Date   

Re: Tek 576 Curve Tracer HV Replacement Transformer

Dave Wise
 

Where do you get your favorite high-voltage pourable RTV? I just did a web search and got overwhelmed by crap hits.

Thanks,
Dave Wise
________________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Chuck Harris via groups.io <cfharris=erols.com@groups.io>
Sent: Tuesday, April 07, 2020 3:00 PM

<snip>

Potting is pretty easy for stuff like this... transformers
are much harder to get right. A two part RTV... any two
part RTV would be great. I have even used a one part RTV,
but in thin layers... the pourable clear RTV sold as a
windshield sealant works very well. You do have to let it
fully vulcanize before you apply HV... which is why only
thin layers.

-Chuck Harris


Re: Delayed trigger jitter on 535A

nicmatfr
 

Hi Chris
I don't have any experience with dual time base scopes, but I've seen trigger jitter on my 531A a few years ago. The problem was due to ripple on the 500 V supply, because of a faulty capacitor. Maybe have a look at the second timebase's supply.

Nicolas
________________________________________
De : TekScopes@groups.io [TekScopes@groups.io] de la part de cmjones01 [chris@stumpie.com]
Envoyé : mercredi 8 avril 2020 11:44
À : TekScopes@groups.io
Objet : [TekScopes] Delayed trigger jitter on 535A

Tek fans,

My much-loved 535A has been getting a lot of use over the last few
weeks. It lives in my home lab which is where I'm now working due to
the coronavirus situation. Generally it's been a delight to use but
there's one niggle I think I need to sort out.

When using 'A' delayed by 'B' horizontal display mode, the trace has
significant horizontal jitter. For example, yesterday I was viewing a
1kHz rectangular wave and using the delayed timebase to examine one
edge. With timebase A set to 0.5us/cm, the viewed edge jitters back
and forward about 1-2us. The fault isn't always there - trying the
same test with the calibrator output, it was steady for the first 10
minutes or so and then got jittery.

If I back off timebase 'A's stability control so that it's triggering
on the edge after the delay, the jitter disappears as expected, so
it's something to do with the delay.

Before I start digging in to find the fault, has anyone experienced
anything like this with a dual-timebase 500 series scope -
535/545/546/547/549? I guess they're all fairly similar apart from
perhaps the 547.

Thank you
Chris


Re: Tek 576 Curve Tracer HV Replacement Transformer

Paul Amaranth
 

On Wed, Apr 08, 2020 at 07:53:49AM -0700, Ernesto wrote:
Old engineers can be like the classical Tektronix instruments, having timeless value.

Ernesto
But they are expensive and ageism is very prevalent in IT and
engineering. If you're building a low end product you don't want to
use high end resources.

I think that's a significant reason why older people with good
technical skills tend to run their own company or are independant
contractors. After 50 it is tough competing in a corporate environment
with young talent that gets paid half as much.

There are exceptions, of course, but I don't think there are a lot.

Paul
--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@AuroraGrp.Com | Linux/Unix


Re: 453 Sweep Problem

Bill
 

Forgot to add that the sine wave was produced using the .35-.75 mHz position on the 191 Generator. The adjusting scale was set on a little past .6. Any frequency higher than this the scope can not slow down enough for you to see the waveform. I don't have a digital signal generator available.
Bill


Re: Tek 576 Curve Tracer HV Replacement Transformer

 

Tektronix (not Danaher or Fortive) seems to be going through some really hard times...

I read an article about "best digital oscilloscopes", https://www.cwtouchkeyer.com/best-digital-oscilloscopes/
where Rigol and Siglent are rated on top, mainly in "value". LOL, I felt so tempted!
But a force in us stronger than pragmatism is LOVE
(that's why one does not trade in one's ancient wife for a brand new one in her 20s...)

I feel so bad, I retract all the negative things I said about Tektronix's (not Fortive's) customer service.

If Siglent and Rigol do good business with inexpensive digital scopes, cannot Tektronix have a line of such products that compete also in price?
While at the same time they preserve the line of very sophisticated, expensive instruments, and build a new portfolio of patents.
Hopefully they didn't retire all the creative ingenious engineers who produced their instruments in the 70s and 80s (earlier ones must be gone by now).
Old engineers can be like the classical Tektronix instruments, having timeless value.

Ernesto


453 Sweep Problem

Bill
 

This 453 serial number is 25900 and Mod. 210H. It is very clean and was rescued from being scrapped about 15 years ago. Has always been dependable and accurate until now. It is an old IBM scope.

I can't get a good waveform with the Time/Div knob if the frequency is over 50khz. Even then it is very touchy. I'm using my Tektronix 191 Constant Amplitude Signal Generator. It has always been spot on in the past.

Here are some pics. The problem is the same on both A and B channels.
https://imgur.com/HLWA0aX
https://imgur.com/orjSHiN
https://imgur.com/dWuxr93
https://i.imgur.com/iFhu4Ie.jpg

From 1khz Cal connector on scope. There is no change in the waveform no matter where you set the Time/Div knob.
https://imgur.com/BB5qJkk
https://imgur.com/Ii1xLAa


Decided to first start checking all the voltages. The scope's Time/Div adjustments has no affect if the frequency is over 50khz. No being able to adjust for a square wave from the calibrator is confusing. I have a good grasp of basic electronics but new to Oscilloscopes.

What do you all think? I do have a manual for it with a full set of schematics. Need to get this problem resolved so I can check out my newly acquired 465 also in excellent condition.

Bill


Re: Newly acquired TDS5054B-NV-AV tips and advice wanted

Harold Foster
 

On a related note: What are the "NV" and "AV" in the name? I've seen scopes with just the "TDS5054B" but I can't find anything in the manuals to tie the additional labels in with options.

Hal


Re: Tek 576 Curve Tracer HV Replacement Transformer

Chuck Harris
 

Tektronix was the victim of a takeover by Danaher.

All the time Danaher owned Tektronix, they traded as Tektronix.

Now that Danaher is done with them, and spun them off to Fortive,
they still trade as Tektronix.

Danaher has even less to do with them now than ever.

It makes no sense your calling them Danaher... they never were.

Should we call you Bruce?

-Chuck Harris

Tam Hanna wrote:

Creature of habit. When I got back to active work, they were Danaher.  I have seen
enough change for one life time.


Either way: you want such a trinket printed or not? If yes: tamhan aeht tamoggemon
roundthing come withouttheeattheend


Tam



Re: Tek 576 Curve Tracer HV Replacement Transformer

Tam Hanna
 

Creature of habit. When I got back to active work, they were Danaher.  I have seen enough change for one life time.


Either way: you want such a trinket printed or not? If yes: tamhan aeht tamoggemon roundthing come withouttheeattheend


Tam



--
With best regards
Tam HANNA

Enjoy electronics? Join 15k7 other followers by visiting the Crazy Electronics Lab at https://www.instagram.com/tam.hanna/


Delayed trigger jitter on 535A

cmjones01
 

Tek fans,

My much-loved 535A has been getting a lot of use over the last few
weeks. It lives in my home lab which is where I'm now working due to
the coronavirus situation. Generally it's been a delight to use but
there's one niggle I think I need to sort out.

When using 'A' delayed by 'B' horizontal display mode, the trace has
significant horizontal jitter. For example, yesterday I was viewing a
1kHz rectangular wave and using the delayed timebase to examine one
edge. With timebase A set to 0.5us/cm, the viewed edge jitters back
and forward about 1-2us. The fault isn't always there - trying the
same test with the calibrator output, it was steady for the first 10
minutes or so and then got jittery.

If I back off timebase 'A's stability control so that it's triggering
on the edge after the delay, the jitter disappears as expected, so
it's something to do with the delay.

Before I start digging in to find the fault, has anyone experienced
anything like this with a dual-timebase 500 series scope -
535/545/546/547/549? I guess they're all fairly similar apart from
perhaps the 547.

Thank you
Chris


Re: 184 Time Mark Gen. - 2nS & 5nS not working

Tom Gardner
 

Make sure you block any DC, and are very careful about the input power! If the DC block is a large capacitor (e.g. works to  kHz rather than MHz), consider whether any transients might be large.

Overkill? Possibly :)

On 08/04/20 03:17, Merchison Burke via groups.io wrote:
If you have a Spectrum Analyser, could that be used to check to 500 MHz output?


On 2020-04-07 9:22 a.m., david via groups.io wrote:
Thanks for the information guys, looks like I don't have the equipment or the knowledge to fix the 500MHz output. Not going to buy Nuvistors if I won't be able to check the results. My 465 is a 100MHz scope, it  shows 130mVpp signal at 200MHz output, so I believe that signal is OK. This 184 is working correctly except for the 500MHz. Only other issue is the 10MHz oscillator frequency does not have enough adjustment range. It is close enough, checking it with a GPSDO at 10MHz it is 9.999xxx, but it is at the limit of adjustment on C11. Any idea why the oscillator is beyond the range of C11 adjustment? Is it just the age of the crystal? Has anyone tried to reduce value of capacitor C11 by putting another cap in series with it? Only need to lower value of C11 a couple pF to fix it. I am amazed at how accurate this 184 is being all analog.
David



Re: 184 Time Mark Gen. - 2nS & 5nS not working

Melvin Gleep
 

Absolutely.

Gesendet von Mail<https://go.microsoft.com/fwlink/?LinkId=550986>; für Windows 10

Von: Merchison Burke via groups.io<mailto:merchison=yahoo.co.uk@groups.io>
Gesendet: Mittwoch, 8. April 2020 04:17
An: TekScopes@groups.io<mailto:TekScopes@groups.io>
Betreff: Re: [TekScopes] 184 Time Mark Gen. - 2nS & 5nS not working

If you have a Spectrum Analyser, could that be used to check to 500 MHz
output?


On 2020-04-07 9:22 a.m., david via groups.io wrote:
Thanks for the information guys, looks like I don't have the equipment or the knowledge to fix the 500MHz output. Not going to buy Nuvistors if I won't be able to check the results. My 465 is a 100MHz scope, it shows 130mVpp signal at 200MHz output, so I believe that signal is OK. This 184 is working correctly except for the 500MHz. Only other issue is the 10MHz oscillator frequency does not have enough adjustment range. It is close enough, checking it with a GPSDO at 10MHz it is 9.999xxx, but it is at the limit of adjustment on C11. Any idea why the oscillator is beyond the range of C11 adjustment? Is it just the age of the crystal? Has anyone tried to reduce value of capacitor C11 by putting another cap in series with it? Only need to lower value of C11 a couple pF to fix it. I am amazed at how accurate this 184 is being all analog.
David



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Re: 2430A Fails Repet

Szabolcs Szigeti
 

Hi,

Yes, you need to use the Dallas nvram, with built in battery. I
suppose it would be possible to restore the external battery but there
are some components that would need to be populated. However, if you
cannot get a replacement nvram (DO NOT buy anything off eBay or
similar sites, they will most likely be fakes, only buy from reputable
source) it is fairly easy to hack an external battery into the chip.
See my earlier post on this, which is actually about a 2430A with
DS1235A nvram. https://groups.io/g/TekScopes/message/136993

There are methods for other nvram models if you have something else
than a 1235A in your instrument.

Once you replace the battery, you will need to do a full calibration,
as specified by the service manual. Do a cold start, do a self cal and
them an ext cal. For the 2430A it will be a quite simple process, if I
remember correctly you will only need a DC source to provide some
voltage levels to the channel and trigger inputs. Look at the service
manual on the exact process. Do not worry, this will restore the scope
to fully working, you do not need to save the old values, etc. Also,
while you are inside the scope, you may as well do the display
geometry adjustment, my experience is that these are almost always off
in old scopes. And it is fun to do, as the scope will provide test
images to set various display parameters.
But whatever you do, study the adjustment section in the service
manual first. And don't forget to have an external fan cooling the CCD
module if you are running the scope without the case. The SM also
points this out.

Szabolcs

Gary Robert Bosworth <grbosworth@gmail.com> ezt írta (időpont: 2020.
ápr. 8., Sze, 2:04):


Can anyone give me the complete low-down on the Ram Battery back-up issue. My CMOS battery ran down, and I now get the 4000 Front Panel low battery error message. Do we HAVE TO replace the Dallas Ram chip block? If I have to replace the backup data black block, will the 2430A automatically do a calibration and load the new calibration data into the Dallas chip? My 2430A does not have an external battery, and there is a wire connecting the + and - terminal pads where the battery would go. Does this mean that I MUST use the same type of internal battery Dallas block? I put a 3.7 Volt Lithium backup battery in the place where the jumper was, but it had no effect on the operation of the scope. I can press the Auto Setup button and the scope works perfect, but the next time I power up the scope it gives me the same 4000 FPP error code again.



Re: Tek 576 Curve Tracer HV Replacement Transformer

 

Thank you Michael, Chuck.

Your reasonable explanations assure me that I haven't overseen something.
The resistor seems to be there for good engineering, a reasonable protection that has practically zero cost.

Ernesto


Re: Tek 576 Curve Tracer HV Replacement Transformer

Mlynch001
 

On Tue, Apr 7, 2020 at 09:34 PM, Ernesto wrote:


Michael, Chuck,

Why is a resistor in series with the multiplying ladder necessary? Isn't the
internal helical coating of the CRT a load and a drainage means of the ladder
capacitors?
In the 547 there is a 1 Mohm 1/4 watt resistor after the ladder, followed by a
500pF capacitor to ground.
In the 7704A there is no visible resistor, and the do-it-yourself circuit does
not show one inside the X14 module.

Ernesto
Ernesto,

I do not know the answer to that question. Chuck indicates that it to prevent being killed by a high current- high voltage from an accidental shock. What I do know is that the Tektronix specifications for the 152-0552-00 call for a series resistance of 510k ohms. This is found in the TEKTRONIX Cross Reference manual. The pictures of a DIY multiplier by member Marcus PP5MS can be seen in a series of pictures at this link:

https://groups.io/g/TekScopes/album?id=13113

Marcus - PP5MS 465-475 HV multiplier

His version clearly shows a resistor in series. His looks like 47K Ohm to me. His x ray also shows something in the Anode wire that could be a resistor.

I do not know all the technical reasons for this. But the specification is there, so there must be a good reason for this resistance.

I will defer to the sharper members to explain it to me.

If I build one of these, I want to match the original as closely as possible.

--
Michael Lynch
Dardanelle, AR


Re: Tek 576 Curve Tracer HV Replacement Transformer

Chuck Harris
 

The resistor is there to protect the tripler if the anode
lead is suddenly shorted to ground. It will drag the capacitors
to ground without allowing the current to get high enough to
damage anything... in theory.

However, if the capacitor simply blows up due to the surge
of high voltage/current across the resistor, how does it matter
that the diodes are still good, but the resistor is shattered
into an open circuit condition?

In the 547, that resistor is a 10M 1/4 watt carbon composition
resistor. But the capacitors in the 547 are quite a bit larger
than I believe the 465's tripler's uses.

In the 547's case, I think they were trying to protect the
wayward technician that gets across the live HV. It could
cause a heart arrhythmia in a properly connected person.

-Chuck Harris

Mlynch001 wrote:

On Tue, Apr 7, 2020 at 06:42 PM, Chuck Harris wrote:


I don't have a schematic of the tripler, so I don't know where this
resistor is located.

I suspect that it is in series with the anode lead. That is often done
for safety reasons. They don't want a full discharge of the tripler's
capacitors to stop your heart...

It was probably a carbon composition resistor, and probably 1/4 watt.

-Chuck Harris

Mlynch001 wrote:
I do have a question about the load resistor. I think it is supposed to be
about 470K Ohms? Does this need to be a special resistor or can you use a
1/2W metal film resistor?
Chuck,

There are some pictures in the TEKScope archive. One of our members posted a lot of pictures, including X-Ray pictures of the internal structures. They show the resistor soldered between the last diode in the chain and the end of the anode wire. I don’t have any carbon comp resistors of that resistance rating, but tons of 1/4W metal film and carbon film resistors. Would either those types be acceptable for this application? I can probably find some carbon comp resistors if absolutely necessary.


Re: 2445A slow

Chuck Harris
 

Just like that. It fits just fine.

The backup battery should last about 30 years. The life
is shortened if the scope is stored in a very hot environment.

-Chuck Harris

Steve wrote:


LOL, so you're saying just put a 100uf 25v radial and solder it to the legs in it's proper polarized pattern? If so cool! Also I checked the voltage of the backup battery while I had the A5 board out and it was teetering between 3.6/7 so I didn't bother ordering one from Mouser.


Re: Tek 576 Curve Tracer HV Replacement Transformer

Tom Bowers
 

Ernesto,

Why is a resistor in series with the multiplying ladder necessary?
I have un-potted the X14 multiplier from a 7904 and there is a 10 Meg Ohm
1/2 W Carbon resistor on the output high voltage lead, connected to the
last diode in the ladder.

The reason I had to un-pot one was to design a replacement, as I had blown
it up by discharging it. If there is even the slighted difference in the
value of the capacitors, a sudden discharge applies unequal voltages to the
diodes and at some point a diode gets destroyed. When doing this, the full
21KV is applied across the 10 Meg resistor.

Carbon is important because it is more forgiving to such a voltage
overload. A metal film resistor is not as forgiving. A 1/2 W resistor has a
higher voltage overload capability than a 1/4 W resistor. In the
replacement that I am building, I intend to put three 3.3 Meg 1/2 W carbon
resistors in series on the output lead.

To anyone who knows where X Ray images might be located, I would certainly
appreciate a clue so I could look at them. Also, I can share pictures of
the one I un-potted. Not pretty, but maybe somewhat useful.

Tom Bowers

On Tue, Apr 7, 2020 at 8:34 PM Ernesto <ebordon@swbell.net> wrote:

Michael, Chuck,

Why is a resistor in series with the multiplying ladder necessary? Isn't
the internal helical coating of the CRT a load and a drainage means of the
ladder capacitors?
In the 547 there is a 1 Mohm 1/4 watt resistor after the ladder, followed
by a 500pF capacitor to ground.
In the 7704A there is no visible resistor, and the do-it-yourself circuit
does not show one inside the X14 module.

Ernesto




Re: Tek 576 Curve Tracer HV Replacement Transformer

 

Michael, Chuck,

Why is a resistor in series with the multiplying ladder necessary? Isn't the internal helical coating of the CRT a load and a drainage means of the ladder capacitors?
In the 547 there is a 1 Mohm 1/4 watt resistor after the ladder, followed by a 500pF capacitor to ground.
In the 7704A there is no visible resistor, and the do-it-yourself circuit does not show one inside the X14 module.

Ernesto


Re: 184 Time Mark Gen. - 2nS & 5nS not working

Merchison Burke
 

If you have a Spectrum Analyser, could that be used to check to 500 MHz output?

On 2020-04-07 9:22 a.m., david via groups.io wrote:
Thanks for the information guys, looks like I don't have the equipment or the knowledge to fix the 500MHz output. Not going to buy Nuvistors if I won't be able to check the results. My 465 is a 100MHz scope, it shows 130mVpp signal at 200MHz output, so I believe that signal is OK. This 184 is working correctly except for the 500MHz. Only other issue is the 10MHz oscillator frequency does not have enough adjustment range. It is close enough, checking it with a GPSDO at 10MHz it is 9.999xxx, but it is at the limit of adjustment on C11. Any idea why the oscillator is beyond the range of C11 adjustment? Is it just the age of the crystal? Has anyone tried to reduce value of capacitor C11 by putting another cap in series with it? Only need to lower value of C11 a couple pF to fix it. I am amazed at how accurate this 184 is being all analog.
David

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