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Re: 5440 No Trace

Rick
 

You would think after all the time you guys have spent with me on this repair I'd learn a thing or two. I should have known exactly what the consequences shunting R410, the 3.3 ohm 1/2 watt resistor to the chassis. The first thing I did was confirm it still had the 44v supply to it and saw the voltage drop across down to 10mV. That was a give away because the current draw from the short would burn open the resistor. At 3.3 ohms that 13 watts and that was clearly pointed out to me 10 messages ago. I missed it. Q400 is good. I realized there was no way that resister couldn't not be 100% open especially since it showed no sign of burns. I replaced it and bingo all works perfectly. Still in calibration. All I needed was the new HV Multiplier and a proper install. I did use several layers of heat activated glue heatshrink.

Thank you to all that chimed in. I promise I won't forget what I learned this time. The beauty is it is always something very simple if you can clear you head and listen to learn from advice.

I have several more Tek projects. I still want to fix the excessively high SG505 output and make a notch filter fixture to calibrate it. Also I have an extra AA501 I need to get working. I'll be back.

Rick


Re: Tek 547 A Sweep display during retrace

Dave Wise
 

BC556 + 220pF is 55ns/30ns, the same on-time as the 2N2207. The Pro-Electron C-B-E pinout makes it easier to use than KSA992.

Two more base-in-the-middle parts:
MPSA56 + 470pF is 55/30.
PN2907A + 470pF is 60/30.

And there's a laugh - the PN2907A was what I tried something like ten years ago and gave up!


Re: First draft of the Tek knob visual index project

Dano
 

On Sun, Dec 31, 2017 at 09:39 pm, Richard Knoppow wrote:

[snipped]
    I think there are some people who do not have a mail server that
Thunderbird or other mail clients can connect to. I agree its much
better to use a mail client for mailing lists and I happen to use
Thunderbird also.
[snipped]

Yes, that's precisely my issue. I have many domains with domain level rules, and no modern mobile email client can handle it correctly. Therefore, it's just much simpler to login to a webpage. I use any device that's near me or on me to read emails, but I have to wait to get to a PC in order to reply. It's a PITA, but redoing a bunch of domain rules just to make that work, isn't something I'm interested in doing right now. (can't stand typing on mobile devices anyhow, lol.)

Thanks for all the suggestions, they will help down the road!

-Dano

(some of you may remember Eudora, wonder whatever happened to them...)


Re: Tektronix PS280

Twig
 

The link from W140.com that tom jobe posted above does indeed have schematics. That is the good news. The bad news is that the schematics are riddled with errors, as I found when doing some troubleshooting a while ago. Best to take them with a grain of salt if you find something that does not make sense.


Re: First draft of the Tek knob visual index project

Dano
 

On Tue, Jan 2, 2018 at 08:55 am, tronix_cal wrote:

Are you using the Common Design Parts Catalog for any part of the project?
While it doesn't have the useable on code (Knob to Model number) listing, the
dimensions, logos, labeling, method of manufacture (molded/machined) and ID/OD
info is all there, with a directory of drawings. I know of a hard copy I
could borrow. The data could be extracted, without outright copying of the
entire content, couldn't it?
I have that manual, and am planning on scanning in the section with knobs to send to Walter. Just a FYI, in case you don't have easy access to it.

I'm still trying to find ANYONE who has more of those volumes, I'd like to get them scanned in and make them available (hopefully without stepping on toes). I realize they, either don't exist, or they do, and no one wants to part with them. Will have to figure out that hurdle, but no one has responded to my prior request, so that's the first step. Anyone willing to work with me? I have a high speed scanner, however it's only 8.5" x Unlimited, so folded pages will be tougher since they're typically 11x~17.

I have Volume 2 (1988 release), but that's it. I'd love to see those microfiche get scanned in too!

I'll start a new thread when I've got my system(s) setup better for scanning workflow. Feel free to response in the meantime though.

Cheers!

-Dano


Re: 5440 No Trace

Rick
 

Thanks for the sympathies Magnus. I will check Q400 tonight. My short at the resistor is before the fuse so it might not put any heavy current through it. Rick


Re: Tek 2465b with down shifted display..

Mark Hatch
 

Siggi

Thank you for the reply! The 2456b did arrive and it now appears to have what appears to be classical u400 failure. Channels 3 and 4 are fine and when you put a sine wave into either channel 1 or 2 and move vertical position up down, it gets compressed vertically at top and bottom.

The only thing that I am still a little worried about is that the output text is shifted down. Wasn’t clear from other u400 reports whether that was a symptom or not.

Any thought whether I am guessing right on the u400? Have a used one on the way and planned to put it in after doing a quick voltage and ripple test for anything that could fry the new u400

Thanks

Mark


Re: TDS-520

jafinch78 .
 

On Wed, Jan 3, 2018 at 12:52 pm, Artekmedia wrote:


Yes both volumes are included in that set
Great, you are correct. PDF scans with links are really a time saver.

I think the HP8640B OPT323 Air Force manuals were a great deal too I downloaded this morning (I'm nonionizingemf also). Thanks for offering the CD's at a better price too.

I'll go ahead and buy now... I can use the more accurate information. Lot's of options and issues with these boards so I mise well upgrade to better quality while I am repairing now.

Thanks DC! :-)


Re: TDS-520

Artekmedia <manuals@...>
 

Yes both volumes are included in that set

We will be here next month :-)
-DC

On 1/3/2018 3:37 PM, jafinch78 . wrote:
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


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


Re: TDS-520

Artekmedia <manuals@...>
 

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

On 1/3/2018 3:35 PM, jafinch78 . wrote:
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.



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


Re: TDS-520

jafinch78 .
 

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


Re: TDS-520

jafinch78 .
 

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.


Re: TDS-520

Artekmedia <manuals@...>
 

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

On 1/3/2018 2:31 PM, jafinch78 . wrote:
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.


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


Re: TDS-520

jafinch78 .
 

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?


Re: TDS-520

jafinch78 .
 

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.


Re: 5440 No Trace

magnustoelle
 

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

On 03/01/2018 05:17, Rick wrote:
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.


Re: Tek 2465b with down shifted display..

Siggi
 

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

On Tue, 26 Dec 2017 at 10:19 Mark Hatch <mark2382@hotmail.com> wrote:

I should put a curfew on eBay... no bids allowed after 8pm. :-)

My latest after hours purchase is a 2465b with a shifted display. Not just
the output text, but also the waveform. Everything is two grids down. If
you want to take a look at the photo (and shake your head at what I paid)
it’s item number 302575456769

Anybody comments on how much I am in for to fix this? (It is still on its
way) Obvious bad power supply (jittering ) but couldn’t find a specific
section in the manual that addressed the downward shift of everything.


Re: Tektronix PS280

tom jobe <tomjobe@...>
 

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

On 1/3/2018 7:17 AM, Malcolm Hunter wrote:
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



Re: introducing myself (and my scope)

Malcolm Hunter
 

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​


Re: Repairing a 466 oscilloscope

Nikolay Belikov
 

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

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