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Re: Spectrum analyzer Tektronix 7L13 on mainframe Tektronix 7603

Nenad Filipovic
 

On Sun, Dec 27, 2020 at 09:18 AM, Thomas Garson wrote:
However, even if it is only a "flat" white noise source, I can see the
utility it offers.
...
I never considered using a broadband noise source as an alternative to
the tracking generator. From your post, it appears that you have done
so, with at least acceptable results.
The eBay ad is a mess but the device is decent, well worth it but won't do wonders for $20. It's a white noise source, just a plain Zener diode hooked to a wideband amplifier. Reference (average) level is approx -30dBm, my specimen has a broad bump of +3dB at around 1GHz and then continuously drops to -5dB at 1.8GHz. However the curve is rather smooth; I mostly use it for spans of just a few MHz and in that case it's virtually flat. For wide spans I use a 7854 program to record a sample of a "flat" reference, and then subsequently apply the inverse of it to correct the actual measurements.

I also have a TR502; its generous output level adjustment is superb and it provides much better SNR in any measurement compared to the noise source. But sometimes funny things happen if you hook it to a DUT which is far from 50ohm, resulting in bumps and tilt of the bandpass curve. I empirically concluded that (this particular) noise source is more resilient to that, so I always try both devices. During Covid lockdown in spring I calibrated the IF of a B/W tube TV receiver from the 60s, and ended up using the noise source. The result was like from a textbook.

Best regards and Happy Holidays,
Nenad Filipovic


Re: Tek 465 Negative 8 volt rail issues

Dave Peterson
 

Thanks Toby and Barry,

I'm becoming partial to Nichicon, not because I think their documentation is better, but I am becoming more familiar with it. And their capacitor series. I've found their Series charts very useful: https://www.nichicon.co.jp/english/products/alm_larg/index.html But I enjoyed reading and learning more about the large power supply cap types. So thanks for the app notes.

I am a bit concerned that the lifetime specs are so much less than the U** series caps, but I see that the "Large Can" types are intended for higher voltage. It's difficult to find a 1200uF, 100V U-series cap, but the "Large Can" L-series can handle that easily. But at a cost of lifetime/ripple current?

LGN2C122MELA40: 1200 uF, 160V, 25/40mm, 3000 hour lifetime @105C, 2300mA ripple current.
UHW1K122MHD: 1200uF, 80V, 16/40mm, 10000 hour lifetime @105C, 3500mA ripple current.

The application is a 465 C1513 which is filtering the unregulated 55v supply. Schematics, and measurement, shows this output is really in the range of 70+ volts. So very near the limits of U-series cap. The existing cap is a 100v cap, so we'll say that's the spec? But the U-series cap above has significantly better lifetime and ripple current. Which is the more important selection criteria here?

And then for the lower voltage, but higher value +15v, +5v, and -8v: the U-series again has significantly higher lifetime and ripple currents at the expense of a lower voltage rating, but still greater than the application. For example: UHE1E562MHD (5600uF, 25v, 10000h, 4200mA) vs. LGY1H562MELA40 (5600uF, 50v, 5000h, 2300mA)

The 1200uF cap seems a little on edge at 80v for U-series. But, within voltage spec, doesn't lifetime and ripple trump the ratio: spec voltage/operating voltage?

Dave


Re: Yet another 'replacing carbon resistors with metal film' question....

Jean-Paul
 

AHA! Yes PG502 is a fine unit, the back term 50 Ohm is handy. I have several, neither has ever has any problem.

For scope cal, the really fast rise pulses are from PG506 and Leo Bodnar's 40 pS pulser

As a general use PG with fast capability PG502 is best.

The resistors you highlight are not critical to the performance and even a 5% value should not affect it.
I dont recommend Removing, testing and replacing the parts if its performing satisfactorily.


Enjoy,

Jon


Re: Tektronix 1A7 and 1A7A Plug-ins

bobkrassa
 

The 1A7A manual is on the Tekwiki site.

Bob Krassa ACØJL


Re: Yet another 'replacing carbon resistors with metal film' question....

Jared Cabot
 

I have the PG502 250MHz Pulse Generator in front of me now (I also have a PG506 to look over but that is another project for another time).

I guess I'll see how the unit performs with the minimum of modifications to get it functional and make a decision once I see what it says as to further repairs.
I've found a lot of these types of resistors have drifted high in a number of pieces of test equipment I've worked on in less critical applications, hence my thoughts on replacing them in this unit, but I guess if it works, then no point fixing it until it breaks.... :)


Here are the schematics with the Allen Bradley style carbon composite resistors in my unit highlighted:
https://i.imgur.com/8WiK5b9.jpg
https://i.imgur.com/g3KXKlN.jpg
https://i.imgur.com/geXFOIK.jpg


Re: Tek 465 Negative 8 volt rail issues

n4buq
 

Regarding snap caps, the leads are bent into a crook so as to allow inserting processes to push the leads into the PCB holes and grip the cap in place until soldered. Otherwise, they're like their ordinary radial-leaded cousins.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: toby@telegraphics.com.au
To: TekScopes@groups.io
Sent: Monday, December 28, 2020 9:25:25 AM
Subject: Re: [TekScopes] Tek 465 Negative 8 volt rail issues

On 2020-12-27 11:10 p.m., Dave Peterson via groups.io wrote:
Paul,

I'm putting together a Mouser project for 465 PS caps. I pulled all 5 as
they appear to have been leaking, it was going to be necessary to get at
the suspected C1513, and once I got going it wasn't that bad, so might as
well do all of them. I also have the adapter boards ordered and waiting
for USPS to get them across country.

I was searching for radial Nichicon caps as I'm pretty happy with the
order I made for C1419 replacements. I didn't catch your earlier reference
to "snap" caps, and I see that these come in higher capacitance and
voltage values than radial. Not that radial's aren't available, it just
appears snap caps are inherently larger?

I've never heard of snap caps before. Aside from the obvious lead
difference, what is the purpose/difference between radial lead caps and
snap caps?
Nichicon publishes app notes and press releases like these:

https://www.nichicon.co.jp/english/products/pdfs/e-al_gui.pdf

https://www.nichicon.co.jp/english/lib/new133.html
https://www.nichicon.co.jp/english/lib/new135.html
https://www.nichicon.co.jp/english/lib/new141.html

via https://www.nichicon.co.jp/english/lib/index.html

Hope some of that is helpful.

--Toby

Dave










Re: Tek 465 Negative 8 volt rail issues

toby@...
 

On 2020-12-27 11:10 p.m., Dave Peterson via groups.io wrote:
Paul,

I'm putting together a Mouser project for 465 PS caps. I pulled all 5 as they appear to have been leaking, it was going to be necessary to get at the suspected C1513, and once I got going it wasn't that bad, so might as well do all of them. I also have the adapter boards ordered and waiting for USPS to get them across country.

I was searching for radial Nichicon caps as I'm pretty happy with the order I made for C1419 replacements. I didn't catch your earlier reference to "snap" caps, and I see that these come in higher capacitance and voltage values than radial. Not that radial's aren't available, it just appears snap caps are inherently larger?

I've never heard of snap caps before. Aside from the obvious lead difference, what is the purpose/difference between radial lead caps and snap caps?
Nichicon publishes app notes and press releases like these:

https://www.nichicon.co.jp/english/products/pdfs/e-al_gui.pdf

https://www.nichicon.co.jp/english/lib/new133.html
https://www.nichicon.co.jp/english/lib/new135.html
https://www.nichicon.co.jp/english/lib/new141.html

via https://www.nichicon.co.jp/english/lib/index.html

Hope some of that is helpful.

--Toby

Dave





Re: need case for 067-0508-00 Amplitude Calibrator

Rick
 

Thank Brian

Rick


Re: Yet another 'replacing carbon resistors with metal film' question....

Jean-Paul
 

For sure DK and Mouser carbon composition resistance are from China and poor quality

We use only Allen Bradley made in USA and have a huge old stock inventory 1/4---1/2-1-2W

Essential for high-voltage.

The original Allen's Bradley were probably used in the Tektronix, so your reliability may be WORSE with the current Chinese garbage resistors.

Jon


Re: Yet another 'replacing carbon resistors with metal film' question....

Jean-Paul
 

Jared, is this the PG502 pulse gen or PG506 calibration gen?

if a CAL gen with high speed edges, I suggest to NOT change any resistance or cap in the fast pulse output section

In our work, since 1970s, carbon comp and carbon film resistance fail with

a/ over dissipation
b/ high-voltage
c/ mechanical stress eg on leads

They dont fail during normal use, very reliable.

Just the ramblings of an old retired EE

Bon Chance

Jon


Looking for Tektronix 4041 EZ-TEST DC-100 Tapes or software files, or other 4041 tapes

Monty McGraw
 

I have been recovering a set of Tektronix 4041 tapes that I received from
Stan Griffiths in 2000 in a box with Tektronix 4051 tapes. The 4041
tapes included EZ-TEST Volume 1 and Volume 2, but the first file on EZ-TEST
Volume 1 tape was damaged due to the original drive belt removing the oxide
from the beginning of the tape when I replaced the belt :(

I have been posting all the tapes I have recovered to my github repository
for Tektronix 4041 located at:
https://github.com/mmcgraw74/Tektronix-4041-GPIB-Controller

Does anyone have the EZ-TEST Volume 1 DC-100 tape?

Thanks,
Monty


Re: Spectrum analyzer Tektronix 7L13 on mainframe Tektronix 7603

Attilio
 

Hi Ian,
I will be very careful not to damage the first mixer of my 7L13, I thought in any case to insert a DC blocker with a blocking capacitor of 1000 pF and two diodes in anti parallel. I have some HP5082-2835 diodes, can
I use them ?

Greetings to all
Attilio


Re: Yet another 'replacing carbon resistors with metal film' question....

 

Personally I would *only* replace CC resistors that were causing out of specification behaviour. If e.g. all resistors in a potential divider have drifted high by the same %age (as is probable) then the divider will still have the correct voltages.

Or put another way if you can calibrate it successfully, then don’t replace anything at all!

David

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Jared Cabot via groups.io
Sent: 28 December 2020 09:47
To: TekScopes@groups.io
Subject: Re: [TekScopes] Yet another 'replacing carbon resistors with metal film' question....

Yeah, I'll be recalibrating for sure, as I intend to use it to calibrate other gear.

I'll test things thoroughly and might do as you say, just replace what is needed. I already tested the capacitors as perfect so they are back in place to continue being used.
I was just thinking to replace all the carbon composite resistors now as they are a known failure point and failures have already started. I just wanted to avoid having to go back in later and end up having to recalibrate etc multiple times.

It looks like Digikey stock carbon composition resistors too, so maybe I should swap like for like for those that are out of spec?


Re: Tektronix 1A7 and 1A7A Plug-ins

um-gs@...
 

Hi Dave,
today I gave my 1A7 (and the manual) a thorough look and found that there is indeed not a dual-Nuvistor pre-amp installed (as the manual says) but instead a PCB which obviously holds different parts (dual FETs?). The PCB is marked "1334XA".
As you mentioned 15 years ago in the above the "field-installable kit" - that might the be the explanation.
Do you by any chance have more references to this kit (and the schematic)?

Regards, Gordian


Re: Yet another 'replacing carbon resistors with metal film' question....

Jared Cabot
 

Yeah, I'll be recalibrating for sure, as I intend to use it to calibrate other gear.

I'll test things thoroughly and might do as you say, just replace what is needed. I already tested the capacitors as perfect so they are back in place to continue being used.
I was just thinking to replace all the carbon composite resistors now as they are a known failure point and failures have already started. I just wanted to avoid having to go back in later and end up having to recalibrate etc multiple times.

It looks like Digikey stock carbon composition resistors too, so maybe I should swap like for like for those that are out of spec?


Re: Yet another 'replacing carbon resistors with metal film' question....

Jean-Paul
 

Mr Cabot: We have PG501, 502, 506, running perfectly with all original parts, needing some switch and pot cleaning on occasion.

Carbon comp are lower self capacitance, and are still used in critical high freq and high voltage applications.

If it needs service, I suggest to replace ONLY failed/out of spec parts causing the issues, and leave all other parts alone.

Most of the changes in resistor type will make no difference.

"if it ain't broke dont fix it"

Regardless I suggest recalibration afterwards.

Bon chance,

Jon


Yet another 'replacing carbon resistors with metal film' question....

Jared Cabot
 

Hi all,

I have a PG502 TM500 module here I'm poking away at, and although the capacitors all test better than the datasheets in all respects (Those Vishay 30D caps are pretty good!), some of the old brown square ended carbon composite resistors have predictably drifted.
I also found also that the 15V trimpot is high resistance unless you press on the dial leading to no voltage rails, so that will be replaced.

I want to replace all of the fixed carbon composite with new resistors, but I'm not sure which way to go...
I have a set of modern 5% carbon film resistors, and also a set of 50ppm 1% metal film resistors too. I'm not too worried about using film resistors on the power supply etc, but the rest of the circuit is what I'm not sure about. I assume in this situation, the metal film is better than the carbon film seeing as they are both spiral cut?

What's the rule of thumb here? Should I just shotgun the metal film resistors and hope for the best, or use carbon composition resistors instead?

Here's the data sheets of the resistors I have:

Carbon film: http://takman-e.co.jp/pdf/rd_rds.pdf
Metal film: http://takman-e.co.jp/pdf/rlc.pdf


Re: Tek 465 Negative 8 volt rail issues

Dave Peterson
 

Paul,

I'm putting together a Mouser project for 465 PS caps. I pulled all 5 as they appear to have been leaking, it was going to be necessary to get at the suspected C1513, and once I got going it wasn't that bad, so might as well do all of them. I also have the adapter boards ordered and waiting for USPS to get them across country.

I was searching for radial Nichicon caps as I'm pretty happy with the order I made for C1419 replacements. I didn't catch your earlier reference to "snap" caps, and I see that these come in higher capacitance and voltage values than radial. Not that radial's aren't available, it just appears snap caps are inherently larger?

I've never heard of snap caps before. Aside from the obvious lead difference, what is the purpose/difference between radial lead caps and snap caps?

Dave


Re: 1S1: Defect trigger functionality repair

Glenn Little
 

Mine does not work.

Glenn

On 12/27/2020 10:09 PM, snapdiode via groups.io wrote:
Can I borrow your curve tracer? I mean after the pandemic.



--
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Glenn Little ARRL Technical Specialist QCWA LM 28417
Amateur Callsign: WB4UIV wb4uiv@arrl.net AMSAT LM 2178
QTH: Goose Creek, SC USA (EM92xx) USSVI LM NRA LM SBE ARRL TAPR
"It is not the class of license that the Amateur holds but the class
of the Amateur that holds the license"


Re: need case for 067-0508-00 Amplitude Calibrator

cougar_lou
 

Rick and the group.I have that rack assembly with the 184 and the amplitude calibrator.It is 110/220 Volt switch selectableUnfortunately,I'm currently 650kms from home visiting my daughter so I can not give you the type number from the name plate,I will be back home next week and will recontact you then.
Best wishes,Brian g

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