Date   

Re: Tek 576 step generator problem

Miguel Work
 

Hi David,

It seems normal, mine jumps from 10 to 65uA

Regards

Miguel
-----Mensaje original-----
De: TekScopes@groups.io [mailto:TekScopes@groups.io] En nombre de Dave S.
Enviado el: miércoles, 13 de enero de 2021 14:11
Para: TekScopes@groups.io
Asunto: Re: [TekScopes] Tek 576 step generator problem

Hello,

thank you very much guys for your help!
So it looks like my step-gen performs ok and like Michael Lynch said it seems to be normal that the waveform flickers a bit more @ 2, 4, 6, 8 and 10 steps.

Anyway i ran into another problem (or is it a problem?!) ... Maybe someone can do another (pretty easy) check/comparison I shorted the C and E terminal, set the vertical range to 5uA and turned up the collector supply to have 2 divisions (10uA). When i change the vertical range now from 5uA to 10uA the reading is not 10uA but suddenly almost 75uA.
Is that normal due to internal change of measurement resistor?

5uA-Range:
https://i.gyazo.com/576b1ab29cb29caf641fe9400db731a3.png

10uA-Range without changing collector supply:
https://i.gyazo.com/9b5e1be8ce8c3baf502ebb193b18ac41.png

BR,
David







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Re: First mixer diode on a 7L18 : how to test (and possibly replace) ?

Miguel Work
 

Wow, a 7l18 I want one!

Can you please upload some photos?

I have some experience with single diode mixers, I have two tek491

Regards!

-----Mensaje original-----
De: TekScopes@groups.io [mailto:TekScopes@groups.io] En nombre de Jose Luu
Enviado el: miércoles, 13 de enero de 2021 23:46
Para: TekScopes@groups.io
Asunto: [TekScopes] First mixer diode on a 7L18 : how to test (and possibly replace) ?

Dear group,

I am fixing a deaf 7L18, it is responsive to a 510MHz signal injected into the second mixer, I still have to test the 510MHz IF, I am anticipating that the first mixer diode has failed (likely from a power overload).

Testing the diode: I suppose I should pay attention to the voltage applied and possibly limit the current, 1V and a few milliamps?
Replacement: the part number I find on the service manual is: 119-0972-02 , googling it does not fetch much, any ideas, is surgery oof the A45 unit possible ?

Thank you for any insight
Jose









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Re: Tek 576 step generator problem

Dave S.
 

Hi,

unfortunately not.
Maybe you could help me and make a quick check for that issue :)

Thank you!

Dave


Re: Tektronix 492BP

 

Frequency not in rage ignored. Also I cannot move the band higher than 15-21GHz. When I press the buttom external mixer it said: UNDEFINED FUNTION.


760 D intensity doesn't work

 

Hi Tek folks,

Working on a 760 D, when I got it the power supply was cycling and the high voltage would not come up. Lifting the output of the quadrupler let the low voltage supply come up, so I assumed it was bad. Bought a 1710B and a 1720 for parts off of eBay for the quadruplers. Swapped the quadrupler out of the 1710B and still had same symptom. And now the low voltage won't come back after pulling the swapped quadrupler. Oops, somehow took backwards step. So pulled entire power supply from the 1720 and swapped in. Now 760 powers up but trace super bright and intensity control on the main board does nothing. I did check for continuity from the intensity connector pin going to the PSU, and can see the resistance change from the pot to ground. Z-axis amp trouble?


Re: Tek 576 step generator problem

Mlynch001
 

On Wed, Jan 13, 2021 at 07:10 AM, Dave S. wrote:


Anyway i ran into another problem (or is it a problem?!) ... Maybe someone can
do another (pretty easy) check/comparison
Did you get an answer to your question? I was going to check and the power went off at the house.

--
Michael Lynch
Dardanelle, AR


Re: CRT book by Keller

Glydeck
 

I had to get my copy of the book and check it out. On Page 24...

"To illustrate the extremes in materials that have been used for CRT envelopes, almost every CRT lab has at one time or another fabricated a "Coketron" made from that one glass envelope that always seemed to be present in any lab, the Coca-Cola™ bottle. A little phosphor settled in the bottom and an electron gun sealed to the neck results in an operable CRT that never ceases to amuse lab visitors."


On Jan 13, 2021, at 1:19 PM, John Griessen <john@ecosensory.com> wrote:

The coketron, a CRT made from a coke bottle, made me smile her in
Albuquerque...
--
John Griessen -- building lab gear for biologists






John Glass

Larry McDavid
 

John Glass please contact me; your email address fails.

--
Best wishes,

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


Re: Tektronix 492BP

John Miles
 

What happens when you try to enter a frequency higher than 21 GHz?

-- john, KE5FX

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
Mike Yepes
Sent: Wednesday, January 13, 2021 7:28 AM
To: TekScopes@groups.io
Subject: [TekScopes] Tektronix 492BP

Hi, I recently adquire this unit I had a diplexder and WG so to be able to
increase the 21GHz frequency but this unit does not go over the 21GHz limit.
It does not appear to have any options but it does has the external mixer
connector and 1st and 2nd LO. Is there any way I can increase its limit?
thanks.
KE6OJE.



Re: 2247A Is this normal?

Tom Lee
 

Hi Tim,

Have you read the fabulous manual? [Who reads manuals??]

The peak-to-peak function of the voltmeter in the 2247A is spec'd to 25MHz, according to Tek. Try making a measurement within that bandwidth and see what you get.

When it comes to using an instrument you intend to rely on, it's a good idea to study the specs to see where, and where not, it is going to be reliable. That way, you'll know what to expect, and know when there's a real problem.

--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 1/13/2021 09:39, Tim / N8TIM via groups.io wrote:
Hello All
I have a 2247a and when I put it in the voltmeter mode and pick Peak to Peak the cursers are not touching the peaks of the wave form. Is this normal or do i need to get the service manual out?

https://groups.io/g/TekScopes/photo/259345/0?p=Created,,,20,2,0,0

Thanks




First mixer diode on a 7L18 : how to test (and possibly replace) ?

Jose Luu
 

Dear group,

I am fixing a deaf 7L18, it is responsive to a 510MHz signal injected into the second mixer, I still have to test the 510MHz IF, I am anticipating that the first mixer diode has failed (likely from a power overload).

Testing the diode: I suppose I should pay attention to the voltage applied and possibly limit the current, 1V and a few milliamps?
Replacement: the part number I find on the service manual is: 119-0972-02 , googling it does not fetch much, any ideas, is surgery oof the A45 unit possible ?

Thank you for any insight
Jose


Re: 2247A Is this normal?

Dan G
 

On Wed, Jan 13, 2021 at 03:10 PM, Tim / N8TIM wrote:

I have a 2247a and when I put it in the voltmeter mode and pick Peak to Peak
the cursers are not touching the peaks of the wave form. Is this normal or do
i need to get the service manual out?
Hi Tim,

The signal you are measuring seems to be close to 110 MHz, which is at the
BW limit of the 2247A. The exact vertical deflection bandwidth of the
scope is unlikely to be exactly the same as the bandwidth of the peak-to-peak
detector, which may be somewhat higher.

I have a 2246 Mod A (well-calibrated to the best of my knowledge), which
shows similar results when measuring a 110 MHz signal from the SG503.
In reality, the signal amplitude is somewhat greater than indicated even by the
p-p detector.

Do you know the actual amplitude of the signal you are observing? (A 100 MHz
scope cannot be used to accurately measure the amplitude of a 100 MHz signal)
At 100 MHz, one would expect a measurement error close to -3dB.

By itself, your photo is not necessarily an indication of any problems with your scope.
Are the cursors closer to the waveform peaks when you measure a 25 MHz sine wave?


dan


CRT book by Keller

John Griessen
 

The coketron, a CRT made from a coke bottle, made me smile her in Albuquerque...
--
John Griessen -- building lab gear for biologists


Tektronix 492BP

 

Hi, I recently adquire this unit I had a diplexder and WG so to be able to increase the 21GHz frequency but this unit does not go over the 21GHz limit. It does not appear to have any options but it does has the external mixer connector and 1st and 2nd LO. Is there any way I can increase its limit?
thanks.
KE6OJE.


2247A Is this normal?

Tim / N8TIM
 

Hello All
I have a 2247a and when I put it in the voltmeter mode and pick Peak to Peak the cursers are not touching the peaks of the wave form. Is this normal or do i need to get the service manual out?

https://groups.io/g/TekScopes/photo/259345/0?p=Created,,,20,2,0,0

Thanks


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

Steve Goldstein
 

Hi Jared,

I was just going through the BOM at Digikey and encountered what may be a typo. C2, which you list as TBM1H105BECB, gives a non-existent part number error. Everything else so far seems to be OK.

I assume the LEDs are 20mA types as the fundamental design is pretty old.

BTW, you don't list a part number for the knob but Digikey PKG90B1/4 looks correct.


Re: T912 storage oscilloscope - No 2.7 KV high Voltage

Roger Evans
 

Attilio,

I am writing this on the phone and I can't easily get schematics at the same time - so no part numbers!

When you disconnect the diodes that generate the CRT cathode and grid voltages (-2.7kV) you effectively disable the negative feedback from the end of the focus resistor chain to the power transistors that energise T460. So the oscillator is running at maximum drive trying to generate -2.7 kV and in the same way is producing too high values for -120V and -220V. When running normally with negative feedback the transformer turns ratio ensures that if -2.7 kV is correct then so are the other voltages.

To me it looks like T460 is OK and so is the circuitry that drives the power oscillator. You have a problem with a failed diode or capacitor on either the CRT grid or cathode supply. If you replace just one of the supplies then the voltage across the two neons causes them to conduct and a fault on either supply will cause the oscillator to stop working.

I am afraid you may have check individual components to find the failure. Quite often a leaking diode or capacitor looks OK with a DMM but the leakage shows up with a high voltage around 1kV. I bought an insulation tester as used by electricians for checking house wiring.

I can go into more detail when back at a decent sized screen!

Best regards,

Roger


Re: 1s1 on ebay

snapdiode
 

Or figure out a solid-state replacement...


Re: T912 storage oscilloscope - No 2.7 KV high Voltage

Attilio
 

Hi Roger,
the CR468 heats only with the C468 condenser connected, if I disconnect it the CR468 remains cold.
I wanted to add that I measured the voltages at pin 2 and pin 7 of the T460 transformer with respect to ground and I find very high voltages (on pin 2 there are 840 Vpp at 53 kHz and on pin 7 there are 484 Vpp at 53 kHz).
From pin 2 through the CR468 diode the - 120 Vdc are generated and from pin 7 through the CR467 diode the - 220 Vdc are generated, 840 Vpp to generate the -120 Vdc seem too many! I suspect an insulation problem in the T460 transformer (?).

--Cheers
Attilio


Re: 1s1 on ebay

Dave Wise
 

?I have on my "to do someday" list, adjusting the heater current to acommodate 12AT7 and see if it's acceptable.


Dave Wise

________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of snapdiode via groups.io <snapdiode=yahoo.com@groups.io>
Sent: Tuesday, January 12, 2021 10:54 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] 1s1 on ebay

If you go by eBay prices, buying two 8416s will bring that "bargain" 1S1 in line with the 200$ range I see for 1S1s these days,

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