Date   

561 scope extender wiring?

 

Since I'm going to be working on this 3T77A plug-in for a while, an extender is necessary. Some years ago I acquired a pair of Amphenol connectors with the intention of building my own extender, but never got around to it.

Does anyone have a schematic so I don't have to figure it out from the 561 manual (I imagine most connections are simple pin-to-pin but do I use coax or twisted pair for the deflection signals?)

thanks

Charles


Re: Selenium rectifiers in Tek equipment

Dave Wise
 

?Coming to the party late, but I seem to recall that the instructions for one of the Se-to-Si Mod Kits stated that the purpose of the added resistance is to avoid excessive regulator input which will overheat the pass tubes. At least in some instruments, there are already resistors ahead of the reservoir caps which (a) reduce inrush and (b) furnish a handy point to estimate current.


Dave Wise

________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Tom Lee via groups.io <tomlee=ee.stanford.edu@groups.io>
Sent: Monday, February 08, 2021 11:50 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Selenium rectifiers in Tek equipment

Exactly. I never followed the lore because, as a teenager, I wasn't aware of the lore. I foolishly replaced blown seleniums with whatever rectifiers I had on hand from Poly Paks ("U test 'em and save"). Never had a problem, but perhaps it was just dumb luck. When I later worked in TV repair, I learned that I had violated proper procedure, but by that time, most gear with seleniums had either been junked or upgraded. I've only replaced a few since then, sometimes with added resistance to drop the voltage, but sometimes not. Always in my own gear, so that I alone bear the risk.

Tom

Sent from an iThing, so please forgive the typos and brevity

On Feb 8, 2021, at 23:13, "Joe Laffey" <joe@thestable.tv> wrote:

On Mon, 8 Feb 2021, Tom Lee wrote:

The short answer is resistance. It's not only a matter of forward drop at low currents (which the oft-quoted 1V number refers to; the drop at rated current can easily be an order of magnitude higher). Selenium rectifiers have considerable forward resistance (hundreds to thousands of ohms, depending on the specific device), compared to the small number of ohms typical of silicon rectifiers. So if you need to emulate selenium rectifiers with silicon ones, you have to degrade the latter by adding series resistance.


Re: Selenium rectifiers in Tek equipment

Matt
 

I purchased a Tek 575 Mod 122C curve tracer a couple of years ago from a Craig’s List seller. There was an original Instructional manual included along with instructions for a Mod kit (040-0223-00) which replaces the selenium rectifiers with silicon rectifiers. This Mod has not been incorporated into the curve tracer and I don’t have the necessary parts to do so. I don’t have the two ceramic strips that were used in the kit (#124-0089-00 Strip, cer, ¾ x 7 notches, clip mounted) or the bracket (#406-0815-00 bracket, silicon rectifier mounting) to mount the new silicon rectifiers. The remaining parts (the rectifiers, and solder lugs and spacers I figure can be obtained from Mouser. I know that I could mount the rectifiers on something other than the ceramic strips, but I am a bit anal (OK, perhaps more than just a bit) and I like to do it the right way.

If anyone has one of these Mod Kits available or just the ceramic strips, I would be interested in purchasing it.

It is interesting to note that the selenium rectifiers are being replaced with silicon rectifiers without any extra resistors for dropping the voltage as was suggested in this thread might be necessary.

As a youngster, I too recall salvaging a selenium stack from an old B&W TV, stripping the paint off and using the plates as a photo electric cell. The biggest challenge was figuring out how to fasten wires to the plates!


Re: Spectrum analyzer Tektronix 7L13 on mainframe Tektronix 7603

Attilio
 

Hi everybody,
sorry for the delay, I made some tests following Ed's instructions. By connecting the oscilloscope to the output of the oscillator control voltage coming from the PLL with the P446 connector disconnected, there is a signal that starts at + 1.6 Vdc rises up to 17.6 Vdc it remains there for 8 ms then it gradually drops to + 1.6 Vdc in 8ms then after about 200ms it repeats and so on. By connecting the P446 connector and the IF output to the input of the amplifier at 100 MHz, the signal on the P446 connector remains the one described above, then connecting the 1st LO output of the 7L13 to the 2nd LO input of the TR503 and tuning the center frequency of the 7L13 to have on the 1st LO output about 2200 MHz (FC at 109 MHz) the signal on P446 changes into an almost square wave that varies from + 14.6 Vdc to + 17 Vdc giving the idea that the PLL is working.
By connecting the 2nd LO output of 7L13 to the 2nd LO input of the TR503, the signal on P446 rises to + 17 Vdc and remains a straight line as if the output were saturated at the maximum level.
I think the problem is the signal level at the input of the 2nd LO of the TR503 (the 1st LO of the 7L13 comes out with + 10 dBm, while the 2nd LO comes out with - 5 dBm).
As soon as I can I do other tests, the problem is that I don't have an adapter to connect to the IF output of the oscillator to measure the frequency.

--Cheers
Attilio


Re: Waking a slumbering 475

 

Jeff (Davis),

Are you open to expanding your offerings? I've been looking (unsuccessfully) for a local MakerSpace with 3D printers, so that I could print a few things (e.g. some kickstands for DMM916s, top and bottom plates for TM500 plugins, TM500 latch release parts, and maybe see what can be done to produce press-on knobs for 2200 and 2400 series scopes). Would you be up for small runs like that?

-- Jeff Dutky


Re: was 549 transformer question

Roy Thistle
 

On Tue, Feb 9, 2021 at 03:32 AM, Michael A. Terrell wrote:


I was self taught
We're all self taught ... eventually.
Some people learn about that sooner than later.


Re: 2445B 2467B - non Tek probes

Mark Litwack
 

Hi Jeff,

The plastic housing around the BNC pulls off. It's a tight fit but it will come off.

Inside you will find the pin, a spring, and a MELF resistor that are all held in place by the housing. They will fall out once you get the housing off, so be careful not to let them roll away on you.

-mark

On Mon, Feb 8, 2021 at 10:47 PM, Jeff Dutky wrote:

Harvey,

I have been trying to figure out how to remove the plastic shell on the BNC
connector and have not had any luck, even where i have connectors that are
partly disintegrated. Maybe I have simply been too gentle in my
investigations. If you can recall how this is done, I would be eager to know.

-- Jeff Dutky


Re: TDS5054 infos...

David Kuhn
 

Did you figure out the PW for the RAR file? I forgot all about this, I got
so busy since last April.

On Sat, Feb 6, 2021 at 11:20 AM mill_glen_chevy via groups.io <brstpr=
aol.com@groups.io> wrote:

Hi,

Miguel very kindly sent me his software for creating the option keys. I
can't access the directions to use the software and don't know how it
works. Does anyone have that handy? I just did the hardware upgrades and
mine works much better. The work you folks did made my job easy.

Thanks

--
Brian St Pierre






Re: TDS5054 infos...

mill_glen_chevy
 

Bump for my previous message

--
Brian St Pierre


Re: 2445B 2467B - non Tek probes

Roy Thistle
 

On Mon, Feb 8, 2021 at 10:33 PM, Jeff Dutky wrote:


My advice, if you really want original Tek probes to go with your Tek scope,
is to try your luck on eBay.
There is only one other market that is "......" than paybay, and that's utube. (Where "......" is a word egregiously disparaging in meaning.)
Like penny stock pumpers... there are those, on both, working hand-in-hand to manufacture bogus value from flumadiddle.
That's my opinion, and I'm sticking to it.


Re: was 549 transformer question

Michael A. Terrell
 

Tom Lee wrote:
Hilarious! Nice improvisation with the Heathkit.

Tom
My motto is, Never piss off the Engineer!. When I got to basic I was told I could be a cook or a truck driver. I told off an E8 and a Captain. I had five medical 4F ratings, but was drafted because I worked in Electronics. They told me I would be given the hardest electronics test in the Army and that I would fail because no one had ever passed. It was 110 questions, and you were given two hours, 15 minutes. The average score was 22/110, and passing was 42/110. They gave me a copy with only 88 questions and laughed. I finished it in 17 minutes, and my score was 82/88. The school was a mix of Electrical and Broadcast engineering that could be converted to the then FCC first phone. My sccore was higher than recent graduates of that school, but I was self taught. I pissed off a lot of people because of it.

I had built the  Heathkit for one of the operators at the station. He was trying to learn TV repair, but was still learning to solder. That station was my first use and repair of Tektronix scopes. I had for RM529 Waveform monitors, and an old scope that I had to repair before I could repair anything else.

I not only worked at the TV station, I did CATV and RADAR  work at Ft. Rucker. They were short handed, so my section loaned me to RADAR for a week. The jerk I was to work with tried to talk down to me, "You might know a little Electronics, working on TVs." I smiled and informed him that RADAR was a stripped down TV, since it had no Chroma or Aural circuitry. When the week ended, the section chief was angry. "RADAR has put in a transfer request, because you did too good! The same happened when I showed the A/V section how to make a custom control panel for the General's conference room. Our section had been asked to design and install the sound system, and they were in my way. My section leader sighed, "You've done it again. A/V is trying to take you from us."

Maybe we should take this to E-mail?


Re: Tek 576 - step generator power amp - how to check?

 

Hi Ozan,

I realigned the step generator of the 576 to specifications without problem. Everything seems fine now, its sitting on a desk awaiting the Metrix tube analyzer so they can play together :-)

For fun, I examined the defective transistors (see the pics here: https://groups.io/g/TekScopes2/album?id=260354).

Q241 (2N 4250 in the step generator):
seems quite open until 9V CE, then resistive with some kOhms, and is totally insensitive to base voltages...

Q725 and Q727 (NPN with Tek number 151-0190-00 in the 75V power supply):
these look OK, but quite different (double the current with same settings). As soon as I put them back the 75V volt supply shuts off. Their function is to protect against all sorts of shorts against other voltages.

cheers
Martin


Re: was 549 transformer question

Tom Lee
 

Hilarious! Nice improvisation with the Heathkit.

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 2/9/2021 03:08, Michael A. Terrell wrote:
Tom Lee wrote:
The CTC-4 used a 6CB5. I can't recall ever having seen an 807 in a color set, so I was very intrigued by your post. Indeed, I only saw a few in very old B&W sets, lots of 6BG6s in later (but still early) B&W sets. I was always on the lookout for 807s, settled for 6BG6s.

Tom
I only saw two CTC4 based chassis, and both were in the early '70s. The first was mine, which I gave to a collector when he bought all of my antique radios before I left for the Army. The second was a rare, video only version that RCA built for TV stations. It was still in use at one of the two TV stations in Fairbanks, Alaska. Most of the station was still early '50s RCA TV equipment. I was shocked that the AFRTS station at Ft. Greely was better equipped, even if my station was Monochrome.

BTW, I transmitted our station ID in color, with no color equipment. I borrowed a Heathkit color bar generator, and fed it into the Genlock input of our dual, Grass Valley Sync Generator. I hand made a 35m slide to position two lines over the color bars. I did it because an ID10T Second Lt. was telling everyone that the station could not be converted to color even though we were waiting for the delivery of new equipment. 15 seconds after I did it live, he was on the phone screaming, "Soldier! You just made a fool of me!" I laughed and said, "Sir, you brag that you are a self made man" and I hung up. He was the base PIO, and a real idiot.




Re: was 549 transformer question

Michael A. Terrell
 

Tom Lee wrote:
The CTC-4 used a 6CB5. I can't recall ever having seen an 807 in a color set, so I was very intrigued by your post. Indeed, I only saw a few in very old B&W sets, lots of 6BG6s in later (but still early) B&W sets. I was always on the lookout for 807s, settled for 6BG6s.

Tom
I only saw two CTC4 based chassis, and both were in the early '70s. The first was mine, which I gave to a collector when he bought all of my antique radios before I left for the Army. The second was a rare, video only version that RCA built for TV stations. It was still in use at one of the two TV stations in Fairbanks, Alaska. Most of the station was still early '50s RCA TV equipment. I was shocked that the AFRTS station at Ft. Greely was better equipped, even if my station was Monochrome.

BTW, I transmitted our station ID in color, with no color equipment. I borrowed a Heathkit color bar generator, and fed it into the Genlock input of our dual, Grass Valley Sync Generator. I hand made a 35m slide to position two lines over the color bars. I did it because an ID10T Second Lt. was telling everyone that the station could not be converted to color even though we were waiting for the delivery of new equipment. 15 seconds after I did it live, he was on the phone screaming, "Soldier! You just made a fool of me!" I laughed and said, "Sir, you brag that you are a self made man" and I hung up. He was the base PIO, and a real idiot.


Re: 549 transformer question

Jean-Paul
 

Hello again

We used many ferrite cores in SMPS and some HV designs since 1970s and have a shelf of old stock, as well as the original printed catalogues. We used Ferroxcube, Stackpole, TDK, in EI, EE, ER, and other shapes, most have no gap, in usual power matériels for 20-50 kHz.

Most standard cores sizes are available today from Epcos, or TDK, in EU. US sources are Fair Rite, TDK.

If you can post clear photos and dimensions I can look at what I have, we might get lucky.

Happy to assist,

Kind Regards

Jon


Re: 2445B 2467B - non Tek probes

Jean-Paul
 

Bonjour a tous::

Since 1970s have used all types of probes and accumulated a huge collection, TEK, and other brands.
The TEK are by far the best in function, specs, ruggedness and reliability. Even HP and Yokogawa probes cannot compare.
I cannot comment on the third party brands , but if they are Chinese clones, I would think they are poorly made and not for serious use.
"Penny wise and Pound Foolish"

2465/7/B have BW 300-350-400 MHz and specify P6137 for the BW mentioned.
Even if an off brand compensates the input capacitance, as mentioned the probe ID and multiplier resistor will be wrong.
I have found the correct probes on epay and Ham fleas in the past, I would suggest patience and keep looking out for the specified probes.

As mentioned, 10X probes are in general not accurate for wideband use as the self capacitance and ground clip inductance affect the observed waveform.
We use either 50 Ohm coax direct to the scope or the very fine Tek Zo probes such as P6156.

Suggest to read the TEK Circuit concepts book "Oscilloscope Probes" for probe considerations and technique.

Just the ramblings of an old retired EE!

Bon Chance,

Jon


Re: Selenium rectifiers in Tek equipment

Tom Lee
 

Exactly. I never followed the lore because, as a teenager, I wasn't aware of the lore. I foolishly replaced blown seleniums with whatever rectifiers I had on hand from Poly Paks ("U test 'em and save"). Never had a problem, but perhaps it was just dumb luck. When I later worked in TV repair, I learned that I had violated proper procedure, but by that time, most gear with seleniums had either been junked or upgraded. I've only replaced a few since then, sometimes with added resistance to drop the voltage, but sometimes not. Always in my own gear, so that I alone bear the risk.

Tom

Sent from an iThing, so please forgive the typos and brevity

On Feb 8, 2021, at 23:13, "Joe Laffey" <joe@thestable.tv> wrote:

On Mon, 8 Feb 2021, Tom Lee wrote:

The short answer is resistance. It's not only a matter of forward drop at low currents (which the oft-quoted 1V number refers to; the drop at rated current can easily be an order of magnitude higher). Selenium rectifiers have considerable forward resistance (hundreds to thousands of ohms, depending on the specific device), compared to the small number of ohms typical of silicon rectifiers. So if you need to emulate selenium rectifiers with silicon ones, you have to degrade the latter by adding series resistance.

Not all circuits need such emulation, but the general practice among old-time radio techs was to be conservative. "You'll pop the filter caps if you don't have that resistance to soften the blow" is a common bit of lore.
I don't think you are going to harm modern caps with inrush current in most cases (as you seem to indicate as well with your "lore" comment). The transformer will usually help buffer this inrush. Old caps are a different story, especially if you are one of those guys who thinks its wise to keep 20, 30, or 40+ year old electrolytic caps in your equipment (not I).

For me the easiest method is to measure the voltage with the selenium rectifier in place (bring it up on a Variac). Then put a series resistor after your silicon rectifier to lower the voltage to the same level (mind the power rating for heat dissipation of course). Use Ohm's Law and then adjust for tolerances or math errors ;-) You may even want to measure the voltage at 117VAC input (or whatever the original expected line voltage was) and then adjust the resistor value to match that output voltage at your normal modern line voltage.

Most old equipment can handle fairly large swings in input voltages. Though it may need to be re-aligned at modern voltages vs. old lower voltages.

--
73
Joe Laffey





Re: Selenium rectifiers in Tek equipment

Ed Breya
 

Yeah, like Tom said, changing Se to Si rectifiers is easy by adding some R. That's close enough to get the job done, and it's not necessary to exactly emulate the I-V characteristics. You just need to get about the same conditions before and after. And yes, higher power Se rectifiers were in stacked plate form, with the number of plates proportional to voltage rating, and the area proportional to current, and they were their own heat sinks. The substrates were almost always aluminum. Even high voltage rectifiers were made from lots of small disks stacked up and then potted. BTW, they were among the first kinds of photo-voltaic cells. I remember when I was a kid, it was a real treasure to find an Se rectifier that had a clear coating (rare), rather than painted, because it could easily become a photocell for experimenting, without any paint stripping needed.

Ed


Re: Selenium rectifiers in Tek equipment

Joe Laffey
 

On Mon, 8 Feb 2021, Tom Lee wrote:

The short answer is resistance. It's not only a matter of forward drop at low currents (which the oft-quoted 1V number refers to; the drop at rated current can easily be an order of magnitude higher). Selenium rectifiers have considerable forward resistance (hundreds to thousands of ohms, depending on the specific device), compared to the small number of ohms typical of silicon rectifiers.  So if you need to emulate selenium rectifiers with silicon ones, you have to degrade the latter by adding series resistance.

Not all circuits need such emulation, but the general practice among old-time radio techs was to be conservative. "You'll pop the filter caps if you don't have that resistance to soften the blow" is a common bit of lore.
I don't think you are going to harm modern caps with inrush current in most cases (as you seem to indicate as well with your "lore" comment). The transformer will usually help buffer this inrush. Old caps are a different story, especially if you are one of those guys who thinks its wise to keep 20, 30, or 40+ year old electrolytic caps in your equipment (not I).

For me the easiest method is to measure the voltage with the selenium rectifier in place (bring it up on a Variac). Then put a series resistor after your silicon rectifier to lower the voltage to the same level (mind the power rating for heat dissipation of course). Use Ohm's Law and then adjust for tolerances or math errors ;-) You may even want to measure the voltage at 117VAC input (or whatever the original expected line voltage was) and then adjust the resistor value to match that output voltage at your normal modern line voltage.

Most old equipment can handle fairly large swings in input voltages. Though it may need to be re-aligned at modern voltages vs. old lower voltages.

--
73
Joe Laffey


Re: 2445B 2467B - non Tek probes

 

Also, I know that some folks don't want to shell out for brand new probes, either out of budget, or out of a desire to keep the scope "genuine" (or because the probes that Tek made for the scope have the right capacitance for the scope). I have, thus far, had remarkable good luck buying second hand probes from eBay, despite both evident mishandling by the sellers (cables too tightly wound or folded), and clear advertisement as being non-working (e.g. a P6106 whose tip end and been replaced with an SMA connector, appeared to be completely defunct when I first tested it. I decided to use it as a donor for another probe with a damaged BNC connector, and while disassembling it I discovered that the cable was unseated in the compensation box. I reseated the cable end and now it works like a charm!)

My advice, if you really want original Tek probes to go with your Tek scope, is to try your luck on eBay. So long as you are spending a lot less than what Probe Master or CalTest charge it seems like there's a fair chance of success.

I will say, however, that the subminiature probes, like the P6131 that goes with the 2465, and the 6137 for the 2465B, seem much more fragile than the earlier modular probes. I've seen a lot of P6131s for sale on eBay that either have broken probe tips, or where the tip assembly is missing altogether. Putting together four good P6131s was much more challenging (and expensive) than putting together six good probes of earlier models (1 pair P6075As, 1 pair of P6106s, and one pair of P6121s). Also, the witches hats for the subminiature probes seem almost impossible to find.

-- Jeff Dutky

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