Grant -
I have both 7934, 7104, and 7904A. I believe the power supplies are interchangable. It would be a good idea to keep the power supply from the 7834 IF is is the same as the 7904.

The Tek switching power supplies are reliable, but difficult to fix. A spare is a good thing to have. Other than the power supplies and some front panel components I'm not sure what is common between 7904 and 7834 - possibly the backplane (with the plug in sockets).

I think I'd consider stripping it for spares. Also note, there are significant differences between the 7904 and 7904A.

Cheers!

Bruce


Cheers!

Bruce

Quoting "G Hopper, KB7WSD" <kb7wsd@...>:

Hello: These usually have bad or failing HV trsf and/or HV mults and PSU lytics.

Parts and repair is not trivial.

The 475B are much later and more desirable.

Typically shipping these is risky and costly, often knobs, CRT or FP damaged.

Advise to se a local P to P site like Craiglist and not to ship far.

Alternative wait for the next Ham radio Flea mkt in your area, see the ARRL site
Jon

-73-


NNNNN

I got a 475 from a ham estate. It is in very good physical shape and appears to be complete. It seems to power up and the controls illuminate as they should. But, no video.

I pull off the cover. Found a 5V rectifier was missing. The owner was a very smart guy. My guess was he diagnosed a 5V failure. pulled the part but never got around to installing a new part.

I bought a part and installed it. No change. So, there is apparently more wrong than the missing 5V rectifier.?

I an not skilled in 'scope repair and will be happy to pass this on to someone who is for the shipping cost.?

Included is full user and service manuals

Ed
WA7EM

Hi all,
I'm looking for a bit of realistic perspective here.? A maybe 8 months back I had purchased some Tek stuff from the 'friend' of a widow (later realized he was a weasel).? I didn't do a close inspection of everything (just the stuff I was specifically interested in) so when I got the lot home, I discovered much to my disappointment that the 7834 had no CRT in the scope.? At the time it had been covered by a Tek Scopecamera and the glass of the bezel mounted to the scope was just dirty enough that I thought there was a tube in there.? Since this discovery, the mainframe has just been sitting because I'm not sure what to do with it.

I have a 7603 that I use with several plugins, and there was 7904 in the lot, so I don't really need a 7834.

I'm not particularly excited by the idea of trying to find a tube for this scope, installing it, and sorting out what ever other things come with installing a new CRT.? And I cannot imagine that this will be a $100 project either.? So I just don't know what to do with it.? Do I take it to a local hamfest (there is one next weekend that I'm planning to go to) where I assume it will sell for a paltry sum (my wife thinks $10, I think $5), or is there enough of a chance that others need parts that endeavor to part this beast out over the next year and do my part to help other 7834 owners keep their scopes running?

Thanks for any advice people would care to offer.

Cheers,
Grant

To close the loop on this question, yes it's entirely possible and not particularly difficult to upgrade a TDS20xxC series.

It takes three pieces/resources/steps.

First is to install the communication software (BOTH packages are required) from Tek, including Openchoice Desktop and TEKVISA.

Then establish communication with the scope (USB cable) via the software and change the model.? First, I read the identity of the scope using the "*IDN?" command via QUERY. Second I sent the PASSWord command and the password INTEKRITY via WRITE (not QUERY).? Older models used PITBULL, but newer models use the newer password.? Then I sent the MODEL command and the new model number "TDS2022C" via WRITE (not QUERY).? Lastly I read the identity of the scope using the "*IDN?" command via QUERY again to see that the model had been changed.

The third step is to run a full factory calibration via the "Adjustment Procedure" instructions via the Service Manual.? If the calibration procesure completes successfully, it will write everything back to storage and the model number change will persist past the power-down of the scope.? The Self Calibration will NOT write the model number change to storage and it will be lost after power-down.

It's not hard to do, but it takes certain resources.? The calibration is the most tedious step and takes a stable power supply that can be adjusted down to 0.015VDC, a leveled sine wave generator, and a square wave generator, as well as a couple of identical coax jumpers, a T and a 50 ohm passthrough terminator.? Check the service manual for the specifics.? With all the messing around, it took around 2-2.5 hours to get this all done.

Cheers,
Grant

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Interleaved:

On Fri, Feb 3, 2023 at 06:38 PM, Harvey White wrote:

?

toggle quoted message Show quoted text

Thanks Harvey. If you're ever doing something with one of your 468 scopes, please take a look at the User Manual Page 76.

I don't have a copy of the user manual with me, may have one elsewhere.?

?

I have done a lot of work on decoding the Tektronix 468 V2 firmware and posted some results in the files section of the Tekscopes group, folder "Tektronix 468 firmware". Specifically a listing of the firmware with accurate labels but minimal comments. Filename: "rom468combined.pdf". Should I copy these files also to the file section of this group?

I'd say so.? Everything we get on the older scopes, the better.?

?

The original firmware for the 468 was written in a language called TESLA ("TEktronix System LAnguage" and is lost, according to one of the original team members. So this is a listing of compiled code.

Lovely work (haven't seen it yet).? I might suggest a slight rework of the hardware:

1) consider replacing the processor with an ARM 32 processor, including the needed level translators.? I'd say that about 512K of FLASH and 256K of RAM would be a good start.? EEPROM can be added easily (24C256 and up, they're inexpensive).? I'd be tempted to take the assembly and rewrite the functions in C++.

2) Consider replacing the LED display with an OLED display or the like.

And yes, I have a long term (lotsa other stuff to do) to program to do a similar thing with a DM5010.

For the 468, I'd think a plugin processor replacement.

?

As I was digging through the code, I realized how inefficient the TESLA compiler was and started my work on a new firmware version. The original V2 firmware is 16 KB in size. My goal was to reduce the code size for a non-GPIB 468 to 8KB so all the code will fit in one 2764 EProm while maintaining all functionality. My current version (I called it V3.C) meets that goal (i.e. fits on one 2764 Eprom), fixes some bugs, add a few features and speeds things up a little.

And that's the other option.?

?

I have posted the binary file in the files section of the Tekscopes group.

I hope someone will be brave enough to try it out!

?

I just might.? Right now I'm trying to debug an NRF24L01 mesh network.? I apparently did some software changes somewhere.....

You will need

1. an EProm programmer

2. a blank 27(C)64 Eprom (or larger)

3. a 24 to 28 pin adapter board (unused address lines pulled low if using a larger Eprom)

4. a Tektronix 468 oscilloscope

Please contact me at jdr at dutchtronix dot com for any questions

I have everything but the adaptor board, I could look at the schematics and design an adaptor.? That's not a big deal.

?

Once this V3.C version is finalized I'll publish the code listing, fully commented.

Thanks, that's very ambitious and an excellent project.

Harvey

?

I am testing several 556's that will be for sale and one has a lower beam that behaves badly with different plugins installed, so the gain in the mainframe is the problem. I can vary the position of a square wave from the cal out up and down with either the lower or upper CRT zone and time base, but on the lower beam the height of the square wave decreases as I position it toward the bottom of the CRT face. I'm going to start reading the manual soon today, but wonder if this is a common thing with an explanation like, "has to be in the last amp before driving the CRT pins", or "Can be the CRT internally damaged...".

When driving the upper beam on the upper CRT zone, height of the square wave stays constant all the way until part of it is off screen.

On Fri, Feb 3, 2023 at 06:38 PM, Harvey White wrote:

?

toggle quoted message Show quoted text

Hi all,
Yesterday I picked up a Tektronix TDS2002C that Dennis Tillman (He says "HI" to everyone) got for me on his last trip down to Rickreall Oregon.

After having a challenge with upgrading the bandwidth according to this thread on the EEVblog: Dennis suggested asking here on the Tek forums figuring that someone has been through the upgrade process successfully.

I'll keep the details brief for this post, but I've installed both TekVISA and the OpenChoice software, have communication with the scope, and entered the two commands according to the posts.? I'm missing some minor thing that seems to be preventing the model number change but for the life of me, I have no idea what that is.

So, I'm hoping someone has been successful in the upgrade and can possibly answer a couple of questions.

Thanks for your time on my question.

Grant Hopper

How many of these were ever made? I have a hankeing to complete my 1LXX collection but I have never seen a 40 or 60, like ever.

For some reason I have a 119-0096-00 mixer for a 1L40 but that's it.

Sam many thanks, never used the Craig or Sweetwater cleaners, have old Miller Stephensen and GC , also use 99% ISO ALC.

Never had any issues .

Problems here are deeper .... access to the MOD pot for the cleaning fluid and failed CAL/VAR PCB switch mechanical latch. and scratch contacts.

Kind Regards,

Jon

(EDITED) Hello all, working on four 7A24, similar question for 7A26...

The CH1/CH2 variable knob controls an elegant multipurpose mechanical

A Push/push on the knob toggles VAR/CAL, red VAR OUT, black CAL IN
To CAL each of the channels to the mainframe, a small screwdriver depresses the center knob ( black, slotted) and latches the CAL trim after rotation, so a second control pot can adjust CAL of the channel.
Releasing the knob fixes the CAL pot position and returns the channel to CAL.

The control shaft has two gaged concentric Bourns MOD pots and the CAL detent mechanism.
On the PCB, a switch to select CAL/VAR, according to the knob push/push control in CAL, black, out, VAR, red.
In restoring these marvelous 1980s..1990s plug-ins, performed MOD pot cleaning procedure, after MOD pot screws loosened for contact cleaner.

PROBLEMS:
1/ VAR/CAL pots still scratchy after spraying Tuner Cleaner/control cleaner (not Deoxit!) down pot shaft and thru loosened MOD pot cases.

2/ PCB VAR/CAL knob toggle switch is still scratchy after contact cleaner in to the PCB switch

3/ on one channel of one plugin , the knob cannot toggle to the OUT VAR red position.

Anyone seen these issues? Suggestions appreciated!

I Can post a photo album if needed.

Mille Mercis et Bon journée
Jon

Well, COVID has died down, the border is now open, the weather is nice, and we have TONS of accumulated goodies to put out for an in-person Stuff Day here at Sphere (West Kelowna, BC, Canada). We will have the event along with our local amateur radio group, OCARC, so there will be even more stuff to see, and people to meet. You won't be disappointed.

You can grab the event poster here ON THE STUFF PAGE:?

Many things (especially heavy ones) that we couldn't put on-line will be there, including three Tek 561B/564B scopes with plug ins, HP 70K items, over 1,000 factory manuals at just $2 each ($5 for the big HP binders), PMI/Wavetek Scalar Network gear, fully cal'd scopes, tools, parts, ham gear, BIG transformers, Tek and HP plug ins, high intensity LEDS, heavy duty terminal strips, connectors, stereo microscopes, and a LOT more. Even a 6 foot relay rack. And, a big pile of $20 as-is items, some great bargains there.

We are cleaning out our storage buildings, so there are MANY boxes of free parts of all kinds, bring your own bags and boxes, and go home with full parts bins!

We hope to see you there, Susan and I are both 74 this year, so we won't be able to have too many more of these, so let's enjoy this one! Have any special REQUESTS? Let me know, we will try and have it out for you.

All the best,
walter (walter2 -at- sphere.bc.ca)
sphere research corp.
https://www.sphere.bc.ca/test/stuffday.html

There is a 400V 4A Version. ? I have used these both successfully.? Mouser has these in the USA.?

My recollection is the holes in the circuit board are a tight
fit on the 2A bridge, so if you try to use a 6A bridge, be prepared
to have trouble mounting it.

-Chuck Harris


On Sat, 4 Feb 2023 14:16:41 -0500 "Michael A. Terrell"
<terrell.michael.a@...> wrote:

The manual lists this as 152-0488-00. They are available from many
sources. NTE 167 is an alternative:

This is a gumdrop component available from many OEM with their own
part numbers. It is a 200V 2A bridge rectifier.I have some, but can
not get to them right now.

On Sat, Feb 4, 2023 at 1:41 PM Ed Mohrman WA7EM via groups.io
<ejmohrman= [email protected]> wrote:

I got a free, but dead Tek 475 scope. When I opened it up, I found
the previous owner had unsoldered CR1462. He was a smart guy, so
apparently he concluded that part was bad, but never got around to
replacing it. It is a Motorola MO960-3 200V, 2.5A bridge rectifier

Does anyone have a good substitution? I can wander around in the
parts sites looking for such a part. I am hoping someone has hit
this problem and can speed things along

thanks

Ed

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sometimes the bulk caps had a bit too much ripple causing a Tant to short which takes out the rectifier. find the bad tant......
I have not yet had to change the rectifier.....I changed the Bulk caps a few yeas back as preventive measure...ripple was on the edge.....
IMHO it is a great scope! I run a pair of them when I need 4 channels! the nice thing is the 2mv lowest range. and it can be cascaded......
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