Re: TDS460A Will not turn on?
Ravi,
I will continue to study this circuit and the materials that you have suggested. Is it your opinion that UC3844A is the oscillator? The Data sheet for the device seems to indicate that it is. The supply that Mr. Carlson studies uses an 14 or 16 DIP IC containing the oscillator, therefore I assumed that the aforementioned component was similar in function. I am in no hurry and I appreciate your feedback.
--
Michael Lynch
Dardanelle, AR
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Perhaps the input circuitry has been blown out by excessive voltage which
is a good hint for what is wrong.
I wish I had a schematic of what is in the unit before I cut into it. I
also wish I were not so stubborn about fixing it as it really is not worth
the time and effort.
Since the probe has a 4 GHz bandwidth (still) even though it oscillates, I
am not sure how to proceed.
Thank you for the suggestion.
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On Sun, Aug 18, 2019 at 10:26 AM G?ran Krusell <mc1648pp@...> wrote: Hi, there is a peculiar property with emitter followers and FET source
followers. Under some circumstances they will provide a negative input
impedance. This with a certain source impedance will start an oscillation.
To prevent this from taking place a series RC link is normally placed from
base or gate to ground. This might be a hint for you.
G?ran
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Re: 2467B focus/astigmatism anomaly...
Maybe the cap IS leaking, and heated some of the resistors on the right hand side of the schematic up?
After disconnecting the cap, the resistors cooled back down and found their normal DC working area, hence the focus stayed ok?
Still interested,
Leo
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Re: 2467B focus/astigmatism anomaly...
An interesting change has occurred from yesterday...
Yesterday, I removed C4403, turned the scope on, adjusted
the focus and astigmatism, played a little bit, and concluded
the dynamic focus circuitry did very little, if anything...
I then turned the scope's beam off, and walked away for a
few hours.
When I returned, and turned the scope's beam back on, I found
the focus was bad once again. So, after tweaking the astigmatism
to sharpen the beam up, I turned the scope off for the night.
This morning, when I turned the scope back on, and turned its
intensity back up, it was still sharp... when totally cold!
Sharp when hot, and still sharp when cold.... Exciting!
I turned the beam back off, and walked away for an hour, and
when I came back and turned the beam back on, it was still
sharp. Then I turned the beam back off, and walked away for
another hour, and turned the beam back on, and it was still
sharp.
I am going to let it percolate for 2 or 3 hours and try again,
and I will report back.
Perhaps C4403 is involved?
I'm having a little trouble explaining last night's focus
shift shortly after I removed the capacitor.
-Chuck Harris
Raymond Domp Frank wrote:
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Hi Chuck,
On Mon, Aug 19, 2019 at 01:58 AM, Chuck Harris wrote:
The scope has been running all afternoon with the
capacitor removed, and frankly I can't even tell it
is gone... A lot of circuitry for such little affect.
However, the anomaly continues exactly as before.
Thanks for checking that, so it's off my mind.
I agree re. Q4432, Q4440, and all of
those high resistance resistors in the focus chain.
Interesting and intriguing!
Raymond
|
Re: Fan Mounts for Brown Case 545
McMaster-Carr has them, as do others
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On 8/19/2019 4:25 AM, Mike Duda wrote: The four rubber vibration damping fan mounts on my circa 1956 brown case 545 have disintegrated. Any suggestions on where I might find suitable replacements?
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Fan Mounts for Brown Case 545
The four rubber vibration damping fan mounts on my circa 1956 brown case 545 have disintegrated. Any suggestions on where I might find suitable replacements?
|
Re: TDS460A Will not turn on?
Hi Michael,
I will check the standard circuit for and around UC3844A and provide my thoughts. The photo of your A5 board will also help in understanding component placement on the board that you have.
Currently, I am away from my home and hence, may not be able to share/send detail replies. Kindly excuse me for couple of days.
Warm Regards,
|
Hello everybody
For the repair of my T912 i need 1 knob Volt/Division ((Tek part 366-1646-00) and 1 x the shaft that goes from its Variable 9red) knob into the potentiometer.
I liven in Amsterdam Netherland. Email: sp856567@.... WhatsApp: -31-65-3206282
Best regards,
Frank
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Re: TDS460A Will not turn on?
On 8/18/2019 10:46 PM, Mlynch001 wrote: Ravi,
I have became a student of Mr. Carlson's about two years ago, I have watched that particular video on SMPS several times. It all makes sense to me at that level. The board level is where I get lost. The traces and components are so tightly packed that it is difficult (for Me) to determine which part is the one that I need to identify. What Paul describes with a few hand drawn components becomes a quagmire of many times more components. Picking the correct two or three out of a couple of hundred is daunting, to say the least.
The TDS460A uses a totally different power supply from the 460. The one that is shown in that video is an older model, common to the 420 and 460 models, but not the "A" models. I realize that in principle, these work the same. However, they appear to take a completely different approach in construction. Mr. Carlson actually did a video where he repaired that exact SMPS. I watched that video several times as well.
On this board, I see a 8DIP UC3844A, which I assume is the oscillator which starts the whole circuit? The first thing I did when reading this is google (or duck duck go) the UC3844A, which is a PWM controller.? I didn't go any further, but it does have application notes.? TI makes it.? If the power supply designers didn't stray too far from the application circuit, that will be a help.??? It looks as if it is intended to be the controller in a power supply, and seems to want between 16 and 28 volts (max) as a power input. That might help as a start. Harvey Therefore, I assume that it is near to this component that I should find that ZENER Diode, Power Resistor and the Capacitor that Chuck is alluding to in his Million dollar hint? The problem is, I do not immediately see a direct connection to the Main filter caps to these various outlying components. To Chuck's hint, I do see a 47uF 25V electrolytic cap that is in one of the traces from IC2 (opto-isolator) back and finally making it's way to pin7 of UC3844A. There is also an SCR in the line to pin#5 of the second opto-isolator. My current problem is that If UC3844A is NOT the oscillator, then I need to figure out what components comprise that oscillator and work backwards from there.
I greatly appreciate your guidance and great patience. I will stay after this until I figure it out.
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Re: TDS460A Will not turn on?
Ravi,
I have became a student of Mr. Carlson's about two years ago, I have watched that particular video on SMPS several times. It all makes sense to me at that level. The board level is where I get lost. The traces and components are so tightly packed that it is difficult (for Me) to determine which part is the one that I need to identify. What Paul describes with a few hand drawn components becomes a quagmire of many times more components. Picking the correct two or three out of a couple of hundred is daunting, to say the least.
The TDS460A uses a totally different power supply from the 460. The one that is shown in that video is an older model, common to the 420 and 460 models, but not the "A" models. I realize that in principle, these work the same. However, they appear to take a completely different approach in construction. Mr. Carlson actually did a video where he repaired that exact SMPS. I watched that video several times as well.
On this board, I see a 8DIP UC3844A, which I assume is the oscillator which starts the whole circuit? Therefore, I assume that it is near to this component that I should find that ZENER Diode, Power Resistor and the Capacitor that Chuck is alluding to in his Million dollar hint? The problem is, I do not immediately see a direct connection to the Main filter caps to these various outlying components. To Chuck's hint, I do see a 47uF 25V electrolytic cap that is in one of the traces from IC2 (opto-isolator) back and finally making it's way to pin7 of UC3844A. There is also an SCR in the line to pin#5 of the second opto-isolator. My current problem is that If UC3844A is NOT the oscillator, then I need to figure out what components comprise that oscillator and work backwards from there.
I greatly appreciate your guidance and great patience. I will stay after this until I figure it out.
--
Michael Lynch
Dardanelle, AR
|
Re: 2467B focus/astigmatism anomaly...
Hi Chuck, On Mon, Aug 19, 2019 at 01:58 AM, Chuck Harris wrote:
The scope has been running all afternoon with the
capacitor removed, and frankly I can't even tell it
is gone... A lot of circuitry for such little affect.
However, the anomaly continues exactly as before.
Thanks for checking that, so it's off my mind. I agree re. Q4432, Q4440, and all of those high resistance resistors in the focus chain. Interesting and intriguing! Raymond
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Re: 7000 series carrying handles - how strong are they?
I once carried a 7704A a little over a mile. I don't recommend it but
I would like to point out that my ability to carry it gave out, while
the handle is still in working order.
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On Sun, Aug 18, 2019 at 9:39 AM Nenad Filipovic <ilmuerte@...> wrote:
Well I suppose this sounds silly, but I just can't get over it. This thin
metal sheet inside the handle is surely tough, high tensile strength steel,
but somehow subjectively it doesn't nearly impress as the rugged 465
handle, for example. In my head thin metal sheets tear and crack. Every
7000 handle end I inspected showed some minor bending around the hole where
it pulls against the main screw.
So my question is, has anyone ever had that handle crack or snap? 7000s are
no longer costly lab instruments handled with utmost care, today we use
them in our homes, shops... They get transported probably a lot more
frequently than they were intended to, possibly against some rules which
were in power back then, now forgotten or never even known. Should the
instrument be supported by your other hand from below?
I don't use my 7104 often, but when I do I need to carry and lift it on the
table. And every time I get shivers in my feet. Some reassurance would help.
Best Regards,
Nenad F.
--
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Bob Albert and Kevin Oconnor,
Please reply to me by email off line so I can provide an update
reach me at
go_boating_fast@...
Bob (S)
|
Re: 2467B focus/astigmatism anomaly...
Hi Raymond,
The scope has been running all afternoon with the
capacitor removed, and frankly I can't even tell it
is gone... A lot of circuitry for such little affect.
However, the anomaly continues exactly as before.
I think it is time to pick on Q4432, Q4440, and all of
those high resistance resistors in the focus chain.
-Chuck Harris
Raymond Domp Frank wrote:
toggle quoted message
Show quoted text
Hi Chuck,
On Sun, Aug 18, 2019 at 07:52 PM, Chuck Harris wrote:
C4403's intended purpose is to make moving changes to the
focus as the trace moves about on the screen.
Yes
Lifting one leg should stabilize the focus issues, if C4403,
or the dynamic focus circuitry, is part of the problem.
I'm curious, probably easy to do.
Raymond
|
Re: 7000 series carrying handles - how strong are they?
With grade 301 with a full hard temper having a minimum tensile strength of 1300 MPa.
Greg
|
Re: Tek Cover Part Number
Gary,
Try 650-0568-00. In the Tek service manual Volume 2 (070-3784-01 available online at ) on page 9-5 is the complete parts list for the cover. The very first line item is believed to be the complete cover assembly however it is not made clear in the description. The hierarchy of parts lists usually state the complete assembly first followed by individual parts breakdown of that item following.
The drawing for the lid follows the parts list.
Greg
|
Re: 7000 series carrying handles - how strong are they?
I was going to say something similar; btw, I recently came across a polymer based material that is both magnetic and an insulator. Not sure how that was accomplished, maybe the iron particles where pre-insulated?
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On Aug 18, 2019, at 3:38 PM, Bruce Griffiths <bruce.griffiths@...> wrote:
Not quite correct.
austenitic stainless (300 series) is non magnetic.
Martensitic (eg 422, 440 and 17-4PH etc) and ferritic grades are magnetic.
Hardened martensitic stainless is stronger than austenitic stainless.
Bruce
On 19 August 2019 at 10:21 "Greg Muir via Groups.Io" <big_sky_explorer@...> wrote:
Not having a 7K handy at the time, I am aware that Tek used to frequently use stainless steel in handles. It has reasonably good tensile strength. The TM500 power modules seem to have some sort of alloy embedded in their handles. The simple way to test for stainless is to bring a magnet near it. If no attraction it is stainless.
HP also used stainless in many of their earlier handles as well. But I, too also am conscious of what could possibly happen when lifting these beasts but have never had a "surprise" episode as well.
The best recommendation is to keep your feet away from being under the item you are lifting.
Greg
|
Re: 7000 series carrying handles - how strong are they?
Not quite correct.
austenitic stainless (300 series) is non magnetic.
Martensitic (eg 422, 440 and 17-4PH etc) and ferritic grades are magnetic.
Hardened martensitic stainless is stronger than austenitic stainless.
Bruce
toggle quoted message
Show quoted text
On 19 August 2019 at 10:21 "Greg Muir via Groups.Io" <big_sky_explorer@...> wrote:
Not having a 7K handy at the time, I am aware that Tek used to frequently use stainless steel in handles. It has reasonably good tensile strength. The TM500 power modules seem to have some sort of alloy embedded in their handles. The simple way to test for stainless is to bring a magnet near it. If no attraction it is stainless.
HP also used stainless in many of their earlier handles as well. But I, too also am conscious of what could possibly happen when lifting these beasts but have never had a "surprise" episode as well.
The best recommendation is to keep your feet away from being under the item you are lifting.
Greg
|
Re: 7000 series carrying handles - how strong are they?
Not having a 7K handy at the time, I am aware that Tek used to frequently use stainless steel in handles. It has reasonably good tensile strength. The TM500 power modules seem to have some sort of alloy embedded in their handles. The simple way to test for stainless is to bring a magnet near it. If no attraction it is stainless.
HP also used stainless in many of their earlier handles as well. But I, too also am conscious of what could possibly happen when lifting these beasts but have never had a "surprise" episode as well.
The best recommendation is to keep your feet away from being under the item you are lifting.
Greg
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Tek 7 series LCD project!
|
Mlynch001
satbeginner
Raymond Domp Frank