Re: Tek 2465b two probes showing slightly different voltages and phases
Since you didn't provide any actual numbers, it's difficult to say anything specific. Generally speaking, though, you shouldn't expect two different types of probes to be exquisitely phase matched -- that's a tough enough requirement even for two probes of the same type. In your case, not only may the cables have mismatched lengths and velocity factors, the compensation networks themselves could have different delays. Those networks are designed to produce maximally flat response in both amplitude and delay, but there's no effort to make the delay themselves additionally some standardized value. Just accept that mismatched probe types will likely have mismatched delays.
As for voltage variations, without knowing to what tolerance you calibrated them and at what frequency you are making these measurements, it's hard to say whether what you're seeing is outside of what one should expect. At dc, the attenuation is set entirely by resistor divide ratios, so if you're seeing errors at dc, those errors should be within the tolerances of the resistances. At high frequencies, the attenuation is controlled by capacitance ratios, so you should be able to fix that by tweaking the probe compensation capacitance.
In short, without giving us actual numerical data, it's not possible to know whether you have a real problem, or whether your expectations are unrealistic.
--Cheers,
Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
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On 12/30/2020 16:38, Mark Hatch wrote: Newbie here with a Tek2465b and multiple 10:1 probes, none the same. (but they have been "compensated using the builtin calibrator of the 2465b). I a am feeding two channels simultaneously from the same HP652a oscillator.
I am seeing slight voltage and phase variations between the two probes. If I switch the channels, the variation follows the probe (i.e. if channel 1 had probe B and it was slightly lower and ahead, putting probe B on channel 2 and now channel 2 is lower and ahead on channel 2).
One probe is a tek p6012 (12.5pf, 9.04 mohms on my fluke)) and the other is a tek 6106 ( 15.6pf, 9.02mohms). I do have another Tek probe, but couldn't get a straight sq wave when I tried to compensate it. In any case, the third probe didn't agree with either of the other two either...
Given the problem follows the probes, it seems like the answer is that the probes are the problem and not the scope's problem.
Comments?
Thanks
Mark
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Re: Rotation direction of fan in 2465
Well as it happens while I've succesfully rewound one of these motors before, but this time after rewinding and reassmbly I must have caught one of the hall effect sensors on the case of the motor and mangled it so I guess it's game over unless anyone has a broken/noisy1AD3001-OA motor from which I can steal the hall effect sensor.... (UK).
Alan
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Tek 2465b two probes showing slightly different voltages and phases
Newbie here with a Tek2465b and multiple 10:1 probes, none the same. (but they have been "compensated using the builtin calibrator of the 2465b). I a am feeding two channels simultaneously from the same HP652a oscillator.
I am seeing slight voltage and phase variations between the two probes. If I switch the channels, the variation follows the probe (i.e. if channel 1 had probe B and it was slightly lower and ahead, putting probe B on channel 2 and now channel 2 is lower and ahead on channel 2).
One probe is a tek p6012 (12.5pf, 9.04 mohms on my fluke)) and the other is a tek 6106 ( 15.6pf, 9.02mohms). I do have another Tek probe, but couldn't get a straight sq wave when I tried to compensate it. In any case, the third probe didn't agree with either of the other two either...
Given the problem follows the probes, it seems like the answer is that the probes are the problem and not the scope's problem.
Comments?
Thanks
Mark
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Re: Firmware for Tektronix 492/496 spectrum analyzer
I got an adapter for using a 27c256 to replace the 4 8K ROMs.
I¡¯ll see how this work (when the other parts arrive). I¡¯m now skeptical that the processor is the problem but I¡¯ll work to get the self test to complete before moving to other parts.
The curious thing is that the intensity control has no effect even though it looks like the processor has no part in that circuit. (I just have a central dot on the screen)
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Re: Rotation direction of fan in 2465
?ann mi?., 30. des. 2020 kl. 17:53 skrifa?i Chuck Harris <cfharris@... : fan blows out the back of the scope. Hey Chuck, Unfortunately that doesn¡¯t help OP, as an impeller will pull the same way whichever direction the motor turns. I¡¯d look at my 2465, except it¡¯s currently somewhat gutted, awaiting a re-cap. Siggi
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Re: 7904A restoration questions
On Tue, Dec 29, 2020 at 06:40 PM, David Campbell wrote:
Any 'gotchas" inside? I read about the blue edge connectors. Any
info/advice on the plugins?
Dave, I have a dozen or so older 4xx, 5xxxx and 7xxx series scopes and considering how many capacitors are contained within those dozen or more of scopes, I can say that I have seen very few really "Bad" caps. Yes, there is an occasional bad electrolytic cap, but far fewer than one would think. I have a 576 that had a few truly "bad" caps in the power supply, that was the worst one that I encountered. In a TM506 I replace a Filter cap in the Power supply. In my host of 465/468 and 475's i have replaced 3 or 4 caps. I have even repaired the SMPS in a TDS460A and it had ZERO bad caps in the supply, I checked them all. Bottom Line is this: If there are no symptoms of problems and no evidence of faults in these caps, then the odds are stacked against you to "improve" the performance of your instrument. David, Tom and Dennis are 100% correct, please consider their advice carefully. These folks will not lead you wrong. Respectfully yours, -- Michael Lynch Dardanelle, AR
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Re: 7904A restoration questions
I agree, except in the case of some TDS 420's TDS 640's etc. the bypass caps are just all bad.
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Re: 7904A restoration questions
If David reads this he should know that you (David C. Partridge) and Tom Lee know what you are talking about and your advice is precisely what I told him as soon as I approved his post. I told him that he shouldn't replace the electrolytics until he at least had a chance to check their ESR with a Dick Smith ESR meter or equivalent.
His reply to me today was not encouraging. It will be a terrible shame if he damages an outstanding 7904A because he thinks he knows better.
---
This is what I got this from David today:
"I can tell you from a lot of electronics repair experience, that not replacing old electrolytics is a ticking time bomb. Not only did they not tend to be vented and can explode if they short, they can go leaky and do serious damage to pass power supplies.
They will all be changed."
---
I hope someone else can talk some sense into him. So far the three of us have failed.
Dennis Tillman W7pF
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-----Original Message----- From: [email protected] [mailto: [email protected]] On Behalf Of David C. Partridge Sent: Wednesday, December 30, 2020 2:35 AM To: [email protected]Subject: Re: [TekScopes] 7904A restoration questions Please don't shotgun replacing electrolytics, the odds are you'll do more harm than good. Some of those multilayer boards can be problematic when de-soldering components - you SO don¡¯t want to strip a PTH. If it works just use it. David -----Original Message----- From: [email protected] < [email protected]> On Behalf Of David Campbell Sent: 29 December 2020 23:05 To: [email protected]Subject: [TekScopes] 7904A restoration questions Ive ordered all the electrolytic caps to do a shotgun replace. If the scope works fine, if the plugins work, finer yet! -- Dennis Tillman W7pF TekScopes Moderator
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Re: Mechanism of CRT Double Peaking (UPDATED)
Nenad,
I have a 5103N that appears to be showing double peaking in its CRT, and I'm willing to try making these measurements.
Am I correct in assuming that I can do this with nothing more than a multimeter?
-- Jeff Dutky
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Re: Mechanism of CRT Double Peaking (UPDATED)
Hi Chuck,
Yes, I agree we derailed the subject by going deep into the cathode issues, but I still instinctively believe that double peaking explanation may be within grasp (without major research). Until someone does the measurements I proposed and triggers the lovely "experiment - check your theory" loop, we cannot say we even tried.
The fact you mentioned about focus is interesting. I believe the solution is related to contamination of g1 and g2 with cathode material, where interaction deforms the field distribution which manifests also as a visible change (loss) of focus. Stray gas is very likely involved, as its presence directly influences the electrode currents. But for any credible theory we need the sufficiently sampled plot of the electrode voltages against the observed intensity and focus.
Nenad Filipovic
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Re: Rotation direction of fan in 2465
fan blows out the back of the scope.
alan.bain@... wrote:
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Very silly question but can anyone tell me which way the impeller type fan in a 2465 is mean to rotate; I have rewound mine and realise I don't know this vital piece of information for phasing the coils from the hall effect sensors.
I think looking at the impeller it is anti-clockwise looking at the fan from behind the oscilloscope, but I've seen both kinds of vane on impeller fans and am no expert!
Alan
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Rotation direction of fan in 2465
Very silly question but can anyone tell me which way the impeller type fan in a 2465 is mean to rotate; I have rewound mine and realise I don't know this vital piece of information for phasing the coils from the hall effect sensors.
I think looking at the impeller it is anti-clockwise looking at the fan from behind the oscilloscope, but I've seen both kinds of vane on impeller fans and am no expert!
Alan
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Re: Spectrum analyzer Tektronix 7L13 on mainframe Tektronix 7603
Hi Attilio No, only the crystal and retune the filter Regards! -----Mensaje original----- De: [email protected] [mailto: [email protected]] En nombre de Attilio Enviado el: mi¨¦rcoles, 30 de diciembre de 2020 22:32 Para: [email protected]Asunto: Re: [TekScopes] Spectrum analyzer Tektronix 7L13 on mainframe Tektronix 7603 Hi Miguel, thanks, if I understand correctly I have to replace the crystal with a 52.5 MHz one and retune the 2nd band pass filter. Do I need to change other components ? Thanks for the info. -- Cheers Attilio Scanned by McAfee and confirmed virus-free. Find out more here:
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Re: Spectrum analyzer Tektronix 7L13 on mainframe Tektronix 7603
Hi Miguel,
thanks, if I understand correctly I have to replace the crystal with a 52.5 MHz one and retune
the 2nd band pass filter.
Do I need to change other components ?
Thanks for the info.
-- Cheers
Attilio
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Tek Scopes and Modules for New Home
I hope this is the right forum for this message. If not, I apologize and please point me in the right direction. I have been acquiring tek equipment for some years but it's time for me to pass these along. I have two working series 7000 scopes (7704A and 7904A Option 3, both with 4 working modules), 21 series 5 and 7 modules (some working some not) and 3 working power modules (515, and 2 504's). I don't want to ship (the scopes and power modules are too heavy and the scopes too fragile), so they are only available for local pick up in Los Angeles. I have pictures available. If there is any interest please email me OFF LIST at tektronix90049 at gmail dot com .
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Re: Rescuing 500s from tube snatchers/scavengers - how much is it worth
I've gotten 100 free listings a month for the last couple of years. Shortly before I decided to get a store they upped it to 200.
Vince.
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On 12/30/2020 03:23 PM, Jeff Kruth via groups.io wrote: Not totally true. Stores cost and they do have hidden fees for listing unless you get free listing privileges. My 23rd year on eBay and boy, has it changed, from great to reasonably sucky.
Jeff KruthIn a message dated 12/30/2020 1:23:04 PM Eastern Standard Time, snapdiode@... writes: eBay doesn't bill for ads. They get a final value fee for sales. And shipping fee as well, they tax your shipping money!
--
K8ZW
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Re: Rescuing 500s from tube snatchers/scavengers - how much is it worth
Not totally true. Stores cost and they do have hidden fees for listing unless you get free listing privileges.? My 23rd year on eBay and boy, has it changed, from great to reasonably sucky.
?Jeff KruthIn a message dated 12/30/2020 1:23:04 PM Eastern Standard Time, snapdiode@... writes:?eBay doesn't bill for ads. They get a final value fee for sales.?And shipping fee as well, they tax your shipping money!
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Re: Spectrum analyzer Tektronix 7L13 on mainframe Tektronix 7603
crystal of 52.5 MHz with 55MHz. tr501 to TR503 TR503 to TR502 501 55MHz to 52.5 I have a TR502 with 1.8Ghz counter and LEMO cables. You can track frequencies with very high precission: /g/TekScopes/album?id=86278/g/TekScopes/photo/86278/10?p=Name,,,20,1,0,0 /g/TekScopes/photo/86278/11?p=Name,,,20,1,0,0 -----Mensaje original----- De: [email protected] [mailto: [email protected]] En nombre de Attilio Enviado el: mi¨¦rcoles, 30 de diciembre de 2020 13:25 Para: [email protected]Asunto: Re: [TekScopes] Spectrum analyzer Tektronix 7L13 on mainframe Tektronix 7603 hi Miguel, hi Tom, great idea, I try to find a TR503, but what value should the crystal have? I am waiting for the 7613 mainframe to replace the 7603 mainframe, with the 7613 mainframe I should make better use of the SA 7L13. Thanks and happy new year Attilio Scanned by McAfee and confirmed virus-free. Find out more here:
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Re: Rescuing 500s from tube snatchers/scavengers - how much is it worth
eBay doesn't bill for ads. They get a final value fee for sales.
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Re: Borrow an extender in U.K.
Robin
No problem. how many do you want?
I am near Bicester in tier 4, so probably not an essential journey for you?
let me know
Chris HJ
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On 30/12/2020 14:50, Robin_Birch wrote: Slip of a finger, it's a 7603
Robin
-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Robin_Birch
Sent: 30 December 2020 14:33
To: [email protected]
Subject: [TekScopes] Borrow an extender in U.K.
Hi,
Need to give my 7003 and some plug ins a good going over. Is there anyone
in the Cotswolds area (U.K.) who has an extender that I could borrow for a
couple of days ?
TIA
Robin Birch
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vk2bea
Michael W. Lynch
Attilio