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Apparently dnmeeks has left this forum. On the off chance that he will be selling another batch of extenders some day, does anyone have his current email address?

I have a P6046 that is missing almost all of its accessories. I need the 10x attenuator, part number 010-0361-00 and 2 of either or both the swivel probe tips, part number 206-0162-00 (hex base) and 206-0164-00 (round base). I have one of the hex base probe tips so one more would make a useable set of tips.

Contact me off list at snossen at ieee dot org if you have any of these parts and would like to sell them.

I just resurrected a 2465A CT. I first want to express my appreciation for the threads here that were such a great help, especially Gregor's "noise on readout" adventure, I thought I would summarize my experience and list some important lessons. As has been noted elsewhere, the 2465A seems to be underrepresented in the boards, and the "CT" version is even less common.

Originally, it was not functional. However, there was some sort of noise on the CRT. I was happy to find that the 2465A uses the stand-alone memory battery, instead of the Dallas nightmares found in the later versions (and so many other models I have dealt with). The battery voltage measured 3.7V, so I left it alone, knowing it will eventually need to be replaced, but not for now.

Testing the power supply rails on J119, I found that the -5V and -8V were dead, so I dove into the power supply. I tested several bad electrolytics. Because of the work involved in extracting the power supply from the case, I decided to replace all electrolytics, the safety capacitors, and the large poly Sprague. After the reassembly, it powered up and appeared to be fully functional. However, the CRT seemed to be a bit out of focus. My rush to clean up the display led to some careless mistakes.

Early 2465A's (before serial number B014330), DO NOT have a CAL 08 (CRT Cal) menu item. Instead, the CRT is adjusted the old fashioned way, without any help from the control board. The procedure for those adjustments is at the very end of section 5 of the service manual.

If one (me) blindly hunts around in the menus on the 2465A CT, for the CRT (CAL08) procedure,they might see an entry called "CT CAL 81". It is important to understand that this is NOT a misprint of "CRT" just missing the "R"! By going into that item, the scope expects you to calibrate the timer settings for the high resolution "Counter Timer Trigger" option (so, I guess it is "CTT", but missing one "T").

If one finds themselves in a menu they don't want to be in, it is important to understand how to navigate with the front panel keys. It is even more important to not panic and shut off the power (yep, that was me). Worse yet, don't go back in to another calibration routine (CAL02, vertical cal) and do the same thing again.

After panicing, there was a "Fail 04 1x" error, and a "Fail CT CAL 81" error. These are indicators of a bad checksum in the battery-backed RAM configuration data, and also out-of-range configuration values. In many cases, these are interpreted as being an indication of a weak memory battery, but the battery still tested at 3.7V. My hope was, if I could successfully complete the two aborted calibration routines, I might get it back on its feet. My hope was that "Fail 04" could be fixed with a successful CAL02, and that the "Fail CT CAL 81" could be fixed by a successful "CT CAL 81", without having to perform a full calibration.

Lesson #1: The following Trigger buttons are how you navigate in the calibration routines:
1. "A/B-Menu" is like an "escape", used to exit the diagnostics / calibration routines
2. "Mode (Up)" and "Mode (Down)" step you through the menu items
3. "Coupling (Up)" is like an "enter" key, and causes the selected item to execute
4. "Coupling (Down)" is like a "backspace", used to back up and redo a step (if the step failed)

Lesson #2: The service manual is nice to have, but is missing some details that are important to know. I found the most help by searching for information here on TekScopes and on the EEVblog forum. Additional help was found on the wb0smx.net web page. The wb0smx page is specific to the 2465A, not the "CT", so it covers the main calibration routines, but not the "CT CAL 81" process. His observations and pictures are very helpful for verifying what the screen should look like before you proceed with "Coupling (Up)".

Lesson #3: If anyone has a working 2465 family scope, there is a simple way to "back up" the configuration data, found in the battery-backed RAM. After my experience, I would recommend that this be done on any working scope, before the cover is removed for any work, and to have on hand in case the memory battery does go dead, or if anything else goes wrong. There is not a clearcut way to restore that data, but having that data might lead to a way to restore operation if other methods fail.

I do not know what variables are associated with the RAM entries, but I think that there may be some interest in deciphering the data. Therefore, I have included a link to a table (below), which includes two sets of data:

/g/TekScopes/files?id=2620985&folder=0

1. The 2/21/21 column was read while both the "Fail 04" and "Fail CT" errors were still active.
2. The 2/25/21 column was read after successful calibration, so is without errors.

The entries in Red can be considered to be the "bad" entries, which were apparently fixed by the sucessful CAL02 and CT CAL 81 calibration procedures. There is a block of 26 entries, right at the beginning, that are all different. Then there are three smaller blocks later in the RAM.

I have read that others have not been able to clear even the Fail 04 1x error without completing ALL calibration routines in order. I can say that this was not true in my case. I only did the two calibration routines, and both of my errors were cleared. Therefore, a partial calibration can not only be saved, but can clear the errors. Since Fail 04 errors could possibly reflect a checksum error from any calibration data, the fact that I actually knew what data I had screwed up may have helped. I guess a point woudl be that "Fail 04" does not mean that CAL04 is invalid, it apparently means that any data could be corrupted. If one is dealing with a bad backup battery, causing much or all of the data to be bad, that may explain why a full calibration might be necessary much of the time.

Lesson #4: This scope seems to be far more forgiving in the calibration requirements than the later TDS models I have tried to "cowboy calibrate". Even with all the wrong calibration equipment, I was able to get it to accept the signals. Some steps did fail, by displaying "Level" instead of proceding to the next step. However, this is where pressing "Coupling (Down)" will back you up and let you "retry" the step. This can be done over and over, until it finally accepts it. I experienced this on the 10V step for the CAL 02 routine. To get the 10V level, I had to use an analog signal generator. Although I could verify and adjust for the 10V level, it may have not been stable enough to succeed. However, after three or four tries, it accepted it!

This scope, now that it is working, is shaping up to be a favorite of mine. It is new enough that it has great analog performance and very flexible triggering capability. However, it seems just old enough, that even I should be able to keep it running for years to come. My TDS digital models always scare me that they are going to suddenly lose calibration and be unrecoverable. I feel like I can use the 2465A as a "daily driver" and enojoy it.

Since this is the "CT" model, it has high-resolution time interval measurment, plus GPIB (woo-hoo!). It may not be state of the art, but it still impresses me. I know I am not the only person here that remembers how expensive this kind of equipment was in its day, and appreciate the value that a $20 purchase can bring today!

The "CT" also supports the P6407 "Word Recognizer Probe". Of course, I had to pick one up to try, and low and behold, it worked! For those who are not familiar with this feature, the Word Recognizer is a simplified logic analyzer trigger probe. It has 16 TTL inputs, an additional "Qualifier" bit, plus a Clock input. It allows digital events to be used as a sweep trigger, arm an analog trigger, etc.

I know I have dragged on too long, but I do have one more item that might be of interest. It has a Tektronix Property sticker, so at some point it was an internal asset. Once I got it up and running, I discovered that the Setup Memory is full, with 30 saved settings. What intrigues me is the Settings saved in location #1 is named "LEROY G". Position #5 is named "ROY". Other set names are more practical, such as "TIMEDLY" and "FUJITSU". This makes me very curious to know if there was a Tek engineer, named Leroy (Roy) G, who may have worked on Fujitsu gear. Does anyone here know Leroy?

Thanks for making it through my rambling,
Brian Nordlund

Hi all sampling gurus,

I am continuing performance check of my 7S14 (B020274). Any idea how many pieces were manufactured?
All the Hg cells were empty (and were leaked also). I replicated with the concept from Miguel.
Some photos uploaded to "Sampling with 7S14" album.

At least ch1 seems to be working properly. Quite noisy I thought (picture labelled first try).
Ch2 shows some sporadic operation.

I measured the power supplies and noticed that +30V was over 40V and -5V was -5.3V.
Replaced faulty U1 and U2 which fixed this problem. Just wondering if this has caused some damage?
I didn't notice tantalum caps issues (didn't remove any boards).
Some push button exercise with IPA and lubricant.

After those actions everything seems to be operational (all other photos).
Noise level seems to be lowered. I didn't dig into schematic but could those wrong voltage levels increase the noise level?

I haven't used 7S14 in my career. Does the screen images look ok?

Best Regards,
Jouko

How come it's always on the "other" coast with pickup only!?
Guys like me on the other end of the country never get a chance!

I will agree with Siggi on this one as far as one or more of those relays
being the likely cause. One of my TDS scopes had the same problem.
Replacing the relays he mentioned solved it. And yes he'll need to be
careful, the hybrid boards are made of pretty thin ceramic.

--Eric

Atillio, the TG may be OK now, producing the right center frequency. You should be able to get the amplitude to peak at narrowest bandwidth, and drop off when the tracking pot goes either way from the peak. Once this is working right, nothing should change in the actual output signal level when you change the SA's IFBW. The amplitude response is then up to proper operation, and calibration of the SA's gain at each IFBW setting. I think each one is adjustable. First, be sure you're not the cause by running the sweep too fast for the BW, - the narrower it is, the slower you have to sweep. I think there's supposed to be a "UNCAL" warning if the SA setup is wrong, but not sure. Just be aware of the issue. If the amplitude response really is wrong or different between settings, then look at the 7L13's calibration.

Ed

Hi Ed,
on the TR502 Tracking Generator manual I read this note "NOTE: If the TR502 is used with spectrum analyzer 7L13 the TRACKING ADJUST may run out of range at high resolution (3 kHz or less) setting because the IF in some early production 7L13 units may deviate a small amount from 105 MHz. If this occurs contact your Tektronix Field Office or representative to correct this situation. ".
Could it be related to my problem?
Even if it were I don't know if I could get an answer from Tektronix.

--Cheers
Attilio

"Hmph. Including the cable?"

I covered the probe amp, probe, and probe cable with aluminium foil grounded to the scope as best as I could. The Pomona connector I used to connect the probe to the input of the PG501 and the external power source were still exposed. I will give this technique another try, covering everything and see if I can get some improvement.

Respectfully,
Steve

Hey Steve,

The classic fault that causes SPC on these scopes is that the signal relays
on the input attenuator hybrids develop high resistance. They are used to
shunt in the internally generated calibration signal that's used for the
signal path compensation.
I replaced a few of those relays on my TDS784D, which cleared the problem.
The relays were readily available at the time, and I could readily measure
which relays were bad by a simple resistance measurement over the NC
terminals. Clipping the old relays out and soldering on the ceramic hybrid
was a little bit nerve wracking, but definitely very doable.

Siggi

On Sun, Feb 28, 2021 at 9:16 AM Steve Hendrix <SteveHx@...>
wrote:

A year or so ago I bought a TDS784C that seemed to be in pristine
condition except for a missing left rear foot. It powered up and
worked perfectly on every signal I tried it on. I found that I rarely
if ever had an actual need for its high bandwidth (1GHz) and I had
other scopes that met my needs with less bench space, so I sold it on eBay.

The buyer has been very polite and cooperative, but requests help
with finding a replacement foot, and also reports that he ran a
Signal Path Compensation which reported an error:

"A compensation error has occurred. Examine the error log and note
the message. Then refer this oscilloscope to a qualified service
technician for repair. It is possible to proceed by pressing Clear
Menu. The oscilloscope, however, may not perform according to
specifications."

According to the error log, this error has been present since 2007,
over a decade before i got hold of it.

Can anyone here offer suggestions?

Steve Hendrix

Hi Dave,

Thanks for the info. Tek did the same thing with their 4663
flat bed plotters, so I am familiar with the technique.

I would very much like not to have to do that, though.

I have bought some of the TMC2219 drivers, and will try them
soon. They are reportedly much smoother, as they use better
math in the microstep algorithms.

What I have read recently is that the motor has a great
preference for being at the full step positions... you can
feel them as detents when you turn an undriven motor's shaft...,
and as such it is like there is a spring trying to pull the
shaft back into the nearest full step position. This tendency
makes for instabilities in the vicinity of the half way points
between full steps. It also makes for noisy dead zones where
the motor cannot maintain position.

The TMC drivers have sensors in the chip that detect the
motor's instability in the dead zone regions, and adjust the
PWM microstep pulsing to eliminate the instability. This makes
for a quieter motor, and more accurate microstep positioning.

We will see...

-Chuck Harris

Dave Wise wrote:

A year or so ago I bought a TDS784C that seemed to be in pristine condition except for a missing left rear foot. It powered up and worked perfectly on every signal I tried it on. I found that I rarely if ever had an actual need for its high bandwidth (1GHz) and I had other scopes that met my needs with less bench space, so I sold it on eBay.

The buyer has been very polite and cooperative, but requests help with finding a replacement foot, and also reports that he ran a Signal Path Compensation which reported an error:

"A compensation error has occurred. Examine the error log and note the message. Then refer this oscilloscope to a qualified service technician for repair. It is possible to proceed by pressing Clear Menu. The oscilloscope, however, may not perform according to specifications."

According to the error log, this error has been present since 2007, over a decade before i got hold of it.

Can anyone here offer suggestions?

Steve Hendrix

Hi Ed,
sorry if I wrote an inaccuracy, the 10 pF capacitor is not between the junction point of the crystal with the varicap diode and ground, but on the other terminal of the crystal towards ground.
However I moved the capacitor in parallel to the varicap diode and it is better. I am left with the problem that from 3 Khz to MAX resolution the track is about 4-5 dB higher on the SA display and I don't know how to bring it back to the correct position.

--Cheers
Attilio

Weird, I just mailed a part to Massachusetts and it got there in two days.

Thanks. Supply rails are (now) good after replacing quite a few capacitors that weren't doing much (after tracing a few bad ones I ended up doing all electrolytics on the low & high voltage psu boards because dismantling took longer than resoldering). I also rewound the annoying noisy fan motor which is thankfully now silent but comes high on my list of not very fun jobs due to those very fiddly hall effect sensors. I do indeed have another scope to help - an HP183 (sorry Tek). But I am guilty as you say of a school boy error. Disconnect X deflection amp and presumably shorting the two sides on the CRT together is a sure way to eliminate X-deflection issues. I think though based on the shape this is a focus issue, but my experience tends to be with more basic crt types.

However I've also noticed that the edge focus is set hard against one endstop and there's something slightly strange with the drive to the third quadrupole lens (there is a LF353 and transistor driving the negative plate and I'm not convinced that is working as I'd expect symmetric voltages there) time for some component checks around that area.

Alan

-> Scope is in x-y mode
-> When both intensity and B intensity control are Conter ClockWise, I read
something like 8.21V at Z OUT DC test point.
BUT !
no matter how much I turn the intensity control, the voltage read at Z OUT DC
point does not change ?

Could you confirm intensity on the screen is not changing as well in XY mode?

I can actually get a voltage modification only if I put vert mode to CH1
(displaying grounded horizontal trace) but nothing happens when scope is in
X-Y mode.

On 485 in X-Y mode, intensity does change the intensity as expected. It could be a logic fault on sheet <12> but it could be because of a dirty switch as well. If you exercise all of the six "VERT MODE" and all of the four "HORIZ MODE" switches few times does anything change?

Next step is to confirm ~ 1V at anode of CR1561 and > 1V at pin U1560 in XY mode.

If these are OK, next step is to measure all the pin voltages of U1560 in XY mode. Inside of U1560 is at:

We can try to figure out the state of U1560 in the faulty condition.
Ozan

Dennis,

Sorry for the late reply, it's been a busy week.

Imagine my surprise to see a response from John Addis. Thank you for forwarding my question to him. I had the privilege of meeting John a couple years ago at the VintageTek museum.

I have access to a PG506 (non-A) so I think I am all set.

It is a remarkable instrument.

Thanks again for passing on John's reply.

Would this P6500 be a suitable substitute while looking for a cheap P6137?

Would it work for an 485 too?

I don't know the quality of P6500 but general view is no-name cheap high bandwidth probes do not have the clean transient response of probes from well known manufacturers.

It not clear to me the relation between the capacitor compensation range and
the input C capacitance. Could you confirm that is related to the charging
added to the circuit under test?

First the compensation range: Your scope has an input resistance and capacitance, usually marked next to the input BNCs. 485 shows 1M-ohm//20pF, 2467B (should be same as 2465B) shows 1M-ohm//15pF. Both can do 50-ohm as well. Probe compensation range should cover the input capacitance of the scope you are using.

For 485 you need a probe that can compensate 20pF. Recommended high impedance probe for 485 is P6053 which has a compensation range of 15pf-24pF.

P6137 has a compensation range of 12pF-18pF. This probe is not a good fit for 485 because 20pF input capacitance is outside the compensation range. However, it works well for 2467B because 15pF input capacitance is in the compensation range.

Probe input capacitance is what you see at the tip of the probe. It depends on many factors such as construction of the probe, length of the cable, etc. P6137 datasheet is at:

Table I shows the input impedance as 10M-ohm//10.8pF. Figure 4 shows impedance vs frequency. Note that beyond 100MHz impedance of the probe is less than 150-ohms.

Ozan

Hi Sean,

I didn't mean to ruffle your feathers. I am sorry for that.

I left a paragraph out that would have tied the shuttle,
automobiles, and our probes together... And included one that
was frictional, and should have been left out...bad me!

Chilling the probe down causes it to instantly pull moisture
from your breath and body out of the air, and condense it on
everything. I don't think you can possibly get the chilled
probe filled and capped quickly enough to prevent that from
happening. Moisture is not your friend in an HV probe.

Minor incidental loss through a single filling of your probe
shouldn't be a cause for concern. That little puddle of 114
in your probe makes gallons of vapor. The concern should
come when you have to fill it again, and again, and again,
because of an unnecessary leak.

If your probe won't hold its freon for 20+ years, as mine
has shown is possible, I think you ought to take some effort
to fix it.

The probe can be made to not leak. One needn't settle for
it needing a fill every now and then.

-Chuck Harris

Sean Turner wrote:

To no one in particular. I have found it useful to cover the under side of my work bench with aluminum foil connected to a binding post convenient to the front of my scope. Jumper cable to scope ground. It really cuts down the local broadcast and 8ft fluorescents above. Separate subject but fluorescent tubes are covered with knit tubular EMI mesh grounded to center of fixture. Mesh is samples from Tecknit.
Eric WB6KCN