Date   

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.


Re: Digest Number 10380

 

Probably the cleanest way to make these is to turn the diameter ina lathe. I would first rough cut the blanks with a band saw, or the like,then clamp and turn them in a lathe, assuming you have one available.

You first need to prepare support tooling. First make the tailstock end support from apiece of scrap metal into a cylinder about 25 mm in diameter and 10 mmthick. Drill a 60-degree recess in oneside for the tailstock center. The faceto be against the PC boards could be undercut so as to leave only a rim about 3mm wide. The headstock support can bemade by chucking a piece of scrap rod about 25 mm in diameter and turning theface square or with a recess as aforementioned. Now clamp the stacked PC boards between these supports (firstwinding them with tape to keep them centered until clamped with pressure fromthe tailstock). At this point thediameter of the boards can be turned with a sharp, round-nose tool.

Should you decide to use a hole-saw or circle cutter. For better quality work it is best toreplace the drill bit with a piece of plain metal rod (of course the centerholes must be pre-drilled first). Thistechnique reduces enlargement of the hole and the resultant chatter from theside of the drill bit chewing on the hole.

Bruce, KG6OJI

-----Original Message-----
From: TekScopes <TekScopes@...>
To: TekScopes <TekScopes@...>
Sent: Thu, Mar 10, 2016 4:54 pm
Subject: [TekScopes] Digest Number 10380







All about classic Tektronix CRT o'scopes Group





15 Messages

Digest #10380









1.1

Re: MAKING EXCELLENT PCBs using toner transfer by "Sergey Kubushyn" ksilinux





1.2

Re: MAKING EXCELLENT PCBs using toner transfer by petrutech





1.3

Re: MAKING EXCELLENT PCBs using toner transfer by edbreya





1.4

Re: MAKING EXCELLENT PCBs using toner transfer by "Mike" mdinolfo2001





1.5

Re: MAKING EXCELLENT PCBs using toner transfer by "Stefan Trethan" stefan_trethan





1.6

Re: MAKING EXCELLENT PCBs using toner transfer by "Stefan Trethan" stefan_trethan





1.7

Re: MAKING EXCELLENT PCBs using toner transfer by edbreya





1.8

Re: MAKING EXCELLENT PCBs using toner transfer by "Dwayne Verhey" torchddv





1.9

Re: MAKING EXCELLENT PCBs using toner transfer by edbreya







2

Books , to trade TEK 2246A by kb5zxm







3.1

Re: 7854 RAM card upgrade only - any interest? by test2cal





3.2

Re: 7854 RAM card upgrade only - any interest? by "David" david_william_hess







4

OT 10Mhz references by mosaicmerc







5

2465A focus by chipbee40







6.1

Re: 7854 Repair & Restoration by "David" david_william_hess












Messages



1.1

Re: MAKING EXCELLENT PCBs using toner transfer





Thu Mar 10, 2016 10:07 am (PST) . Posted by:

"Sergey Kubushyn" ksilinux




On Thu, 10 Mar 2016, Peter Hildebrandt petertech99h@... [TekScopes] wrote:

One step omitted before electroless copper plating is sensibilization,
99.99% of time done with palladium chloride. Copper layer has very poor
adhesion to FR-4 (or whatever) without it if deposited at all.

Then, with properly electrolytically plated vias and Nickel plating you
don't have to protect vias when etching but it only works with ammonium
persulfate, not FeCl3. It is also possible to use solder plating instead of
Nickel but for small vias it is kinda tricky because it requires intense
agitation and fluoboric plating solution with high free HBF4 content that is
quite expensive. Nickel is also easier to strip afterwards if needed. It is
also cheaper to plate and plating bath is very simple without exotic
reagents like fluoboric acid and lead/tin fluoborates. Sulfamate Ni bath is
better but regular NiSO4/NiCl2/H3BO3 (Watts bath) is simpler and much
cheaper. Sulfamate bath deposits Nickel without high internal stresses as
Watts bath does but Nickel Sulfamate is not available on every corner and
more expensive.

Etching in HF right after drilling also helps getting proper vias
metallization tremendously if drilling was done at high RPM, even at regular
Dremel 20K RPM or so. Even for lower drill speeds it helps a lot.

Jim Popwell & others interested – Plate thru holes The commercial process: (short version) In fab shops I often visited for various new PCBs, theprocess was like this:1- The 2 sided fully copper clad board (includingmultiplayer boards) has tooling holes just outside the board outline. 2 - The board is CNC drilled for all the holes. Usually thisis in a stack of panels plus thin aluminum entry and exit panels to controldrill wander and burrs.3- The boards are hung in a immersion copper plate tank,copper lines the holes and also coats the foil.4 - The boards are moved to an electro copper plate tank fora ‘plate up’ that also thickens the coating in the holes. Holes are usuallydrilled .002” bigger so parts still fit, critical if CNC thru hole partsinserter is used – back then.5 – The boards are rinsed and dried then sensitized.6 – Boards are then aligned with photomask of circuit tracesvia tooling holes and exposed.7 - Image is thendeveloped and rinsed off!
. Negative image for next step. 8 - Since solderplate is common, it goes to a plating tank. This plating becomes the etching resist by covering the tracks. (For boards with a solder ink mask thensolder plated pads a different process is used.)9 – With a plated solder pattern, the original photoresistnegative image is stripped off. 10 – The board is now etched to remove unwanted copper onboth sides. – Done! The at home process:The home process is a lot easier then you think. If you want to do a lot of PCBs considerassembling a X Y CNC table to guide a dremel over the board to make a lot ofboards, however there are options: 1 - make a spare copy 1:1 scale for the circuit pattern youhave.2 - tape down the fully clad PCB to a flat wood base, tapeyour spare pattern over it.3 - Use a dremel in a dremel drill press or free hand anddrill straight holes thru your pattern and the PCB. (Dremel did have a mini 3jaw chuck the can hold # 30 to # 60 drills, I’ve got!
one)4- source some‘immersion copper plating solution’ (ask for an ‘engineering sample’ ie 1 litre/ quart or buy as needed) then soak the board and agitate to pass solution thruthe holes for 20 minutes or so, experiment with different times on dummy parts.5 – source some ‘electro copper plate solution’, and somesmall copper bars, rods or wire. Get a car battery 6V/12V charger of at least10 Amps. Set up a tank or tray. Controlthe current by switching 6V or 12V and spacing the copper rods further from thePCB and also the size of the copper anodes actually in the solution. Plate for 30 minutes at 10A to 20A. Agitate the solution to keep fresh solutionnear the holes.6 – Dry the board. Sensitize, image and develop your way.7 – At the point you start the etching, plug each hole fromboth sides with masking compound, let dry, to be sure the holes don’t getetched out, then etch.8 – As mentioned earlier, Ferric chloride diluted with hot/warm water etched better then 100 % ferric chloride. Go figure!8 – Dry the board and !
pick off the masking compound and testyour plate thru holes for continuity! Done! 9 – (I also did selective gold plating on PCBs at home,easier then it sounds, looks good too!!)

On Monday, March 7, 2016 8:13 PM, "gmt1@... [TekScopes]" <TekScopes@...> wrote:


Hi Folks,
You can make PCB boards of the highest quality using the toner transfer method.
The secret is to use Pulsar’s Transfer Paper and Pulsar’s Green TRF Foil (both products made in the US) and
a modified laminator .Pulsar products are sold worldwide i gather.

Use Ferric chlorides etchant.
I have no connection with Pulsar (just a happy customer)

I struggled for years to make decent PCBs and this is by far the best DIY system avaliable.
You can produce boards that match Photographic methods and make very fine tracks.
All electronic enthusiast should be able to make there own PCBs and produce there own TEK

extender boards relatively cheaply.
Not a lot of info on Pulsar,on the net, for some reason but i found this excellent writeup
from a local mob here in Australia see......
http://ultrakeet.com.au/write-ups/makepcbs http://ultrakeet.com.au/write-ups/makepcbs
Regards
George








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------------------------------------


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1.2

Re: MAKING EXCELLENT PCBs using toner transfer





Thu Mar 10, 2016 10:40 am (PST) . Posted by:

petrutech




I need to cut a round pcb, exactly 30 mm diameter. It is a double sided PCB, but I cannot find a decent method. Any ideas?

Thanks in advance!

P.S. I produce perfect PCBs using a glossy thin paper cut from old magazines. No matter the text or picture, I print above the initial text / picture. I tried different printers and toners. The best one so far is HP (I use an old 1010 HP printer) - but ONLY original toner, it's a huge difference between this toner and the replacement.

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1.3

Re: MAKING EXCELLENT PCBs using toner transfer





Thu Mar 10, 2016 11:09 am (PST) . Posted by:

edbreya




For one or a few, you can jig up some wood blocks, clamps or screws, and use properly-sized hole saws (the metal cutting type), even with a hand held drill. The main thing is to make a saw guide through-hole in one block so that it can run without the centering/pilot drill bit. The workpiece can be clamped between the guide block and a bottom block, then the hole saw with the pilot bit removed can be run through it. It takes some experimenting to get it right, especially to get the right board OD, which will be the saw ID, minus the kerf. Every time it's used, some of the wood guide will be worn away, so it will get sloppier - this is not a high volume solution.

On a milling machine or sturdy drill press, you can make centerless holes by securely clamping the workpiece to the table, but go very slow and steady with the cutting force.

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1.4

Re: MAKING EXCELLENT PCBs using toner transfer





Thu Mar 10, 2016 11:15 am (PST) . Posted by:

"Mike" mdinolfo2001




Regarding cutting a 30 mm diameter round PCB (Q- should this have maybe
been started as a new topic??)- Can you live with a pilot hole in the
center of the disc? If so, a hole saw might be viable to cut the disc.
30 mm is about 1.18", which is pretty close to 1-1/8 inches, which is an
available size for a hole saw (in the US at least- I don't know your
location). You might be able to find a 1-1/16" hole saw which might be
a better fit. I don't know what tolerance you consider to be "exact",
though, so even a metric 30 mm hole saw- available, for example, from
mcmaster.com- might not be sufficiently accurate.

Or you could try either a coping saw or a jig saw, followed up by hand
filing of the edge.

Mike N4MWP

On 03/10/2016 01:40 PM, sales@... [TekScopes] wrote:

I need to cut a round pcb, exactly 30 mm diameter. It is a double
sided PCB, but I cannot find a decent method. Any ideas?

Thanks in advance!

P.S. I produce perfect PCBs using a glossy thin paper cut from old
magazines. No matter the text or picture, I print above the initial
text / picture. I tried different printers and toners. The best one so
far is HP (I use an old 1010 HP printer) - but ONLY original toner,
it's a huge difference between this toner and the replacement.

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

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










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1.5

Re: MAKING EXCELLENT PCBs using toner transfer





Thu Mar 10, 2016 11:17 am (PST) . Posted by:

"Stefan Trethan" stefan_trethan




Minus the runout. I have been bitten a few times by that, those hole
saws can cut quite a bit more kerf than you would expect.

Another option might be to punch them, if you can find a way to align
the punch. It would be easy to find a 30mm greenlee punch, but you'd
need a press to bring it together precisely without the draw bolt. It
_might_ work in a very precise vice if you mount the dies with the jaw
bolts.

If it's just a couple, cut a polygon with a shear and clean them up on
a sander. If it's more than a couple I don't really see why you
wouldn't order them nicely routed out for a small fee.

ST

On Thu, Mar 10, 2016 at 8:09 PM, edbreya@... [TekScopes]
especially to get the right board OD, which will be the saw ID, minus
the kerf.










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1.6

Re: MAKING EXCELLENT PCBs using toner transfer





Thu Mar 10, 2016 11:26 am (PST) . Posted by:

"Stefan Trethan" stefan_trethan




On second thought, the punch is probably a bad idea. Greenlee punches
are designed to deform the slug....

ST

On Thu, Mar 10, 2016 at 8:17 PM, Stefan Trethan <stefan_trethan@...> wrote:
Minus the runout. I have been bitten a few times by that, those hole
saws can cut quite a bit more kerf than you would expect.

Another option might be to punch them, if you can find a way to align
the punch. It would be easy to find a 30mm greenlee punch, but you'd
need a press to bring it together precisely without the draw bolt. It
_might_ work in a very precise vice if you mount the dies with the jaw
bolts.

If it's just a couple, cut a polygon with a shear and clean them up on
a sander. If it's more than a couple I don't really see why you
wouldn't order them nicely routed out for a small fee.

ST

On Thu, Mar 10, 2016 at 8:09 PM, edbreya@... [TekScopes]
especially to get the right board OD, which will be the saw ID, minus
the kerf.









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1.7

Re: MAKING EXCELLENT PCBs using toner transfer





Thu Mar 10, 2016 11:34 am (PST) . Posted by:

edbreya




Yes, things can get pretty jiggly on hole saws. For best results, never use the retractable torque tangs on the arbor - always tighten it so the saw base is snug against the arbor shank, and the tangs are fully withdrawn. When it comes time to take it apart, you will have to use pliers and wrenches to unscrew the saw from the arbor. You can't do much about the eccentricity runout - these are not precision tools, but some are made better than others. As always, experiment first to make sure it will work as needed.

Ed












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1.8

Re: MAKING EXCELLENT PCBs using toner transfer





Thu Mar 10, 2016 1:03 pm (PST) . Posted by:

"Dwayne Verhey" torchddv




Some have mentioned hole saws, but that may not be accurate enough for a
piece "exactly 30 mm in diameter". For greater precision, try a
trepanning jig (aka circle cutter). Ideally they are piloted, but with
the workpiece firmly clamped, a nice sharp bit with slow speed and a
gentle feed in a drill press or mill should work well.

On 10/03/2016 1:40 PM, sales@... [TekScopes] wrote:

I need to cut a round pcb, exactly 30 mm diameter. It is a double
sided PCB, but I cannot find a decent method. Any ideas?









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1.9

Re: MAKING EXCELLENT PCBs using toner transfer





Thu Mar 10, 2016 4:40 pm (PST) . Posted by:

edbreya




Yes, this "exactly 30 mm diameter" could be a problem. There are two main parts to this: the diameter, and the center reference point on the board surface. Both should have some realistic tolerance. Sometimes the acceptable tolerance is subjective, depending on the application and the equipment available.

A fairly precise (but not "exact") non-NC machine solution could be done on a lathe. Presuming the raw board is a square or rectangle somewhat bigger than the desired finished diameter, it could be mounted in a 4-jaw chuck, and aligned to the proper center reference with a point tool mounted in the tailstock. The proper diameter could be set and cut to whatever precision the lathe and operator are capable of. There has to be enough waste margin, and backup sacrificial material, to allow the cutting operation without crashing any of the machinery, or having the piece collapse.

For larger quantity production, it would be best to have some tooling reference holes in the margin, and make a mandrel to hold the raw boards. A proper mandrel mounted in a 3-jaw chuck could clamp and center the raw boards by virtue of the tooling holes. Once the cutting diameter is set up, the operation could be repeated as often as necessary.

If possible, I'd recommend loosening the spec to something like "it has to fit inside this pipe" or whatever it is, and just using a hole saw that's close enough. If it does have to be quite precise, then a lathe would be a good way to go. Use a carbide tool, and protect the lathe with plastic film wrapping as much as possible, to keep glass particles from getting into everything.

Ed

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2

Books , to trade TEK 2246A





Thu Mar 10, 2016 10:30 am (PST) . Posted by:

kb5zxm




I got two original books for Tek 2246a one is full size and the other is quick bench ref. Can't see how to add pix.








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3.1

Re: 7854 RAM card upgrade only - any interest?





Thu Mar 10, 2016 10:44 am (PST) . Posted by:

test2cal




Fantastic, David.

Is the keyboard interface card modified?


Since we will almost certainly be using the new firmware, we may have a solution. I suspect that the marker bits test is still there in the new version because there are some rare scenarios that need it (initial manufacturing startup of the memory card, a system fault corrupting memory or a battery replacement) that would be handled by it.


The more I look into this, the more I realize that the old and new backup scenarios are fundamentally different: the old question was "has the RAM EVER lost power since the last power off?" and the new one is simply "What is the position of the switch at power on time?". Except for the rare scenarios of memory loss above.


I will look at the new diagrams later today.


Cliff


PS: I speculate from your last comments that you have or had a Tektronix connection. I am a retired IBMer.



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3.2

Re: 7854 RAM card upgrade only - any interest?





Thu Mar 10, 2016 3:16 pm (PST) . Posted by:

"David" david_william_hess




On 10 Mar 2016 10:44:14 -0800, you wrote:

Fantastic, David.

Is the keyboard interface card modified?
I managed to track down what they did and I do not think the MPU,
front panel, or calculator keyboard were modified.

I am not sure what it was used for, but the MPU drives the KBID line
allowing it to identify the external calculator keyboard based on an
internal jumper inside the keyboard which can be in one of 8
positions. The switch they added for the memory backup behavior
steals the 8th position which I assume was never used. I do not even
know if any of the other identification positions were used other than
the 1st one.

I am not sure what the external calculator keyboard identification
function is for. Maybe Tektronix planned on having more than one type
of external calculator keyboard.

I think the modification Tektronix made to rear panel connector board
A32 can be simplify enough so that no new board needs to be produced.
Instead of adding the 74LS05 and using 3 gates and 2 pullup resistors,
just add a series connected resistor and diode in series with the base
of a transistor to replace U15F. The collector goes to the switch and
the emitter goes to ground. The transistor operates as an open
collector inverter just like U15F. The resistor limits the base
current and the forward voltage drop of the diode increases noise
immunity.

Another way it could be done is to replace jumper K0 inside of the
external calculator keyboard with a diode and add another diode to
jumper K7. Then the oscilloscope would start up in self test mode
erasing the memory when the external keyboard is not attached and
start up in memory backup mode when the keyboard is attached.

Since we will almost certainly be using the new firmware, we may have a solution. I suspect that the marker bits test is still there in the new version because there are some rare scenarios that need it (initial manufacturing startup of the memory card, a system fault corrupting memory or a battery replacement) that would be handled by it.
That is what I would assume.

The more I look into this, the more I realize that the old and new backup scenarios are fundamentally different: the old question was "has the RAM EVER lost power since the last power off?" and the new one is simply "What is the position of the switch at power on time?". Except for the rare scenarios of memory loss above.
I agree.

I will look at the new diagrams later today.

Cliff

PS: I speculate from your last comments that you have or had a Tektronix connection. I am a retired IBMer.
Nope. The most I can claim is that Tektronix runs in the family from
my father working at LRL and I inherited a 2246 and 2247A from a
father-in-law who got them from his son who worked at Tektronix.










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4

OT 10Mhz references





Thu Mar 10, 2016 4:39 pm (PST) . Posted by:

mosaicmerc




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















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5

2465A focus





Thu Mar 10, 2016 4:40 pm (PST) . Posted by:

chipbee40




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.

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6.1

Re: 7854 Repair & Restoration





Thu Mar 10, 2016 4:53 pm (PST) . Posted by:

"David" david_william_hess




On 09 Mar 2016 19:24:54 -0800, you wrote:

Found it.

After hooking the jumpers back up and running it a while with the sweep, I'm able to tap on U50 (kinda hard) with a ceramic screwdriver and induce the exact fault. Beamfinder deflected to the top of the CRT.

I can also tap on it again and it goes back to normal.

So then, I guess U50's non-soldered connections just need to be cleaned to make full-time positive contact again?

If Francis couldn't get a display on the scope before, I guess that the roughness of shipping caused the connections to rub and make partial contact again. That would have led to me being able to get a display on it once I powered it up...
I finally found a diagram showing a lead welded to the top of the 12
pin TO-8 package used for U50. That lead is suppose to be welded so
maybe the weld came lose. I verified on my various 400 MHz 7000
mainframes that the case of U50 is suppose to be grounded but it is
not clear how ground is used by the hybrid and the schematics do not
show anything.

Given this, I still think you have a bad solder joint or
intermittantly open resistor *near* U50.

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.









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Re: 7854 Repair & Restoration

Ed Breya
 

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


Re: 7854 Repair & Restoration

Brian Bloom
 

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

Yes, that is exactly what mine appears to be.


Re: 7854 Repair & Restoration

Ed Breya
 

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


Re: 7854 Repair & Restoration

Brian Bloom
 

I finally found a diagram showing a lead welded to the top of the 12
pin TO-8 package used for U50. That lead is suppose to be welded so
maybe the weld came lose. I verified on my various 400 MHz 7000
mainframes that the case of U50 is suppose to be grounded but it is
not clear how ground is used by the hybrid and the schematics do not
show anything.

>Given this, I still think you have a bad solder joint or
intermittantly open resistor *near* U50.

Next chance I get I will visually inspect the solder joints, then carefully remove the vertical amp board and clean & re-seat the leads of U50 & U150. If any solder joints look suspect, I will reflow them.

As for the lead to the top of U50 - I'll confirm whether mine was/is welded to the can. It just looks like a brass ball point contact pressed against the case. The contact looks pressed into the spring loaded bracket that holds U50 down.

>>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.