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Re: Sampling head remove/install with scope power on?

 

Roger M wrote:
Still, one may think of hot plugging as a "bad idea", much like:
...
- putting down your beer, and saying "here,... watch this..."
Which is, of course, why you always ask someone else to hold your beer

-- Jeff Dutky


Oddly Small Curve Tracer Test Fixtures/Adapters

 

I recently obtained a 7CT1N curve tracer plug-in to use in my (still non-functional) 7623A (or in my also non-functional 7603). I had planned to build a custom test fixture with multiple, paired sockets, and a switch to allow comparison of devices, but then I saw a couple of test fixtures for relatively good prices (each below $50) on eBay, and ordered several of them.

Two of the fixtures (an 013-069 and an 013-070) are obviously intended for use with the 7CT1N as they have only three banana plugs, arranged in a row, and spaced correctly to plug in to the binding posts on the 7CT1N, but three others, which came only as populated circuit boards are, surprisingly, about 30% narrower than the first two, and the banana plugs are too close together to fit either the 7CT1N or any of the 57x curve tracers.

The boards bear silk screening that indicates they were made by Tektronix in Holland in 1989. One of them bears a full Tek part number (369-0769-00, which I have not been able to find on TekWiki, or in a general web search), while the other two have a part number with XXXX in the middle position. The one that bears a full part number is populated with three sockets, one a linear set of three pin sockets, the other two are three pin sockets for two different sized can devices (like TO-18 and TO-39/TO-52).

I have uploaded pictures of the adapters to the photos section in an album titled "Small Curve Tracer Text Fixtures"

Was there another kind of curve tracer made by Tek in the late 80's that used a closer spacing of the binding posts/banana sockets?

-- Jeff Dutky


Re: fs- Tek Oscilloscope 533 - $20.00 Orange/Los Angeles county, pickup only.

benx618(g)
 

SOLD- 533 scope.
I am informed that the 533 scope has been collected by a new owner with restoration intent.


Re: Sampling head remove/install with scope power on?

Roger M
 

I would bet my bottom dollar that the issue of hot plugging a sampling head
was discussed by its designers and would have been documented as a
no-no (or blocked by some mechanism) if there was chance of failure.

Still, one may think of hot plugging as a "bad idea", much like::
- playing with elemental mercury as a kid
- sanding lead based paint
- swimming right after eating
- waiting over 5K miles to change your oil
- "floating" a scope
- ripping up your asbestos laced flooring
- looking into a laser with your good eye
- putting down your beer, and saying "here,... watch this..."
-Roger


Re: 2nd life for a 575 after resting for 30+ years in the attic #photo-notice

Keith
 

Interestingly, tube manufacturers produced a whole series of special tubes for computers. Most of them were twin triodes, the later ones loosely based on the same general physical design as the familiar 12Ax/Ay/Au/7.

The uniform features touted by the manufacturer for these so-called “special quality” computer equipment tubes was generally something like this

“Specially designed to operate for long periods in cutoff” etc.

Here’s an example - the 7044 from about 1969

https://frank.pocnet.net/sheets/127/7/7044.pdf

Here’s another one - a true SQ computer tube built for 10,000 hours...the EC180 - circa 1968

https://frank.pocnet.net/sheets/009/e/E180CC.pdf

(The “regular” version of this tube was the 7062)

In these computer tube designs, they were ruggedized with an emphasis on functioning as an on-off switch rather than a linear amplifier. Not a surprising design quality, given the application.

Much to the chagrin of the audiophooles, these design features mean they generally don’t make very good choices for Hi-Fi. Of course this doesn’t stop them from using them on occasion and applying the usual audio-fool language. “Broad soundstage! Z-axis Sonic dimensionality is breathtaking, blah blah blah” 🤣


Re: 2nd life for a 575 after resting for 30+ years in the attic #photo-notice

 

Martin,

I expect that finding faults in the ENIAC was pretty much the same as finding faults in any digital computer: unlike a tube radio (or oscilloscope) a digital computer is composed of a bunch of relatively loosely coupled subassemblies, and faults can be easily isolated to the subassembly before you need to start doing detailed tests. Assuming a parallel organization (not a very good assumption for machines of the vintage of ENIAC) the memory system would be composed of a set of identical amplifiers and flip-flops (and the storage devices, maybe a mercury delay line). If a tube failed in one of the amplifiers it would be immediately obvious because you would have a single bit stuck on or off in every word fetched from memory. Similarly for a failure in the logic or control assemblies.

I also expect that they had test routines designed to detect and isolate all sorts of specific failures (I don't know about the ENIAC, but these sorts of test routines were commonplace by the 1960s), so you would be able to narrow down the source of a malfunction pretty quickly using the test routines, and then only have to test several dozen tubes in the failed subassembly.

-- Jeff Dutky


Re: Sampling head remove/install with scope power on?

 

Thanks Albert. I KNEW I had seen that phrase somewhere in all my manuals, just couldn't find it! :)
I've been hot-swapping them, at least the S-1 and S-2, multiple times without incident.
In fact, I've inadvertently pulled them more than once because I forgot to set the lock, and those GR connectors are stiff.

Anyhow, I agree that it's better to err on the side of caution.
(The S-4 is safely in its antistatic bag with an SMA shorting plug installed, where it will sit until I get a Leo Bodnar pulser to check its risetime. It is now no longer repairable since there is no source of replacement diode hybrids).


Re: 2nd life for a 575 after resting for 30+ years in the attic #photo-notice

 

On 1. Apr 2021, at 01:37, Michael W. Lynch via groups.io <mlynch003=yahoo.com@groups.io> wrote:
.... In contrast to most audio gear, most tubes in TEK instruments do not need to be at the pinnacle of their operational function to work as designed. Tektronix made sure that a tube that might test "weak" in a tester will still operate acceptably in their instruments...
Very interesting remark. I think Tek has been obliged to make a very tolerant desigg. When you sell a scope with 100+ tubes inside, making it work with even "weak" tubes is not a nicety but really a necessity. Otherwise you would end up with a doorstop.

Makes me think of the ENIAC and its 18000 tubes. They say they always had to replace a handful of tubes when they switch it on (or so). The design must have been very tolerant, too, otherwise it would not have been usable at all. But I don't think they had to swap 18000 tubes to find out which one created a problem. Anybody knows how they detected the tubes that made problems within a reasonable amount of time?

cheers
Martin


Re: A6302/P6302 current clamp questions and parts.

Albert Otten
 

There hardly can be more inside. That metal collar piece is a bus. Its other end presses the plastic pin block in position. It's screwed into the body by means of the external 3 turn outer screw thread in the middle. The pins and wires are inside the bus.
It feels as if the sleeve can hardly slide over the cable, even when cap is removed. The mm space in my photo is because sleeve+cable came out together. Going on would destroy wiring. Anyway, I still think that rubber compressed by the end cap also secures the cable.
My A6302 has the shiny plug version.
When new considerable force is needed to insert or remove plastic pin block. To remove I use a length of thin wall metal pipe which falls just around the pins and slides through the plug body. For the test plug I mentioned I could also use this "tool" to insert the pin block because I could attach the BNC connector later on.

No doubt there are other members who can help you immediately.

Albert

On Thu, Apr 1, 2021 at 06:02 PM, Jared Cabot wrote:


Looks the same as mine except my plug is chrome plated. :)
That inner metal collar piece around the rubber boot will also unscrew
allowing you to withdraw the whole assembly (with a little push to the pins to
ease the pin assembly out).

So far it looks identical to the way my plug is, but I'm not sure about what's
supposed to be going on deeper inside. I won't ask you to go deeper unless you
are comfortable though. :)


Re: Sampling head remove/install with scope power on?

Albert Otten
 

S-2 Ceck and Recal procedure.
Step 2a, remove the extender cable from the sampling head: " ... the oscilloscope power may be left on".
Step 2c: reconnect, no remarks about power.
I prefer to go for safety.
Albert


Re: A6302/P6302 current clamp questions and parts.

Jared Cabot
 

Looks the same as mine except my plug is chrome plated. :)
That inner metal collar piece around the rubber boot will also unscrew allowing you to withdraw the whole assembly (with a little push to the pins to ease the pin assembly out).

So far it looks identical to the way my plug is, but I'm not sure about what's supposed to be going on deeper inside. I won't ask you to go deeper unless you are comfortable though. :)


Re: chinese witches hats for old probes help

dave G8SFU
 

Hi all..
This is my report on the chinese witches hats.
First my thanks to all who replied. No-one was able to say for certain if they would fit my probes.

I ordered six of the widely advertised ones
(6 New Probe Hook (Gray) for Tektronix Probes, P6139A, P6138A, P6109, P6105)
from seller sharpseller2000. The price was £11.26 delivered.
Ordered on 19 March, delivered in two packages, first on 29 March and the other a couple of days later.

I have no genuine Tek ones to compare.
They are made of two plastic parts, the metal hook and a spring.
There is no earthing part inside. I expect the genuine ones to continue the probe earth sleeve some way inside the hat.

The fit to all the probes listed in my original query below is satisfactory. The inner plastic sleeve fits on the earth sleeve of the probe quite firmly.

I dont think they would have lasted many days on Jim Williams' bench but they are going to be good enough for me for now.
I recognise and understand their limitations and am happy with my purchase.

I hope this helps others.

Dave G8SFU

On 10/03/2021 17:01, dave G8SFU via groups.io wrote:
Hi. I'm looking for a bit of guidance here please.
Since moving house a couple of years ago I am only just getting some test gear set up.
I find I have 4 good genuine Tek probes to go with the 4 Tek scopes.
(466, 468, 475 and 2246)
Other scopes make do with inferior probes.
The Tek probes are P6062B, P6101A, P6053B, and P6011.
All seem to be in good order, but none of them have witches hats,(sprung hook clips).
All seem to be the same fitting around the tip area with the earth sleeve diameter being 4.4 mm diameter or just a bit larger.
I had a good look on the site for chinese ones, but they are all specified for newer probe models, so I was not sure enough to order any.
Each of the Tek par numbers for the witches hats is slightly different but they look to me as if they would all take the same hat.
Can anyone who has bought from china give me any guidance please.
I realise the quality will be what it is, but it seems they would be worth a punt if anyone can confirm the size.
thanks for reading   Dave    G8SFU


Re: A6302/P6302 current clamp questions and parts.

Albert Otten
 

Here is another attempt. Tekwiki again. Picture of plug with cap removed and strain relief pulled out a few mm. I didn't take the risk to dismantle the plug any further. The thicker rubber cannot go further in then halfway the inner metal part with the flats. I think the rubber is long enough to get compressed when the cap is screwed on. It might be that the thicker rubber is not part of the sleeve itself, difficult to see.
I made a test plug with an original Amphenol 185-9 plug. There a short rubber bus goes in followed by a short metal bus. The metal bus gets pressed in by the cap and then compresses the rubber. (This is at least the way I thought it was intended.)

Albert

On Wed, Mar 31, 2021 at 08:57 PM, Albert Otten wrote:


Ah yes, I was too quick because I remembered that photo I took years ago. I
made the special test plug but that was without the strain relieve. I guess
the inner part of the official strain relieve gets compressed (to less inner
diameter) when the end ring is screwed inward.
Albert

On Wed, Mar 31, 2021 at 07:58 PM, Jared Cabot wrote:


Thanks for that but it's actually the big metal plug that attaches to the
AM503 module that I'm looking for photos of.

Jared.


Re: Tektronix 2247A not starting

Andrey Ulyanchenko
 

The problem has changed a bit. Sometimes there is a start. calibrated perfectly. and with warming up for about 5-10-15 minutes, the input test signal is turned off. The measurement symbols remain on the screen. Re - power on- indicates the chip 160-3493-00. startup is unstable. This is a definite problem. The output transistors heat up to no more than 53 Celsius. Please advise who could solve this problem. Added a photo (please see).


Re: Odd 453A on ebay UK

ChrisBeee
 

Hey,
FYI: this is a typical over-sensible behavior when drugs are involved and to be honest, I would not be surprised if that's actually the case. I am pretty well sure that this crackhead does not realize what BS he is talking. So, better stay away from this seller, whatever stuff he is offering!
Besides that: I am wondering what would happen if all forum members would go and ask him about the CRT... Mushroom cloud? =D
Chris


Re: Persuading a 7S12 to play nice with a 7934.

Albert Otten
 

On Wed, Mar 31, 2021 at 04:07 PM, Albert Otten wrote:


I measured about 0.5 mV more positive level of A17 during the active parts of
interdot blanking. That doesn't look impressive, but the effect of 0.5 mV
change in Z-axis is very well visible.
Sorry, it was 5 mV, not 0.5 mV. Albert.


Re: 2nd life for a 575 after resting for 30+ years in the attic #photo-notice

Renée
 

I have always believed in the wisdom told to me eons ago- the best test bed is the equipment itself, if the circuit works leave it alone. most circuits were designed to work just fine at 50% tube functionality...so far that has held true..there are always exceptions...but then the circuit was not working.....
Renée

On 3/31/21 4:37 PM, Michael W. Lynch via groups.io wrote:
On Wed, Mar 31, 2021 at 04:28 PM, Brenda wrote:

The only thing that I would say is not to rely on your tube tester for testing
tubes. Tektronix says it over and over in the manuals for the scopes that I
have, I don't know the quote right off-hand, but manuals do say not to rely on
tube testers, replace only when that tube is actually causing a problem,
otherwise leave it alone.
In contrast to most audio gear, most tubes in TEK instruments do not need to be at the pinnacle of their operational function to work as designed. Tektronix made sure that a tube that might test "weak" in a tester will still operate acceptably in their instruments. Laughably, those people who scavenge tubes from this old gear probably do not realize that many of these tubes are not in the best condition. I guess that they think since the tubes are in that pretty TEK Blue Cabinet, that this imparts "magical powers" to said tubes.


Re: 2nd life for a 575 after resting for 30+ years in the attic #photo-notice

Michael W. Lynch
 

On Wed, Mar 31, 2021 at 04:28 PM, Brenda wrote:


The only thing that I would say is not to rely on your tube tester for testing
tubes. Tektronix says it over and over in the manuals for the scopes that I
have, I don't know the quote right off-hand, but manuals do say not to rely on
tube testers, replace only when that tube is actually causing a problem,
otherwise leave it alone.
In contrast to most audio gear, most tubes in TEK instruments do not need to be at the pinnacle of their operational function to work as designed. Tektronix made sure that a tube that might test "weak" in a tester will still operate acceptably in their instruments. Laughably, those people who scavenge tubes from this old gear probably do not realize that many of these tubes are not in the best condition. I guess that they think since the tubes are in that pretty TEK Blue Cabinet, that this imparts "magical powers" to said tubes.

--
Michael Lynch
Dardanelle, AR


Re: 7D15 internal trigger not working

Mark Vincent
 

Steve,

Check R2409. I suspect it is high or open by the voltages you measured. A bad IC will also make the voltages off. Good you will get a replacement 0022. If bad, use a 1/2W resistor with the size about 3,5x10mm. The original is 1/8W. More wattage is being dissipated than the resistor is rated, ,133W dissipation of a ,125W resistor. I am glad you found your 7D15 is working. That is a nice plug-in.

Raymond Frank is exactly right! Do NOT hot-swap the plugins. This advice should be observed on the 5000 and 11000 series as well.

Mark


Re: 2nd life for a 575 after resting for 30+ years in the attic #photo-notice

Brenda
 

Hello Joe,

First off, I just want to say that's great that you got that 575 up and running! The only thing that I would say is not to rely on your tube tester for testing tubes. Tektronix says it over and over in the manuals for the scopes that I have, I don't know the quote right off-hand, but manuals do say not to rely on tube testers, replace only when that tube is actually causing a problem, otherwise leave it alone. I have several tubes in my Tektronix 535A and both of my 561A's that have issues, but I use them because they are not causing any problems. With tubes getting harder to find NOS, in my personal opinion, use that tube until it does create a problem.

Brenda

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