Date   

Re: SUCCESS! The "sick" 475A is now the "fixed" 475A!

 

It looks like I might have declared success a little bit prematurely. While the Z-axis amp now works, I am having some trouble in the calibration process (and not simply because I don't have any of the calibration fixtures).

I did step 1: Adjust Power Supply DC Levels, and a little tweak brought the 50V supply up to just below the 50.25V maximum.

I skipped step 2: Check High Voltage Power Supply, because I (still) lack a high voltage probe, and because this is just a check, there is not process to make any changes if the supply does not meet the spec. (I've ordered an HV probe for my DMM and will check the HV test point when that arrives after Christmas).

Step 3: Adjust CRT Grid Bias is where my difficulty starts. I can't get a visible dot on the CRT at the prescribed 15V level. I have to turn the intensity knob up almost to maximum, a reading of 24V at TP1364 before I see anything on screen. I also don't have any room to adjust the trim pot, R1375, to brighten the spot; R1375 is already turned to it's limit, and turning the other direction dims the spot on screen.

The result is that the remainder of the grid bias process fails because the trace brightness is much too low.

This seems a little odd, as under normal use I only need to set the brightness control at about the 40%/11 o'clock mark to get a visible trace, so I know that the CRT isn't pooping out. I suspect that there is still something broken in the Z-axis/beam intensity system.

I'm currently looking over the schematics to see what might be causing this, and to understand how I should go forward diagnosing it, but I would appreciate any suggestions.

-- Jeff Dutky


Re: Interfacing 576 Curve Tracer to 7633 Storage Scope

Jean-Paul
 

Dear Dennis WOW! great idea, never thought of that.

Instead of a CRT storage scope I would use a modern digital scope. A 4 channel scope could he used in A-B for differential input. One could take a screen shot and export to a computer via USB, HPIB etc.

Can you please detail or post a markup of the 576 amplifiers showing the pickoff points you wired for the connection?

Many thanks


Jon


Re: Asking for Help with Verifying Genuineness of 2465B from Ebay

Jean-Paul
 

Eric: Notice that 2465, 2465A and 2465B are different entirely, though in the same series.

Check the A5 control board see if any SMD tant leaking.

Does it pass CAL and all self tests?

Check BW and transient response?

Jon


Re: Asking for Help with Verifying Genuineness of 2465B from Ebay

Jean-Paul
 

Who was the seller:

There are some unethical Epay sellers that had many such issues.

You should be suspicious of such sellers. Board numbers ar enot definitive and the white suffex 2 digit sticker is normal.

What was the epay lot # ?

Jon


Re: Interfacing 576 Curve Tracer to 7633 Storage Scope

 

Hi Jay,
Several years ago my 577 HV transformer failed and I found myself without a curve tracer for the first time in several years. It was not going to be easy to find a replacement HV Transformer. But Walter Shawlee came up with a temporary solution for me by thinking outside the box. Why not pick off the X and Y signals before they get to the deflection plates and feed them into one of your other scopes.
It was easy to find the right spot in the vertical amplifier circuit and in the horizontal amplifier circuit to connect to and bring them out to a DB-25 connector since, for some reason, my particular 577 had an optional factory installed DB-25 cutout with a cover plate since it was not actually used for anything. I never noticed this before that moment and I can't say I have ever seen it on any other 577. But it was perfect for my needs. I was using the differential signals for both X and Y so I added a DB-25 connector, wired the deflection signals to 4 pins, made an extension cable to plug into the dB-25 connector and plugged the differential signals into a pair of 7A13 or 7A22 Differential amplifier plugins (I don't remember which I used) (one was in a vertical slot and one was in a horizontal slot) of one of my 7000 scopes. It worked perfectly. So your idea is a sound one.

There are easier (and cheaper) ways to do this but since I happened to have the amplifier plugins I needed that is what I used. There are hundreds of simple double-ended (differential) to single-ended OpAmp circuits you could use that will work fine and cost just a few dollars. They would also have the advantage of working with almost any kind of scope so you don't need specialized plugins or even an expensive scope.
Google "Images for differential to single ended amplifier circuits" and you will find hundreds of examples.

Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of rellikjm via groups.io
Sent: Saturday, December 19, 2020 12:18 PM
To: TekScopes@groups.io
Subject: [TekScopes] Interfacing 576 Curve Tracer to 7633 Storage Scope

Hello all!

I'd like to interface my 576 Curve Tracer to my 7633 Storage scope. It would be nice to have the features of the 577D1 Curve Tracer available to the 576. I have the 176 High Power Fixture for it and it doesn't trace anything but DC points. I'd also like to do push pull matching and true 0 bias point measurement.

Is the best way to grab the deflection signal right from the CRT pins and only use 1/2 of the differential signal that the deflection plates need or do the differential signals need to be integrated some how? I was thinking that if I used the (+) side of the horizontal and vertical deflection plate signals I'd be able to feed that into the storage scope in X-Y mode. My concerns are I don't want to do any damage to the 576 and I'm thinking it would be smart to use some sort of coupling capacitor from the deflection plate signal so I'm not coupling to the +225VDC that powers the deflection plate transistors. If I couple to the deflection plates should I leave the 576 CRT in circuit with the intensity turned down while feeding an external storage scope or should the CRT be disconnected and suitable load resistors connected to substitute for the disconnected 576 CRT?

Thanks in advance,

Jay







--
Dennis Tillman W7pF
TekScopes Moderator


New Tektronix Curve Tracer Adapters - Semiconductors and Vacuum Tubes

pinefloor@...
 

Hi Everyone!

I've been a proud owner of a Tek 576 for about 6 months or so now but I recently became increasingly frustrated with using minigrabbers to hook up DUTs so I decided to design some new test fixtures. I've tried to stay true to the form factor of the original Tektronix types but I'm not in a position to have plastic boxes made custom. So I've compromised with a dual layer PCB design. This leaves a bit to be desired from a safety standpoint but I figure curve tracer users should already be knowledgable about their high voltage/ current capabilities.

I currently have three types available if anybody is interested: A small signal outline, a flat/ tab/ inline type, and one for vacuum tubes with 9A/ 9AJ basing (12ax7, 6922, etc.) I have them listed on ebay here:

https://www.ebay.com/itm/264951846052
https://www.ebay.com/itm/264953083999
https://www.ebay.com/itm/264982302678

If anybody is interested, I'd be happy to sell them direct at a 10% discount.

I have a few more ideas that I'm sorting out, namely fixtures for surface mount transistors, but I'm most curious about what you all would like to see in a test fixture. Do you find the Kelvin connections particularly useful or that you have large measurement errors without them? I plan on making more tube fixtures as well but the solution by Mr. Tillman already covers just about everything you would need.

Anyways, thought I'd share with the group. Thanks to everyone for making this group so helpful and interesting!

-Chris


tek 454 for parts available

Bill Cromwell <wrcromwell@...>
 

Hi,

I have a Tek 454 in a 453 case that quit working about 30 years ago. I
suspect power supply caps. In those days my solution involved getting
another scope and I have not checked anything in this machine. Irecall
removing the horizontal output transistors and not sure I put them
back. They seemed to be okay out of circuit. That from 30 year
old memory. Without powering it up I feel pretty sure it has not self
healed with 30+ years on the shelf. I would like it gone. It *will* be
gone in the next couple of days if nobody speaks up. I am in north
central Michigan. The scope is available for pickup. I doubt it is
worth the cost of shipping but that is to be decided by anybody who
wants it.

I screen calls from unknown numbers. If you call my phone identify
yourself on my voicemail and I will call you back. Private email
preferred.

Bill

989-534-1409


Asking for Help with Verifying Genuineness of 2465B from Ebay

Mr. Eric
 

Hi Everyone,

I just purchased a 2465B from ebay. I'm trying to verify that it actually is a 2465B and not a rebadged and hacked lower bandwidth tek scope. From my understanding the best way is the serial number from the A1 board which I got. 670-9268-07. I looked up in the service manual and I saw that the A1 boards listed were:
670-9268-02
670-9268-04
670-9268-06
But I didn't see any mention of my A1 board: 670-9268-07 in that manual.

I also noticed that the last 2 digits "07" on my A1 board is actually a little white sticker with 07 written on it. I looked under the sticker and I didn't see anything else.

I'm a little thrown off, and I was wondering if anyone here had more insight to this. I just want to make sure that I indeed did get a genuine 2465B as I know others in this group have gotten "burned" on ebay. I did not purchase this 2465A from the ebay seller that has been mentioned in a few posts for hacking 2445s into 2465As.

Thanks in advance everyone!!!
Best Regards,
Eric


Thoughts About Modern Tek Scopes

 

I plan to get a modern DSO at some point, either a Rigol or Siglent 4 channel scope at 100 or 200 MHz, but just saw a TDS5054 on eBay for about the same price as the Siglent scope I've been thinking about. Aside from the higher bandwidth, the 5054 also has separate controls for each vertical input, which I would prefer to the the single multiplexed control on the Siglent (and most modern low-end DSOs).

My only concern is that the 5054 is clearly running Windows, which I don't like, but I feel that I should not dismiss it out of hand just because they used an operating system I detest.

I don't expect a modern DSO to deliver the same kind of user experience that I'm used to with the analog scopes from the 70s and 80s, but I'd like to know what other people's thoughts on using a newer Tek scope are.

So my questions:

Is this a good scope?
Is it worth getting this rather than newer Chinese scope?
What about buying a non-working unit, are they repairable?

-- Jeff Dutky


Re: 475A Chop Blanking and a Theory Question

Jim Ford
 

Similar jokes about the first smartwatch; it was so clunky that people said, "I'll wait for the portable version!"    Jim Ford Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: Tom Lee <tomlee@ee.stanford.edu> Date: 12/20/20 8:55 PM (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] 475A Chop Blanking and a Theory Question Actually, the first Powerbooks were gray. They were preceded by the much less successful, light beige Portable which, given the bulky size and lead-acid battery, was an unintentionally comical name. But you could use them to jump-start your motorcycle in a pinch.-- Tom-- Prof. Thomas H. LeeAllen Ctr., Rm. 205350 Jane Stanford WayStanford UniversityStanford, CA 94305-4070http://www-smirc.stanford.eduOn 12/20/2020 20:17, Jeff Dutky wrote:> It's also fairly obvious that Apple took their design cues from GRiD with the first Powerbooks (also all-black, like the GRIDs, but without the magnesium case, sadly).> -- Jeff Dutky>>> >>


Re: 475A Chop Blanking and a Theory Question

Harvey White
 

I have software for that chip for both the AVR (it takes a good processor) and ARM (again ST micro F446 or better).  I have a TEK related project this (or something like it) will eventually show up in.

(C and/or C++)

Harvey

On 12/20/2020 11:17 PM, Jeff Dutky wrote:
Harvey,

Yes, that's a later model than what I have, I think it was called a GRiDPad. The first model was released just before the pen-computing craze of the early 90s. Prior to the GRiDPads they made the GRiDCase line of PC compatible laptops, and before that they made the GRiD Compas, which is well known as "the first laptop in space." GRiD also held the patent on the clamshell case design for many years. Prior to the GRiD Compass portable computers looked more like a portable oscilloscope (probably for the same reason: you needed space for the neck of the CRT). It's also fairly obvious that Apple took their design cues from GRiD with the first Powerbooks (also all-black, like the GRIDs, but without the magnesium case, sadly).

You are probably right about the interface to the gas plasma display having parallel data lines: there are eight lines with voltages in the mV range, as measured by my multimeter, that I hadn't figured out what they were for. I was just starting to get a good look at them with the scope when it blew a cap on the sweep board, and I started down my current path of acquisition, repair, and calibration.

The Epson part looks quite promising. I was expecting to put an Arduino between the RasPi and the laptop hardware, and bit banging the display interface from there, but this looks like a much better solution.

-- Jeff Dutky





Re: 475A Chop Blanking and a Theory Question

Tom Lee
 

Actually, the first Powerbooks were gray. They were preceded by the much less successful, light beige Portable which, given the bulky size and lead-acid battery, was an unintentionally comical name. But you could use them to jump-start your motorcycle in a pinch.

-- Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 12/20/2020 20:17, Jeff Dutky wrote:
It's also fairly obvious that Apple took their design cues from GRiD with the first Powerbooks (also all-black, like the GRIDs, but without the magnesium case, sadly).
-- Jeff Dutky




Re: 475A Chop Blanking and a Theory Question

 

Harvey,

Yes, that's a later model than what I have, I think it was called a GRiDPad. The first model was released just before the pen-computing craze of the early 90s. Prior to the GRiDPads they made the GRiDCase line of PC compatible laptops, and before that they made the GRiD Compas, which is well known as "the first laptop in space." GRiD also held the patent on the clamshell case design for many years. Prior to the GRiD Compass portable computers looked more like a portable oscilloscope (probably for the same reason: you needed space for the neck of the CRT). It's also fairly obvious that Apple took their design cues from GRiD with the first Powerbooks (also all-black, like the GRIDs, but without the magnesium case, sadly).

You are probably right about the interface to the gas plasma display having parallel data lines: there are eight lines with voltages in the mV range, as measured by my multimeter, that I hadn't figured out what they were for. I was just starting to get a good look at them with the scope when it blew a cap on the sweep board, and I started down my current path of acquisition, repair, and calibration.

The Epson part looks quite promising. I was expecting to put an Arduino between the RasPi and the laptop hardware, and bit banging the display interface from there, but this looks like a much better solution.

-- Jeff Dutky


Re: When a metal pin comes off the back of a CRT

Dave Seiter
 

I've never had an issue with the rear pins, but the deflection pins scare me. I've heard they are delicate, so I'm always really careful when removing and installing their leads.  I bent one on a 7488 once (maybe 30-35º), and bent it back very gently without a failure.  If it was a 7104 crt, I would have probably just left it as is.  If I did it again, I'd probably hold the bent portion stationary and make a new bend further out to get it pointed in the right direction.
-Dave

On Sunday, December 20, 2020, 02:06:38 PM PST, DW <wilson2115@outlook.com> wrote:

Thanks for the reply

This type of incident probably rarely happens where more often the pins just get bent.

I have dealt with removing various plugs and boards off CRT's before, I gently pull on the plug while very slightly rocking around until I work it off. When I install I make sure I am aligned and with a gentle push and slight rocking around I work the plug back on until it is fully seated. This technique seems to be the most gentle with the least amount of force.


Re: Readout for 5s14n - please validate my idea

Michael W. Lynch
 

It might be more difficult on the 5xxx and 51xx, but it can be done. How it is done and the black magic or witchcraft that is involved; is way over my head. However, the 5D10 Digital Storage plug in adds display readouts to the lowliest versions of the 5000 series Scopes.

--
Michael Lynch
Dardanelle, AR


Re: Firmware for Tektronix 492/496 spectrum analyzer

J. L. Trantham
 

The MC68766 is programmable with the BP Microsystems programmers, at least with the 1410 (and likely later and perhaps some earlier programmers).

I can certainly program the chips you need if you have the chips and tell me what specific files need to be programmed.

I looked at your link to the images and I can download the files and program the chips. However, it seems you don't need these two but your 'error' suggests you have a problem with a chip you do not have installed.

I guess I'm confused.

Happy to help if I can. I'm in NW FL USA.

Merry Christmas and Happy New Year.

Joe

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Steve Dench
Sent: Saturday, December 19, 2020 9:54 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Firmware for Tektronix 492/496 spectrum analyzer

There are a number of 24 to 28 pin adaptor boards on eBay as Ye Old
Commodore 64 computers have the same issue. I used some in my 468 some time
back with the usual Mostek Rom failures. Some of these adaptors are very
slim and fit the 468 well.

On Sun, 20 Dec 2020, 2:11 pm vk2bea via groups.io, <vk2bea=
yahoo.com@groups.io> wrote:

I have a 492 Spectrum Analyzer that has developed a fault with the ROM
(self test indicates a checksum failure).
The test blinks 14 times which, according to the manual, means that U2012
fails checksum. I do not have this ROM populated on the board (just U2023
and U2028)

Does anyone know what's going on here?

The ROMs are 8K x 8 one time programmable (it appears) part. (its also
possible that it is an ee programable part but that is unlikely I think).
The chip markings are custom - 160-0839-00 & 160-0838-00 (Tek #) and
SCM92217CR (with Motorola logo) & data code of 8343 and 8402.
8K 24pin DIP parts seem scarce (Although I found a Motorola MCM68766 thats
pin compatible ... I just don't see how I'll program it 8-( )

What is the standard practice for this repair? Use a 28 pin package and
add the appropriate mod wires ?
I found the firmware binary here ..
http://w140.com/tekwiki/wiki/ROM_images






Re: TEK 7603 REPAIR

Tom Lee
 

Many things can cause diminished brightness. Don't overlook simple possibilities, such as misadjusted or noisy trigger thresholds and holdoff (or any other trigger-related controls).  Check easy stuff like that first, before going on to Z-axis circuit-related hypotheses.

--Cheers,
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 12/20/2020 16:46, David Collier wrote:
Dear 7603 owners,
I just got serial no. 704170 'parts and repairs' from ebay. Mostly it works, including the graticule bulbs. The regulator board already has an uprated 30K resistor as standard; there is also a fan.
I took apart the rectifier and regulator boards to check before switching on. All TO-3 transistors had betas in the high 30's. All electrolytics are original and with low ESR; when switched on the minus 50V was spot on.
I took apart everything with gay abandon, not noting what wire came from where. Was able to work out rectifier and regulator board connections and placement, but am now left with the signal output board: where is P339 (for a white plastic 4-pin plug), and where do the three left hand co-ax sockets connect to (one green 4-pin plastic plug and one brown 2-pin plug)?
There is a minor fault in that the trace is dim. Once it brightened up when selecting a low sweep speed, but then reverted to a trace that cannot be adjusted to be brighter (and goes out of focus when you try). Something to with the Z axis circuit? But all transistors are OK on this board, mostly already replaced with 2N3906 & 2N3904.
Next possibility the CRT control circuit, getting bias voltage via two 27pf capacitors?
Thanks & Regards,
David Collier




Re: TEK 7603 REPAIR

Jim Ford
 

Uh, (DC) bias wouldn't be provided through capacitors, that much I know.  (32+ years practicing EE; one of these days I'll actually get it right! ;))   Jim Ford Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: David Collier <dc888@tpg.com.au> Date: 12/20/20 4:46 PM (GMT-08:00) To: TekScopes@groups.io Subject: [TekScopes] TEK 7603 REPAIR Dear 7603 owners,I just got serial no. 704170 'parts and repairs' from ebay.  Mostly it works, including the graticule bulbs.  The regulator board already has an uprated 30K resistor as standard; there is also a fan.I took apart the rectifier and regulator boards to check before switching on.  All TO-3 transistors had betas in the high 30's.  All electrolytics are original and with low ESR; when switched on the minus 50V was spot on.I took apart everything with gay abandon, not noting what wire came from where.  Was able to work out rectifier and regulator board connections and placement, but am now left with the signal output board: where is P339 (for a white plastic 4-pin plug), and where do the three left hand co-ax sockets connect to (one green 4-pin plastic plug and one brown 2-pin plug)?There is a minor fault in that the trace is dim.  Once it brightened up when selecting a low sweep speed, but then reverted to a trace that cannot be adjusted to be brighter (and goes out of focus when you try).  Something to with the Z axis circuit?  But all transistors are OK on this board, mostly already replaced with 2N3906 & 2N3904.Next possibility the CRT control circuit, getting bias voltage via two 27pf capacitors?Thanks & Regards,David Collier


TEK 7603 REPAIR

 

Dear 7603 owners,
I just got serial no. 704170 'parts and repairs' from ebay. Mostly it works, including the graticule bulbs. The regulator board already has an uprated 30K resistor as standard; there is also a fan.
I took apart the rectifier and regulator boards to check before switching on. All TO-3 transistors had betas in the high 30's. All electrolytics are original and with low ESR; when switched on the minus 50V was spot on.
I took apart everything with gay abandon, not noting what wire came from where. Was able to work out rectifier and regulator board connections and placement, but am now left with the signal output board: where is P339 (for a white plastic 4-pin plug), and where do the three left hand co-ax sockets connect to (one green 4-pin plastic plug and one brown 2-pin plug)?
There is a minor fault in that the trace is dim. Once it brightened up when selecting a low sweep speed, but then reverted to a trace that cannot be adjusted to be brighter (and goes out of focus when you try). Something to with the Z axis circuit? But all transistors are OK on this board, mostly already replaced with 2N3906 & 2N3904.
Next possibility the CRT control circuit, getting bias voltage via two 27pf capacitors?
Thanks & Regards,
David Collier


Re: 475A Chop Blanking and a Theory Question

Tom Gardner
 

On 20/12/20 22:12, Jeff Dutky wrote:
For the 6809 I was considering trying to dig up an AM9511/2 or WTL1032/3 coprocessor, but I'm not at that point yet. Using the LS181s to build an FPU is something of a departure from my plans, but it does tickle another long-standing interest of mine: implementation of floating point and extended precision math operations, so now I'll have to think about it
My first paid job, as a vacation student in 1976, was to implement 32-bit floating point arithmetic on a 6800. It wasn't that difficult, I still have listings somewhere, and IIRC sin/cos (using CORDIC) took around 40ms.

A few years later, I also remember being unpleasantly surprised how little speed improvement there was doing mul/div on some-ic-or-other external to a Z80.

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