Re: FG 504 function generator odd behaviour

Colin Herbert

Oops! I have checked the voltages and while the +25V (+24.99), +15V (+14.98)
and -15V (-14.98) are just about bang on, the -25V is sitting at -3.58V. I
really can't remember if this was the case when I checked previously, but it
is now. I did manage to short something out with the DMM probes, so that may
have given this problem, but sure as sure it needs to be fixed, but how?
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Dave
Daniel
Sent: 10 July 2020 18:13
To: TekScopes@groups.io
Subject: Re: [TekScopes] FG 504 function generator odd behaviour

The first thing to do is measure the power rails to make sure that the
voltages are in spec and clean.

DaveD

On Jul 10, 2020, at 13:04, Colin Herbert via groups.io
<colingherbert=blueyonder.co.uk@groups.io> wrote:

I have an FG 504 which is showing some odd behaviour. The triangle-wave
shows asymmetry in that the negative peaks of the wave are rounded-off at
any frequency and the positive ones have a similar but lesser problem at
higher frequencies. This also seems to manifest itself as what looks like
cut-off on the negative peaks of the sine-wave and lesser cut-off on
positive peaks. While the triangle-waves are more-or-less symmetrical, the
sine-waves are definitely not so, showing a nearly three-to-one voltage
ratio in favour of positive peaks. There is also noticeably overshoot on the
square-waves at anything above 1kHz and only a DC offset at frequencies
below 80Hz.
I am totally ignorant of how this function generator produces
triangle-waves, but I do understand that the square-waves and sine-waves are
derived from the triangle-wave. Does anyone have any help that they can
offer? I would be grateful to get this useful function-generator working
properly.
Colin.

Re: Tektronix 2230

Hi Raymond
Thank you for the information.
Saroj

Re: Tek 465 Turns on, No Dot, No Trace

There is a wire jumper at board location A-5 that provides the ground to the HV multiplier. (note that I am going from old memory so take with a grain of salt). Measure to ground to see if it is grounded. It is next to a mounting screw for the multi module. Just lift one end and see if the HV osc comes up.

If the HV osc is not running, all the CRT vltage readings will be off.

Regards

On 7/11/2020 6:31 AM, Stephen wrote:
I notice something I didn’t pay attention to before. That is TP1486 should go from 15V to 75V depending on the position of the Intensity control knob. However, mine goes from 15V to only 31V with the intensity maxed out...
Hmmmmm.... Interesting... There is definitely something there as well.

PS: Where do I lift the HV multiplier lug?

--
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

Re: Looking for

stevenhorii

For those seeking a 7J20/J20 or parts, after the other posts on this, I’ve
decided I won’t continue searching for one other than out of interest of
what the price might be. It would be a novelty for me as I have equipment I
need to do the testing I do.

By the way, there’s an interesting module on eBay:

https://www.ebay.com/itm/1pp-1-qty-tektronix-dp-100-digital-video-probe/264388939882

Apparently a TM500 plug-in (TekWiki) and a pod is shown with it on the
TekWiki page but not by the seller on eBay.

I have several older Tek NTSC video test items. I had a 1910 digital
generator that was useful in the days of SDTV. If I am not mistaken, Tek
equipment. The Tek test signal generators, waveform monitors, vector
scopes, sync generators, etc. were made by Tek.

Steve H.

On Sat, Jul 11, 2020 at 11:27 Kurt Swanson <kurt2135@frontiernet.net> wrote:

I have a 7J20. Unfortunately, I don't have the sampling head. I've had
it for a long time, and when I got it, I knew it was uncommon, but I
figured a sampling head would eventually turn up. No such luck - at least
so far.
I got it wanting to do some optical spectroscopy work, and still would
like to get it working for that purpose.

If anyone has a sampling head, let me know, otherwise I might reluctantly
let this one go for sale or trade (and I do mean reluctantly).

Regards - Kurt

Re: Tektronix 2230

Hi Satbeginner

Understood
Thanks

On Sat, Jul 11, 2020, 10:12 PM satbeginner <castellcorunas@gmail.com> wrote:

Hi Saroj,

Connect one winding to oscillator, also Ch1 of the scope to the same
winding.

Now use Ch2 of the scope to check the other windings.

I would connect the dot-side of the first winding to the signal generator,
the other side of the winding to ground.

That way on the other windings the dot-side should be in fase with the
winding connected to the oscillator.

Keep going, success,

Leo

Re: Tektronix 2230

satbeginner

Hi Saroj,

Connect one winding to oscillator, also Ch1 of the scope to the same winding.

Now use Ch2 of the scope to check the other windings.

I would connect the dot-side of the first winding to the signal generator, the other side of the winding to ground.

That way on the other windings the dot-side should be in fase with the winding connected to the oscillator.

Keep going, success,

Leo

Re: Tektronix 2230

Hi Satbeginner
Right now I am looking for kapton tape in the market. Yes, I have another
scope and signal generator.If I am not wrong, probing at dotted points
scope should show voltages at same phase.
Thanks
Saroj

On Sat, Jul 11, 2020, 3:04 PM satbeginner <castellcorunas@gmail.com> wrote:

Hello Saroj,

Another thing popped into my mind:

Before putting the transformer back, if you have another scope and a sine
generator, you could verify the fase of the windings.

And another one:

Once you are at the point of powering on again, connect a voltmeter to the
first switcher to check the 43V it is supposed to generate.

It could be the first time -because of the wrong feedback signal- the
voltage of the first switcher was way to high, and the scope was saved by
the second regulator and the crowbar circuit.

Succes!!

Leo

Re: Tektronix Blue paint - source in the UK ??

Dave Daniel

The other problem is that once mixed, it is difficult (but not impossible) to spray it on the parts to be painted. If one has a paint sprayer, it’s not too big a deal, except for having to clean the sprayer afterwards.

I heard a while back that one or more paint vendors would mix it and package it in spray-paint cans. I don’t know that was or still is the case.

DaveD

On Jul 11, 2020, at 11:57, Robin_Birch <robinb@ruffnready.co.uk> wrote:

Yes,
All automotive paint suppliers will colour match and create a good match for you. The problem with quoting a specific paint supplier’s base or mix colours is that only works where that manufacturer’s colours are available.

Cheers

Robin
On 11 Jul 2020, at 15:31, Stephen Hanselman <kc4sw.io@kc4sw.com> wrote:

﻿I’m not sure about folks outside of the US but if it were me I’d take a side panel down to the paint store and have them color match it. I’ve used this method on my house where it works well, no reason it shouldn’t work on test equipment

Regards,

Stephen Hanselman
Datagate Systems, LLC
On Jul 11, 2020, at 04:26, Colin Herbert via groups.io <colingherbert=blueyonder.co.uk@groups.io> wrote:

﻿There has been communication on Tek blue paint ever since I joined this Forum. May I respectfully suggest that you have a search through the past posts to find all you can. There is a lot of information there, though a good deal relates to US providers, I am sure that some UK-dwelling members have contributed.
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of chris gare
Sent: 10 July 2020 11:41
To: TekScopes@groups.io
Subject: Re: [TekScopes] Tektronix Blue paint - source in the UK ??

I'm from the UK and don't quite understand the "Bluebase 79126" reference? The the other colors are fine as they are in Ounces?

Chris

Re: Looking for

Dave Daniel

The J20/7J20 spectrometer had two (optional) fiber optic probes available. As nearly as I can tell, the base instrument did not come with a probe. One of the optional probes was described in the (1975) catalog as transferring light to the entrance slit. The second was described as a UV quartz fiber optic probe for transferring UV light. Both came with mounting rings (there are photos of the UV probe on the TekWiki site).

There were also an external normalizer and a filter holder available as accessories.

In some 20-odd years of looking for this instrument I have only ever seen one J20/7J20 come up for sale. I’ve never seen a standalone probe come up for sale.

DaveD

On Jul 11, 2020, at 11:26, Kurt Swanson <kurt2135@frontiernet.net> wrote:

I have a 7J20. Unfortunately, I don't have the sampling head. I've had it for a long time, and when I got it, I knew it was uncommon, but I figured a sampling head would eventually turn up. No such luck - at least so far.
I got it wanting to do some optical spectroscopy work, and still would like to get it working for that purpose.

If anyone has a sampling head, let me know, otherwise I might reluctantly let this one go for sale or trade (and I do mean reluctantly).

Regards - Kurt

Re: Tektronix Blue paint - source in the UK ??

Yes,
All automotive paint suppliers will colour match and create a good match for you. The problem with quoting a specific paint supplier’s base or mix colours is that only works where that manufacturer’s colours are available.

Cheers

Robin

On 11 Jul 2020, at 15:31, Stephen Hanselman <kc4sw.io@kc4sw.com> wrote:

﻿I’m not sure about folks outside of the US but if it were me I’d take a side panel down to the paint store and have them color match it. I’ve used this method on my house where it works well, no reason it shouldn’t work on test equipment

Regards,

Stephen Hanselman
Datagate Systems, LLC
On Jul 11, 2020, at 04:26, Colin Herbert via groups.io <colingherbert=blueyonder.co.uk@groups.io> wrote:

﻿There has been communication on Tek blue paint ever since I joined this Forum. May I respectfully suggest that you have a search through the past posts to find all you can. There is a lot of information there, though a good deal relates to US providers, I am sure that some UK-dwelling members have contributed.
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of chris gare
Sent: 10 July 2020 11:41
To: TekScopes@groups.io
Subject: Re: [TekScopes] Tektronix Blue paint - source in the UK ??

I'm from the UK and don't quite understand the "Bluebase 79126" reference? The the other colors are fine as they are in Ounces?

Chris

Re: tektronix 2465b rom.

James Theonas

Thank you my friend!

On Saturday, July 11, 2020, 5:12:06 PM GMT+3, Chuck Harris <cfharris@erols.com> wrote:

Yes, and no...

You know what the values should be, and you know
relatively where they exist in the calibration file,
but you have no idea how, or where, they exist in
the 2K RAM.

Tektronix went out if its way to avoid telling you
that little tidbit of information.

Looking at your screen pictures, and looking at the
data in a hex editor, you can probably figure out
where in the 2K byte RAM the constants are, but you
also have to figure out where the checksums for the
whole file exist.

I know there is a routine in the EPROM that lets
you write back the calibration data, but it is not
available to the unwashed masses.  Someone told me
about it once many, many, years ago, but I remember
nothing about it, only that it exists.

Well, that's not quite true, I recall it is a simple
button press from within the EXER02 routine.

Tektronix would never use such a routine, outside
of development, as they would simply recalibrate the
scope to restore any errant calibration data.

-Chuck Harris

James Theonas via groups.io wrote:
Hi guys! I opened exerciser 2 on my scope and copied all the data from 00 to ff by looping through all of them as I was recording a video. If I input the said data in my programmer and flash a new chip will it work? Is that all that is needed?

Thanks everyone for the fantastic people in this group!

Re: Looking for

Kurt Swanson

I have a 7J20. Unfortunately, I don't have the sampling head. I've had it for a long time, and when I got it, I knew it was uncommon, but I figured a sampling head would eventually turn up. No such luck - at least so far.
I got it wanting to do some optical spectroscopy work, and still would like to get it working for that purpose.

If anyone has a sampling head, let me know, otherwise I might reluctantly let this one go for sale or trade (and I do mean reluctantly).

Regards - Kurt

Re: New member with a currently-dead 2465

Siggi

On Fri, Jul 10, 2020 at 8:02 PM Tom Miller <tmiller11147@comcast.net> wrote:

Just replace U2556. It is a cheap part. Cut the leads close to the chip
package, remove the package, then unsolder and remove each pin one at a
time. Clear the holes and put in a new 74LS04. I wager a cheeseburger
that is the problem.
In an over-the-counter repair shop, this would be sage advice, and I'm not
sure I'd take you up on that bet.
I believe Vincent is, however, more interested in the journey than the
destination, and by measuring and thinking through all the things, you

Re: Cleaning TM500 module pushbutton switches

J Mcvein

Early on e.g. 1960's, WD-40 used fish oil. It changed to petroleum
around the 1970s when fish oil became more valuable as a food
supplement. That has not stopped the salmon fishermen out here
from spraying their herring baits with it. Old practices die hard.

JimMc

-----Original Message-----
From: "Greg Muir via groups.io" <big_sky_explorer=yahoo.com@groups.io>
Sent: Friday, July 10, 2020 9:18pm
To: TekScopes@groups.io
Subject: Re: [TekScopes] Cleaning TM500 module pushbutton switches

Roy,

My experience with WD40 came when working on a project in Hawaii under high humidity conditions. The stores sold WD40 in gallon cans because everyone was using it to prevent their tools from rusting.

I followed the crowd and applied heavy coatings to anything ferrous with the stuff. Some of the tools went for several months before they were brought into use. But when they came out it was found that the WD40 coating on them had turned into something similar to Cosmoline and required washing it off with solvents to clean them before they could be used.

Obviously the tools did not rust. But there was something at play here that made the WD40 very messy. May have been the humidity. And from that I decided that WD40 was not very useful other than for storing things and loosening frozen items.

I’m wondering if WD40 Company has changed the formulation since then.

Greg

Re: New member with a currently-dead 2465

Siggi

On Fri, Jul 10, 2020 at 7:33 PM Vincent Mallet <vmallet@gmail.com> wrote:

Tested +5V and GND pins of U2556 and they are as expected.
I tested the 3-4 inverter by bringing pin 3 to +5V or GND (like you
mentioned, although using a 22R shunt briefly instead as this is what I had
laying around) and hmm I didn't see much reaction on its output 4.
That's not too surprising. The only inverter input where it is reasonable
to do is the 1-2 inverter. The input there is weakly biased, rather than
being positively driven from another logic output.

Surprising things happened next when I tested the 1-2 inverter. I started
by putting my scope probe on pin 1 to make sure my 22R shunt was having the
desired effect on the input. The input was sitting at about 1.05V. I
briefly applied +5V to pin 1 (via 22R) and bam! I started seeing a sine on
pin 1. The sine had a 840mV pk-pk amplitude sitting right above a 1V
offset, 10Mhz. I touched pin 1 again and a 2.24V pk-pk sine appeared (again
sitting right above 1V), and I saw something appear on the 2465 display!
The scope had booted up! Things vanished shortly after.

I redid the experiment after putting another probe on TP505 U2092-37 and I
saw different results. Once I got a nice 2.24V pk-pk sine on pin 1 which
gave me a 1.25Mhz (almost) square on TP505 which is matching the expected
value from the service manual. It lasted 5s, then the pin1 sine shrunk to
~840mV pk-pk again. Touched it again and I got a 400mV pk-pk (offset 1V)
but this one was ~30Mhz! The resulting TP505 more-or-less square wave was
at 3.75Mhz, three times the expected frequency. Touched it again and pin 1
sine became a not-so-sine wave, 10Mhz, 560mV pk-pk.

Sounds like there's something just marginal in the oscillator. If you catch
the oscillator napping, you can infer the values of the biasing resistors
(R2571/R2573/R2553) by the voltage drop across them. You also want to
validate that the output of the 1-2 inverter is making the right output
voltages. Low is below 0.8V and high is above 2.0V, if the output is in
between there, you're nowhere. Same for the inputs. You measured 1.05V,
which is in no-man's land, so now you need to figure out why. Either the
biasing resistors have drifted (this happens with carbon comp resistors in
particular) or your 1-2 inverter is marginal or bad, or there's leakage
somewhere.

I pulled the legs of C2565, C2566, C2572 to measure them with an LCR
meter.
C2565: 84.5pF (specs: 82pF, 5%)
C2566: 33.3pF (specs: 33pF 5%)
C2572: 100.1nF (specs: 100nF 20%)

I do not know how to measure leakage current yet.
If you catch the circuit in a non-oscillating state, you can measure the
voltage drops across the respective resistors. From Ohm's law and the
resistor nominal values, you should then be able to guestimate the current
going through them. If things don't add up, you either have resistors that
are out of spec, or you have leakage through the capacitors - measuring the
resistors will tell you which. You can probably get quite near the truth
by measuring the resistors in-circuit.

I should have access to a better desoldering tool soon and I'll pull the
resistors and U2556 so I can measure / test them out of circuit.

Good luck!
Siggi

Re: Tek 465 Turns on, No Dot, No Trace

Stephen

On Fri, Jul 10, 2020 at 12:10 PM, Tom Miller wrote:

Can you go back and measure all the other low voltages in the HV
circuit? The base being positive so much says the HV oscillator is not
running.
I think now I understand what you asked me to do. If you were referring to these wave forms shown before the CRT section I should be expecting at different points, I don’t. Point 87 (J6-10) and 88 are just fat and blurry traces. Nothing like the square waves shown in the service manual. Of course I used the same settings (5ms/50mV)

Re: FG-504 not-so odd behavior

John Ferguson

with the FG 504 set at start freq 10, stop freq 40, multiplier at 10^2, sweep off,

measured on my 2445b, Sine freq 982.3 Hz, Sawtooth 975.9 Hz and Square wave 24.5 mHz.

The square wave is an asymmetrical  sine wave, not the Sawtooth I was expecting.

Since I have two of these things and this one at least does this, and also the sweeps and other functions, all except a square wave, and the other one does nothing, this might be the one to fix.

What do you think?

john

Re: DP512 12 GHz Digital Prescaler

Holger Lübben

HI!

A german Tektronix fan constructed three plugins:

1) RO510 10MHz Rubidium Oszillator. Two protoypes were built.
http://w140.com/tekwiki/wiki/RO510

2) DP512: A 12GHz 1:1000 prescaler. One prototype was built. It worked up to 14GHz.

3) GS510: A 10MHz Oszillator based on a trimble GPS module. One prototype was built
http://w140.com/tekwiki/wiki/GS510

All prototypes were constructed around this card:
http://w140.com/tekwiki/wiki/SD_TEK_500_Prototype_Card

There was a plan to finish the construction and to sell these plugins. But unfortunately the constructor died.
None of the involved people had any relationship to Tektronix.

Holger

Re: Tektronix Blue paint - source in the UK ??

Stephen Hanselman

I’m not sure about folks outside of the US but if it were me I’d take a side panel down to the paint store and have them color match it. I’ve used this method on my house where it works well, no reason it shouldn’t work on test equipment

Regards,

Stephen Hanselman
Datagate Systems, LLC

On Jul 11, 2020, at 04:26, Colin Herbert via groups.io <colingherbert=blueyonder.co.uk@groups.io> wrote:

﻿There has been communication on Tek blue paint ever since I joined this Forum. May I respectfully suggest that you have a search through the past posts to find all you can. There is a lot of information there, though a good deal relates to US providers, I am sure that some UK-dwelling members have contributed.
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of chris gare
Sent: 10 July 2020 11:41
To: TekScopes@groups.io
Subject: Re: [TekScopes] Tektronix Blue paint - source in the UK ??

I'm from the UK and don't quite understand the "Bluebase 79126" reference? The the other colors are fine as they are in Ounces?

Chris

Re: DP512 12 GHz Digital Prescaler

stevenhorii

I believe at one time a company called Spectracom built a TM500 rubidium
frequency standard plug-in.

On Sat, Jul 11, 2020 at 04:36 Egge Siert <eggeja2@hotmail.nl> wrote:

Hi Joe,

From a German eBay Member (I assume a former Tektronix Germany employee) I

"Guten Tag, ja ich weiß es, es sollte mal einen Eigenbau eines Prescalers
bis 14 GHZ werden, das Projekt wurde aber nie gestartet.

Mfg Klaus Chudzinski"

The earlier mentioned Rubidium Standard Plug-In was in fact a 10MHz GPS
Standard named GS510. Pictures of it are now in the posession of TekWiki.

Greetings,

Egge Siert

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