Date   

Re: 3D printable feet for TDS500/600/700

Mlynch001
 

On Tue, Feb 18, 2020 at 10:19 AM, Abc Xyz wrote:


Monty,

Great Job in those Feet! Now if I just had a File for 465 Feet...
JR

You need a file for the cordwrap feet of the 465 Series? That file is on THINGIVERSE.

HERE: https://www.thingiverse.com/thing:1410827

I can e-mail you the STL File, as I have that as well.

I have printed dozens of these for my various 4XX Series scopes plus some for my brother as well.

Hope this helps.


--
Michael Lynch
Dardanelle, AR


Re: help tek 475 power supply

Roger Evans
 

Roberto,

If everything works before Q1446 fails then the simplest explanation is that Q1448 has failed with its collector open circuit and Q1446 is passing all the current to the +15V output through the base emitter junction of Q1488. The regulator will still function to provide the correct +15V. Much more current will be drawn from the output of U1454A since there is less current gain in the regulator and U1454 will draw more supply current via VR1418 so VR1418 will also be hotter than normal.

Regards,

Roger


Re: 3D printable feet for TDS500/600/700

Abc Xyz
 

Monty,

Great Job in those Feet! Now if I just had a File for 465 Feet...

JR

On Mon, Feb 17, 2020, 10:34 PM Monty Montgomery <xiphmont@...> wrote:

Hi folks,

While putting a TDS7xx back together, I required several new feet, so
I modeled some. Files ready to print are at

https://www.prusaprinters.org/prints/22192-replacement-feetpads-for-tektronix-tds-500600700-s
for anyone who'd like them.

Cheers,
Monty




Re: help tek 475 power supply

Roberto
 

hi Roger
Yes, the track is there that performs all its functions, but after a few minutes the CRT backlight turns off and the reason is missing the + 15v, the voltages are all up when 2n222 fails even the 24v zener I noticed that it heats up
thank
Roberto


Re: 5116+5D10 intensity problem

Harvey White
 

Ok, several things after searching the  manuals.

1) the liquid is fluorocarbon 114.  SF6 is used in the AWACS transmitter unless they rebuilt it.

2) the P6015 has the liquid, the P6015A has a silicone filler and no liquid.

3) the P6013 (IIRC) may have neither and is rated for about 12KV or so, while the P6015 is rated from 20KV to 30KV depending on circumstances.

4) I did not find the specs on the 6015 without dielectric fluid, not in the internet material I have at the moment.


Harvey

On 2/17/2020 3:26 AM, Paul Cohen wrote:
Or maybe SF6 (nasty) gas which is used in HV

בתאריך יום ב׳, 17 בפבר׳ 2020, 10:22, מאת Yeun-Jung Wu ‏<
B0190@...>:

Hello Harvey:

Thank you for your hint on future diagnosis. I will start collecting more
information on epoxy coated transformer first.

5D10 seemed to work fine except read out information had been expanded
outside the screen. Now I understand why red LED "possible under-sampling"
would lit: I was using slow time base to watch two nearly identical 7kHz
since wave superimposed together to form a nice envelope. There were lot of
wave form variation during long accuqsition time but the available memory
space for storing waveform was limited. When I select faster time base such
that several cycles was within the range of one horizontal division that
warning went away.

More than 5 year's ago I bought a Tek high voltage probe from eBay. There
was an empty can supposed to contain liquid with high dielectric strength,
something similar to banned CFC freon. For 4.5kV maybe I can fill some
other liquid and give it a try.

Best Regards,

Yeun-Jung Wu




Re: 547 scope HV transformer problem. One practical solution.

John Griessen
 

On 2/16/20 4:43 PM, Ernesto wrote:
I have added a toggle switch on the side cover of the scope, close to the CRT. Now after initial power up, I wait for a reasonable time for the instrument to stabilize (something that takes time with the 1A1 plug in!) Then I turn on the display and make adjustments and measurements, and 5 minutes is plenty of time. Then I turn the display off
Sounds like a good way to enjoy your 547 while waiting for a transformer!


Re: 3D printable feet for TDS500/600/700

magnustoelle
 

wow, Monty, I am envy of your skills. Thank you for your generousity! 
Cheers,
Magnus


Re: 3D printable feet for TDS500/600/700

dnmeeks
 

Thanks Monty! Very generous to put it up for us to use. I need to check all my mainframes to see if I need any - I'm sure I'm missing some. If I print them I'll let you know how it turns out.
Dan


Re: help tek 475 power supply

Roger Evans
 

Can you explain what you mean when you say 'after a few minutes it turns off'? Do you mean that initially there is a trace on the CRT but after a few minutes it disappears? The 475 should show a light behind the V/div knob of the vertical channel that is selected - does this light stay on when the scope 'turns off'?

Can you measure the voltages on the low voltage DC supplies, +50V, +15V, +5V, -8V, -15V and also '+15 unregulated'. Do any of these these change between first turning the scope on and the 'turn off'? If the only problem is with the regulated +15V then we can trace the voltages through the regulator.

Measuring Q1446 in circuit may be misleading since there are many parallel components.

Regards,

Roger Evans


Re: 547 scope HV transformer problem. One practical solution.

Albert Otten
 

On Tue, Feb 18, 2020 at 07:34 AM, Ernesto wrote:


One detail that worried me somewhat is the initial very bright blur of the
image when turning the supply on. I am working on this issue.
Hi Ernesto,

Interesting story and solutions. Though I hope my 547 keeps going on without those HV problems!
The bright blur when turning on the HV supply is not amazing.
See message https://groups.io/g/TekScopes/message/108397. The cap mentioned is C562.
This cap has no effect when the 547 is already on and you switch off/on the HV at a later moment.

Albert


Re: help tek 475 power supply

Roberto
 

Thank Chuck Harris
I checked the tracks where the negatives seem to be going well, the tensions would all be there and the only problem is the one exposed in the previous message
Roberto


547 scope HV transformer problem. One practical solution.

 

Hi, I am a retired electrical engineer having designed electronic equipment for measurements in oil wells for over 30 years.

About 40 years ago I picked up a 547 scope with an 1A1 plug in left as surplus by my employer. It went into my garage, and it was never powered up. After some decades, I developed a fear of powering it up, concerned over the degradation of the large electrolytic capacitors in its voltage supplies. A few weeks ago I needed an oscilloscope to troubleshoot an old record player, and I decided to bring this ancient oscilloscope back to life.

I disconnected all the big capacitors and over hours raised their voltage with an external supply while monitoring leakage current. All of them got restored! I did some general inspection and studied the schematics of all the functional blocks. I removed the timer tube and powered up just the filaments to check on the tubes. All lighted up. I reconnected the capacitors and the timer tube, and removed the oscillator tube of the CRT supply. While monitoring the regulated supplies I brought up the power with a variac. They came up fine within specs, no smoke. I was able to activate the sweep generators and see the flashing on the neon beam position indicators.

Then I placed back the 6AU5 tube of the HV oscillator, powered up, and to my amazement I saw come on that beautiful sharp bright trace on the CRT. Overcome with emotion, tears rolled down my cheeks and I started playing with the controls using the calibration signal. The oscilloscope was basically WORKING! After 40 years of being dead!

After some short time the beautiful trace started to fade away, and I realized that I had a problem with the CRT high voltage. After investigating, I learned about the now classical problem with the HV transformer. First I replaced the vacuum diodes with silicon diodes, and the power consumption of the supply improved (as measured on the pentode grid 2), but the time to failure only increased slightly. I measured it as 15 minutes after power-up cold. The failure of the transformer is an insurmountable problem. I speculated that if clamping the pentode's grid 2 at a higher voltage than 125v the oscillator could provide more power, or I could easily replace the 6AU5 with a power MOSFET after some minor modifications, and then increase drastically the available power to the Hartley oscillator. But this could be a dangerous modification if it could burn out the transformer, and then this could end the life of the instrument since there are no replacements. I could still build a new larger transformer with a ferrite pot core that would fit in the available space, with sufficient space for reliable HV insulation of the windings (and NO impregnation). But I lack the basic design of the transformer, like the turn ratios of its winding, although I could measure them on a working transformer or calculate them from the existing design.

I realize that I have fallen in love with the 547. No other test instrument, be the 7000 series, the digital scopes, etc. have this effect on me. The scope is now in my office, and each time I see it my spirit lights up. So I searched for a solution.

First, I realized that the HV supply is overpowered. If the 325v unregulated supply (about 350v in my scope) is powered down, regulation is maintained until the voltage is down to 195v. The HV could be powered from the 225v supply instead, but this one simply regulates down the 325, so this does not save power but transfers some to the 225v regulator. My experiments with an external variable supply gave me an idea: while the scope is on, why not have a switch to turn on and off the HV power and so allow the scope to be used for an indefinite time, as long as the display is turned on only when needed, and maintaining an adequate low duty cycle.

I verified that the supply tolerates a 50% duty cycle of 5 minutes on and 5 minutes off. Or, a 10 minutes on followed by a longer period off. One can do a lot of measurements in 5 minutes. I have added a toggle switch on the side cover of the scope, close to the CRT. Now after initial power up, I wait for a reasonable time for the instrument to stabilize (something that takes time with the 1A1 plug in!) Then I turn on the display and make adjustments and measurements, and 5 minutes is plenty of time. Then I turn the display off, while doing other things. I am perfectly fine using the oscilloscope like this. Cycling the HV supply does not seem to affect the stability of the scope, the readings remain the same.

One detail that worried me somewhat is the initial very bright blur of the image when turning the supply on. I am working on this issue. First I have reduced the voltage to the supply by 120v with a string of 10 zener diodes, 12v 5w, which are dirt cheap on Amazon. With 230v the supply runs fine. Next I am building with a MOSFET and some timing components a means to raise these 230v slowly, and reduce this first bright flash in the first second of power on. I had measured that the current provided to the supply is 26mA, which doubled when it reached a safe degradation. So the consumption of the HV supply will stay below 25 watt, an amount of power easy to handle.

With this last modification I will be satisfied to have brought back to life this superb instrument, which I plan to keep in my office forever, for whatever little experimenting I will fancy to do.
I might try to improve it again whenever Chuck Harris is able to produce workable HV transformers, and I would like to be one of his clients.


Re: Help diagnosing a Tek 2755 spectrum analyzer

Jaap Rusticus
 

Hello Neill,

I'm new to this group in writing. Reading allready for a long time. I'm in the Netherlands.
As I have been reading here on the Tek forum (Chuck Harris and perhaps others too), the several dipswitches can be unreliable and this can lead to strange behaviour. I changed them all in my 2756P.

Jaap


Re: 5116+5D10 intensity problem

Paul Cohen
 

Or maybe SF6 (nasty) gas which is used in HV

בתאריך יום ב׳, 17 בפבר׳ 2020, 10:22, מאת Yeun-Jung Wu ‏<
B0190@...>:

Hello Harvey:

Thank you for your hint on future diagnosis. I will start collecting more
information on epoxy coated transformer first.

5D10 seemed to work fine except read out information had been expanded
outside the screen. Now I understand why red LED "possible under-sampling"
would lit: I was using slow time base to watch two nearly identical 7kHz
since wave superimposed together to form a nice envelope. There were lot of
wave form variation during long accuqsition time but the available memory
space for storing waveform was limited. When I select faster time base such
that several cycles was within the range of one horizontal division that
warning went away.

More than 5 year's ago I bought a Tek high voltage probe from eBay. There
was an empty can supposed to contain liquid with high dielectric strength,
something similar to banned CFC freon. For 4.5kV maybe I can fill some
other liquid and give it a try.

Best Regards,

Yeun-Jung Wu




3D printable feet for TDS500/600/700

Monty Montgomery
 

Hi folks,

While putting a TDS7xx back together, I required several new feet, so
I modeled some. Files ready to print are at
https://www.prusaprinters.org/prints/22192-replacement-feetpads-for-tektronix-tds-500600700-s
for anyone who'd like them.

Cheers,
Monty


475 Module claimed

Bruce Lane
 

The vertical module I offered earlier, for the 475, has been claimed.

Thanks much.


--
---
Bruce Lane, ARS KC7GR
http://www.bluefeathertech.com
kyrrin (at) bluefeathertech dot com
"Quando Omni Flunkus Moritati" (Red Green)


Re: 475 Module: Anyone need it?

Bruce Lane
 

Thanks, Renee, but it ended up going to another fellow who has a broken
'scope he's trying to fix.

Best of the week to you.

On 16-Feb-20 10:54, Renée wrote:
Hi Bruce-
I use the 475  as my preferred scope...so If it is still available...I
will take it.
we should do this off list from here ....k6fsb dot 1 at the gmail place
Renée

On 2/16/20 10:43 AM, Bruce Lane wrote:
Fellow Tekkies,

    While hunting for a part this morning, I came across a Tektronix
module
which I think is the vertical driver board for a 460 or 470 series. The
part number is 670-3023-02.

    I don't need it, as I sold my 475 some time ago. First offer of $5
plus
postage gets it, priority to those who might need the thing to repair an
existing 'scope.

    Thanks much.


--
---
Bruce Lane, ARS KC7GR
http://www.bluefeathertech.com
kyrrin (at) bluefeathertech dot com
"Quando Omni Flunkus Moritati" (Red Green)


Re: 2215 cleaning + recap

ridderg@...
 

Thanks! I checked again and it turns out I missed a second screw on the top left that attaches to the preregulator board. So there are 7 screws in total.


Re: Repairing my Tektronix 454 oscilloscope need some advice

Albert Otten
 

Victor,

Before accusing the HV transformer ... some remarks.
How "very low" was HV at the test point? Is the oscillator amplitude at Q1430 also (in ratio) very low?
What voltage did you have at Q1423-emitter (or pin "P")? The shown voltage -4.35 V is not more than an indication; also there is ripple of 1 V or so. The oscillator starts with base current to Q1430 provide by R1425. Amplitude increases rapidly when Q1423 conducts at the negative going peaks of "P" voltage (at about -1 V). With too high load that situation might not occur.
Did you check HV pot R1401?
Did you measure the current via F1437? Normally about 0.27 A.

It might be possible to test the transformer (and load) to some extend. Remove F1437. Apply + 10 V (w.r.t. GND) or so at C1437. Apply about -2 V at "P". Apply a signal generator output (via DC blocking cap) to Q1430 collector, keeping the amplitude below about 4 V. This way no semiconductors will start to conduct. There should be resonance at about the normal oscillator frequency, about 25 kHz. Turns ratios can be checked when when you can access the secondary winding ends or rectified voltages. (Just an idea, I have never tried this in my 454.)

Albert


Re: Repairing my Tektronix 454 oscilloscope need some advice

Dave Wise
 

If I understand correctly, the 454 HV is similar to the 453. I successfully rewound a 453 transformer using a low-tech process which I documented in topic and photo album titled "453 HV Transformer Rewind".

HTH,
Dave Wise
________________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Victor via Groups.Io <vmcfer=aol.com@groups.io>
Sent: Saturday, February 15, 2020 10:40 AM
To: TekScopes@groups.io
Subject: [TekScopes] Repairing my Tektronix 454 oscilloscope need some advice

Hi members,
I have since many years a tek 454. Few years ago the trace stop to show. Since I have more spare time to dedicate to my small lab I would like to repair it.
The first step was to repair the power supply witch is working now fine. Then I discover that the CRT circuit is not working (very low voltage on the TP 1469 (-1960V)) and no voltage on the CRT heater.
I test all the parts on the Z Axis circuit board feeding the HV voltage and I couldn't find any trouble. I open the plastic box containing the HV transformer for testing and all the parts seems fine except a 1 Mohm resistor which I replace it. Is not easy to work on this circuit with few information but I think the HV transformer is dead.
A very well know Canadian supplier for Tek parts doesn't have any spare available for the HV transformer. So I'm looking for some advice or any members experience on this scope or additional test to confirm my suspicion. Also any specs about the HV transformer will be welcome.
Thanks in advance.
Victor