way counter-clockwise.
In that position the display is as sharp as the other scopes, so I've never
looked in to why it is the way it is, but something odd must be going on.

This probably isn't a lot of help to you but it shows that oddness with the
focus control is not unknown.

Chris

On Fri, Mar 11, 2016 at 1:40 AM, chipbee40@... [TekScopes] <
TekScopes@...> wrote:



Hi, All you 24xx experts.
Just had a customer bring a 2465A in. Has a 2016 expiry cal cert from a
reputable source. Customer complaint is poor focus. Sure was. Focus at end
stop. I'm limited to what I can adjust because it may get returned but
opening it up edge focus was also at end stop. (customer twiddling?) Power
supply ripple and volts all good, well within spec, very clean scope, How
can you check hours use on this?.
So I did the focus and astig adjustments and got a reasonable display but
I'm not convinced this is the best a 300Mhz scope can do.
So how good is this scope display supposed to be? I don't get many 24xx
scopes, the last 2445 was a couple of years back and it didn't stand out as
particularly blurry. I must admit I'm comparing to my Fluke PM3394B which
is ultra sharp but this is on par with a 2230 or slightly worse. Text and
traces are not as sharp as I would expect, not out of focus but just not
sharp. Also I seem to have to continually correct the focus depending on
signal or display option. doesn't seem right to me.
I checked the resistors in the focus circuit, all bang on.

Do the tubes soften on these? Anything I should check before I tell the
guy this is as good as he can expect?
TIA.

[Non-text portions of this message have been removed]



[Non-text portions of this message have been removed]


Re: OT 10Mhz references

 

The inputs on your instruments are not picky about waveshape. The
Rigols expect a signal level in the range of about 0dBm to 10dBm and
the HP VNA supports a much wider input range.

Your Rigol spectrum analyzer has a reference output which can be used
to feed another instrument. If you just want all three instruments to
be locked to the same reference, then this output could be fed to the
Rigol signal generator and the HP VNA.

On 10 Mar 2016 16:39:15 -0800, you wrote:

Hi all:
I'm hoping to ref. a Rigol DSA815, a Rigol DG1022A sig gen and an HP 8753D VNA....to a good 10Mhz ref.
I see a heap of them here:
http://stores.ebay.com/Flyingbests-Equipment/High-reliability-OCXO-/_i.html?_fsub=908870013&_sid=282770553&_trksid=p4634.c0.m322

IDK what voltage is optimal or which unit to chose (*sine/square, single or double OXCO) and need some advice on this.
tx


Re: OT 10Mhz references

poldhu1901@...
 

With any crystal oscillator, no matter how good they might be, or how well
calibrated to start with, if that's all you have there will always be the
issue of not knowing how well it is calibrated ongoing unless you find
someone else to check it.
Although rubidium oscillators have much better long term stability this is
still an issue, and buying any of the surplus oscillators, or surplus
oscillator based products, from China is definitely taking pot luck.

Some of that kit is very good, and there are indeed bargains to be had,
but the same product from the same seller can give you a good result one week
and a duff one the next, and don't be fooled by the Chinese listings
showing lots of fancy test gear, experience shows that isn't any guarantee of
quality or competence.

It's a bit of a chicken and egg situation and you really need quite a well
equipped timing lab to start with before chancing your arm on something
that is just treated like scrap before it gets into the hands of the Ebay
sellers.

Although more expensive you would be well advised to consider a 10MHz GPS
frequency reference, the Trimble Thunderbolt for example is well thought of
with software freely available to monitor its performance, and once
installed properly there are no ongoing calibration issues.

Regards

Nigel
GM8PZR

Hi all:
I'm hoping to ref. a Rigol DSA815, a Rigol DG1022A sig gen and an HP 8753D
VNA....to a good 10Mhz ref.
I see a heap of them here:
http://stores.ebay.com/Flyingbests-Equipment/High-reliability-OCXO-/_i.html?
_fsub=908870013&_sid=282770553&_trksid=p4634.c0.m322
http://stores.ebay.com/Flyingbests-Equipment/High-reliability-OCXO-/_i.html?_fsub=908870013&_sid=2
82770553&_trksid=p4634.c0.m322

IDK what voltage is optimal or which unit to chose (*sine/square, single
or double OXCO) and need some advice on this.
tx


Re: 7854 RAM card upgrade only - any interest?

 

On 10 Mar 2016 20:20:46 -0800, you wrote:

David,

Owners can choose from the two switching approaches. The memory card design is not affected.
I agree but make it three switching approaches as I have thought of
another outlined below.

Putting it in the external keyboard is not obvious or intuitive, and some 7854s may not have keyboards. I would personally prefer a small mod in the mainframe and a rear panel switch like the original. Others may prefer the easier keyboard change.
Linking the backup memory function to the calculator keyboard has a
certain engineering elegance that appeals to me but I suggested it
knowing that it is not really feasible do to operational concerns. One
easy mistake and the contents of memory are lost. I thought of a
better way however.

Replacing printed circuit board A32 to duplicate the uprated 7854
design will add considerably to the cost and work involved so I think
this should be avoided if possible. I think the best option for this
kind of solution is to air wire the necessary circuit or include a
small circuit board section as part of the memory card which can be
snapped off and affixed to the inside of the rear enclosure. That
will duplicate the original stock look and operation.

There is another way though. All of the necessary signals for
emulating the backup memory function switch are present on the D
connector where the cable for the calculator keyboard attaches. A D
connector dongle could be made with the backup memory function circuit
inside of it. If the dongle is attached, then the firmware boots in
memory backup mode.

The circuit needed for any of these options just requires a transistor
inverter comprised of a series connected resistor and diode connected
to the base of a NPN transistor which will operate in place of a
74LS05 gate just fine.

On an unrelated subject, it might be fun to change the keyboard id and see what mnemonic the firmware brings up for each key / shifted key. Some day when I have nothing better to do...

Cliff
I have only used my keyboard long enough to verify that it works but
decided to take it apart for inspection. The ID jumper is soldered
into place and on my late model keyboard, it is still the first
jumper. It would be easy enough to alter with a soldering iron. I
suspect Tektronix did this to support keyboard revisions if it ever
became necessary to release an incompatible keyboard or maybe one with
a different key arrangement. I assume this never happened.

I also noticed that the serial number on my keyboard matches the
serial number on my 7854. The cable is marked with the keyboard part
number as well as "C.A.I. 01/88 REV.C". The middle part is obviously
the production date but I do not know about the rest.


Re: 7854 Repair & Restoration

Ed Breya
 

I'm pretty sure that these canned hybrids are always plugged into Berg sockets that sit nearly flush with the board surface. These are among the most reliable IC pin connector types I know of, despite their low profile and simplicity. I've never seen a bad one except where abused by the wrong lead diameter or chemical attack.

The pins on the solder side of the board are fat, indicating they are likely Berg sockets. Tomorrow I'll see if I can pull the hybrids out of one of the spare amplifier boards. This should also tell whether or not there's thermal grease underneath.

There are at least two types of low profile socket pins - the Bergs that I often refer to are made from tiny drawn and crimped sheet metal components, and are usually pressed into the board early in the build process. They often have a white silicone elastomer glob seal on the opening, which is punctured by the part lead when installed. Tek often used these for transistor and IC pins, and also as the center conductor receptacle for board-mounted Peltola connectors.

The other kind are high quality machined sockets, originated by Augat, I think, and commonly used in very good IC sockets and low profile in-board pins and strips. I think HP used a lot of these.

Ed


Re: OT 10Mhz references

Craig Sawyers <c.sawyers@...>
 

On 10/03/2016 7:39 PM, mosaicmerc@... [TekScopes] wrote:

Hi all:
I'm hoping to ref. a Rigol DSA815, a Rigol DG1022A sig gen and an HP
8753D VNA....to a good 10Mhz ref.
I see a heap of them here:
http://stores.ebay.com/Flyingbests-Equipment/High-reliability-OCXO-
/_i.html?_fsub=908870013&_sid=282770553&_trksid=p4634.c0.m322
http://stores.ebay.com/Flyingbests-Equipment/High-reliability-OCXO-
/_i.html?_fsub=908870013&_sid=282770553&_trksid=p4634.c0.m322


IDK what voltage is optimal or which unit to chose (*sine/square,
single or double OXCO) and need some advice on this.
tx
Other ways of skinning the cat is a 10MHz Rb oscillator. Main ones are Efratom and FEI. Lots from
USA and China from decommissioned comms racks. Also lots of options - sine, square, ones that have
a synthesiser so you can set the frequency over quite wide limits (but that increases the spurs
quite a lot) - lots of info on the web.

Or (what I use) is a GPS standard - a Trimble Thunderbolt from eBay. That locks to the Caesium
standards in orbit, so is bang on frequency to 1 part in 10 to the lots of zeroes, and about 20fs
noise. You need a bullet antenna too - I've got mine on a short pole attached to the end gable of
the house. Supported by Tboltmon (s/ware from Trimble, or Lady Heather (again lots on web).

But both those options are relatively expensive as compared with an ovenised clock module.

With that in mind, the Trimble 10MHz OCXO is the core of the Thunderbolt - and that is on your list.
That has ultralow phase noise, measured here http://www.ke5fx.com/tbolt.htm

But it depends on how accurate you want your 10MHz, and what phase noise/Allen deviation you want.
And how deep your pocket. And how anal you are (I'm pretty anal).


Re: 7A13 Knob

 

The first thing I would try is knurling the outside of the metal
insert and using epoxy or hobby grade cyanoacrylate glue to set it
within the plastic. Ideally the fit should be an interference fit to
provide for proper centering.

I am tempted to start an index of which plug-ins use which knobs.

On Fri, 11 Mar 2016 07:24:21 +0100, you wrote:

It'll work fine with the thermoplastic 3D printing material.
I have inserted nuts before to get a stronger thread, just used a
soldering iron to heat them up.

With something large and thin like a knob, I would recommend to have
cold water nearby so you can set the plastic as soon as the insert is
in place. Otherwise the stored heat will transfer from the metal into
the plastic and possibly deform it on the outside.

I don't see why you couldn't make it a slip fit and epoxy it in.

ST


Re: 7854 Repair & Restoration

 

On 10 Mar 2016 17:48:33 -0800, you wrote:

I just found vertical amp board that was from a 7844 or 7904 - marked 670-2768-02. The driver and output cans are both held by the same type of plastic clamp. The clamps each have two special screws holding them to the board, with a spring at one end for compression. There is a contact in the center of each one, with a lead going to the board (ground?). There is also a sheet metal layer about 0.032" thick added to the component side of the board in this area, apparently to serve as a ground plane and for cooling. So, the compression force is probably essential also for good thermal contact of the cans to the plane. I can't tell if there's any thermal grease underneath. The contacts are definitely not welded to the cans - in fact, the clamps have notches on one end to allow them to swing away for access to the cans without removing the screws.

Ed
I have always been reluctant to mess with the various hybrids for fear
of damaging them but I took a closer look at U50 in my 7854 and
confirmed your description of the construction and analogaddict013's
observations about the lead attachment. I have not messed with one of
these since my 7834 and there I only removed the vertical CRT
amplifier and did not mess with U50. The notched end of the plastic
clamp can easily be pushed down relieving it of the screw head so that
the clamp can be slid to the side. Doing this reveals that the top
lead attachment is *not* welded to the TO-8 can and just makes contact
under light pressure. Earlier I found a figure showing the lead
welded to the top of the TO-8 package but that must not have been
literally accurate.

This provided an opportunity to run a test however. I slid the clamp
to the side disconnecting the top lead and powered up my 7854. The
display on the CRT was completely normal. I think this confirms that
the problem with analogaddict013's 7854 where the display shifts to
the top of the CRT when U50 is tapped is not caused by the top lead
connection to U50.

I did not try to remove U50. Is it soldered into place or does it use
collet socket pins embedded into the printed circuit board?


Re: 7A13 Knob

Brian Bloom
 

:
That sure looks like it. How did you find it? Searched "Tektronix knob" and
waded through all the results? Thanks!
Nathan KK4REY

.........
I'm actually that guy that stalks the Tektronix listings religiously. It came up in the "ending soonest" category. I hope it's the one you're looking for!


Re: 7A13 Knob

stefan_trethan
 

It'll work fine with the thermoplastic 3D printing material.
I have inserted nuts before to get a stronger thread, just used a
soldering iron to heat them up.

With something large and thin like a knob, I would recommend to have
cold water nearby so you can set the plastic as soon as the insert is
in place. Otherwise the stored heat will transfer from the metal into
the plastic and possibly deform it on the outside.

I don't see why you couldn't make it a slip fit and epoxy it in.

ST

On Thu, Mar 10, 2016 at 12:11 AM, Nathan Johnson jdownj@...
[TekScopes] <TekScopes@...> wrote:
That would almost surely work with a cast/molded part... The million $ question
is how various 3D printed materials would behave in that application.
I drew something up quick n dirty in OpenSCAD and I'm going to send it out to
try Shapeways and maybe another service. I'm sending a good original to a guy
who does CNC work. My impression is that not many knobs were made as spares, and
that most knobs for sale come at the expense of a complete plugin. Combining the
fact that this knob is unique to the 7A13(Not quite, I think it's used on the
calibrator controls on the 7904 non-A), the fact that the 7A13 is slightly rare,
and slightly more expensive contributes to why there aren't many around.
Nathan KK4REY


Re: 7A13 Knob

Nathan Johnson
 

That sure looks like it. How did you find it? Searched "Tektronix knob" and
waded through all the results? Thanks!
Nathan KK4REY

Sent using CloudMagic Email
[https://cloudmagic.com/k/d/mailapp?ct=pi&cv=7.4.15&pv=9.1&source=email_footer_2]


Re: 7854 RAM card upgrade only - any interest?

Cliff Carrie
 

David,

Owners can choose from the two switching approaches. The memory card design is not affected.


Putting it in the external keyboard is not obvious or intuitive, and some 7854s may not have keyboards. I would personally prefer a small mod in the mainframe and a rear panel switch like the original. Others may prefer the easier keyboard change.


On an unrelated subject, it might be fun to change the keyboard id and see what mnemonic the firmware brings up for each key / shifted key. Some day when I have nothing better to do...


Cliff


Re: 7854 Repair & Restoration

Ed Breya
 

This just occurred to me, from the depths of memory. If your problem is intermittent connections on the vertical amplifier hybrids, it may be wise to pull them out and inspect the leads. I have seen a few times on various ICs, and maybe on these kind too, where a part was improperly installed such that a lead got crumpled up or bent over, yet still made contact with the socket pin even though it wasn't actually inserted. When this happens, it can work just fine for many years, but can eventually lose contact. If this is the case here, it may be as simple as carefully straightening out the lead, and properly reinstalling the device. I haven't followed this discussion closely, and don't know what steps have been done, so please disregard this if it's redundant.

Ed


Re: OT 10Mhz references

n4mf_sc
 

I use a Lucent RFG-RB Rubidium reference here. Wanted Cesium but a bit more pricey than I got this for on fleabay.

Mitch
N4MF


Re: OT 10Mhz references

Torch Fireman
 

I bought one of these last year:

http://www.ebay.com/itm/262326560037

The advantage of this module over the bare oscillators on the page you reference is that it is ready to go, complete with dual outputs and power input, and has been calibrated -- no NIST certificate or anything, but from the photos and description, he seems to know what he is doing. From what I can tell with my limited test capability, it is accurate and very stable. If you have better equipment, there is an adjustment on the board.

However, it is a sine wave output. As a reference, a nice sharp square wave might be easier to use.

On 10/03/2016 7:39 PM, mosaicmerc@... [TekScopes] wrote:

Hi all:
I'm hoping to ref. a Rigol DSA815, a Rigol DG1022A sig gen and an HP 8753D VNA....to a good 10Mhz ref.
I see a heap of them here:
http://stores.ebay.com/Flyingbests-Equipment/High-reliability-OCXO-/_i.html?_fsub=908870013&_sid=282770553&_trksid=p4634.c0.m322 http://stores.ebay.com/Flyingbests-Equipment/High-reliability-OCXO-/_i.html?_fsub=908870013&_sid=282770553&_trksid=p4634.c0.m322

IDK what voltage is optimal or which unit to chose (*sine/square, single or double OXCO) and need some advice on this.
tx


Re: 7A13 Knob

Brian Bloom
 


Re: 7854 Repair & Restoration

 

On 10 Mar 2016 17:15:23 -0800, you wrote:

...

So then... about the CRT circuit... DS47 is supposed to have a slight glow? Isn't that chain of neons supposed to be circuit protection?

I wonder if other scopes of the 78**/79** series have the same thing going on..
I have never noticed such a glow but I have not specifically looked
for it either. As far as I know, those neon bulbs should not be
glowing at all except during a fault.
I'm really curious why Francis had circled the diodes in the focus-grid dc restorer. I guess I should just ask him.
I asked Francis about this and the glowing neon - he said he vaguely remembers that he noticed it as well, so he checked all of the voltages around the Focus-Grid DC Restorer circuit and everything had seemed fine. He didn't look any further into it.

I've heard of these old neons going ' soft ' and the voltage at which they conduct lowering too much with age. Have you? After dealing with the vertical board and verification that problem is fixed, I'll check the voltages and waveforms of the related circuits, and if all checks out maybe I should just replace the neon and see what happens... I think I do have some of those type somewhere.
Unlike the bulbs in the z-axis DC restorer, the bulbs in the focus DC
restorer do not hold the focus lead close to the cathode voltage so I
am not sure what purpose they serve.

I pulled the high voltage shield off of my 7854 and in a dark room,
none of the bulbs I could observe showed any activity. They were all
completely dark. When I first powered the oscilloscope up, I could
hear the crackling from the high voltage.

If there is a problem, hopefully work on the vertical amplifier around
U50 will solve it. If not, then I think it will be easier to just
shotgun rebuild the DC restorers instead of trying to diagnose them.

On 10 Mar 2016 17:27:36 -0800, you wrote:

If you guys are referring to the TO-8 and bigger canned hybrids in the vertical amplifiers, as I recall, on some models they had a plastic clamp type thing with a contact and wire lead that would both press the can leads into the socket pins, and make electrical connection to the can top, but only by contact force from compression, not a weld.

Ed
Maybe there are two different versions of the package. All of the 400
MHz 7000 mainframes mostly use the same ICs and U50 is identical in
all of them but I have never had one of the vertical amplifiers apart
far enough to see if that lead is welded or attached with compression.

I do not think it matters though. There is no ground connection to
U50 that I have been able to find which would cause the observed
vertical deflection behavior. I think the lead is for shielding
purposes.

Knowing exactly where in the circuit that wire connects would probably
reveal what it is for.