That is apparently a typo in the original manual It is actually on 11-12  Upper right hand corner, (not 11-14).

Another reason to have a "text searchable" Artek Manuals scan. Although I will be the first to tell you that OCR driven text searching is not 100% infallible

-DC
manuals@artekmanuals.com

--
Dave
Manuals@ArtekManuals.com
www.ArtekManuals.com

On Wed, Jan 3, 2018 at 12:15 pm, Artekmedia wrote:

We offer BOTH Vol1 and Vol2 of the service manual

I am curious to know where you got a copy of Vol2

Are both Vol1 and Vol2 combined with the "FULL SCHEMATICS" purchase?

I was thinking to purchase. Though trying to push off until next months budget plan.

I'm not sure where I found the Vol2. I deleted my older browsing history and found somewhere online hunting on Google for information.

Thanks in advance for your time

On Wed, Jan 3, 2018 at 12:15 pm, Artekmedia wrote:

There is a note on the schematic that R199 is not installed on boards with 8K
RAM and 32K RAM

I don't see the note regarding RAM, where are you finding this?

I don't see the A11-14 5A either on the schematic referring to R1998 or R1999.

All

I have not been following this thread closely  but here is what I see in my scan of the TDS520 service manual R1998 and R1999 are located between U12 and J2 in as shown in Vol2, Figure 9-112. at locator D4 ( there are two locator designations , one for the schematic and one for the board overlay ...I perceive that perhaps the you may have confused the two)

There is a note on the schematic that R199 is not installed on boards with 8K RAM and 32K RAM

We offer BOTH Vol1 and Vol2 of the service manual

I am curious to know where you got a copy of Vol2

Regards
-DC
manuals@artekmanuals.com

--
Dave
Manuals@ArtekManuals.com
www.ArtekManuals.com

On Wed, Jan 3, 2018 at 06:29 am, Siggi wrote:

Yeah, a 0 Ohm resistor is essentially just a link, and here they tie an
input line on an IO register either high or low. There's a note regarding
R6-R17 on the schematic:

"VERSION ID RESISTOR PLACEMENT:
PLACE U4 AND R12-517 ONLY ON BOARDS THAT HAVE EXCEEDED THE ID NUMBER
11110XXX.
IN THIS CASE, THE VERSION NUMBER IS DECODED VIA PINS 2, 3, 4 OF U4.
R7, R9, R11 ARE NOT PLACED & PINS 5-9 OF U3 ARE WIRED HIGH."

U4 isn't present on my board. R7, R9 and R11 are placed though. I do see the note now related to version ID resistors.

I wonder if this was causing issues?

I don't see an ID number on my board. Where is this found?

On Wed, Jan 3, 2018 at 06:31 am, Siggi wrote:

On which schematic page did you find R1999? To determine whether R1998 is a
strapping resistor, you might see whether one of the unused pads shares a
track with one end of R1999. If so, then it's likely that their purpose is
to select some kind of an alternative.

I didn't find either R1998 or R1999 on the schematic, though they were listed in the parts locator as 14, 5A. R1999 is on my board in between J2 and U12. Yes, they share a trace and pad.

Are these boards capable of 1GHz and 4GS/s like say the 744a?: https://www.eevblog.com/forum/testgear/conversion-of-500mhz-tds744a-to-1ghz-tds784a/

I did just purchase the HP8640b OPT323 Airforce manual from Artek.

Artek TDS-520 Component Level Diagnostic Repair Manual shows all the boards? I have a volume 2 with A10 thru A21. Not Volume 1 through.

Hello Rick,

You have my sympathy for this mishappen- really that fuse F410 did not protect anything... Bummer!

Just a sanity check: Is Q400 ok ? As it controls transistor Q410 in the primary side-oscillator and somewhat prone to fail as far as I can see.
It is located right above the HV-multiplier U410.

Cheers,

Magnus

Hey Mark,

Did you get the scope yet?
Looks like the positive vertical deflection signal is MIA.
Obviously you need to look through and probably fix the LV power supply,
and look for leaking caps on the A5 board first.
If that doesn't fix it, then I'd look at the vertical centering trimmer on
the vertical termination assembly, though I'd be surprised if it the trim
has that sort of a range. If that trimmer has gone bad, that's probably the
best case, as often a clean and a tweak will restore those. Could be as
simple as a disconnected vertical deflection plate, or a termination
resistor gone open. Might also be upstream from there, e.g. something from
channel switch to output hybrid. Worst case it'll be the vertical output
hybrid.

Siggi

/See if this link has the schematics you want for the PS280?//
/w140.com/tek_ps280_ps283_service.pdf
tom jobe...

Hi Bill,

On 28 February 2017 at 19:34, k7wxw@arrl.net [TekScopes] <
TekScopes@yahoogroups.com> wrote:

hmmm... i could tell you that it is a very rare model used only by
un-named intelligence services for black troubleshooting operations.

or i could admit that i had a brain freeze and mis-typed the model number.
what a way to introduce myself.!

my new/old scope is a 475A. the CPS250 is a three output, metered bench
supply that is (I think) a rebranded B+K product.

​Sorry for the late reply - I've been in passive lurk mode for a while. Did
you get anywhere with the CPS250? I have one of these as my general use
supply.

Malcolm​
​

So I had some time to work on the scope and finally came out with this contraption < https://imgur.com/a/GPr8k > made of four BD135-10 transistors, which despite being ugly and a tiny bit (lol) overkill, turned out to be effective. The transistor pairs have similar temperature and don't drift away anymore. The assembly with the impeller mounted consumes about 115 mA after warm up when placed on my bench, however, when fit into the chassis the current drops to less than 80 mA. I have no idea why so, as the air flow is hampered inside there and thus the work done to move the air must be larger.

I put everything together and turned on the instrument to find out that the fan, when the scope warms up, becomes rather loud with distinct 400-425 Hz (depending on its speed) tone prevailing over white noise. The fan was rather quiet on the bench, though. Again, I don't know if this is the property of the air path inside the instrument, or something is resonating inside and this is normal, or something's happened when I installed the fan. Anyway, I'm fine with it for now, but if one day I'd happen to find a cheap replacement, I'd take it.

Next, I attempted to clean the potentiometers (nearly all of them are intermittent). I flushed ones I could reach with isopropanol and gave them quite a few turns and it seemed to help, although didn't fix the problem completely. I couldn't find DeoxIT locally and I don't know any analogs that are safe for old plastics, so I probably will continue with the isopropanol treatment (and prepare myself for removing some PCBs to reach for hidden ones).

Next, I noticed that in Chop mode, any signal fed into one channel can be seen on the other channel, inverted and attenuated. This is noticeable when the other channel is grounded. To illustrate this I made two photos. I connected the calibrator output to CH 2 with a X1 probe, set coupling to DC, attenuation to 50 mV/div, CH 1 to GND, mode to CHOP, 20MHz BW pulled on, sweep rate to 0.5 ms/div. You can see the resulting display here: < https://imgur.com/lPtdRft > (don't mind the fuzzy trace on bottom left corner, it seems that someone was smart enough to measure signals with a caliper so the plastic screen is severely scored in that area). To take things even further, I reduced attenuation to 5 mV/div, so that the signal does not fit in the display, and the effect on the channel 1 is even more pronounced: < https://imgur.com/eSoxgD0 >. This effect is also present on ALT mode setting with sufficiently high sweep rates, e.g. 50 us/div or less, so I don't think it is related to the channel switching circuit.

After spending some time with the service manual (I'm very glad I got the printed manual with the scope, I think it is a piece of art on its own) I began to suspect that the problem is Output Low-Frequency Compensation calibration (see section C, #17) being way off. I tried to confirm this, but since I got no proper equipment, I could only check the performance with poor man's 1 kHz square wave generator (aka probe compensation calibrator) (see photo < https://imgur.com/FOXmMGr >, 50 mV/div, DC, 20MHz BW pulled on, 0.5 ms/div) and poor man's 250 kHz square wave generator (aka CHOP oscillator) (see photo < https://imgur.com/vjNrdVQ >, both channels to GND, CHOP, adjust vertical positions as needed, 20MHz BW pulled on, 2 us/div).

To me, the compensation seems to be off, but it is still well within the generous 3% tolerance specified by the manual. This raises several questions (given that, again, I have no previous experience and don't know how things should be, and it's really hard to even put in words a search query), which, as I hope, someone here could answer:
- Is the whole issue a fault of this particular instrument or is just a limitation of an old oscilloscope design that you have to live with? (While I glanced over other checks and adjustments I found that other things that in my opinion require recalibration, e.g. the Geometry adjustment, see section B, #3, are instead well within the specs.)
- Should I try to do these adjustments without proper instruments or I will definitely make things worse than they are now? They seem to be easily done just by eyeballing, but this simplicity may be deceptive.
- Last but not least, am I right about the cause of the observed behavior?

Again, thanks a lot.
Nik

On 3 January 2018 at 15:10, magnustoelle via Groups.Io <
magnustoelle=yahoo.com@groups.io> wrote:

Ah, well, I have just read the official Tektronix manual 061-4124-02 for
the PS-280.
And the adjustments for calibration are also included there - see
https://www.tek.com/ps280-manual/bench-test-instruments-and-
handheld-oscilloscopes-technical-reference

​Qservice sells the service manual with schematics.

Malcolm

Ah, well, I have just read the official Tektronix manual 061-4124-02 for the PS-280.
And the adjustments for calibration are also included there - see https://www.tek.com/ps280-manual/bench-test-instruments-and-handheld-oscilloscopes-technical-reference


Cheers,
Magnus

Yes, that will be used to fill in any missing details once all the other data, especially photos, are in. that document is not especially helpful for identifying knobs, which is why I started this project in the first place. At this point, I have a pretty deep selection of visuals (turns out I had more of the original style knob pics than I thought), and I have also written an overview of the three big chronological waves of design that affected these knobs and how they were created and used. It is interesting to see how they evolved over time, and I have made up displays for each era to show the styles.

I think the final doc will be very useful, it has already solved a few mysteries for me here while I was working on it. The "used on" data would be very helpful, but only Hakan has that, and it is on literally hundreds of microfiche documents and thus is very hard to work from, I think I will just have to work back from other information to fill that portion in..

all the best,
walter (walter2 -at- sphere.bc.ca)
sphere research corp.

Good Day,

I can absolutely confirm this assessment about the PS280.
This was an OEM-design for Tektronix made by Goodwill Instruments / Taiwan and China. Model GW GPC-3020D.
Common practice in the T&M equipment industry.

And - great minds think alike - I have also modified my unit to reduce the fan noise - same as Twig did.
Hint: The rear heat sink has a spare place. It's basically intended for four TO-3 transistors. But the design uses only three of these. So, I have cheated and used the free place for a very simple, NTC-controlled fan speed driver with a 2N3055.

Please let me know if you need the service manual. Some postings in several internet forums claim that there is none, but I have one available here.
Schematics are not included, but the test and calibration instructions are complete.

Cheers,

Magnus

On Wed, 3 Jan 2018 at 00:44 jafinch78 . <jafinch78@gmail.com> wrote:

I was able to review the schematic and all the missing resistors are 0 Ohm.

The only resistor I can't find on the schematic is R1998. I have R1999 on
my board and is 0 Ohm.

Am I safe to say R1998 is 0 Ohm or does anyone know on their TDS-520 what
R1998 is?

On which schematic page did you find R1999? To determine whether R1998 is a
strapping resistor, you might see whether one of the unused pads shares a
track with one end of R1999. If so, then it's likely that their purpose is
to select some kind of an alternative.

Also, are the 0 Ohm resistors 1%, 0.125W, TC=100PPM, 1206, T&R like on the

TDS-520B?

Would be nice to have volume 1 also of the component level service manual
available.

Artek Manuals will sell you Volume 1 & 2 in a very good scan.

On Sun, 31 Dec 2017 at 22:46 jafinch78 . <jafinch78@gmail.com> wrote:

I appreciate you dealing with the PITA issue. Thanks for your time. No
hurry on my end as I am taking a break for the holidays to do more not as
technical projects, plus I did find the manual though there is only volume
2 (070-8313-00). Any ideas on volume 1? At least volume 2 has A10 through
A21 modules detailed. Man, schematics are a PITA on a laptop.

What is a strapping resistor... like a resistor placed to make a trace
bridge basically so different models can use different values or "strap"
directly?

Yeah, a 0 Ohm resistor is essentially just a link, and here they tie an
input line on an IO register either high or low. There's a note regarding
R6-R17 on the schematic:

"VERSION ID RESISTOR PLACEMENT:
PLACE U4 AND R12-517 ONLY ON BOARDS THAT HAVE EXCEEDED THE ID NUMBER
11110XXX.
IN THIS CASE, THE VERSION NUMBER IS DECODED VIA PINS 2, 3, 4 OF U4.
R7, R9, R11 ARE NOT PLACED & PINS 5-9 OF U3 ARE WIRED HIGH."

Seems I read somewhere that in the firmware the scopes can determine what
hardware model boot processes to load based on resistor configurations like
you note.

Is that correct? I guess that would be the EPROM instructing the Firmware
chips. Though aren't the Firmware chips on the firmware board for the
TDS-520?

I'm guessing the hardware version relates to such things as CPU clock rate

and maybe processor type, and perhaps other features of the CPU board. The
ACQ board has its own ID and storage for calibration data.

I am guessing later models use the NVRAM since looks like later model
boards have two Dallas/Maxim NVRAM chips. Is that correct?

I don't know - maybe someone else here does.

Seems I read somewhere in later models... that was changed so there are no
firmware modules.

Thanks and I appreciate you taking the time to look into.

Happy Holidays!

On Tue, Jan 2, 2018 at 09:44 pm, jafinch78 . wrote:

0 Ohm resistors 1%, 0.125W, TC=100PPM, 1206, T&R

I'm thinking 0 Ohm would just be jumper since just strapping as noted above.

I was able to review the schematic and all the missing resistors are 0 Ohm.

The only resistor I can't find on the schematic is R1998. I have R1999 on my board and is 0 Ohm.

Am I safe to say R1998 is 0 Ohm or does anyone know on their TDS-520 what R1998 is?

Also, are the 0 Ohm resistors 1%, 0.125W, TC=100PPM, 1206, T&R like on the TDS-520B?

Would be nice to have volume 1 also of the component level service manual available.

The brand new HV multiplier arrived today. I popped it in and the trace came right back. Everything is looking good. In fact R410 stays very cool. Looking good.

When I put the HV cover back, turned it back on and there was no trace. I didn't realize that R410 was close enough to touch the HV cover and shorted the 44 volt line to ground. I moved it away and the trace didn't come back. I figured I blew the fuse. Fuses all good. All voltage rails are good on LV board and coming into the HV board. Nothing at -3kV test point. Yikes. This is frustrating. I guess I'll undo the multiplier and see if the -3kV comes back. If it does then I guess screwed up the new multiplier.