Hi All, Just having gotten one of these (free, broken), I'm starting to evaluate what may be wrong with it.? Reportedly, it stopped working suddenly with a POP! The owner assumes a tantalum cap went bust, but he doesn't recall a lot of smoke or anything like that, so I'm not convinced it's that.? Some initial observations:?
- Upon opening the case, I immediately became suspicious of the Schaffner line filter, but then I do get 120V out of this AC line input module, so maybe it's not that.?
- From the same module, the fan is NOT getting power.?
- I am not able to find any DC on the PS output header (tried the most accessible 5 or 6 pins).?
I am uploading supporting pics on the files area of the forum. Obviously, it's going to all be a bit of a blindfolded pursuit, not having a decent service manual (by that, I mean component-level). I am reading through Figure 6-31 Primary Troubleshooting Procedure see if I can come up with a culprit. Thank you for your input in advance. Radu.?
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Check all the voltages on all the low voltage power supplies. ?It looks like you have a problem there.
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Hi.
The domed mesh PDA CRT's, always appear to defocus as you increase intensity, especially at low or zero sweep* speeds, but that's only because of the extra "bloom" from the mesh, making a noticeable "halo" around the spot.
(* Take care, the screen has quite a high resistance to burning, but a prolonged high intensity spot stuck in one place will eventually mark the screen.? Or worse...??? While debugging CRT issues, always best to fully defocus the beam, in case you loose intensity control and allow an uncontrolled beam to hit the screen.)
If you observe a stable (but fast) waveform at high sweep speeds, you'll find that the beam itself does not appreciably defocus as the intensity increases, because the "bloom" or "halo" being at a lower intensity level is not as visible at high sweep speeds as the main beam itself.
Regards.
Dave G0WBX (Ex Tek UK.)
--
Created on and sent from a Unix like PC running and using free and open source software:
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Thanks, I¡¯ll give cleaning a try.?
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I'm sure others have mentioned it, but when focus changes
greatly within the normal intensity range, it is often a sign
that the CRT has reached its end of life.
There is a phenomenon called intensity double hump, which is
identifiable by focusing the CRT with a dim beam, and then
slowly advancing the intensity. If you see the intensity
get brighter, and then get dimmer, and then start to brighten
again, but get blurry, you likely have an end of life CRT.
The other common cause of focus/intensity problems is a dirty
focus/astigmatism section of the circuit board. It can sometimes
be fixed by washing all of the board around the HV section,
including all focus/astigmatism resistors and capacitors, with
99% IPA. Don't forget to clean the tripler module, and let it
get good and dry before restoring power.
Good luck!
-Chuck Harris
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On Fri, 02 Sep 2022 17:12:56 -0700 "DG" <grind.fix@...> wrote: My tech tried adjusting astigmatism as described above. We are in the
same boat. I'll upload images shortly. The smallest dot is per
Astigmatism adjustment instructions. The other two are with increased
intensity halfway and 3/4 way up. The fourth image is the square wave
taken from the calibration post on the front panel.
He is saying that Increasing the brightness (intensity) will defocus
the image. The focus adjustment passes the midpoint. Signals at the
deflection plates are clean. He doesn't see any noise, ripple, or
oscillation while watching on the separate scope. He also said that
focus and intensity pots are partially in series and intensity
adjustment suppose to add compensation to the focus circuit. Both
pots and their sections show expected results when activated from end
to end but CRT doesn't take the circuit compensation. I hope this
makes sense because I'm trying to translate his words with only a
partial understanding of what's happening. What he showed me in his
simplified circuit drawing is that one of the Intensity pot sections
is reducing or increasing ground resistance for the focus circuit
depending on the pot position.
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My tech tried adjusting astigmatism as described above. We are in the same boat. I'll upload images shortly.?
The smallest dot is per Astigmatism adjustment instructions.
The other two are with increased intensity halfway and 3/4 way up.
The fourth image is the square wave taken from the calibration post on the front panel.
He is saying that Increasing the brightness (intensity) will defocus the image. The focus adjustment passes the midpoint. Signals at the deflection plates are clean. He doesn't see any noise, ripple, or oscillation while watching on the separate scope.?
He also said that focus and intensity pots are partially in series and intensity adjustment suppose to add compensation to the focus circuit. Both pots and their sections show expected results when activated from end to end but CRT doesn't take the circuit compensation. I hope this makes sense because I'm trying to translate his words with only a partial understanding of what's happening. What he showed me in his simplified circuit drawing is that one of the Intensity pot sections is reducing or increasing ground resistance for the focus circuit depending on the pot position.?
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Re: TDS-460 component-level service manual?...
This seems like a pretty good overview:?. It even includes a BOM for recapping the entire scope, which?is really useful.
There is not a component level manual that I have ever found.? I have two of these scopes and it is either ¡°Board level¡± repairs or just dive in and take an educated guess and hope you can fix it. ? Michael Lynch
From My I-Phone
479-477-1115?
On Sep 1, 2022, at 11:40 AM, Radu Bogdan Dicher <vondicher@...> wrote:
? Thank you for that, Doug, but no component level schematics in that document, nor in any that I've seen.?
---------- Original Message ---------- From: "Radu Bogdan Dicher" < vondicher@...> To: [email protected]Subject: [TekScopes2] TDS-460 component-level service manual?... Date: Thu, 01 Sep 2022 08:25:17 -0700 Hi all, I'm looking for this (see subject line). It doesn't look like Artek has it (though maybe I am missing it).? Is this something anyone has seen? It seems a product build recently enough that they may have not issued "CLIPs" for it at all. Thank you, Radu.?
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Re: TDS-460 component-level service manual?...
There is not a component level manual that I have ever found. ?I have two of these scopes and it is either ¡°Board level¡± repairs or just dive in and take an educated guess and hope you can fix it. ? Michael Lynch
From My I-Phone
mlynch002@...
479-477-1115?
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Show quoted text
On Sep 1, 2022, at 11:40 AM, Radu Bogdan Dicher <vondicher@...> wrote:
? Thank you for that, Doug, but no component level schematics in that document, nor in any that I've seen.?
---------- Original Message ---------- From: "Radu Bogdan Dicher" < vondicher@...> To: [email protected]Subject: [TekScopes2] TDS-460 component-level service manual?... Date: Thu, 01 Sep 2022 08:25:17 -0700 Hi all, I'm looking for this (see subject line). It doesn't look like Artek has it (though maybe I am missing it).? Is this something anyone has seen? It seems a product build recently enough that they may have not issued "CLIPs" for it at all. Thank you, Radu.?
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Set to XY mode. ?Normal brightness. ?Unfocus till the spot is a large round circle. ?Turn ASTIG adjustment until the spot is perfectly round as you can make it. ?Refocus to make a tiny spot again. ? Michael Lynch
From My I-Phone
mlynch002@...
479-477-1115?
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On Sep 1, 2022, at 11:41 AM, Tom Phillips <tjtomphillips@...> wrote:
?On Thu, Sep 1, 2022 at 08:31 AM, DG wrote:
Could you help me find the Astig adjustment procedure in the manual? I searched through and find no mention of it so far.
The ASTIG adjustment info is on pg 2-5 (Circle 18) of the original version of the 465B manual and on pg 2-4 (Circle 18) of the S/N B060000 and up version of the manual. It simply says "...used in conjunction with the FOCUS control to obtain a well-defined display." You won't damage anything by turning the control through it's whole range so I suggest that you give it a try to determine if it affects your display. This isn't a formal "Calibration Procedure" and no test point need to be accessed or monitored. You basically alternate between the ASTIG and the FOCUS control until you get the sharpest trace. I also like the method described by Harvey White in his post at #15822 because I think it's a nice way to see when the astigmatism is optimized for the best display. Cheers, Tom
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On Thu, Sep 1, 2022 at 08:31 AM, DG wrote:
Could you help me find the Astig adjustment procedure in the manual? I searched through and find no mention of it so far.
The ASTIG adjustment info is on pg 2-5 (Circle 18) of the original version of the 465B manual and on pg 2-4 (Circle 18) of the S/N B060000 and up version of the manual. It simply says "...used in conjunction with the FOCUS control to obtain a well-defined display." You won't damage anything by turning the control through it's whole range so I suggest that you give it a try to determine if it affects your display. This isn't a formal "Calibration Procedure" and no test point need to be accessed or monitored. You basically alternate between the ASTIG and the FOCUS control until you get the sharpest trace. I also like the method described by Harvey White in his post at #15822 because I think it's a nice way to see when the astigmatism is optimized for the best display. Cheers, Tom
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Re: TDS-460 component-level service manual?...
Thank you for that, Doug, but no component level schematics in that document, nor in any that I've seen.?
---------- Original Message ---------- From: "Radu Bogdan Dicher" < vondicher@...> To: [email protected]Subject: [TekScopes2] TDS-460 component-level service manual?... Date: Thu, 01 Sep 2022 08:25:17 -0700 Hi all, I'm looking for this (see subject line). It doesn't look like Artek has it (though maybe I am missing it).? Is this something anyone has seen? It seems a product build recently enough that they may have not issued "CLIPs" for it at all. Thank you, Radu.?
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Re: TDS-460 component-level service manual?...
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---------- Original Message ---------- From: "Radu Bogdan Dicher" <vondicher@...> To: [email protected]Subject: [TekScopes2] TDS-460 component-level service manual?... Date: Thu, 01 Sep 2022 08:25:17 -0700 Hi all, I'm looking for this (see subject line). It doesn't look like Artek has it (though maybe I am missing it).? Is this something anyone has seen? It seems a product build recently enough that they may have not issued "CLIPs" for it at all. Thank you, Radu.?
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XY mode, both inputs GND. Move spot near the screen centre. Reduce brightness until you can only just see the spot. Twiddle focus and astig to get smallest symmetrical spot (adjust brightness if necessary)
Hi,
I have one manual, still waiting for download approval from Artek for SN correct SM.?
Could you help me find the Astig adjustment procedure in the manual? I searched through and find no mention of it so far. Manual is huge and easy to overlook.
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I think by now, you have had enough advice to decide "Is this hum
from other circuits (Shorted input, different? time settings and
look for vertical deflection in absence of horizontal "dither), or
is it s CRT circuit fault.
I am not sure what type of resistors the 465B uses in its EHT
circuits. If they are the VR37 variety, probably all perfect, but
if ordinary carbon resistors (the manual should say), then that is
the second route.
IF you find vertical hum on trace, then certainly look at low
voltage electrolytics, but just saying "electrolytics and
tantalums" at this stage is time wasting and pointless.
Earlier a reference (not by you) was made to anode voltage of
-2500v. That of course should be CATHODE voltage, with grid within
about -70v of cathode.
Les.
On 9/1/22 15:13, DG wrote:
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Hi,
I've heard that some oscilloscope tubes have audio use. I never
had any to try.
Thanks for your offer on parts, we first need to know where the
problem is. I think, and it's a gut feeling, the problem is in
either aging LV power supply capacitors or if this unit uses any
Tantalum capacitors as interstage couplings, those are trouble.
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Hi,
I have one manual, still waiting for download approval from Artek for SN correct SM.?
Could you help me find the Astig adjustment procedure in the manual? I searched through and find no mention of it so far. Manual is huge and easy to overlook.
Thanks!
|
TDS-460 component-level service manual?...
Hi all,
I'm looking for this (see subject line). It doesn't look like Artek has it (though maybe I am missing it).?
Is this something anyone has seen? It seems a product build recently enough that they may have not issued "CLIPs" for it at all.
Thank you,
Radu.?
|
Hello DG, I was able to exactly duplicate the fat unfocused looking trace that your photo shows by purposely mis-adjusting the astigmatism on my 465B. Therefore, let's try the simple stuff first before diving into the scope's internal circuitry. Before this discussion goes any further, please verify that you have adjusted the astigmatism control. It is a screwdriver pot accessible on the front panel of your 465B located between the Intensity and focus knobs. It is labeled "ASTIG." Any version of the 465 or 465B manual that you download will describe the adjustment. Reference the posts at? #15809 by jon and at? #15822 by Harvey White for previous mentions of the astigmatism adjustment. Cheers, Tom
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One thing of note with the 465B (and other Tek instruments from the same era)...
They use CRT's with a "Domed Mesh PDA*" forming an electron lens to allow for a relatively short distance between the deflection plates and the screen.?? (* Post Deflection Accelerator.)
See:
Sadly, that "naturally" causes some "fuzziness" of the beam, but I've never seen one "That" bad before.? Neither my 465 or 468 have that amount of defocus.
If you fully defocus the beam, one way or the other, at some point you'll get a "projected image" of the mesh pattern on the screen. It is perhaps worth manually sweeping the entire screen to check for a uniform mesh pattern, showing no holes, obstructions or other damage..
I'd certainly also check all the power rails for any instability (HF oscillations etc.)?? From the photo's I've seen so far, it is odd that the beam seems as wide as it is high, indicating a fundamental focus issue, or something else strange going on.
The manual for those 'scopes is very good, especially in the Theory of Operation section, plus the HV/CRT schematic, and deflection amp drawings are littered with typical voltages (and waveforms) that you can compare with.
Lastly, check for any evidence that someone has been in there before you.? Has the CRT been replaced (wrong type) or the PDA multiplier module (again different type) and other changes or adjustments made to compensate for any different deflection factors.? (Check the sweep timing is accurate per division, likewise the vertical V/div accuracy.)
Hope something helps.
Dave B.? (Ex Tek UK.? From way back in the Harpenden & Maidenhead years.)
--
Created on and sent from a Unix like PC running and using free and open source software:
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Hi,
I've heard that some oscilloscope tubes have audio use. I never had any to try.
Thanks for your offer on parts, we first need to know where the problem is. I think, and it's a gut feeling, the problem is in either aging LV power supply capacitors or if this unit uses any Tantalum capacitors as interstage couplings, those are trouble.
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Michael
Tom Phillips