Date   

Re: New member and owner of a dead 2225

phillip.lyne.barrett
 

Thanks, David, Tom, Tom and Glen.

I've seen those videos. Dave's tear down is really good though my wife makes me wear headphones for any of his videos - she's a non-fan. I kind of get her point...

After following the circuits on the schematic, I think the 38V/67.5V feeds are probably OK because there doesn't seem to be anything particularly sensitive there. Two 100n 50V ceramics are worth looking at, one on the X-Axis Amp and one in the vertical output amp. Everything else feeds though resistors. Though the lowest is 330 so bears looking at a bit more.


It looks like Q912 is not blown, at least a resistance check across the collector and base sees a cap charging up - probably C909 though the 2.2K resistor on the base. Not sure how to determine if either TL594 is dead. I've got the datasheet but haven't looked yet. Will probably order a few just in case, they're cheap.


On the caps, I've found what look like decent replacements - reasonably low ESR, same or better tolerance and all are 105C. However, not a single lead pitch matches. I can make them fit by bending the leads in an L to make them fit the original pitch. I assume that there is no issue with that. So, not worried except for C900 - the big 2200 uF 80V on the mains input board. The only matches are snap-in caps with fat, stiff, stubby leads and the wrong terminal pitch. (10mm vs a measured 12mm on the one that's there now). I guess I can make a little adapter but it will be a bit ugly. If I was industrious, I'd 3D print a foot for it to keep it from moving around - though it will probably be hot glued instead.


Another question. There are at least 9 10 uF axial electrolytics in various places. I should replace them as well? I'm not wild about removing the attenuator/timebase board, though it's probably easier than it looks.


Once I get my ESR meter (due this Friday), I'll hopefully find a smoking gun.


Anyway, again, thanks for all the help. I really do appreciate all your efforts.


Phil


Re: DIY TD Pulser

Chuck Harris <cfharris@...>
 

Pardon, two of the 067-0513-00 pulse generators that David
mentioned wanting to see the inside of.

Which can be arranged, as I have two of them.

-Chuck Harris

Jeff Davis n0dyjeff@hotmail.com [TekScopes] wrote:

Not sure what exactly you have two of... 😊


I've posted some test results from two samples of the build I did following the notes from Sergey Kubushyn. The test was conducted over the noon hour on an 8 GHz digital Tektronix scope at work - didn't catch the exact model number.

I posted captures of the rise time photos under "DIY TD Pulser" in the Photos section. Got 159 pS on the first build. Was a little more careful with the output construction on the second and got down to 119 pS with it.


Jeff


________________________________
From: TekScopes@yahoogroups.com <TekScopes@yahoogroups.com> on behalf of Chuck Harris cfharris@erols.com [TekScopes] <TekScopes@yahoogroups.com>
Sent: Monday, November 13, 2017 6:46 PM
To: TekScopes@yahoogroups.com
Subject: Re: [TekScopes] Re: DIY TD Pulser



I have two of them. One has a bad TD, the other works, but
is easily 10 times slower than the spec's say it should be.

I had heard that when tektronix made them they had no real
way of measuring the pulse risetime, so they guessed.

-Chuck Harris

David davidwhess@gmail.com [TekScopes] wrote:
Why can't you use the random sampling capability on the 7T11? Then at
least no delay line should be required. A power divider might still
be desirable to separate the sampling kickout from the trigger.

Tektronix had a slightly more complex tunnel diode pulse generator
which generated a pretrigger:

<http://w140.com/tekwiki/wiki/067-0513-00>

It would be interesting to see the inside to see how it was
constructed.


Re: DIY TD Pulser

Jeff Davis
 

Not sure what exactly you have two of... 😊


I've posted some test results from two samples of the build I did following the notes from Sergey Kubushyn. The test was conducted over the noon hour on an 8 GHz digital Tektronix scope at work - didn't catch the exact model number.

I posted captures of the rise time photos under "DIY TD Pulser" in the Photos section. Got 159 pS on the first build. Was a little more careful with the output construction on the second and got down to 119 pS with it.


Jeff


________________________________
From: TekScopes@yahoogroups.com <TekScopes@yahoogroups.com> on behalf of Chuck Harris cfharris@erols.com [TekScopes] <TekScopes@yahoogroups.com>
Sent: Monday, November 13, 2017 6:46 PM
To: TekScopes@yahoogroups.com
Subject: Re: [TekScopes] Re: DIY TD Pulser



I have two of them. One has a bad TD, the other works, but
is easily 10 times slower than the spec's say it should be.

I had heard that when tektronix made them they had no real
way of measuring the pulse risetime, so they guessed.

-Chuck Harris

David davidwhess@gmail.com [TekScopes] wrote:
Why can't you use the random sampling capability on the 7T11? Then at
least no delay line should be required. A power divider might still
be desirable to separate the sampling kickout from the trigger.

Tektronix had a slightly more complex tunnel diode pulse generator
which generated a pretrigger:

<http://w140.com/tekwiki/wiki/067-0513-00>

It would be interesting to see the inside to see how it was
constructed.

On Mon, 13 Nov 2017 23:53:05 +0000, you wrote:

Hey Joseph,

I built one of those, and the complexity/value is not in the circuit. It's
mostly in the characterization of the behavior of the physical construction
of the circuit. Mine has a rise time of ~200ps, as determined by my TDS
784D and some maths. Plenty good to calibrate the transient response of my
485 and 2467, though I do worry about the pre-shoot and overshoot I see on
the TDS.
I'll need to look closer one day, now that I have a 7834, 7S11/7T11 - just
need a decent power splitter and a delay line, and a few more little things
:).

Siggi

------------------------------------
Posted by: David <davidwhess@gmail.com>
------------------------------------


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

Yahoo Groups Links




Engine Analyzer Plug-In Modification

Gary Robert Bosworth
 

Does anyone know the specific modification that was done to the 2B67 horizontal sweep plug-in to make it work with the Engine Analyzer that Tektronix offered back in the 1960's and 1970's? Physically, does it show on the outside of the plug-in?


Re: DIY TD Pulser

Chuck Harris <cfharris@...>
 

I have two of them. One has a bad TD, the other works, but
is easily 10 times slower than the spec's say it should be.

I had heard that when tektronix made them they had no real
way of measuring the pulse risetime, so they guessed.

-Chuck Harris

David davidwhess@gmail.com [TekScopes] wrote:

Why can't you use the random sampling capability on the 7T11? Then at
least no delay line should be required. A power divider might still
be desirable to separate the sampling kickout from the trigger.

Tektronix had a slightly more complex tunnel diode pulse generator
which generated a pretrigger:

<http://w140.com/tekwiki/wiki/067-0513-00>

It would be interesting to see the inside to see how it was
constructed.

On Mon, 13 Nov 2017 23:53:05 +0000, you wrote:

Hey Joseph,

I built one of those, and the complexity/value is not in the circuit. It's
mostly in the characterization of the behavior of the physical construction
of the circuit. Mine has a rise time of ~200ps, as determined by my TDS
784D and some maths. Plenty good to calibrate the transient response of my
485 and 2467, though I do worry about the pre-shoot and overshoot I see on
the TDS.
I'll need to look closer one day, now that I have a 7834, 7S11/7T11 - just
need a decent power splitter and a delay line, and a few more little things
:).

Siggi

------------------------------------
Posted by: David <davidwhess@gmail.com>
------------------------------------


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

Yahoo Groups Links




317 in Lyons, Colorado

Kurt Rosenfeld
 


Re: A fool and his money ...OR ... moneywell spent

 

On 13 Nov 2017 18:11:41 +0000, you wrote:

The test is to coaxially connect the probe tip through a 50 ohm feedthrough termination (Tektronix made this as a special adapter) to
a fast reference level pulse generator like a PG506 (not quite fast enough) or tunnel diode pulser like the Tektronix 067-0681-01 which is what was actually recommended for the 2465 calibration. Then the transient response can be compared with and without the probe on the oscilloscope itself.
I got the Agilent probes and they seem to be performing well with the Tek 2465 CTS but I really can't check the upper part of the bandwidth. I looked at getting a Tektronix 067-0681-01 (Calibration fixture / tunnel diode pulser) and was quite shocked on the availability and cost - more than I paid for the scope, shipping, and three of the four probes. Guess I'll be on the lookout for one of these. Not going to pay $250 that some folks want for these.
The Tektronix 067-0681-01 in particular is pretty expensive but I
think that is because there is high demand from those who do not know
of alternatives.

The Tektronix 067-0513-00 and Type 284 tunnel diode pulse generators
could also be used with a GR874 adapter. Tektronix even made GR874
feedthrough termination to coaxial probe tip adapters which are
intended for exactly this application; the part numbers are
017-0088-00 for miniature probe tips and 017-0520-00 for subminiature
probe tips. They were intended for low-z and active probes much
faster than 300 MHz so would be overkill for your application.

There are some other hobby level fast edge pulse generators available
which could be used. Some are avalanche transistor based and others
use the output signal from a CML or ECL gate.

<https://www.eevblog.com/forum/projects/yet-another-fast-edge-pulse-generator/>
<http://www.leobodnar.com/shop/index.php?main_page=product_info&cPath=124&products_id=295>


Tektronix 485s for sale

Dave Daniel
 

All,

Due to mounting pressures to sell my property I need to unload a few test equipment items.

I have two Tektronix 485s that I think I need to sell. I have powered them up and performed very basic testing. I have limited time and don't plan to do any exhaustive testing on either of them. They are not in calibration.

Below are descriptions:

1. Tektronix 485. It has serial number B192687. It has Option 78 - P11 phosphor. It is in good cosmetic shape. Channel 1 is rock-solid while channel 2 is a bit jittery; I suspect the front panel controls need cleaning. It has the rare front panel snap-on plastic cover. $300.

2. Tektronix 485. It has serial number B155872. Some of the button legends are worn off; I placed white label-printer labels with the legends on most of the buttons where the legends were missing. The mode buttons on this 'scope are in serious need of electrical cleaning. They operate stiffly and do not fully switch between modes (for instance, when the mode is set to CH1 or CH2, there is a second trace on the screen, as if the mode is really "sort of" ALT or "sort of" CHOP; putting additional pressure on the CH1/CH2 mode button eliminates the second trace). It also has the rare front panel snap-on plastic cover. I think I might have a few button caps that could be used to replace the ones on this 'scope where the legends are worn off; I will need to check. If so, I will include whatever I have with the 'scope. If not, Walter at Sphere or Qservice (or someplace else) may have them. $250.

I would like to sell these for the prices listed above plus the cost of shipping (and maybe for packaging materials if I have to buy them), more or less. The prices are negotiable; we'll see what responses I get. I will endeavor to pack them well so that they are not damaged in transit (I've shipped several largish Tektronix products around the globe and have not had any complaints, and received one compliment). I would use either USPS or UPS (not FedEx) at the buyer's discretion. Local pickup in the Lyons, Colorado (front range) area would be preferable. Payment would be by PayPal or cleared personal check.

I have one original manual which I would include for $10 with one of the 485s. I believe I have a printed copy of a PDF of the manual and, if I can find it, I would include that with the other 485. If not, then the other 485 would come without a manual.

If you are interested PLEASE CONTACT ME PRIVATELY using "kc0wjn at gmail dot com". Please do not reply to the list (I will ignore any such replies).

I am not at all pleased about having to sell these, as I had a 485 as one of my two "personal" 'scopes for many years at StorageTek many years ago and these 'scopes are old friends. But I think this is probably the right thing to do.

I also have a partially-working HP 8558B/853A spec an combo that I also need to sell, if anyone is interested in that.

Thanks for the bandwidth.

DaveD


Re: New member and owner of a dead 2225

n4mf_sc
 

I have the 1982 version I think and one from a website that is no longer there called Tek-cross-ref-free. It has a sig in the pdf of www.aa4df.com http://www.aa4df.com which is available for someone to purchase but no longer online. I can't post either because they are way past the limit on upload sizes. Transistors and IC's are in both..

Mitch
N4MF


Re: New member and owner of a dead 2225

Tom Jobe <tomjobe@...>
 

Hi Phillip.
I see you are getting some very good help on this problem, and when you
combine that with the fact that your voltages are only down by half, I'd
say the 2225 is only lightly wounded and that you will have it working
perfectly very soon. In order for the low voltages to be half there,
most of the power supply must be fundamentally sound.
The 2225 needs all of the aluminum electrolytic capacitors 10 uF and
larger changed anyway to regain that sharp trace you once had, and the
new ones might possibly help with your current problem as well. Get
brand new high quality 105 degree caps from a major electronics parts
supplier if you can.
There are several variations of the architecture of the small 22xx power
supplies but there are not many problems with the 2225 type of power
supply that ever show up on the Tekscopes Group .
When I read your original post about your 2225 problem, I looked on
YouTube to see what kinds of videos were available about the 2225.
Take a look at these two when you have time. This 2225 Dave Jones bought
worked just as it was received, and he gives you quite a nice lesson on
its use and claibration, as well as a tour of much of it's inner
workings (less the power supply unfortunately). He also gives you some
good common sense tips about working around the high voltages present in
the oscilloscope.

EEVBlog #196 operational review of the 2225
https://www.youtube.com/watch?v=8GR_6QH3uZk

EEVBlog #208 teardown and calibration of the 2225
https://www.youtube.com/watch?v=mHODWDBcQDg

Best of luck!
tom jobe...




On 11/12/2017 3:29 PM, phillip.lyne.barrett@gmail.com [TekScopes] wrote:

Long term electronics hobbyist. I've had a Tek 2225 for about 15 years
and used it a lot. The other day I turned it on to test a circuit I'm
prototyping and nothing. Dead. Check outlet, fuse, power cord. Nope.
The only sign of life is a little blip on the power and leds - maybe
half a second. I'm guessing it's the power supply. This scope has been
an old friend.


I got the service manual and pulled the chassis out of the case. Found
a loose torx screw inside though It didn't appear to be shorting
anything and after removing it the symptoms persist. The scope had
been sitting on the bench in the same spot for a couple of years so I
doubt the screw was the problem. Inspection didn't show anything
obvious - burnt components, bulging caps, blue smoke. In fact, it was
surprisingly clean for 30 year old scope.


Anyway, I took some test point measurements on the bottom of the main
baord and all the voltage levels were around half what they were
supposed to be. More confident it's the PS. Looked at the mains input
board. rectifiers (CR901-CR904) are ok. Pulled the board and pulled
the big @ss 2200 uF cap (C900). It tested out ok (2270 uF).


Next step is to look at the preregulator section after I put the mains
input board back.


I'm just following a fairly logical path here but thought there might
be smarter people than me here that could help short cut the process.
Any suggestions of where to look would be greatly appreciated.


Phil

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



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


Re: DIY TD Pulser

 

Why can't you use the random sampling capability on the 7T11? Then at
least no delay line should be required. A power divider might still
be desirable to separate the sampling kickout from the trigger.

Tektronix had a slightly more complex tunnel diode pulse generator
which generated a pretrigger:

<http://w140.com/tekwiki/wiki/067-0513-00>

It would be interesting to see the inside to see how it was
constructed.

On Mon, 13 Nov 2017 23:53:05 +0000, you wrote:

Hey Joseph,

I built one of those, and the complexity/value is not in the circuit. It's
mostly in the characterization of the behavior of the physical construction
of the circuit. Mine has a rise time of ~200ps, as determined by my TDS
784D and some maths. Plenty good to calibrate the transient response of my
485 and 2467, though I do worry about the pre-shoot and overshoot I see on
the TDS.
I'll need to look closer one day, now that I have a 7834, 7S11/7T11 - just
need a decent power splitter and a delay line, and a few more little things
:).

Siggi


Re: New member and owner of a dead 2225

 

I think U940 would have been overvoltaged. Max is 41 volts. It would have seen 67 - 15 or 52 volts. But those are very cheap and available. C972, 470/50v could have survived a 17 volt overvoltage. But they are cheap and available. I agree Q912 is probably ok as long as the stressor didn't get it before 913 shorted.

Hell, I would sure try to bring it back to life.

Tom

----- Original Message -----
From: David davidwhess@gmail.com [TekScopes]
To: TekScopes@yahoogroups.com
Sent: Monday, November 13, 2017 6:12 PM
Subject: Re: [TekScopes] New member and owner of a dead 2225



A shorted Q913 should have protected driver Q912. Q911 should have
protected TL594 U910.

The linear series regulator would have tried to control the output
voltages until Q923 overheated and likely failed shorted. Switching
regulator controller U940, another TL594, operates open loop to drive
the inverter but uses one of its error amplifiers to detect the supply
voltage to the inverter and if it rises above 42.5 volts, it shuts
down so the rest of the oscilloscope circuits should be protected.

I am not sure about how the +40 volt supply rising to +67.5 volts is
going to affect the sweep circuit on schematic 5 and the vertical CRT
amplifier on schematic 5. Normally both circuits should be able to
protect themselves until they overheat but when the low voltage
outputs shut off, they may not be able to. I am inclined to believe
Tektronix took this into account but the theory section says nothing
about Q913 failing as a short.

On Mon, 13 Nov 2017 01:01:56 -0500, you wrote:

>That's not good. The Q913 is a TIP30C and is available pretty cheap. The analog pass xistor Q923 is also on ebay. You should also check the driver to Q913, Q912. Probably pull Q913 to double check it and follow up with some other measurements.
>
>The switching regulator is a TL594. They are common. Two are used. probably both are now toast.
>
>You will need to check everything that is supplied the pre-regulated voltage (38 volts) as it would have exceeded many ratings. Besides the power supply schematic #7, check schematics 2 and 5 as this overvoltage goes to those sections.
>
>Good luck,
>Tom M


Re: DIY TD Pulser

Siggi
 

Hey Joseph,

I built one of those, and the complexity/value is not in the circuit. It's
mostly in the characterization of the behavior of the physical construction
of the circuit. Mine has a rise time of ~200ps, as determined by my TDS
784D and some maths. Plenty good to calibrate the transient response of my
485 and 2467, though I do worry about the pre-shoot and overshoot I see on
the TDS.
I'll need to look closer one day, now that I have a 7834, 7S11/7T11 - just
need a decent power splitter and a delay line, and a few more little things
:).

Siggi

On Mon, 13 Nov 2017 at 18:14 joseph@danyabutter.com [TekScopes] <
TekScopes@yahoogroups.com> wrote:



Sergey - thanks for the information. I looked at the schematic from the
data sheet and you are correct, this is not a very complex circuit. Not
sure why folks want over $200 for it. Guess they are hard to come by - law
of supply and demand.


Re: New member and owner of a dead 2225

 

If I had to order any parts, then I would include replacement aluminum
electrolytic capacitors.

On 13 Nov 2017 18:34:01 +0000, you wrote:

I'm wondering if I should just replace all the electrolytics and be done with it.


Re: New member and owner of a dead 2225

 

Absolutely there is; it is called the Tektronix Semiconductors Common
Parts Design Catalog and a search for that will turn up scans.

On 13 Nov 2017 19:20:14 +0000, you wrote:

One other question, is there an authoritative cross reference between the tektronix PN and the actual part number? I see a goodgle search on the tektronix part number typically gives at least one hit that shows it. A lot of places just show the Tek PN and list an amazing high price (one I saw was $8 for $0.50 part). I'll buy from Mouser, if I can.


Re: 7854 sticky keyboard buttons repair

Siggi
 

On Mon, 13 Nov 2017 at 15:14 Nenad Filipovic ilmuerte@gmail.com [TekScopes]
<TekScopes@yahoogroups.com> wrote:



Hi Everyone,

Sorry to hear you're having trouble looking at the photos. I tried to open
my own link both at home and from work (using Firefox), and images loaded
fairly quickly.
I had no luck loading images from Yahoo's albums all weekend, works fine
now. Guess something derailed over the weekend, and only got fixed bright'n
early Monday morn'.


Re: A fool and his money ...OR ... moneywell spent

Joseph Butter
 

Thanks Jeff
BTW - I think I inadvertently responded to that earlier thread.
Great information.


Re: DIY TD Pulser

Joseph Butter
 

Sergey - thanks for the information. I looked at the schematic from the data sheet and you are correct, this is not a very complex circuit. Not sure why folks want over $200 for it. Guess they are hard to come by - law of supply and demand.


Re: New member and owner of a dead 2225

 

A shorted Q913 should have protected driver Q912. Q911 should have
protected TL594 U910.

The linear series regulator would have tried to control the output
voltages until Q923 overheated and likely failed shorted. Switching
regulator controller U940, another TL594, operates open loop to drive
the inverter but uses one of its error amplifiers to detect the supply
voltage to the inverter and if it rises above 42.5 volts, it shuts
down so the rest of the oscilloscope circuits should be protected.

I am not sure about how the +40 volt supply rising to +67.5 volts is
going to affect the sweep circuit on schematic 5 and the vertical CRT
amplifier on schematic 5. Normally both circuits should be able to
protect themselves until they overheat but when the low voltage
outputs shut off, they may not be able to. I am inclined to believe
Tektronix took this into account but the theory section says nothing
about Q913 failing as a short.

On Mon, 13 Nov 2017 01:01:56 -0500, you wrote:

That's not good. The Q913 is a TIP30C and is available pretty cheap. The analog pass xistor Q923 is also on ebay. You should also check the driver to Q913, Q912. Probably pull Q913 to double check it and follow up with some other measurements.

The switching regulator is a TL594. They are common. Two are used. probably both are now toast.

You will need to check everything that is supplied the pre-regulated voltage (38 volts) as it would have exceeded many ratings. Besides the power supply schematic #7, check schematics 2 and 5 as this overvoltage goes to those sections.

Good luck,
Tom M


Re: Ebay seller playing shenanigans on scope auction

Ovidiu Popa [Business]
 

The funniest GSP happening with P-B was when they slapped one of those colorful eBay round stickers right on the nicely printed address. It took one month until a genius from the local postal service (so after arriving in Canada) had the brilliant idea to lift the %$^%&^ sticker and retrieve the stinkin' house number and postal code for delivery.

42921 - 42940 of 184691