Date   

Re: Tektronix 465B servixe manual containing waveforms 56-70

pdxareaid
 

i have a free manual i just checked and it has the same problem. i guess i never really used it.
i use a very good artek pdf manual purchased at http://artekmanuals.com/manuals/tektronix-manuals/
both hi and low serial number manuals available. just enter 465b into search box for options.


Re: 485 super weak brightness control

Ozan
 

The node 1312/1318 is 0.0V in A and -0. 6V in B in the 521 mode
0.9V in A and -0. 6V outside of the 521
That looks suspect
I agree this needs to be investigated further. Easy explanation is N4 signal on <11> is wrong but we looked at it before.

--- copied from our earlier exchange --
In sheet <12> N4 is expected to
be -3V in B sweep and 5/2/1n mode. What voltage do you see at N4 when you
are in B sweep vs A sweep 5/2/1n?
I can see -3.6 when 521 is selected, -3. 7 when B is selected and -5.3
when there is A selected and outside of the 521 range
-- end copy ----------------------------------

Confirming again is a good idea.

How do waveforms look in the following points in 521n setting A vs B at:
"A sweep from Q888" left side of R1307
"B sweep from Q1236" left side of R1322

Again we expect no change.

Ozan


Re: Tek 1503C TDR

Harvey White
 

In one of the TM5000 series function generators with an LCD display, I was able to replace the Tek display (with an EL backlight) with a standard 2 line x 16 character off the shelf LCD display.  The two displays looked physically identical with the exception of the EL backlight, of course.

Harvey

On 4/26/2021 11:44 AM, Jeff Dutky wrote:
Judging by the pictures on TekWiki those LCD displays could use replacing even when they were "working."

It looks like the LCD is getting 8-bit parallel data from the CPU with 3 address lines and read and write strobes. The display modules are only referenced using Tek part numbers (672-1241-00 below SN B023854, 118-9050-01 after), but I wonder how hard it would be to decipher that protocol. At the very least you could read the Z-80 assembly that generates the video output straight out of the ROMs.

That would be a lot easier to read with a modern LCD and backlight, or a nice, old-school gas plasma or vacuum fluorescent display.

-- Jeff Dutky





Re: Tek 7844 Alphanumeric Display Issues

 

On Mon, Apr 26, 2021 at 10:56 AM, David C. Partridge wrote:


If you are asking where to find schematics of the EPROM version of the readout
board, I can't help
The RO board wasn't unique to the 7844. I'm pretty sure that some later 7904A's had the same board. I guess (free) SM's are available. I'd look for schematics there.
Just checked: My (ArtekManual's) 070-4593-00 contains two RO versions; one of them is the EPROM-one.

Raymond


Re: 485 super weak brightness control

Ondrej Pavelka
 

Hi,

The horizontal control is -3.6V and -3.7V with A and B. That's very much
ok. It changes to 1.16V when XY is selected

The node 1312/1318 is 0.0V in A and -0. 6V in B in the 521 mode
0.9V in A and -0. 6V outside of the 521
That looks suspect

The node 1358/1356 is 0.545V in A and 0.6V in B and only changes to -0.7V
in XY mode


Unfortunately I didn't have time to pull out the two translators and test
them out

On Sat, 24 Apr 2021, 08:40 Ozan, <ozan_g@erdogan.us> wrote:

Hi Ondrej,
Great news that relays fixed many of the issues, congratulations.

As you know in 521 setting only B sweep is used so if you look at "B sweep
from Q1236" on sheet <11> it should look the same as you press "A" or "B".
Base node of Q1312 and Q1318 select A or B (should be in B in 521
regardless of switch), that node should be the same voltage in "A" or "B"
in 521 mode. Base node of Q1358 and Q1356 select sweep or XY mode, should
also stay the same in "A" and "B".

Once you know which node misbehaves you can find the root case, most
likely in sheet <12> or one of the switches that feed into <12>.

Ozan



Guys,

New Relays arrived and nearly all is healed. When B is selected all works
flawlessly, when A is selected everything works up till the 521 range. In
521 it's not displaying properly. More in the video

I'm so happy it's nearly there now!

https://youtu.be/xCO4kJbXaMw






On Fri, 26 Mar 2021, 01:21 Raymond Domp Frank, <hewpatek@gmail.com>
wrote:

On Fri, Mar 26, 2021 at 12:48 AM, Ozan wrote:


I agree sometimes stepping back and looking with fresh eyes helps.
Let
us know
when you want to bounce off ideas again.
Ozan
I fully concur, Ozan.

Raymond










TM500/5000 plug-in failure modes.

Dave Peterson
 

Hi all,

I'm going through a number of unknown TM500/5000 plug-ins and have encountered a couple that seem to fail in the same mode: a trace to pin 9B of the rear edge connector (33v common) overloads and begins to burn. I had one go completely smoky before I realized what was happening. After that I caught another one in time because I was monitoring the power supplies and saw a drop in the supply (not huge). It still caused noticeable trace damage.

The thing is, some plug-ins load this supply (and pin) and others don't. The one's that don't test just fine. Not that they work necessarily, they just don't go up in smoke. Now whenever I plug-in a unit that does include 33v sources I of course see a load on the power supplies. I don't have sophisticated load monitoring yet, but I do know about the issues with power supplies, pass transistors, and the TM500/5000s tester. For now I just blip the power on and immediately off if I see any load on 33v/17.5vac.

This has also happened on a couple of different power supply units: a TM503 and a TM504. These units test good for supply level, ac phase, and basic pass transistor continuity. I don't have a curve tracer at hand at the moment, but no shorts before and after testing. Also the failure mode does not appear to be on the pass transistor. Though I cannot be certain that the pass transistors aren't involved as I don't have good knowledge of the plug-in internals. But pin 9B isn't a pass transistor pin.

I'm pausing my testing for now until I have this sorted out so I can know the difference between a load on 33v and a plug-in on its way to death.

I'm thinking a current monitor on 33v common, but don't know how I'd implement that. Otherwise I'm left watching the 33v supply - 17.5vac also shows load when this happens. I can't tell the difference (yet), in a quantitative way, between a normal load and impending death. You can imagine, I'm not keen to sit and watch another plug-in load those supplies and wait to see if it's dying or just a normal load. Some of these are valuable.

So my question is, is this "33v common/pin 9B" overload a known thing? And how do I definitively monitor for it? Why the common pin and not the TM504 33v supply (or other) fuse?

I'm new to the TM500/5000 world and I'm trying to catch up. There's a lot out there to review, but I haven't seen anything yet on this failure mode.

Thanks,
Dave


Re: Tek 1503C TDR

 

Judging by the pictures on TekWiki those LCD displays could use replacing even when they were "working."

It looks like the LCD is getting 8-bit parallel data from the CPU with 3 address lines and read and write strobes. The display modules are only referenced using Tek part numbers (672-1241-00 below SN B023854, 118-9050-01 after), but I wonder how hard it would be to decipher that protocol. At the very least you could read the Z-80 assembly that generates the video output straight out of the ROMs.

That would be a lot easier to read with a modern LCD and backlight, or a nice, old-school gas plasma or vacuum fluorescent display.

-- Jeff Dutky


Re: Tek 1503C TDR

Dale H. Cook
 

Good luck - failure of the LCD is a frequent problem in the 1502/1503 A/B/C TDRs. That is why I own a 1503 (as Scotty said in the NextGen episode "Relics", "No bloody A, B, C, or D").

Dale H. Cook, GR/HP/Tek Collector, Roanoke/Lynchburg, VA
https://plymouthcolony.net/starcity/radios/


Re: Tek 7844 Alphanumeric Display Issues

 

We already replied to you that the fault is most likely to be in the auxiliary input of the 2nd Vertical amplifier, and that the readout vertical position pot is R2700 on the vertical amplifier board.

If you are asking where to find schematics of the EPROM version of the readout board, I can't help, but none of the original boards had a vertical position pot on the RO board, and none of the later 80C31 versions did either, so its my bet that the EPROM version also didn't.

David

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Liam Perkins
Sent: 22 April 2021 05:34
To: TekScopes@groups.io
Subject: [TekScopes] Tek 7844 Alphanumeric Display Issues

I have a 7844, ser. no. B173417, that works fine but for the character
display which is shifted upward 5 divisions, making of course the top
portion of the display invisible.


Re: Cannot delay the B sweep on a 465B

Ozan
 

Hi Torquil,


I have a problem with my 465B where the delay time position 10-turn pot for
the B sweep has no effect. Everything else seems to work. Please see this
youtube video for a demonstration:

https://youtu.be/17ZGEw_jOmo

The intensified portion of the A sweep trace always starts on the leftmost
part of the display no matter how much I turn the delay time position knob.
However, the holdoff knob does make the B sweep duration/length vary, in a
periodic manner as I turn the holdoff knob slowly clockwise.
------
I don't have a 465B but B sweep delay circuit works similarly on several scopes. On sheet <7> Q7067 compares delay potentiometer voltage to "A ramp" voltage. Depending on where ramp crosses the delay pot voltage, B sweep starts with that delay. "A ramp" waveform (node 60) is not shown in the PDF I found but it is the same signal as node 82 which is in the manual. First check is whether the pot changes comparator threshold. Voltage on C7052 should change from 2.8V to 12.9V as you turn the delay pot.

If the delay pot voltage is OK next check is voltage at R7157 & R7152 junction. Looking at the schematic I expect it to be ~ -0.5V when "A ramp" is more that the delay pot voltage and should jump to ~ +1V when it goes below.

If you report back the observations there may be other suggestions.

Ozan


Re: Unable to see some images in 75th anniversary consolidated pdf

 

Dave

Thanks so much.
A real trip down memory lane!

Menahem Yachad


Re: 465 Scope Question

Dave Hills
 

C1562 is not doing its job, the AC voltage should be much less, I would expect
less than a volt.
You can calculate the DC load current from the measured DC voltage across R1569.

Dave


The input AC voltage at the bridge rectifier CR-1561 is 12.3vac. The AC
voltage on the DC output of CR1561 is 4.5vac.

Thank you,
Bill


Re: Good storage solution for collection of 500-series plugins?

-
 

I agree that it's a good idea but unless it's something that I'm going
to leave for a LONG time I seldom bother and I've never had a problem. I've
stored Tek and other electronics for five plus years in silver bags and all
of it has been fine. I have ammo that has been stored in ammo cans without
desiccant since I reloaded it in the 1960s and it still looks and shoots
like new. In fact, I even have some WW-II US made MIL ammo that still looks
and shoots fine. This is in Florida heat and humidity. As long as
everything is DRY when I seal it, nothing that I've sealed up seems to
deteriorate. But a word of caution, regular ziploc bags are just about
worthless except for keeping the dust off. Moisture passes right through
them.

On Sun, Apr 25, 2021 at 1:43 PM Roy Thistle <roy.thistle@mail.utoronto.ca>
wrote:

On Sat, Apr 24, 2021 at 12:30 PM, - wrote:


I store my plugins in one of the silver colored ziplock anti static bags
If one is going to do that, either displace the air with dry nitrogen
gas... which I assume everyone has... or put in a new (or properly
salvaged) desiccant bag.
Here in the colonies, the military always seems to put them in.
If you don't... unless you live in the Mojave Desert.. you might regret it.

--
Roy Thistle






Re: Unable to see some images in 75th anniversary consolidated pdf

Dave Brown
 

The museum did two projects to celebrate Tek's 75th anniversary. The first was a 75 exhibit slideshow tour. We chose this format since organizing a tour during Covid is a bit challenging. Even doing slides the tour takes 90 minutes. We had 6 different volunteers narrate the slides so the audio quality varies by home setup. The slides have photos of the actual exhibits at the museum with just a few exceptions.

The second project was to post a historic page a day. I started on February 4th, the day the company registered the name Tektronix. I've posted a page a day every day less about 5 days when I was without power and we migrated the website. The last posting was yesterday. Since all the pages have been posted I replaced the individual photos with a PDF. Links to both are on the home page.

Our thanks to the volunteers who took the time to put these together. Both were considerable efforts.

Dave


Re: 465 Scope Question

Bill
 

The input AC voltage at the bridge rectifier CR-1561 is 12.3vac. The AC voltage on the DC output of CR1561 is 4.5vac.

Thank you,
Bill


Tektronix 465B servixe manual containing waveforms 56-70

Torquil Macdonald Sørensen
 

Hi!

Does anyone here have a scanned version of a 465B service manual which
contains the waveforms 56 through 70, as well as the accompanying
oscilloscope settings?

In the one I have they are missing (while some other waveforms are scanned
twice). In another the pages have been cropped so the waveforms are outside
the page.

Best regards,
Torquil Sørensen, Norway


Cannot delay the B sweep on a 465B

Torquil Macdonald Sørensen
 

Hi!

I have a problem with my 465B where the delay time position 10-turn pot for
the B sweep has no effect. Everything else seems to work. Please see this
youtube video for a demonstration:

https://youtu.be/17ZGEw_jOmo

The intensified portion of the A sweep trace always starts on the leftmost
part of the display no matter how much I turn the delay time position knob.
However, the holdoff knob does make the B sweep duration/length vary, in a
periodic manner as I turn the holdoff knob slowly clockwise.

Any pointers for things to check in the circuit ? The voltage rails are
fine. Anyone here seen this problem before?

I have just fixed a problem with a reduced trace length on this scope, by
"cleaning" the X1 Gain pot with IPA. Maybe something similar could cause my
B sweep delay problem?

Best regards,
Torquil Sørensen, Norway


Tek 7844 Alphanumeric Display Issues

Liam Perkins
 

I have a 7844, ser. no. B173417, that works fine but for the character
display which is shifted upward 5 divisions, making of course the top
portion of the display invisible.

According to the 7K-series Readout System on the TekWiki here:

https://w140.com/tekwiki/wiki/7000_series_readout_system

there were three versions of the driver hardware; a) the initial ROM-based
all-analogue, b) the late-80s 2732 EPROM-based system instead of the
earlier analogue ROMS and, c) a third generation readout board designed
around an 80C31 micro‐controller.

Mine is the EPROM version and despite buying hard copy off eBay and
downloading everything off the TekWiki I cannot find a manual describing my
unit so I don't know where to find the pots that'll put the display where
it belongs; assuming that's what is the problem.

Anyone have any experience with this,or access to the correct manual or
the version number of same ?

TIA
Liam @ PEARL, Inc.


Tektronix SA 2782

Vik Danchuk
 

Hi !
can you watch the video and tell us your opinion about it
https://groups.io/g/TekScopes/files/tek%202782.mp4

thanks in advance
Vik


Tek 1503C TDR

warren.stirling@...
 

Hi all,

Does anyone, by faint chance, have a replacement lcd assembly for a 1503C TDR?

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