Date   

Re: 549 transformer question

Michael A. Terrell
 

Tom Lee wrote:
Hi Michael,

I think you meant to say that 807s were used in early B&W sets, not color ones. The 6BG6 was very popular in the early sets, and was basically an 807 in octal form.
I think that it was used in the RCA CTC4 chassis. I gave that set away in 1972, when I went into the Army so I could be wrong. Early TVs like the small electrostaticly deflected Pilot TVs didn't use a flyback, so it was a free running oscillator for the HV supply. It was basically a low grade X/Y scope with video applied to the Z axis. They used a three inch round CRT with a P4 phosphor.It was the mid '60s, the last time that I saw a Pilot TV.


Re: 549 transformer question

Roger M
 

Hi Chuck,
Yes, I agree, the best solution is a rewind of the transformer.
Yet, in the continuum of poor, fair, good, better, and best, there
may be a method that is acceptable to the extent that its "good
enough".

This topic interests me but I have to admit I'm hampered by not
having even one failed transformer in my possession. In my life
I've owned and used a prototype 546 (for some 25+ years),
a rack mount 547 (some 15 years) and now a couple of recently
acquired bench model 547's. None of which have ever exhibited
the HV disease.

Some weeks ago I purchased some Tek parts needing a new home.
Among which are some apparently rewound 120-0308-00 transformers
at least one of which I'd swap for one in otherwise good condition
that has the thermal runaway issue.

On the topic of the unobtainable ferrite cores I should ask:
was Tek's vendor Stackpole? Do we know the mix type of the ferrite?
Not wanting to risk damage in disassembling a transformers I have
on hand, I assume the core is gapped at one or both of the center
legs. Have you noted what the gap dimension is?

Looking at what is currently (and readily) available, there's
the Ferroxcube core E47/20/16 in 3C94 material (for example).
Its too thick for direct fit into Tek's plastic HV enclosure,
but that's what a clamp jig and a Home Depot (Harbor Freight?)
diamond blade tile saw are for.

I plan to order some and "dink around" as time permits...

-Roger


Re: Waking a slumbering 475

Jeff Davis
 

Hi guys,

Thanks for the kind words on the N0DY scope feet. It was kind of a happy accident that I started making them. I had the same problem with feet crumbling to dust on the 465s and 475s that I was repairing, so I decided to see if I could make my own.

Just as an FYI, for those folks outside of California, you can save a couple of bucks on sales tax by going to the n0dy.com site instead of eBay (no Marketplace Facilitator sales tax has to be collected). And regardless of location, most items are slightly cheaper on the web site since there's no cut that has to be paid to eBay.

Jeff / N0DY

________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Glydeck via groups.io <glydeck=aol.com@groups.io>
Sent: Monday, February 8, 2021 3:35 PM
To: TekScopes@groups.io <TekScopes@groups.io>
Subject: Re: [TekScopes] Waking a slumbering 475

Ward,

I’m a happy customer of N0DY as well. He’s also a member of TekScopes. Here’s the link to his online store.

https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.n0dy.com%2F&;data=04%7C01%7C%7Cc7fa058671d446d94c2608d8cc8a4e33%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637484241678757361%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=WpPK27B0F5mbqkttEI%2Fp2bWb9VKaJYQo3KqSfmaJe80%3D&amp;reserved=0

George KD6NEW
On Feb 8, 2021, at 2:01 PM, Jeff Dutky <jeff.dutky@gmail.com> wrote:

Ward,

Running the 475 up slowly on a variac is actually one of the performance test procedures, as it will verify that the LOW LINE indicator is working, so if you have a variac and feel like starting the 475 up nice and slow, it will be fine.

The 475 with DM44 does not have a vernier on the delay time position control, rather it has a simple knob (like yours, and as you have seen in pictures): the calibrated delay is, I believe, indicated on the DM44 LED display.

The cord wrap feet do not hold up well over time. I second the recommendation of n0dy-jeff as a source for excellent 3D printed replacements.I have several sets of his cord wrap feet for a couple of 475s and a 475A, and could not be more pleased.

I also have a personal connection to these instruments: my father was a service engineer working on laboratry equipment and data machines, and used a Tek 475 for many years. I have that 475, now 45 years old and still working: it is a wonderful instrument. I have also done some repair and restoration work on the 475 and 475A, and have found it to be enjoyable (if not always easy). I hope you get plenty of enjoyment out of your 475.

-- Jeff Dutky





Re: 2445B 2467B - non Tek probes

Harvey White
 

Right, if you mean the entire box, then that has the compensation network in it.  If you mean just unscrewing the BNC connector and transplanting that, the resistor is about a 1/10th watt resistor hidden in the probe innards.  It is possible to take the probe apart and gain access to that resistor.  At the moment I don't remember exactly how, but the BNC plastic shell is NOT molded in place and can be removed.

IIRC, the ID function is in the probe itself, and shorts an additional wire to ground, (try shorting the ring to ground at the scope end).

What the plugin does is up to it (move trace, "identify" or ground trace....

Harvey

On 2/8/2021 8:45 PM, Jeff Dutky wrote:
Harvey, Ondrej,

I've had a lot of success merely swapping the BNC assembly (hex nut and BNC with readout pin in the plastic shell) from one probe box to another. I've done this successfully for P6121s, P6131s, and P6106s, using similar (otherwise damaged) probes as the donors. The scale resistor, at least, seems to reside entirely in the plastic housing around the BNC connector.

I have NOT tried this with any probes that have the ID function.

-- Jeff Dutky





Re: TDS510 or TDS460A or 485 scopes as upgrade

 

I'll throw in my recommendation for the 2465 (no A, no B), especially if you can get one with the counter/timer option. It's lower bandwidth than the A or B models, but it has direct physical controls, rather than rotary encoders, and it doesn't have a (now likely dead) battery backing up it's NVRAM.

Also, you are less likely to run into a counterfeit (maybe I'm just paranoid about that now, but the fact there are people out there mangling 2445Bs to rebadge them as 2465Bs makes me very wary).

I've been lusting after a 485 for a while, but my bench is already groaning under the weight of 40 year old scopes, and I've got enough to worry about keeping a 475 working.

I will leave it to others to sing the praises of a 7000 series mainframe.

-- Jeff Dutky


Re: 2445B 2467B - non Tek probes

 

Ondrej,

I've been looking at the very nice passive probes manufactured by Probe Master, as replacements for Tek's P6075A, P6106, and P6131, as they offer probes with the right specs that also have a scale readout pin. Tyrosys and CalTest also offer probes with readout pins, and the prices seem reasonable.

-- Jeff Dutky


Re: 2445B 2467B - non Tek probes

 

Harvey, Ondrej,

I've had a lot of success merely swapping the BNC assembly (hex nut and BNC with readout pin in the plastic shell) from one probe box to another. I've done this successfully for P6121s, P6131s, and P6106s, using similar (otherwise damaged) probes as the donors. The scale resistor, at least, seems to reside entirely in the plastic housing around the BNC connector.

I have NOT tried this with any probes that have the ID function.

-- Jeff Dutky


Re: TDS510 or TDS460A or 485 scopes as upgrade

Ozan
 

Hi Giuseppe,
I am sure you will get many opinions but here is the opinion from someone who owns a 1054Z, few analog Teks, and few TDS class Teks. TDS510 and TDS460 bandwidths only give you the advantage for repetitive signals otherwise ADC sampling rate is not fast enough to capture at the BW of the scope (usually you need to stay below sampling_rate/2.5). In summary I don't think TDS460 (even TDS510) would give anything over 1054Z. They have much better user interface than 1054Z but lack several good features like Ethernet/USB/Logic decode.

I own a 485 and it is a great scope. If you can get one cheaply 2465B and 2467B would be even better. Note that 485 doesn't have cursors (need to read from graticules), 2465B/2467B have cursors. Although 485 is older it competes nicely with my 2467B, I like them both.

I am sure there will be others trying to convince you to 7000 series analog scopes, they look interesting if you have the space.
Ozan


Re: Sick SG504

Tom Lee
 

Ah, yes, great example, Chuck. Hometaxial no more. The later 3055 clones, though, at least pretended to conform to the original datasheet numbers. The BFR94A variants don't even make a half-hearted effort to do so.

-- Cheers
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 2/8/2021 17:16, Chuck Harris wrote:
How about 2N3055?

-Chuck Harris

Tom Lee wrote:
Thank you for the very helpful information, John. One thing that's always mystified
me is that the Philips/NXP BFR94A doesn't even have the same die as the "original"
BFR94A in the SOT122E. The breakdwon voltages, capacitances, max IC, ft, etc. are all
different. I can't remember ever encountering a similar situation where the same
transistor part number is used for such different devices (I'm excluding the
data-compressed SMD marking codes).

--Tom


Re: Sick SG504

Chuck Harris <cfharris@...>
 

How about 2N3055?

-Chuck Harris

Tom Lee wrote:

Thank you for the very helpful information, John. One thing that's always mystified
me is that the Philips/NXP BFR94A doesn't even have the same die as the "original"
BFR94A in the SOT122E. The breakdwon voltages, capacitances, max IC, ft, etc. are all
different. I can't remember ever encountering a similar situation where the same
transistor part number is used for such different devices (I'm excluding the
data-compressed SMD marking codes).

--Tom


Re: 2445B 2467B - non Tek probes

Harvey White
 

The passive probe pin for readout scaling requires an offset pin.  Electrically it's a resistor to ground.  I haven't seen any replacement BNC connectors like that, so you'd have to adapt an existing probe box with the proper resistor to the task.  Dead 6xxx probes with readout pins are relatively common, so you could redo the box with a BNC on one end, and the existing BNC (and pin) on the other.

Harvey

On 2/8/2021 6:54 PM, Ondrej Pavelka wrote:
Hi folks,

I have 2445B for quite many years, thanks to this awesome group and some super helpful members like Siggy or Chuck and others I dealt with leaky caps on the A5 board, backed up and copied calibration over. It's all good and I can't really be happier. Well except I just acquired 2467B in basically new condition. The only problem I have the P6136 probes becoming brittle and falling apart. The 2467B came with two Testek 600MHz probes but as much as I could live without the ID button, not having the coded ring is a nightmare when swapping between probes.
Anyone on here managed to 3D print or make in any other way adapter which would make the probe coded? I can clearly see the Testek probes are superior to P6136 but the lack of the coding ring is driving me mad. I was swapping between coded and unconditional probes during one calibration of an instrument and guess what..... Yes I completely ruined the calibration and had to redo the entire 6 hour process again......

Any way to convert the Testek probes oris there a pass through adapter to make the probe coded?
I didn't really appreciate the ingenuity of the coded probes up until I lost it.





Re: I built a TM500 mainframe tester, and updated the design. Someone might find this useful?

Larry McDavid
 

Here is another update on our group purchase of the set of four circuit boards for Jared Cabot's TM500 tester described in his original email below.

I have received the circuit boards from PCBWay in China. The boards look really good! Standard green FR4, solder-masked and silk screened. The main board is ENIG gold plated and two other boards are HASL solder coated. The outside front panel board is solder-masked white and silk screened with black nomenclature.

I am packaging the boards in sets of one each of the four boards and stretch-wrapping them to a stiffener for the flat mailer envelope I will use for shipping. I've heat sealed each board in its own poly bag for protection. There is actually a lot of work in all that! I'll report again when I have shipped the boards.

I have a few extra complete sets of boards but I have a list of members who asked after I closed the orders; I'll ask those members individually and announce here if there are any more sets left after that.

I do have a few extra boards, except for the main circuit board with the edge connector. I have a few front panel boards with circuitry, some rotary switch wiring boards and some silk-screened front panel nomenclature boards. The nomenclature boards might be especially nice if you are building your own tester. I will price each of these boards at $4 plus shipping. Shipping will be easier since there is no long main board available to ship. Please contact me ***off-list*** if you are interested in any of these extra boards.

Larry

On 12/31/2020 11:27 AM, Jared Cabot via groups.io wrote:
Hi all,
I have been accumulating TM500 modules and mainframes for a little while, so I recently finished building an 067-1201-99 TM500 mainframe tester from the Tek construction notes floating around.
I updated the design somewhat and designed it for simplified construction (Not a single wire to strip and solder!) and I thought someone here might be interested in taking a look or even building one themselves.
Here's a link to the youtube video:
https://www.youtube.com/watch?v=Afwqtc6Fxd4
And here's a link to the google drive with all the gerbers and schematics and stuff. I went so far as to rewrite the manual with the alterations and corrections included.
https://drive.google.com/drive/folders/1yj52Z_BtGZ7Q9BB2jS9Lf2Uz39turS4-
Direct link to the new manual:
https://drive.google.com/file/d/1iqpcqheb01qMioQwcUhyWv6A37v2HPro/view?usp=sharing
Let me know what you think, and let me know if you see any errors that need correcting. :)
Regards
Jared...
--
Best wishes,

Larry McDavid W6FUB
Anaheim, California (SE of Los Angeles, near Disneyland)


Re: Wrong cable... How bad is it?

Jean-Paul
 

Hello all

Mia culpa for a few errors,

To Dave Brown, sorry for my Poor mémoire on the RG numbers...6 vs 8....
the Tektronix précison cable for SG503 is not 1/2m but 36"
12-0482-00
Special double braid cable and specific precision BNCs.
Look on epay and ham fleas....
Years ago I bought a bunch new in original tek packing from an ex Tek engineer.

Dennis had made fine TDR measurements on several cables in this thread,
https://groups.io/g/TekScopes/topic/my_tdr_evaluation_of_the/31377831

Bon Soirée

Jon


Re: Wrong cable... How bad is it?

Tom Lee
 

The solution depends on what problem you're trying to solve. If you need to meet the stringent flatness spec of the SG503, then you need the cable (or equivalent). Dennis has published an excellent analysis comparing off-the-shelf cables with the official Tek cable. To meet Tek's spec, you cannot assume that "50 ohm cable" is 50 ohm cable. Most are 52 ohms, nominally, and not controlled to that value with any precision.

The need for the special cable is caused by the SG503's sensing the amplitude at the front panel connector, not at the ultimate point of delivery. As such, any load mismatch will cause some non-unity VSWR and thus, some departure from flatness. Also, cable loss won't be corrected, either, but that's a secondary problem.

If you don't need the factory-level flatness, you can get by with short lengths of regular cable. The degradation in flatness will certainly be measurable, but may be acceptable (again, depending on your use case). Note that the SG503's sensitivity to cable characteristics is shared by virtually every other sig gen on the planet.

The SG504 replaces the need for expensive coax with the need for a special levelling head (which is almost never found accompanying the plug-in -- see the many efforts to homebrew them, such as the nice one by our own David Partridge). The 504 uses a different arrangement where the amplitude  is sensed at the point of delivery, rather than at the generator's front panel connector. If you use no (or negligible) additional cable, the amplitude will be controlled to exquisite precision by the levelling/leveling loop.

-- Cheers
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 2/8/2021 14:20, G Hopper wrote:
This is an interesting thread since I, like Stephen, have long assumed my
cables were ok. I'm no longer 100% sure and need to check them.

However, what REALLY caught my attention was Jon's comment "For use over 20
MHz eg with SG503 or SG504 or fast pulses like PG506, a calibrated
special 1/2 m Tektronix cable is preffered..."

Having one of those devices, and not having the special cable, what's the
solution?

Is the solution to the issue: getting/building a cable (with 50 ohm coax)
of exactly 1/2m length? or is it something else? There must be a solution
other than acquiring an original cable since Tektronix would have had a
specification and had cables made to that spec. I've got to believe that
it's something that mere mortals can reproduce. :-)

If it is, where can one gather the information?

Cheers,
Grant

On Mon, Feb 8, 2021 at 2:09 PM Jean-Paul <jonpaul@ix.netcom.com> wrote:

Stephen welcoming to the wonderful world of wired transmission of Signals,
researched since the earliest days days of Telegraph, telephone and vidéo.

First, câble Zo is important in a matched system eg 50 ohm cal gen and 50
ohm load.
For audio tests with 1 M Ohm , no difference.

As the frequency, and bandwidth go up, and rise times get short, the Zo
is more and more critical to obtaining low reflections, as is the cables
VSWR, attenuation and phase vs legnth and frequency.

Thus RG174/u is 50 ohm, but dia ~ 3 mm so rather high atten. db/ meter,
while RG58/u, is thicker and RG6/u very thick 12 mm so much mess atten per
m thoughts all are 50 Ohm.

For use over 20 MHz eg with SG503 or SG504 or fast pulses like PG506, a
calibrated special 1/2 m Tektronix cable is preffered . Generally the
shorter the cables the better for cal use.
Finally the wire and insulation quality and connectors precision are
factors.

We use the Tektronix and Genrad precision cables for critical applications
and avoid the cheap, poorly made Chinese clones.

Suggest that you consult the Belden Wire site papers and applications
notes, as well as the detailed specifications on whatever cables,
connectors and wire you use.

Bon courage

Jon










Re: 2445B 2467B - non Tek probes

 

On Tue, Feb 9, 2021 at 12:54 AM, Ondrej Pavelka wrote:


I can clearly see the Testek probes are superior
to P6136 but the lack of the coding ring is driving me mad.
I couldn't find 600 MHz Testec (Testek?) passive probes, 500 MHz being the max. What did you find that makes the Testek probes superior to P6136's? Are you talking about the (1.2 GHz) active ones?

In most cases, it doesn't make much sense to use any passive probe at these high frequencies, because of their large input capacitance of around 10 pF min. I don't know any passive 1:10 probes spec'ed higher than 500 MHz.

Tek P6137's aren't very expensive and recommended for the 2465B/67B. I guess that makes more sense than trying to add a readout feature.

Raymond


Re: Sick SG504

Tom Lee
 

Thank you for the very helpful information, John. One thing that's always mystified me is that the Philips/NXP BFR94A doesn't even have the same die as the "original" BFR94A in the SOT122E. The breakdwon voltages, capacitances, max IC, ft, etc. are all different. I can't remember ever encountering a similar situation where the same transistor part number is used for such different devices (I'm excluding the data-compressed SMD marking codes).

--Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 2/8/2021 16:08, John Bennett wrote:
Eric,
I misspoke regarding the package type for Q70 (I should have looked it up). You want the 4-tab studded package (it has two emitter tabs) referred to in various data sheets as SOT122E, SOT48, and I think TO-117 (not TO-128). In any event, the BFR94A in that form factor should work. I have also used the the Motorola MRF587 and MRF511 with some success, although there are trade offs:
Typ. fT (GHz) VCEmax (V) Max Diss (W) ICmax (ma)
BRF94A 3.5 25 3.5 300
MRF587 5.5 17 5 200
MRF511 2.1 30 5 250

I generally go with the BFR94A, which are usually easy to find on eBay.
Good luck with your project!
john




Re: 549 transformer question

Chuck Harris <cfharris@...>
 

Anything you put on or in a coil like this is going to
affect the winding's capacitance, leakage, and Q.

You can use a layer wind, preferably a retrace wind on
these transformers, where you wind one layer, from left
to right, put a wrap of kapton tape, return to the left
side, cover the "retrace" with a bit of kapton tape, and
then wind the next layer... wash rinse, repeat.

It is more effort in the winding, but will ultimately do
just as good of a job. You have to use bifilar for the
first 500 or so turns, though.

No corona dope is necessary. If you use a layer of kapton
tape over every layer, on impregnation is necessary, as the
adhesive will do a good enough job.

There is no good reason to wind with anything bigger than
#38. It is already bigger than necessary.

RTV is a bad idea, unless it is a two part meant for coil
winding. It will affect the capacitance, leakage, and "Q"
of the finished coil.

I have wound hundreds of these coils with good success.

I would guess there are no more than another 100 customers
for 100 more transformers left in our community. That hardly
qualifies as plenty of business.

-Chuck Harris

Mark Vincent wrote:

Chuck or anyone else with knowledge,

I was wondering if any/some/none of the following could be used in the rewinding of the transformers that might make operation like it should be for a long life. Kapton between the layers, corona dope over layers and GE RTV or similar over the completed core. I did use the RTV under the original white RTV and around the PDA of a crt that the original white had separated from the outer envelope. It now works fine with no corona or arcing. This is the 21kv PDA type crt.

Would increasing the wire size, e.g. 38ga to 36ga, be better for winding(s)? I know the Cu loss would be lower and may be easier to work with being a larger diameter.

By the replies looking for a rewinding source, the one(s) that get a way to rewind the cores that work and hold up would be getting plenty of business. If I had a transformer rewound that the core was too large to allow the filament windings for the 5642s, I would not mind using high voltage solid state diodes. That one modification to have a working scope would be great.

Would Amidon have ferrite cores that would work? I know they make excellent quality products.

These are ideas I threw out to see if any are any good.

Mark






Re: Sick SG504

John Bennett
 

Eric,
I misspoke regarding the package type for Q70 (I should have looked it up). You want the 4-tab studded package (it has two emitter tabs) referred to in various data sheets as SOT122E, SOT48, and I think TO-117 (not TO-128). In any event, the BFR94A in that form factor should work. I have also used the the Motorola MRF587 and MRF511 with some success, although there are trade offs:
Typ. fT (GHz) VCEmax (V) Max Diss (W) ICmax (ma)
BRF94A 3.5 25 3.5 300
MRF587 5.5 17 5 200
MRF511 2.1 30 5 250

I generally go with the BFR94A, which are usually easy to find on eBay.
Good luck with your project!
john


Re: Help for DC503A universal counter repair

Attilio
 

Hi everyone,
I solved the problem by inserting a pull-up resistor on the blanking line (pin 11 of the LS7031).
One problem remains: the zero before the decimal point does not stay lit, I think it is the DPI input, pin 10 of the LS7031, but I leave it like that, just know it.

I doubt that the original Tektronix LSI LS7031 is slightly different from the standard LS7031, or it may be that the original is from 1983, while the one I found is from 1980, or finally that the new LS7031 is faulty, I don't know...

--Cheers
Attilio


2445B 2467B - non Tek probes

Ondrej Pavelka
 

Hi folks,

I have 2445B for quite many years, thanks to this awesome group and some super helpful members like Siggy or Chuck and others I dealt with leaky caps on the A5 board, backed up and copied calibration over. It's all good and I can't really be happier. Well except I just acquired 2467B in basically new condition. The only problem I have the P6136 probes becoming brittle and falling apart. The 2467B came with two Testek 600MHz probes but as much as I could live without the ID button, not having the coded ring is a nightmare when swapping between probes.
Anyone on here managed to 3D print or make in any other way adapter which would make the probe coded? I can clearly see the Testek probes are superior to P6136 but the lack of the coding ring is driving me mad. I was swapping between coded and unconditional probes during one calibration of an instrument and guess what..... Yes I completely ruined the calibration and had to redo the entire 6 hour process again......

Any way to convert the Testek probes oris there a pass through adapter to make the probe coded?
I didn't really appreciate the ingenuity of the coded probes up until I lost it.

6821 - 6840 of 184798