Malcom, those look great!

FYI, There's a guy selling reproduction feet for the 4xx scopes on eBay (not the lathe-turned round ones‎.) I won't name him since he didn't give me permission but some of you probably know him. He doesn't always have them listed but I'll just say they're absolutely fantastic. They are identical to the originals but with a bit harder plastic. He sells them for $25 for a set. Their only downside (and it's very minor at that) is that one side is a bit unfinished due to how they are cast but the set I put on my 475 look and work great.

As a side note, I sent him some 335 & 314 feet to reproduce and, in my opinion, he did a fine job on them, though he wasn't as happy with the end product so he decided not to continue making any more. On these particular feet the rough side ended up having to be the face/bottom of the feet and he didn't like the way they turned out. Since the 335/314 feet are unavailable anywhere (and they're worse than the 4xx feet for breaking) ‎I am 100% satisfied with them. It's off topic for this thread but if anyone is interested in 335/314 feet let me know off list. If there are enough out there maybe he'll make some more for us, casting imperfections aside.

John

Sent from my BlackBerry Z30 smartphone.
From: Malcolm Hunter malcolm.r.hunter@gmail.com [TekScopes]
Sent: Saturday, March 12, 2016 13:14
To: TekScopes@yahoogroups.com
Reply To: TekScopes@yahoogroups.com
Subject: [TekScopes] 465 foot 3d model


Hi,

I modeled a replacement cable-wrap foot (actually for my spares 475). It's
on Thingiverse if anyone would like to make use of it.

http://www.thingiverse.com/thing:1410827

I just needed something to stop the scope from tipping over. I used PLA,
which is good enough for that. I'm not sure what would be the best material
to print it with and how well it would hold up in general use.

Malcolm


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

Perfect - Thanks!

I buzzed out the rest of the transistors and diodes across the A10 board, and found only one more - CR1947.

On 12/03/16 18:14, Malcolm Hunter malcolm.r.hunter@gmail.com [TekScopes] wrote:

I modeled a replacement cable-wrap foot (actually for my spares 475). It's
on Thingiverse if anyone would like to make use of it.

http://www.thingiverse.com/thing:1410827

I just needed something to stop the scope from tipping over. I used PLA,
which is good enough for that. I'm not sure what would be the best material
to print it with and how well it would hold up in general use.

I would expect
http://www.shapeways.com/materials/strong-and-flexible-plastic
to be a good starting point.

Hi,

I modeled a replacement cable-wrap foot (actually for my spares 475). It's
on Thingiverse if anyone would like to make use of it.

http://www.thingiverse.com/thing:1410827

I just needed something to stop the scope from tipping over. I used PLA,
which is good enough for that. I'm not sure what would be the best material
to print it with and how well it would hold up in general use.

Malcolm

Any well-regarded cross reference for some of the Tek transistor p/n's?

http://www.reprise.com/host/tektronix/reference/default.asp http://www.reprise.com/host/tektronix/reference/default.asp

Found 3 shorted transistors so far: Q1942, Q1944, and Q1948. Might be a few others in this area.

Any well-regarded cross reference for some of the Tek transistor p/n's?

I have always been suspicious of the mini-Berg sockets and have run

>into a couple cases where good contact was not being made. I think
>the machined collet pins which you mention below are more reliable.

What I can do while I have the amplifier/driver out is take a 22 gauge wire, insert it into the socket, and check continuity/resistances while I give the wire a wiggle. If one of those sockets shows an intermittent connection or a resistance, would you suggest I replace all of them with augat machined sockets? I have some 24pin dip sockets I can pull apart. I also have the berg sockets from some old 475 boards.


A question for you that's a bit off topic - I want/need a decent current probe for troubleshooting these 485's. (I'm sure I'll want it for other things in the future as well.) Can you recommend a good current probe arrangement that I can keep an eye out for that actually might show up on the market for less than a couple hundred dollars? I'd like to get something close to or sub $100, but I don't want to go over $200.

It's too bad that I didn't get in on the whole AM503 & probe market while they were going for $50 each...

Hello all,


This is very interesting topic, to which I was somewhat familiar about 3-4 years ago.
Anyway:
1- I am interested in such a board, count me in, if ever gets produced.
2- I am also interested in David's board extenders (2 of them actually), if they get produced again.
3- Is there a downloadable/purchasable manual for this above B1000000 version? I would like to have a copy.
4- Late to the party, I know, but I managed to replace the FPLA, with code directly injected into the ROMs. If anyone interested, let me know. I still have the files, though you can find them here, if one is searching through my postings...


Best regards,
Bogdan

The problem with the "replacement" knob on the 'bay is that the Al insert is more in front (from the faceplate) than with the original. The hex fastening screw is as well. I'm not at all convinced that it (the inner knob) would fit, even after removing the plastic black insert. I have both one of those knobs (I think). I'll be in my lab again early next week and can try if it fits my 7A13.


Raymond

hi Laura, tried your procedure to no avail
While I was there I also tried the so called EXERCISER 03 (EAROM clearing) described at page 6-16 of the manual ( both in CAL/NO CAL position) : also to no avail : the dots re still there
Thanks anyway; let me know if you have any other idea
adri










---In TekScopes@yahoogroups.com, <vegibear11@...> wrote :

Before you replace the old EAROM try this:

Turn the power off.
Move the cal/nocal jumper to cal.
Turn the power on.
Move the cal/nocal jumper to nocal.
Turn power off.
This will force a refresh write to the EAROM and may cure your dots.
Refer to the service manual page 5-9 if needed.

Laura

It's a matter of what kind of precision you need with regards to what you work with. I became a little frustrated with drift of some less-than-best reference oscillators in some of my test equipment when working at GHz frequencies. I now use a HP Z3816A GPSDO feeding a HP 5087A distribution amplifier whose multiple outputs feed all of the equipment on the bench via their external reference inputs. It's nice when generating or measuring a signal to know that you are basically spot on.

And the reference standard is there if needed to calibrate other oscillators. For that I use either a HP K34-59991A phase comparator, a 3575A gain-phase meter or simply an oscilloscope. The scope and K34 unit is for less demanding applications while the 3575A gives me reference/DUT phase comparisons at 10 MHz down to 1/10 of a degree accuracy.

And, no, I am not a "time nut." My wristwatch runs about 30 seconds fast each month and the old analog clock on the wall keeps me properly on time for everything in my life.

Greg

The dongle makes economic sense if there is no keyboard (and no plans to add one). One D connector and a standard backshell - not costly at all, and no internal mods (except for plugging in the new memory card).

Good test from the keyboard connector. Was that on a B100000 scope or an earlier one? Should I repeat it on mine (B063xxx; old RAM & separate ROM cards)?


Everything in the mainframe that is MPU controlled and is not a physical control position seems to be backed up in RAM. The Vertical and Horizontal mainframe modes, the CRT Display Mode (Scope / Stored or Both), the cursor on / off state, the cursor positions, and all on-screen text are retained. Even the GPIB ID button version report comes back. You saw the Self Test Completed message in memory back up power on only because you did not clear it before turning the scope off. And as you said, it only beeps after a self test.


No plug-in information is stored, but the latching pushbuttons and switch settings don't need backing up. There are a few exceptions (7D11, 7M13 come to mind). Overall, this is as close to a non-volatile scope as you are likely to see. All the more reason to upgrade the memory to internal battery back up.


I think I would prefer to just tack 3 wires onto the A32 board and put the rest on a perfboard on the back of the switch. It can be preassembled away from the scope and means less fooling around with A32.


Cliff

After doing research on the issue, it appears that the economical approach was a Trimble 65256 OCXO ($16) as it is well respected, has low phase noise, is sine wave and is SC cut.
Morion 89A was a close second. The Epson Toyocom TCO- 6920, while interesting, I can't find any data on it and it's signal was under 0 dBm.


As a low risk approach I ordered a $16 Trimble OcXO, 12V, 10Mhz Sine, o - 7dBm output unit that didn't look banged up and the current draw isn't unreasonable.
Once all is well I'll make a low noise linear PSU and an isolated 50 ohm distribution amp and feed the various instruments.
As a useful spin off, I'll do a divide by 2 reference for my DC505A counter to replace its tank circuit. I believe it's a 5MHz ref.

On 10 Mar 2016 23:49:17 -0800, you wrote:

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.

I have always been suspicious of the mini-Berg sockets and have run
into a couple cases where good contact was not being made. I think
the machined collet pins which you mention below are more reliable.

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

I cut those out of sockets and SIPs to use them as low profile collet
pins for ICs, transistors, and any other leaded part I might want to
replace later.

http://www.mouser.com/Search/ProductDetail.aspx?R=310-93-164-41-001000virtualkey57510000virtualkey575-193164

On 11 Mar 2016 12:01:09 -0800, you wrote:

I looked at that vertical amp board again and found that the cans are plugged into Berg sockets, and there is thermal grease underneath for better cooling. Also, I hadn't noticed before that two of the pins on the bigger output amplifier are much longer, and were passed though unplated, un-socketed holes, for connection to the deflection plates. There's no solder on them either, and I can't remember if I clipped them off from other leads (very unlikely), or if they were plugged into loose Berg sockets attached to the CRT lead wiring.

What color was the thermal grease? I assume it was white indicating
zinc oxide?

I never removed one of the hybrids from its board.

If the 7854 hookup is made that way, that's another possible location for intermittent connections.

I had my 7834 vertical amplifier board removed several times when I
was messing with the CRT to try and fix its geometry problem. The
first time I did not realize that the leads from the output hybrid to
the deflection plate pins had collet socket pins on the CRT side and I
unsoldered the wires from the collet socket pins leaving the collets
pins in place. The wires were soldered to the thick leads from the
output hybrid.

I must have taken the vertical amplifier board off of my 7854 to
replace R160 but the only thing I remember about it is the lesson from
my 7834; I pulled the collets straight off of the CRT leads instead of
unsoldering the wires. I think the wires were soldered directly the
thick leads from the output hybrid. (I just verified this with visual
inspection.)

On 11 Mar 2016 16:49:17 -0800, you wrote:

Thank you for looking into the TO-8 amplifier arrangement for me, Ed & David. Now I know exactly what to expect.

From your descriptions, I feel the best way to go about pinpointing and solving the issue is going to be to pull the board, carefully pull the U50 driver, inspect, clean off the old paste and the leads with IPA, inspect again, reapply thermal paste, then gently re-insert the amp into the sockets. I might as well do the same for U150 while the board is off.

First and foremost, I am going to put magnification to the board and check all the solder joints of surrounding components and reflow any suspect ones.

Also, only U50 on mine has the plastic clamp.

I checked and all of mine, 7904, 7834, and 7854, are built the same
way. They have the plastic clamp and ground connection on U50,
insulated leads on the output hybrid soldered to wires, and a stud on
the output hybrid bolted to the aluminum bracket under the board.

Hopefully this solves the problem. I did 'spudge' the potentiometers and resistors on the board, but only tapping or pressing on U50 induced the fault. I don't think this alone can rule out the possibility of a faulty component in the driver or amps surroundings. Ensuring all of the connections are positive is definitely the #1 step.

The only major question I have here is about thermal paste.... all I have on hand is Arctic Silver from RS. It's the higher end stuff that they carry. Do you think that will be sufficient? Should I find a resource for a Tek recommended thermal compound - or try to salvage the 25-35yr old stuff that's already there?

Don't reuse the old thermal paste. Tektronix probably used a standard
silicon oil and zinc oxide thermal paste like Wakefield 120. It is
not critical so use anything you happen to already have as long as it
is not electrically conductive.

First off, please forgive my mis-spelling in the title...

It was a typo, honest, I know how to spell Tektronix...


So, I've found a interesting hint. The 1.4V supply, which I guess is supposed to be regulated to 1.4V by Q2092/Q2094 is sitting at -1.8V all the time - even through an erase cycle. What I haven't figured out yet is what is supposed to source current into the 1.4V rail, as Q2094 appears to be a shunt regulator of sorts...

I guess it's a question of what you mean by 'precision'. If you are happy
using WWV as your 'reference' and 'zero-beating' your 'house standard'
against that, then you don't need anything else. However, if you want
something that is 'always right', a GPSDO is hard to beat.



It's also reasonably affordable.



I've had GPSDO's 'die'. Therefore, having the ability to turn it on and
have it up and accurate in 20 or 30 minutes or so is very nice. Having a
separate 'house standard' that you, from time to time, 'adjust' to bring
back 'on frequency' and is more easily replaced is, in my opinion, a good
combination.



Now, if you want to dig deeper into the performance/math of the systems, you
can spend a lifetime (or remaining lifetime, in my case) doing that. It is
quite satisfying if you can spare the time to do it. No pun intended.



Joe



From: TekScopes@yahoogroups.com [mailto:TekScopes@yahoogroups.com]
Sent: Friday, March 11, 2016 12:23 PM
To: TekScopes@yahoogroups.com
Subject: Re: [TekScopes] Re: OT 10Mhz references





I am curious what you guys are doing that requires that sort of
long-term precision?

On 11/03/2016 8:44 AM, 'J. L. Trantham' jltran@att.net [TekScopes] wrote:

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.

Yes, Håkan. Exactly what I was looking for.

Thanks!
Barry - N4BUQ

For some reason, I can't seem to open the file on your hard drive ;-)

I suppose I can see the need for ultimate precision and stability for those of you set on proving Einstein right about the effect of gravity on time. But for us plebeians who are still living in a world populated with 100 or 200MHz scopes, it might be overkill. ;-)

On 11 Mar 2016 13:20:45 -0800, you wrote:

The dongle approach would add the cost of two connectors and a housing, Also all of the cable wires would have to be connected through (another circuit board or a wire and soldering iron session).

I was thinking that the dongle could be used instead of the external
keyboard.

The snap off printed board adds to the area ($) and would have to be the full height of the memory board, I guess, which is too big and it would have to snap in two to discard the excess area.

It would probably not be worth the extra cost given the simplicity of
the circuit. See below.

I tried to open my keyboard and ran into a problem with one screw that is so badly jammed that I may have to drill it out and replace it. Maybe inside the keyboard is not so easy after all.

I had the same problem with the keyboard and used a small socket
wrench with a T10 Torx bit to force the screws out. If it does not
turn, force it. If it breaks, it was defective anyway.

All of these seem like overkill to install just three components. If buyers will be doing all of their own mounting and soldering of sockets and components on the memory card, a tiny piece of perfboard with copper around the holes is a very common prototyping item for less than a dollar. We could just add that to the kit with instructions. All options will require some soldering somewhere, so no one solution has the advantage there, unless we provide a fully preassembled dongle based version at considerable extra cost.

I tested the single transistor open collector inverter wired onto a D
connector and it worked fine. The 7854 booted up in memory backup
mode instead of memory test mode when the dongle was attached to the D
connector in place of the external keyboard. I will make some
measurements of the signal voltages to verify good noise margin.
Adding a base-emitter shunt resistor might be necessary.

I had not really taken notice before but in self test mode, the 7854
beeps and displays the self test message. In memory backup mode, the
7854 displays the self test message without beeping.

Also in memory backup mode not only is the state of the vertical and
horizontal mode switches maintained, but so is the CRT mode of scope,
stored, or both. Tektronix thought of everything. I wonder if any
state *isn't* retained.

The rear A32 area may be the easiest to access after all.There is room in there to stick on a small pefboard using double faced foam tape, or the board might be soldered directly on the terminals of the new switch. Getting the three ribbon cables correctly replugged to A32 does take good light and a bit of dexterity.

Cliff

I would air wire it to the existing A32 rear panel connector board.

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

Well that's a bummer.

I wonder if it's just a variation of the same knob, or if there is some other difference such as the shaft diameter..
If the only difference is the black plastic insert... well..
If I was the person needing that knob, I would buy this one and cut the black insert out.
The only problem is that I would have to physically have the knob in order to make sure that it'll fit the 7A13 in the first place.

Maybe the seller wouldn't mind breaking out a caliper and taking some measurements, though...?

*Actually, this knob appears to be the very same knob that is used on the 454 for V/div control. If it is, I have ones on my 454A that I could measure so we'll know if it's the same apart from the insert*


Making ones own replacement knobs may well end up being a very useful project for many people, though. Tek replacement knobs are bound to disappear at some point.

A database of replacement knobs would be useful... then part B of that database project could be adding 3D scans of good knobs so people can print off or machine replacements.

-Brian