开云体育

I’ve been troubleshooting the oscilloscope further, focusing mainly on the Vertical Amplifier board. I’ve attached pictures of the boards and the schematic diagram from the service manual, with two connectors marked because disconnecting them impacted the behavior (you need to log in to view these pictures):
Main Board: /g/TekScopes/photo/299721/3870949/Verical%20Output%20-%20Circuit%20Board.jpg?p=Created%2C%2C%2C20%2C2%2C0%2C0
Thick Film Hybrid Board: /g/TekScopes/photo/299721/3870951/Verical%20Output%20-%20Thick%20Film%20Circuit%20Board.jpg?p=Created%2C%2C%2C20%2C2%2C0%2C0
Diagram: /g/TekScopes/photo/299721/3870950/Verical%20Output%20-%20Schematic%20Diagram.jpg?p=Created%2C%2C%2C20%2C2%2C0%2C0

Here are my findings:
1. Disconnecting P442 completely resulted in a horizontal line at the screen's center. Adjusting the Vertical Position knob had no effect, and pressing the Beam Finder switch only shortened the line without changing its position.
2. Connecting only Pin 5 of P442 (+75V) gave the same result as disconnecting it entirely.
3. Connecting Pins 3, 4, and 5 of P442 also had the same result.
4. The line disappeared if Pin 1 or Pin 5 of P442 was connected.
5. Disconnecting P385 while P442 was fully connected caused the line to reappear.
6. Connecting only Pin 1 of P385 moved the line slightly upward.
7. Connecting only Pin 2 of P385 kept the line at the center.
8. The line disappeared if both pins of P385 were connected.
9. When the line was centered, voltages on the upper and lower rails matched closely.

Looking at the schematic, the 'Thick Film Hybrid' board (btw, it's a PITA to solder on it) connects to the main vertical amplifier board via diodes VR363 and VR463 and through P385. Additional findings:
1. Feeding +12V to L369 and +75V to L385 simultaneously seemed to have caused the vertical deflection to malfunction.
2. Voltages at the emitters of Q314 (~6.27V) and Q414 (~3.67V) suggested the trace was off-screen.
3. When the horizontal line was centered, both emitter voltages were around -3.85V, a notable difference.

At this point, I feel close to identifying the fault but am unsure which direction to take next. Any insights or suggestions would be much appreciated!

Ozan,

Apologies for calling you Onan in a previous post!

I also installed a new 2N2219. But installing the 2N3565 was the part that brought it to life!

I will upgrade to a 2N2219A when it comes in.

Thank you sir! You taught me a lot in a short while!

Barry

Hi Barry,
Good news. We did try shorting C-E of Q8051 and it didn't change the output, it should have eliminated any effect of Q8051 as the only root cause, i.e. there must have been something in addition to possibly bad Q8051. Perhaps the test was done before you fixed the broken traces and/or swapping 2N2219A. Congratulations for the repair, it was an interesting puzzle.

Ozan

If you do a Google search on "TDS8000" ... and click on 'images'... you will see that... about 90%... of those pictures show the TDS8000 frame sans the 'heads"
Now why is that?
I reckon... the heads are way more valuable then the frame.
That's just exactly my experience.
Having some working 'heads' ... it's relatively inexpensive to acquire a frame.
The other way around... not so much.
By the way... what does one do with just a TDS8000... without a 'head?'
One answer would be...if you are cynical... sell it on Ebay.
--
Roy Thistle

On Dec 28, 2024, at 08:19 , Gianni Becattini via groups.io <Giovanni.becattini@...> wrote:

Triggered by the original post by be_moulton, I got a DSA and wrote some notes.

Gianni,

That post was on 12 December, and you posted that you were expecting the DSA on the 15th. I'm not sure if I'm more disturbed that you found time to lay out 100 pages with text, photographs, tables, and diagrams in two weeks, or that you refer to it as "some notes." :)

Very interesting read that helped satisfy my curiosity about this beast, so thank you for your work!

Adam

Triggered by the original post by be_moulton, I got a DSA and wrote some notes.

You can find theme here: ,if you,like.

Any comment welcome, you are allowed to shoot the pianist...

Gianni

I finally got to the bottom of this! A great learning for me. The bottom line is that the Q8051 transistor needs a lot of gain to drive 2n2219A. The original transistor was a PN3565, 151-0341. The original was bad so I couldn't measure it. I had only 2 of those on hand and the one with a gain of 465 worked.

Onan, Thanks for all the help you provided me. I am sorry if some of the information I provided was a bit unclear. In the end I learned a lot. Many thanks!

Barry

Thanks!

Hi Richard,

The lead free solder does indeed have a higher silver level and a considerably higher melting temperature than the usual silver-bearing leaded variety.
In addition to the preferred usage of silver, one of the other expressed concerns of Tek is the usage of excessive heat when working with the ceramic terminal strips.

I would think that so long as you use an appropriate wattage iron with good sized tip (ie with adequate thermal mass) you should be able to complete the soldering quickly without causing damage to the strip. Also, Tek has stated in their literature that for occasional repair work, regular tin/lead solder is acceptable.

Art

Hi all,

After my TDS8000 eBay bargain turned out to be a nicely working unit, I’m now looking for the expensive part, a Tektronix 80E04 sampling head.

I know those modules are for sale on sites like eBay, where they for 3K, 4K or even higher, if you filter out the broken ones.. But what do you guys consider a fair price for such a device?

If anyone has one for sale; please please let me know !

I have used lead free solder with success on the ceramic strips. The solder used was Kester 24-7068-1402 Sn96.5 Ag3.0 Cu0.5. My current understanding is the issue is not the lead it is the LACK of silver cant say for sure so I don’t have a large enough sample size but I have repaired a number of ceramic strip units with no trouble. 3% silver was the highest silver content I could find with out going highly exotic with highly exotic pricing. In terms of temp I used a really high powered iron Hakko FM203 with a thermal mass tip. I found the melting point of the solder to be less of an issue given how much heat the ceramic soaked out of the iron. I don’t mind working hot with an iron but I am also used to working fast.

Zen

If we're talking about the same thing, it's an overlay of multiple waveforms.? What it shows is how long the transition takes and how uncertain it is (in time), and where the stable part of the waveform is.

One use is in communications where you measure the jitter of the channel (it's called an eye diagram there, IIRC).? It is a good predictor of how well you can extract stable data from the stream.? If there's no stable eye, forget the data.

so you get an indication that shows:

UNSTABLE...... STABLE....... UNSTABLE...... STABLE.......

and you want to sample the data in the middle of the "stable" area.

Harvey

Hi,
I am playing around with the DSA 602A and I am rather confused by histograms. I could create them, but I cannot imagine a way to make them useful (the manual does not say what they are for).
Surely this is a limit of my limited knowledge... would someone help me ?

Thanks

Gianni

Apologies if this has been answered but I couldn't find in a search:

I'm about to restore my first piece of Tek kit. understand the potential issue with the silver deposit ceramic strips and have electronic solder to hand that is 95% Tin, 3.8% Silver and 0.7% Copper.

This appears to exceed comfortably the desired silver content, but it will be higher melting point (227 degC) than lead-containing variants.

My question is "do I need to buy yet another reel of solder such as Sn62/Pb36/Ag2 which will be 179 degC melting point but lower silver or can I use what I already have?".

Another way of asking: provided solder is silver-containing how much does temperature vs. silver content matter?

Thnak you.

On Dec 20, 2024, at 07:55 , Adam R. Maxwell via groups.io <amaxwell@...> wrote:

I'm waiting on an AT5058 that will hopefully be an actual fix for this.

For the archives: the transistors finally arrived, and replacing Q1769 fixed the 7904 autofocus issue, allowing me to complete all the steps in the Z-axis service procedure. Ironically, the readout now isn't as sharp as it was before, so I may play with this further when I get bored.

Adam

On Dec 26, 2024, at 13:47 , ed breya via groups.io <eb@...> wrote:

In the old tube scope days it was common to give detergent and water washing, but I don't think it would be OK for newer stuff like 7K without some caveats. Maybe, maybe not - it would take some investigation to see.

I tried it with a 7704A that was pretty filthy, after reading the article here on scope washing and noticing the photo on the last page is of a 7K scope being washed at the Factory Service Center:



It also says "The 7000-Series plug-ins are washed with the side panels in place. This saves time and prevents a mix-up in panels." This gave me further confidence to try it.

After success with the 7704A, I did the same thing with a 7904, also with success. Unfortunately, the 7904 frame doesn't separate top and bottom to fit in the oven like the 7704A does, so I relied on summer heat to dry it.

I think Hypcon hybrids and elastomer switches are where washing becomes a bad idea, from my reading of the 7104 maintenance note, so did not try it with the 7104, 7A29, 7B10, etc (and would not with a 7904A, either).

If you need to do instrument cleaning regularly, another option that's effective and totally dry is to invest in an air powered walnut shell blast cleaner. You can get the whole shebang at Harbor Freight, for instance. Years ago I got a vibratory tumbler cleaner and a huge box of walnut shell from them for cleaning ammo brass, but I've never tried it in an air blaster on surfaces. I believe that Tek used this method instead of water in the later years.

I'd like to try blasting for other reasons, but wonder about dust? Walnut and corncob both make a lot of really fine dust in my vibratory tumbler, but I'm lazy and tumble my brass too long.

thanks,
Adam

Hello all,

Many thanks for the tips
Was not so, bad nor encrusted, just a soft brush and gently blowing, then isopropyl alcohol. About ESD the scope was grounded, damp and rainy weather.

The upper Rear casting by HV section had embedded brown deposits, metal corrosion, I used fine steel wool!

Next to clean the HV to CRT connector and lead, then perform the CRT, HV and Z axis calibrations.

Enjoy

Jon

Forgot to mention - in real anti-static work environments it's common to have grounding leads or other conductors to keep any air or vacuum nozzles from charging. You can do that too easily enough, if there's a concern.

Ed

Check the dust with your fingers before going through a lot of effort. On most old gear I've seen, there is a "loose" dust coating that wipes or blows off easily, but underneath there's a gritty hard dust, grime, and corrosion coating that's tough, and needs solvent washing to get mostly off. Even then, it's hard to get perfectly clean like new, unless it was stored in very good conditions for its entire time. You can feel the surface to get an idea of what it will take.

For loose dust, I'd recommend a paint brush along with vacuum or compressed air, outdoors. Unless it's a very dry environment, I wouldn't worry at all about ESD. You can also dampen the brush a little with water or IPA to minimize static buildup. It would help the cleaning a little too, but might leave streaks that can look worse than a nice uniform dirt finish. Pretest all of your methods on a small scale before committing. Good luck.

In the old tube scope days it was common to give detergent and water washing, but I don't think it would be OK for newer stuff like 7K without some caveats. Maybe, maybe not - it would take some investigation to see. If you need to do instrument cleaning regularly, another option that's effective and totally dry is to invest in an air powered walnut shell blast cleaner. You can get the whole shebang at Harbor Freight, for instance. Years ago I got a vibratory tumbler cleaner and a huge box of walnut shell from them for cleaning ammo brass, but I've never tried it in an air blaster on surfaces. I believe that Tek used this method instead of water in the later years.

Ed

Hi,
I recently picked up the hobby of ( trying to ) repairing old test equipment and got a TDS540.
I have been trying to get it to boot up but it is stuck with a flashrom checksum error.
It seems somehow the firmware got compromised.
All caps have been replaced and the boards ( A10, A11, display ) look good with no apparent visual damage.
NVRAM has been replaced with a preprogrammed version from kellyjo_13 / ebay.
After reading to multiple posts on different forums I guess I am more confused than before...
My questions are :
Where can I download a working firmware version for my TDS540 ?
How to update the FW ( in Windows ? , DOS ? )
Which ( if any ) GPIB to USB converter would work or do I need an old 488.2 card ?

The boot message looks as follows :
Enabling Bus Control register. Value = 0x67
IMR 1 Register test passed.
Misc. Register test passed.
Timer Interrupt test (Auto-Vector) passed.
NVRam DSACK test passed.
NVRam Write protected.
Flashrom DSACK and JumpCode test passed.
Invalid Flashrom Header checksum = 0x3efc, should be 0xfefb
Flashrom Checksum test failed.
Cannot transfer control to Flashrom.
Transferring control to the SDM (monitor).

Any help is very much appreciated.

Hans