Re: What calibration items to buy.
Wondering if any have experience with the below inexpensive DC Voltage "standard" or similar items (no affiliation) :
Would these represent practical use to interested TekScope members ?
a)
( has a description of their calibration chain).
b)
( using the LT1021 IC, low cost voltage reference.)
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Re: Tek 317 odd trace behavior after warm-up
Hi John,
That's what I get for guessing... :)
Thanks,
Barry - N4BUQ <- Amateur Radio Callsign
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Hi Barry,
It's actually the chassis code for my favorite car, the Mitsubishi Lancer
Evolution 10.
Regards,
John - CZ4A
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Re: Tek 2465a grid bias and brightness problems
If 240K works, it wouldn't be a sin to use it.
For all you know, your 2465A CRT could have been replaced with
a CRT from a 2465, or your U950 may be an old revision.
Put another way, tektronix once found 240K to work, and later
found something changed that made 390K work better. Your scope
may need the resistor to be 240K.
Also, at voltages and impedances as high as these, thin films
of environmental gorp (smoke, soot, radon daughters, cleaner
fumes, vacuum pump oil, ...) can easily cause changes like
what you are seeing.
If you want to take a stab at curing this, you could also try
washing the CRT's neck, socket, base, and the HV section's
board, resistors, capacitors, ... very clean, and see what
happens.
Others have found cleaning of these parts to help.
-Chuck Harris
Francesco wrote:
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After a lot of testing, I can give some more insight on my problem, and I sincerely need your opinion of experts on the matter. I have replaced and tested with a working U950, a nos and tested complete a9 board and I have checked all the DI and ROI lines from pots to U950, the problem doesn't change. The AC waveform is clamped at the low end by the vz out from intensity pot and U950 vz out but grid bias even if dc restorer works in spec can't completely turn off the crt. It only works if I lower the value of one of the DC restorer resistors out of spec: r1992 is marked on the schematic as a 240k but in reality is a 390k from later 2465 serial numbers on to 2465b (you can see this on material list), if I use a 240k resistor instead of the 390k everything works fine and the crt completely dims off and I can complete cal08 with no problems. Still this is not in spec for a 2465a. It seems a crt problem at this point, have you ever seen anything like this? It seems like a leak between g1 and cathode. Can you give some advice? Should I replace the crt?
Thanks in advance
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Re: What calibration items to buy.
It has been so long since Weston last made standard cells of any
stripe that it is doubtful that yours is measuring within its
accurate range. I would imagine that by now, Weston's site has
been cleaned of most of its mercury and cadmium contamination,
and is probably only just barely considered a superfund site...
What type (saturated or unsaturated), and what voltage is your
cell reading?
OBTW, a 10M DVM is a little on the high side as far as loading
goes for a standard cell. Protocol requires that you to use a
balanced bridge type measurement, and draw no current from the
cell.
-Chuck Harris
Robin Birch wrote:
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I¡¯ve got an old Weston standard cell that sits on my bookshelves and I check the DVMs against that. I¡¯ve never calibrated it but it seems close enough. I don¡¯t really ask much of my calibration, within two or three decimal places is fine.
Robin
On 17 Mar 2018, at 05:28, Craig Sawyers <c.sawyers@...> wrote:
assume
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Re: Tek 317 odd trace behavior after warm-up
Oops ! The last two lines of my previous message, after the signature.. what are they doing here... just ignore them.
Unfortunately unlike forum posts, you can't edit/correct e-mails... once it's sent, it's sent...will proof read better next time, sorry :-/
Vince
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Re: Tek 317 odd trace behavior after warm-up
Hi John,
Oh, so you found my topic on EEVblog... well, not much I can add then...
I think however you should not waste time and money replacing all these tube and caps (other than the obvious paper caps of course), unless proven faulty.
The scope has to be diagnosed first, then once the fault is pinpointed, you just replaced what actually is faulty.
Hell, even the paper caps weren't that bad on my unit. I replaced them for good measure (though like you, I still haven't found the motivation to get to the ones hidden in the rotary switch assemblies... a real pain in the butt aren't they !), but really it didn't make any difference. Only the two in the HV / CRT section were bad and causing my trace going dim and disappearing off scale/drifting after a minute. But all the other paper caps still aren't bad to the point of creating any noticeable symptom...
You have one good thing going for you : your fault is not intermittent ! You can reproduce it at will and therefore do all the necessary measurements.. so eventually you will narrow it down.
Again, even if you don't have second scope to check waveform, I would think that once the fault has manifested itself, and is "stable", you should be able to find something wrong somewhere, just by simply checking DC levels with a DMM, using the schematics. This is easy and cheap to do... as you probably have a DMM I would think (?), and if not, given that you only need very basic DMM for this particular task, then even a good brand/quality DMM, bought used, should be cheap. I don't know, an old Fluke 75 or something, whatever. Oh, just checked your Eico 950B... so you really are into tube stuff... if you are "against" modern digital multimeter, then you can still get a high-impedance voltmeter, I saw that in the tube era there existed high-impedance meters, that used a tube on their input stage, as buffer/high impedance votlage follower.. so you could use that. But then you would have to find one, and spend time and money restoring it... would be easier, short term, to help you in diagnosing that 317, to just get a cheap DMM for the time being...
As from the single-leaded clamped electrolytic, yes the can is negative,just like the big cans in the LV power supply, and just like... I think any metal can cap ?!... Even on my 1980 vintage counter (the Enertec 2618, also on EEVBlog), hence much more modern than the 317, the filter caps in the powers supply section were all of the can type, with the negative connected to the can, and a single lead in the center.
Sure enough you can replace those with a modern/two lead cap, which I did. It's just a cap... no magic there.
As for buying a brand new canned cap with a center lead... I don't know if you can get them, other than some specialized sites selling recap kits for particular devices that are popular. so most people who want to retain the looks of the old can, just reuse/restuff it. I am not aware of a cap manufacturer that mass produces this type cap... though would be great of course, would male restoration easier...
CZ4A, ROTFL ! Every time you see such a signature it's a call sign, for once it's not, loved it ! :-)
Vince - L48Y08 then
Btu again, I would not waste and effort doign anything to them
Once you have the DMM, check all voltage
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Re: Tek 2465a grid bias and brightness problems
After a lot of testing, I can give some more insight on my problem, and I sincerely need your opinion of experts on the matter. I have replaced and tested with a working U950, a nos and tested complete a9 board and I have checked all the DI and ROI lines from pots to U950, the problem doesn't change. The AC waveform is clamped at the low end by the vz out from intensity pot and U950 vz out but grid bias even if dc restorer works in spec can't completely turn off the crt. It only works if I lower the value of one of the DC restorer resistors out of spec: r1992 is marked on the schematic as a 240k but in reality is a 390k from later 2465 serial numbers on to 2465b (you can see this on material list), if I use a 240k resistor instead of the 390k everything works fine and the crt completely dims off and I can complete cal08 with no problems. Still this is not in spec for a 2465a. It seems a crt problem at this point, have you ever seen anything like this? It seems like a leak between g1 and cathode. Can you give some advice? Should I replace the crt?
Thanks in advance
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Re: What calibration items to buy.
I¡¯ve got an old Weston standard cell that sits on my bookshelves and I check the DVMs against that. I¡¯ve never calibrated it but it seems close enough. I don¡¯t really ask much of my calibration, within two or three decimal places is fine.
Robin
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On 17 Mar 2018, at 05:28, Craig Sawyers <c.sawyers@...> wrote:
assume
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Re: Tek 317 odd trace behavior after warm-up
Hi Vincent,
I've read your thread on eevblog, which was helpful. The reason I focused on the horizontal amp is that unlike the situation with your 317, the traces are still there after warm-up, just in the wrong position and malformed. The caps in the horizontal amp section are all dogbone-shaped ceramic or mica. It's possible they've gone bad, but IIRC ceramic and mica caps last longer than paper or old electrolytic.
All the paper caps in this serial # are Good-All rather than Sprague. I've replaced the paper caps on the chassis, but still need to get to the paper caps on the rotary switches.
I hope the flyback transformer isn't damaged! Besides the two paper caps I replaced in the HV circuit there is an electrolytic (C807, 8uf, 450V). I've never seen a single-lead cap like it before. It's held to the chassis with a clamp. Looks to be body-negative. Another one is C154 (500uf, 6V) in the preamp. Are these still available outside of fleaBay, or will it suffice if I get modern two-lead caps and route the negative leads to the chassis?
I have an Eico 950B cap bridge I can test the caps with. I do need to get pictures and measurements from the LV rails, but right now I don't have the scope in front of me. I'll be sure to post back here with my findings.
Hi Barry,
It's actually the chassis code for my favorite car, the Mitsubishi Lancer Evolution 10.
Regards,
John - CZ4A
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Re: What calibration items to buy.
What I do is periodically take my voltage transfer standard to a lab, and get it measured. I then
take
my now known transfer standard, and use it as my shop standard when calibrating all of my meters
and calibrators. I've done precisely the same thing. I had my old Cropico DC 10V voltage standard traceably calibrated. And it was within the last decimal place (7 of them) as it was when it was originally calibrated by the manufacturer in 1987. Why did Cropico (the Croydon Precision Instrument Co) exit the voltage standard business? I talked to them about that - actually the original designer: "Fluke entered the market, and as a small company we could not compete" So I've stopped worrying or getting paranoid. I'm going to assume the voltage is what it says it is on the tin. Craig
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Help with cleaning up this 485 for good
I have calibrated everything I could with what I have. This scope is a mashup of several scopes. 2 different attenuators a vertical amp from another 485 and all new capacitors. I would like to clean up the square waves. Pictures are of the scope calibrator 5V 1khz. 50mV and .1V are both using a 5x attenuator and 50ohm cable the 1V is just the 50 ohm cable. I dont know if this is able to be done with what I have. 50Mv /g/TekScopes/photo/37195/8?p=Name,,,20,1,0,0 .1V /g/TekScopes/photo/37195/0?p=Name,,,20,1,0,0 1V /g/TekScopes/photo/37195/1?p=Name,,,20,1,0,0 this is another scope at 1V /g/TekScopes/photo/37195/7?p=Name,,,20,1,0,0
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Re: Tek 317 odd trace behavior after warm-up
Thanks for the info.. I am no radio amateur so it didn't make any sense to me I must admit...
I guess I am old fashioned but I prefer to call human beings via their real name, feels more natural and fitting to me ?!
It's also easier to remember a real name than a call sign, at least for the average human being that I am.
Anyway, looks like he is not far from a diagnosis on his Tek 317, though would be nice to have a few piccies showing the problem, and/or uploading a little video on Youtube maybe ?
Vincent Trouilliez - VT7760... err no, just made that up, just Vince, that will do fine :-)
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Re: What calibration items to buy.
Hi Kevin,
Absent a calibration, or comparison of your meter's readings
to a standard value, how will you even guess if it is right?
What is often called calibration is really verification and
documentation of your meter's performance as compared to what
the manufacturer claimed its performance would be.
Is it worth it? I cannot know what you value. Some just buy
new meters whenever they suspect that their old meter may be
performing incorrectly. Others repair and calibrate the old
meter. Still others don't really need a meter that can do much
more than verify that a D cell is about 1.5V, so for them,
calibration is just a new D cell away...
What I do is periodically take my voltage transfer standard to
a lab, and get it measured. I then take my now known transfer
standard, and use it as my shop standard when calibrating all
of my meters and calibrators.
Is it truly right? No. My transfer standard starts to change
the instant I stop comparing it to the calibration lab's
transfer standard, which started to change the instant that
NIST stopped comparing it to NIST's standards, and every time
UPS went over a bump...
OBTW, your thermocouple calibrator is not even in the same
league as your 5.5 and 6 digit DVM's... it is kind of like
comparing a pro baseball game to the toddlers playing T ball.
-Chuck Harris
Kevin Oconnor wrote:
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Hi Chuck, to you and others....
Let me address calibration from a different angle. I'm not so concerned about scope cal. I am concerned about DC meter cal. I have a number of 5.5 & 6.5 DMMs that are well beyond their last cal date. I have an Ectron 1100 thermocouple calibrator that is good to 1uv resolution at 100mv FS I think. Last cal was 1990.
I got a quote from Tek in Phoenix to cal the 1100 for $385. What that gets is before and after data on calibrating 1100 to Ectron specs withe certificates. Is it worth the money to know my D.C. Standard for the other meters is up to date?
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Tek 160-series module clones?
This auction includes some funny-looking 160-series modules? Are they clones or are they Tek?
thanks, -Kurt
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Re: Tek 317 odd trace behavior after warm-up
CZ4A is most likely an amateur radio call sign (Canadian).
Thanks,
Barry - N4BUQ
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----- Original Message ----- From: "Vincent Trouilliez" <vincent.trouilliez@...>
To: [email protected]
Sent: Friday, March 16, 2018 3:25:16 PM
Subject: Re: [TekScopes] Tek 317 odd trace behavior after warm-up
Hello anonymous ! :-) I guess "CZ4A" is not your real name ;-)
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Re: Tek 317 odd trace behavior after warm-up
Forgot : the caps you actually need to worry about are not the electrolytics (at least not at first), but rather all the paper caps, the black and red "Sprague" ones. You already have replaced the two from the CRT/HV section... maybe there is one causing trouble in the horizontal section...
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Re: Tek 317 odd trace behavior after warm-up
Hello anonymous ! :-) I guess "CZ4A" is not your real name ;-)
Well I am hardly an expert with tube stuff, as I only have one of these beasts.... yes, a Tek 317 just like yours.
Got it last summer, fixed it a few months ago, learned some stuff along the way... thanks to the people on here obviously.
My first thoughts :
- Don't lose sleep on the big electrolytics... it so happens that they were top quality and more often than not, they are still good today ! Mine certainly are, and my unit is even older than yours (SN# 2369). All power rails were spot on, and ripple on all f them was negligible.
- You say that the trace brightness is good at power up, but dims a bit once fully warmed up (an indication of how much time that actually means, might be useful : 2 minutes, 30minutes ?). I guess that can only mean that there is still some issue in the CRT/ HV section that needs sorting out. You already replaced the two paper caps in the CRT section (I did too, that fixed the dimming trace issue on my scope, would dissapear after only 60 seconds), but I gather that another common problem on these scope is the HV transformer which becomes lossy once, precisely... warmed up). So maybe you need a new tranny. The issue is so common, that there is someone on here who used to wire them by the dozen to help others fix their scope...
- As I understand you, you already have narrowed it down to the horizontal section of the scope... so well, just keep trouble-shooting it further, thanks to the comprehensive service manual, and your existing experience working on tube stuff... shouldn't take you too long I would think ! :-)
I understand this is your first scope... however it's gonna be difficult checking ripple and waveforms at various points, without... a second scope. Just pick the cheapest/crapest basic old analog scope you can find locally. Even if just single channel, even if just 1MHz B/W... that would still be night and day to assist you in trouble shooting your 317. Obviously you will need to use x10 probes, given that voltages can go up to, IIRC, 400+ Volts (for the CRT circuit). A HV probe would be nice too, to check what voltage you actually get on the CRT anode... I picked a decent 40kV one for 75 Euros shipped. You can find cheaper since here you only need a 10kV probe.
But at first, you can start by checking all DC voltage levels indicated on the schematics (in the area of interest), using a simple digital multimeter...
Of course start by checking all the voltage rails. You can use your DMM in AC mode to get a first taste for ripple levels, short of a scope at the moment.
Keep us posted on your progress :-)
Regards,
Vincent Trouilliez
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Re: 7633 fan possible to repair?
Very good explanation Fabio. It¡¯s as if I was there. Thanks
Raymond C?t¨¦
KD9CCZ
Heaven goes by favor.
If it went by merit, you would stay out and your dog would go in.
-Mark Twain
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On Mar 16, 2018, at 09:01, Fabio Trevisan <fabio.tr3visan@...<mailto:fabio.tr3visan@...>> wrote:
Hello Lop,
Apparently we will walk hand in hand with our two recently acquired 76xx scopes (mine is a 7623A).
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Re: 7633 fan possible to repair?
Oilite is a registered tradename for a sintered bronze
bearing material.
Oilite bearings need to be precharged with oil. This
is done by heating the bearing, and then placing it in
a container of oil. When the bearing cools, the fresh
oil will be drawn into the bearing. It doesn't have
to be real hot, probably about 100C... don't want to
ruin the oil.
When an oilite bearing is put into service, it is
common to put the oilite into contact with an oil
soaked felt pad. The worn out oil will be replenished
with fresh oil from the pad.
Oilite is more abrasive than the steel shaft (usually),
and when wear happens, the steel usually does the
wearing.
The oilite can get damaged through being run dry.
The little bronze lined cells... sort of like a sponge...
get smeared, or hammered, shut by the friction, and
rattling that happens when the oil runs out. They
can sometimes be cleaned well enough by heating them
to get the old oil (and dirt) out, and allowing fresh
oil to charge the bearing.
Usually, a bearing that has been run dry will not wick
oil adequately, and will just throw the oil you add,
and again go dry.
Also, it is imperative that oilite be run with close
tolerances. It works by meniscus action of the oil
in the oilite against the shaft, forming a film of
oil that supports the shaft... The shaft isn't supposed
to rub against the oilite.
-Chuck Harris
Fabio Trevisan wrote:
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Hello Brasscat,
What a world of experts and specialists this is.
In my small world, I never thought there were different kinds of bronze bushings... To me, there was sintered bronze bearings, for cheapo, less demanding applications, and ball bearings for serious stuff.
I've got to do some research to answer your question, since I didn't have a guess of what "Oilite" meant.
Now I know there's plain sintered bronze bushings, often (but not always) made of phosphor bronze, and there's Oilite, which I understood as being a specialized type of sintered bronze bushing... one that's auto-lubricant (e.g. that doesn't require additional oil, IF I got it right).
Never having seen an Oilite bearing or, at least, not knowing that I saw one, I can only offer an assumption.
This fan has 2 very generous lint pads (say 1" x 3/4" x 1/8th") that surrounds the bronze bushing... So I THINK it's not Oilite.
Rgrds,
Fabio
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Re: 7633 fan possible to repair?
On Fri, 16 Mar 2018 12:41:47 -0700, you wrote: Hello Brasscat,
What a world of experts and specialists this is.
In my small world, I never thought there were different kinds of bronze bushings... To me, there was sintered bronze bearings, for cheapo, less demanding applications, and ball bearings for serious stuff. There's also sleeve bearings, which may or may not be lubricated (and likely ought to be). I've got to do some research to answer your question, since I didn't have a guess of what "Oilite" meant.
Now I know there's plain sintered bronze bushings, often (but not always) made of phosphor bronze, and there's Oilite, which I understood as being a specialized type of sintered bronze bushing... one that's auto-lubricant (e.g. that doesn't require additional oil, IF I got it right). I think you do. Oilite is a sintered bronze, made up of tiny little welded together bronze spheres. As such, it has a lot of internal space. It's oil impregnated to "avoid" the need for continuing lubrication. It is supposed to be permanent lubrication. Cleaning them with a solvent may require them to be re-lubricated. Sleeve bearings are a shaft running in a tube, I think there's no question about lubrication, they have to be. Never having seen an Oilite bearing or, at least, not knowing that I saw one, I can only offer an assumption.
This fan has 2 very generous lint pads (say 1" x 3/4" x 1/8th") that surrounds the bronze bushing... So I THINK it's not Oilite. I think you're right. Harvey Rgrds,
Fabio
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Vince
Raymond Cote