Date   

OT: AVO Model 8

Malcolm Hunter
 

Hi,

Sorry for the non-Tek post. I bought an AVO Model 8 Mk IV from ebay as it
has the 3KV scale, and might prove useful for measuring the cathode voltage
on scopes. Unfortunately the seller sent it in a shoebox with one layer of
bubble-wrap so understandably it arrived as a 3D jigsaw puzzle. Fortunately
the front panel is intact and the movement is only slightly out. Does
anyone in Europe have a faulty Mk IV with a good case they would like to
sell me?

Thanks,
Malcolm


Re: Tek 314

Bert Haskins
 

On 12/21/2015 09:12 PM, John Clark johnclark05@... [TekScopes]
wrote:

Well, I've been probing all through this scope and so far the only
real fault I can find, aside from no display, is that I get no
waveform on the vertical output. I know that Q215 is no good but I
don't get any waveform prior to that either. However, since removing
the vertical deflector leads didn't give a trace I'm going to let that
be for now.

I've been all through everything and am now suspicious of the HV
circuit or the CRT itself. I've been testing as much as I can (I don't
have a HV probe) and have gotten to Q712, 151-1018-00, which is a
2SKL11 N Channel FET according to the cross reference website but the
part I pulled out is a Toshiba 2SK12 with the 4th lead cut off. I
cannot get it to test good according to any of the sites I've used for
instruction. I've used both the diode function and the ohms function
on my meter. On ohm function the only reading I get is 141 ohms with
black on the gate and red on the source. It's OL on all other
connections. On diode function I get 143mV on that same connection.
Nothing on any other connection. I suspect that it's no good.

If it's no good, would failure of this cause no trace? I can't test
much further since beyond this it's 1900V and my Fluke 87V goes only
to 1000v.

Thanks,
John
If you are aware of this, just let it go by...
On the 314 blanking is accomplished by a extra deflection plate which
moves the beam off screen.
When blanked the deflection voltages are not relevant.



.



Re: Seeking extenders and pinouts

Mark Wendt
 

On 12/21/2015 04:44 PM, leetmaster4004@... [TekScopes] wrote:
Its been several days and I've gotten some PMs back about the TM5000 extender and the 7000 extender. I am still hoping someone knows about the 5000 extender and the pin-out for the 5000 connector as well.
The pinout diagram is usually in both the mainframe and plugin service/operations manuals. It should be pretty much identical to the TM500 series connector.

Mark


Tektronix modular system - these plastic frames

Christoph
 

What again is this modular system of plugin units called? The SG503, PG506 and what not all they are called.
When buying these units these days you will hardly find one single unit that hasn' it's frame chipped out or broken.

Possibly an ideal task for a 3D-printer nowadays, but is there a good source for these plastic frames, knobs, frontplates etc.?


Merry Christmas and a Happy New Year everyone,

Christoph


Re: Thank you, garbage fairy!

Tim Phillips <tim@...>
 

----- Original Message -----
From: "snapdiode@... [TekScopes]" <TekScopes@...>
To: <TekScopes@...>
Sent: Tuesday, December 22, 2015 1:00 AM
Subject: [TekScopes] Thank you, garbage fairy!


from Tim P (UK)

I once rescued a tangled mass of BNC cables that someone probably didn't fancy untangling, and, buried in this rats-nest were two P6062B probes ! (Both work - no cable breaks.)

I was walking to the grocery store and I found a Combibind on the sidewalk with the recycling...


Yay!!!






Re: Thank you, garbage fairy!

Craig Sawyers <c.sawyers@...>
 

I was walking to the grocery store and I found a Combibind on the sidewalk with the recycling...
Result!


Re: Tektronix 7904 Intensity Problem

Opto Tinker
 

Thanks. Good to know U1615 is OK. I haven't seen many chip like that one, must cost a fortune.

I took the clue on DC restorer and did a search. Here is what I found.

http://sci.tech-archive.net/Archive/sci.electronics.repair/2006-02/msg01175.html

It is on a different model but the symptoms are very similar. Could it be the same problem?


--------------------------------------------

On Mon, 12/21/15, hewpatek@... [TekScopes] <TekScopes@...> wrote:

Subject: [TekScopes] Re: Tektronix 7904 Intensity Problem
To: TekScopes@...
Date: Monday, December 21, 2015, 8:17 PM


 









> But I don't know how to test the two 12Kv
diodes and the 7x multiplier chip

>

The multiplier (U1615) is OK. Brightness would be very low
if it wouldn't be.

Even with the blooming you currently see, keep the image out
of focus as far as possible. At high beam intensity, a
focused image greatly increases the risk of CRT screen
burn-in.



Are you sure you didn't accidentally move the CRT bias
adjustment?

I suspect your problem may be in the DC restorer circuits
(dwg 11, center area) and the surrounding circuits.

Also checking the chain from +130 V through the focus pot
all the way down to the CRT cathode may reveal something.



You may temporarily remove the PDA voltage from the
CRT's high voltage anode connection. Make sure you fix
it in a safe spot where it can't do any harm!

Since I haven't studied how the feedback (circuits Beam
Sense and I Sense) will behave if you remove the HV
multiplier's * input* , I can't recommend that. With
non-tapped multipliers, that's a safe and easy way to
temporarily remove the PDA voltage.



*** Be careful, the HV remains on the CRT and on the anode
lead after you switch off ***.



You may even be able to see a screen image without the PDA
voltage, albeit (very) dim.

HV caps may become leaky at higher voltages only, making
ohmmeter measurements useless. Sometimes it's best /
easiest to just replace them. The same holds true for HV
diodes.



Raymond



[Non-text portions of this message have been removed]













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Re: 576 HV transformer

Ed Breya
 

Update. The whole thing crapped out, so I'm not sure about the HV xmr issue until I fix the main supply. Found an interesting thing - the -75V supply is running about -38V, and the +100 is about +48V, even with the HVPS disconnected - roughly in proportion, so I think every supply is likely about one-half the correct value since they're referenced from the -75V.

I found that C719, a 3 uF wet-slug Ta cap in the -75V supply looks like it leaked and corroded. I have another supply board from a junker, and it looks like the same problem. I started scraping crud off around the elastomer seal, and some of the sulfuric acid electrolyte oozed out - these need to be yanked ASAP before they do any damage. It's pretty clear that the wet Ta cap was used here for the combination of high CV density, high enough voltage rating, and low leakage - it's in the feedback loop of the -75V regulator. If it gets leaky, the -75V will be too low. A plastic cap should fix it, but will be quite a bit larger. I think there's enough room on the back side of the board to fit new plastic caps there instead.

I don't know if this is the only problem, but I'd recommend that 576 owners consider this. I will update on this again after I get a chance to replace the cap and get the supply running right. Then I'll deal with the HV problem.

Ed


Re: Tektronix 7904 Intensity Problem

 

But I don't know how to test the two 12Kv diodes and the 7x multiplier chip
The multiplier (U1615) is OK. Brightness would be very low if it wouldn't be.
Even with the blooming you currently see, keep the image out of focus as far as possible. At high beam intensity, a focused image greatly increases the risk of CRT screen burn-in.

Are you sure you didn't accidentally move the CRT bias adjustment?
I suspect your problem may be in the DC restorer circuits (dwg 11, center area) and the surrounding circuits.
Also checking the chain from +130 V through the focus pot all the way down to the CRT cathode may reveal something.

You may temporarily remove the PDA voltage from the CRT's high voltage anode connection. Make sure you fix it in a safe spot where it can't do any harm!
Since I haven't studied how the feedback (circuits Beam Sense and I Sense) will behave if you remove the HV multiplier's * input* , I can't recommend that. With non-tapped multipliers, that's a safe and easy way to temporarily remove the PDA voltage.

*** Be careful, the HV remains on the CRT and on the anode lead after you switch off ***.

You may even be able to see a screen image without the PDA voltage, albeit (very) dim.
HV caps may become leaky at higher voltages only, making ohmmeter measurements useless. Sometimes it's best / easiest to just replace them. The same holds true for HV diodes.

Raymond


Re: Thank you, garbage fairy!

petertech99h
 

I'd get inside the machine and lightly oil and wipe down the punches and punch plate before rust makes then unusable!  Some day you'll have to copy and repunch a bad page before re-binding!
Pete

On Monday, December 21, 2015 8:00 PM, "snapdiode@... [TekScopes]" <TekScopes@...> wrote:


  I was walking to the grocery store and I found a Combibind on the sidewalk with the recycling...

That's crazy, they still sell 'em for hundreds... Took it home, wiped off the rain, blew in warm air from the vacuum cleaner, I now have a fully working binder thing for those plastic combs that hold Tek manuals together!!

I no longer have to go to the university paper store to re-bind the occasional manual!

Yay!!!



[Non-text portions of this message have been removed]

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[Non-text portions of this message have been removed]


Tektronix 7904 Intensity Problem

Opto Tinker
 

Hi,

I have been asking around here for advice on repairing my Tektronix 7904. It came without trace but the readout is good, showing "mV", "nS" readings as shown in the 1st picture below. Later it developed the "ticking" problem on its own.

I changed a few capacitors and the trace comes up. But it seems to be too bright and the readout is burnt into a blur, as shown in the 2nd picture below. The characters are sharp for a moment as the tube is turning on.

The intensity knobs are in the full clockwise position. Turning them counter clockwise would blur the trace without reducing intensity.

The readout knob has to be in full clock position too (max intensity). Turning it counter clockwise would cause the power supply to tick again at some point. Doing so has no visible effect on the intensity, which remains too bright. The PSU ticks if I turn readout to "off".

I checked all diodes and transistors on the Z-axis board with an ohm meter and they seem to be fine. The resistors in the high voltage enclosure are OK visually. But I don't know how to test the two 12Kv diodes and the 7x multiplier chip.

All voltages on the PSU are fine, unless a ticking condition is produced by reducing (!) the readout intensity.

I would appreciate any suggestions. I am running out of ideas.



All about classic Tektronix CRT o'scopes https://groups.yahoo.com/neo/groups/TekScopes/photos/photostream/lightbox/1982050881



https://groups.yahoo.com/neo/groups/TekScopes/photos/photostream/lightbox/1982050881

All about classic Tektronix CRT o'scopes https://groups.yahoo.com/neo/groups/TekScopes/photos/photostream/lightbox/1982050881 All about classic Tektronix CRT oscilloscopes, their use, repair, and collecting. (If you want to join, please make sure you write something relevan...



View on groups.yahoo.com https://groups.yahoo.com/neo/groups/TekScopes/photos/photostream/lightbox/1982050881
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All about classic Tektronix CRT o'scopes https://groups.yahoo.com/neo/groups/TekScopes/photos/photostream/lightbox/618473724



https://groups.yahoo.com/neo/groups/TekScopes/photos/photostream/lightbox/618473724

All about classic Tektronix CRT o'scopes https://groups.yahoo.com/neo/groups/TekScopes/photos/photostream/lightbox/618473724 All about classic Tektronix CRT oscilloscopes, their use, repair, and collecting. (If you want to join, please make sure you write something relevan...



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Re: Mystery lamps

 

Hi Colin and David,
All neon lamps are pretty much the same. They have a 70 to 90V breakdown
voltage. The inner structure is a dead giveaway because there is no
filament, just two parallel thin metal rods about 1/4 inch long. They
usually need a 50K to 100K series resistor as a current limiting ballast
since once the gas breaks down the resistance of the bulb drops. You can
throw them on a curve tracer and observe the curve. Set the curve tracer to
AC, set the series resistor to 50K to 100K and turn the voltage up slowly to
100V. At about 70V the neon will break down and the current will increase.
They are extremely simple to manufacture and to use.

As far as their use in Tek scopes you can find them in many places. The most
obvious place is at the top of every front panel just above the CRT of every
530, 540, 580 series scope. They lit up to tell you which way the beam was
off screen.

They are often found in the HV sections of transistorized scopes where they
can act as limiters or very simple voltage regulators.

Finally, there was a time in the 1950s that Tek used them for DC level
shifting between stages in their amplifiers. But I think the noise of the
neon gas molecules proved to be their downfall and they quickly fell out of
favor for that application.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...]
Sent: Monday, December 21, 2015 11:35 AM
To: TekScopes@...
Subject: Re: [TekScopes] Mystery lamps

They could probably be used as replacements in the high voltage protection
circuits and anywhere an NE-2 neon bulb is called for.

http://www.donsbulbs.com/cgi-bin/r/b.pl/rt2-32-1a~donsbulbs.html

On 21 Dec 2015 11:26:53 -0800, you wrote:

Hi,
I purchased some lamps a while ago, believing them to be for 7000-series
graticule illumination, but they are nothing of the sort, as they are neon
lamps, by the look of it. The are wire-ended, just over 2cm in length and
~5mm diameter. They bear the words "SIGNALITE RT2-32-1A" in white lettering.
Does anyone know what these lamps are and if they have any application to
Tektronix 'scopes?
Colin.
------------------------------------
Posted by: David <davidwhess@...>
------------------------------------


Re: Delay sweep time measurements question

John Clark
 

Dwayne,
I'm glad you asked this. I, too, never noticed the grey background linking that text to the .02 and .01 settings. When I read that the other day I had to go pull the cover off of my 475 and look close with glasses and a flashlight. I've played around with the delayed time position knob and finally have a fairly good idea how it works, I even managed to check the calibration of it, but didn't put it together that the note referred to just those two settings.

I've actually been using my 475 today to probe my dead 314 and it's been a joy to use. I really like it.

John

Son-of-a-pup.

In my defense, it may have been "clearly" marked when new, but even
after I read your post I had to use a jeweler's loupe and a bright light
to see the 33 year old grey box on a grey background linking that text
with .02 and .01. I wondered what the text meant -- it seemed to apply
generally to the whole dial and in that context made no sense to me. The
manual makes no reference to it -- at least, not in the "Time Duration
Measurements" section on page 49. In fact, it says to use the fastest
sweep speed possible:


Re: Tek 314

John Clark
 

Well, I've been probing all through this scope and so far the only real fault I can find, aside from no display, is that I get no waveform on the vertical output. I know that Q215 is no good but I don't get any waveform prior to that either. However, since removing the vertical deflector leads didn't give a trace I'm going to let that be for now.

I've been all through everything and am now suspicious of the HV circuit or the CRT itself. I've been testing as much as I can (I don't have a HV probe) and have gotten to Q712, 151-1018-00, which is a 2SKL11 N Channel FET according to the cross reference website but the part I pulled out is a Toshiba 2SK12 with the 4th lead cut off. I cannot get it to test good according to any of the sites I've used for instruction. I've used both the diode function and the ohms function on my meter. On ohm function the only reading I get is 141 ohms with black on the gate and red on the source. It's OL on all other connections. On diode function I get 143mV on that same connection. Nothing on any other connection. I suspect that it's no good.

If it's no good, would failure of this cause no trace? I can't test much further since beyond this it's 1900V and my Fluke 87V goes only to 1000v.

Thanks,
John


Re: New 500 series mainframe plugin idea

mosaicmerc
 

Ok, Well, I'll keep the first version simple then.With an Analog 'manual' load sweep plus digital controls for the trigger set points I/O.

Perhaps another analog manual resistance sweep to output useful 'thermistor' values which can be displayed as temperature on the LCD. I can build in the thermistor temp/resistance profile based on user input Beta and 25°C resistance to get a °C representation.

That gives two operating approaches;
1) Set a thermistor temp. (resistance out) and sweep the load. Digital controls can allow preset load sweep range limiting so you can't overload the D.U.T.
2) Set a load and sweep the temp.(resistance out).

V,I, and thermistor °C are always displayed for analog feedback.

Augmented by selecting a good data log sampling rate so that the unit can up link a V,I,°C curve to EXCEL for analysis. Start and stop sampling parameter limiting can be useful to examine particular ranges of V,I or°C.
So if you're doing a ten second load sweep or so you can set the sample rate to say 1024 samples or thereabouts per channel (I,V,°C)to provide a manageable data set to analyze.

[Non-text portions of this message have been removed]


Re: EPROM Checksums

 

On 21 Dec 2015, at 23:45, hahi@... [TekScopes] <TekScopes@...> wrote:
Does anyone know how Tek did the check of F/W EPROM's at power up in general and in TM5000 plugins
in particular ?
Looking at Tek ROM images, I have seen signs of numerous different checksum algorithms being used. I haven't bothered reverse engineering any particular one of them.


--
Soren


Thank you, garbage fairy!

snapdiode@...
 

I was walking to the grocery store and I found a Combibind on the sidewalk with the recycling...

That's crazy, they still sell 'em for hundreds... Took it home, wiped off the rain, blew in warm air from the vacuum cleaner, I now have a fully working binder thing for those plastic combs that hold Tek manuals together!!

I no longer have to go to the university paper store to re-bind the occasional manual!

Yay!!!


Re: New 500 series mainframe plugin idea

John Griessen
 

On 12/21/2015 04:29 PM, Stefan Trethan stefan_trethan@... [TekScopes] wrote:
It measures the "unused" section of
a potentiometer so as not to interfere with the charger.
Nice thinking. :-)


Re: Seeking extenders and pinouts

 

The TM5000 extenderi the same part number as that for the TM500 series.
There was also an additional extender for the GPIB if needed (generally
not). connectors, but normally not.

Dave

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...]
Sent: 21 December 2015 21:45
To: TekScopes@...
Subject: [TekScopes] Re: Seeking extenders and pinouts

Its been several days and I've gotten some PMs back about the TM5000
extender and the 7000 extender. I am still hoping someone knows about the
5000 extender and the pin-out for the 5000 connector as well.


Re: Delay sweep time measurements question

Dwayne Verhey <yg@...>
 

Raymond,

Let's be kind and say that Tektronix assumed their scope manual readers are usually more experienced than I so they don't need to be spoon fed. ;-)

If nothing else, this scope has been a great learning experience for me.

Thanks again,-

Dwayne

73261 - 73280 of 195514