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Re: Working on the HV Section of a 533A
¸é±ð²Ô¨¦±ð and Harvey,
The scope still has it's emergency spool of silver solder, apparently unused, but I also bought three 0.35 oz coils of Kester 62/36/2 silver solder when I was working on the 475 or 475A HV sections a few months ago. When you say "high heat" ¸é±ð²Ô¨¦±ð, what temperature are we talking about? I already replaced one blown resistor in the LV section, and I used my old Weller iron (the kind with the magnetic tips that you have to change to select the temperature). It was not easy to do, but I think some of that was because I did not clean the area very well before applying the heat. I also have a surface mount rework station with a soldering iron attached, and it allows me to adjust the temperature with a dial. What temperature should I be using on the ceramic strips? I'm was already planning to test all the electrolytic cans, so testing the axial leaded caps is only a little more work. I'm glad that mylar caps will do as replacements, as I already happen to have a good supply of those that I have been using on some EICO instruments. -- Jeff Dutky |
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Re: Working on the HV Section of a 533A
Kieth,
That's an interesting trick to know about, but I already invested in a 40 kV probe (and heavy rubber gloves) back when I was working around the HV section of my 475. I think I'll stick to the HV probe. I haven't worked long enough around HV to lose my skittishness about it, and "holding a neon bulb near the HV section" while it's operating is well outside my comfort zone. -- Jeff Dutky |
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Re: Working on the HV Section of a 533A
Jeff-
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make sure you use silver bearing solder on the ceramic strips. sometimes the strips can be cleaned...but ya have new ones on the way moot point. too much heat too long will also cause the silver to come loose from the ceramic...use high heat get in and get out! ( don't ask how i know.....) personally ,I have had mixed luck with the old oil/paper caps. I would look at those last they may be just fine. tek used pretty good ones!. however, ..If they are cracked they go otherwise... replacement - mylar have been fine in some of my restorations. some will say Orange drops....both will work fine and are most likely superior in the long run. ¸é±ð²Ô¨¦±ð On 7/19/21 6:52 PM, Jeff Dutky wrote:
Fresh off of several victories with my 7603 and plug-ins, I turned my attention tonight to the 533A and found the courage to peek inside the left half of the HV section (the section on the opposite side from the CRT, with the five 5642 rectifier tubes). The section was entirely covered in soot, which is expected where you have high voltage, but after I got done cleaning the soot off of everything a possibly serious problem became apparent: two of the ceramic terminal strips at one end of the row of rectifiers was still pitch black. |
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Re: Working on the HV Section of a 533A
I've heard that you need to be careful how you solder to those ceramic strips.? What I did hear is that you do not put the iron tip in the notch.? Pleas check to make sure I got it right.
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Harvey On 7/19/2021 10:03 PM, Brenda via groups.io wrote:
Hi Jeff! Great to see you are working on your 533A! I have one as well, but it's in really bad shape on the inside. Those 2 back strips is perfectly normal. My 535A and my 545A is like that as well. I read somewhere on the forum that it's called corona dope, since that is where the 10KV is. I think that you will find that after a really good cleaning of the HV board that everything will be just fine. You really do want that coating to be on those last 2 strips, but don't worry, it's really hard to get off. As far as those 2 Black Beauties goes, most likely, those will be just fine. It's a "newer" scope as by this time, Tektronix got rid of the bad capacitors as your HV section has ceramic and those will be just fine as well. I have a few scopes that use these Black Beauties with the red writing to be fully functional. The ones with the yellow writing are most likely going to be very leaky. |
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Re: [OT] Datasheet for NC7033 or NCR7033 NVRAM needed.
The story I'd heard was that Intel learned that silicon nitride is excellent at gettering or otherwise blocking sodium. They pissed away a fortune trying to make a good gate insulator out of the stuff, but threshold stability was even worse than for the oxide they were trying to replace. That Intel was experimenting with nitride was not a well-kept secret, and Moore was asked at a conference about it. His reply was "We found pretty much what we expected." Interpreting that as "nitride is good", AMD and others immediately ramped up their research into nitrides, pissed away fortunes, then angrily approached Moore at yet another conference about his earlier statement. His reply was, "Engineers always expect disappointment, and so we found pretty much what we expected."
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-- Tom -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 350 Jane Stanford Way Stanford University Stanford, CA 94305-4070 On 7/19/2021 18:19, Jim Ford wrote:
Yeah, Tom, I remember reading about Gordon Moore or somebody else at Intel meeting with a gentleman from another semiconductor house and revealing the sodium issue in exchange for the solution to another vexing process problem.? I don't remember the details, but the story was hilarious!? Laugh out loud funny!? Maybe you know the details?? ? ? ?Jim Ford?Sent from my Verizon, Samsung Galaxy smartphone |
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Re: Working on the HV Section of a 533A
Guessing you both know the trick about holding a little NE-51 or similar neon bulb in close proximity to the HV section to confirm its operation? If your HV section is working, the little neon will light up from the radiated energy.
Cool to see and an easy way old fashioned service trick to know something is there without having to resort to the high voltage probe, etc. Keith Coolblueglow |
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Re: Working on the HV Section of a 533A
Jeff,
Brenda is right about the corona dope. Leave those strips in. Clean them to remove dust. I have not seen any of the black beauties any good. These are a wax condenser in a plastic case. I replace them on sight. The Good-all ones I also replace on sight. Replacements I use are Sprague Orange Drops or other high quality ones at 630V, e.g. Panasonic. Radial types work fine to replace axial. Mark |
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Re: Working on the HV Section of a 533A
Brenda
Hi Jeff, I am glad that I was able to contribute this this forum.
I would have to say, in my opinion, since you started to clean that section, you should keep cleaning it until it is spotless. I have read from another post that you don't clean this section well, that you would actually create leakage and that would throw your HV into chaos. Once it's all clean and dry, you should be able to power it up without any problems. My 545A was filthy, more so than yours most likely was. Mine was covered in all that soot, but was covered in cigarette tar so I had to clean it. I mean, it was pure yellow and sticky and I am not that knowledgeable so I learned the hard way that all this smoke and tar gave me a LOT of HV issues. I am sure that others on this group will chime in as I am still learning about these old scopes with my 535A being my favorite. I would also advise to check and reseat the 12AU7A and the 6AU5GT tubes that are on the underside of the HV oscillator, at least that is what I would do myself. Brenda |
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Re: Working on the HV Section of a 533A
Brenda,
thanks for that tip; I had never heard of "corona dope" before, but a quick google search (on the correct term) reveals all. Any idea how I would test be certain that everything is okay? I mean, I guess I can just power the instrument up and wait for the arcing to start, but maybe there are less reckless approaches? I can guess that I won't simply be able to check resistances, because any leakage would be expected to be at high voltage. I am currently building a small HV power supply in order to test capacitor leakage, but it will only go up to 500 V, and I'm guessing that the voltage on those terminal strips is in the kV range. -- Jeff Dutky |
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Re: Working on the HV Section of a 533A
Brenda
Hi Jeff! Great to see you are working on your 533A! I have one as well, but it's in really bad shape on the inside. Those 2 back strips is perfectly normal. My 535A and my 545A is like that as well. I read somewhere on the forum that it's called corona dope, since that is where the 10KV is. I think that you will find that after a really good cleaning of the HV board that everything will be just fine. You really do want that coating to be on those last 2 strips, but don't worry, it's really hard to get off. As far as those 2 Black Beauties goes, most likely, those will be just fine. It's a "newer" scope as by this time, Tektronix got rid of the bad capacitors as your HV section has ceramic and those will be just fine as well. I have a few scopes that use these Black Beauties with the red writing to be fully functional. The ones with the yellow writing are most likely going to be very leaky.
Brenda |
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Working on the HV Section of a 533A
Fresh off of several victories with my 7603 and plug-ins, I turned my attention tonight to the 533A and found the courage to peek inside the left half of the HV section (the section on the opposite side from the CRT, with the five 5642 rectifier tubes). The section was entirely covered in soot, which is expected where you have high voltage, but after I got done cleaning the soot off of everything a possibly serious problem became apparent: two of the ceramic terminal strips at one end of the row of rectifiers was still pitch black.
I have uploaded pictures of the HV section to this album: /g/TekScopes/album?id=266270 I have already ordered replacement ceramic terminal strips, but I don't really know what I'm doing. I assume that I will need to unsolder the rectifier tubes both to replace the terminal strips, and to verify that there isn't more damage to components beneath the rectifiers. I'm also wondering if I'm going to need to replace those black axial leaded capacitors that can be seen in the foreground. I think that there are more like that elsewhere in the scope, but I have done a detailed inventory yet. If I need to replace them, what do I replace them with? Any advice is appreciated. -- Jeff Dutky |
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Re: [OT] Datasheet for NC7033 or NCR7033 NVRAM needed.
Yeah, Tom, I remember reading about Gordon Moore or somebody else at Intel meeting with a gentleman from another semiconductor house and revealing the sodium issue in exchange for the solution to another vexing process problem.? I don't remember the details, but the story was hilarious!? Laugh out loud funny!? Maybe you know the details?? ? ? ?Jim Ford?Sent from my Verizon, Samsung Galaxy smartphone
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-------- Original message --------From: Tom Lee <tomlee@...> Date: 7/19/21 5:23 PM (GMT-08:00) To: [email protected] Subject: Re: [TekScopes] [OT] Datasheet for NC7033 or NCR7033 NVRAM needed. Early yes, standard not so much.The 7033 is an MNOS (sic) EAROM. The underlying enabling principle was discovered when Gordon Moore punked the entire industry into chasing nitride gates as the solution to MOS's notorious threshold shift problem. Nitrides turned out to be even more unstable then sodium-contaminated oxide (Intel had already pissed away big bucks finding that out; Moore helped everyone else experience the pain). That instability was exploited to make EAROMs, but they could never really stabilize the instability, if you get my meaning. These devices could not tolerate many write cycles. Their primary use was as channel memories in TVs and cable boxes, where reprogramming was a very rare event.The datasheet is the last appendix of the following: this helps. Good luck!-- Cheers,Tom-- Prof. Thomas H. LeeAllen Ctr., Rm. 205350 Jane Stanford WayStanford UniversityStanford, CA 94305-4070 7/19/2021 16:48, David Slipper wrote:> Sorry for the OT but I'm getting desperate - it's supposed to be a > standard early NVRAM but it and it's data-sheet seem to be unobtanium.>> Regards,> Dave>>>>> >>
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Re: [OT] Datasheet for NC7033 or NCR7033 NVRAM needed.
Aargh. "more unstable than", not "more unstable then", of course!
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Aargh. Ptth. -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 350 Jane Stanford Way Stanford University Stanford, CA 94305-4070 On 7/19/2021 17:23, Tom Lee wrote:
Early yes, standard not so much. |
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Re: [OT] Datasheet for NC7033 or NCR7033 NVRAM needed.
Early yes, standard not so much.
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The 7033 is an MNOS (sic) EAROM. The underlying enabling principle was discovered when Gordon Moore punked the entire industry into chasing nitride gates as the solution to MOS's notorious threshold shift problem. Nitrides turned out to be even more unstable then sodium-contaminated oxide (Intel had already pissed away big bucks finding that out; Moore helped everyone else experience the pain). That instability was exploited to make EAROMs, but they could never really stabilize the instability, if you get my meaning. These devices could not tolerate many write cycles. Their primary use was as channel memories in TVs and cable boxes, where reprogramming was a very rare event. The datasheet is the last appendix of the following: Hope this helps. Good luck! -- Cheers, Tom -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 350 Jane Stanford Way Stanford University Stanford, CA 94305-4070 On 7/19/2021 16:48, David Slipper wrote:
Sorry for the OT but I'm getting desperate - it's supposed to be a standard early NVRAM but it and it's data-sheet seem to be unobtanium. |
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Re: Looking for data on 9-pin Vacuum time delay relays used in old Tek-scopes
A few years ago the time delay relay in my 555 died and lacking a replacement I had to cobble up a substitute. I repurposed an old device I had made to trigger a super 8 movie camera (remember them?) for time lapse. That device was designed to work form a 9 volt battery. I started by rectifying the 6.3 volt supply for the time delay relay using a half wave voltage doubler with the input capacitor deliberately kept to a small value to allow the output voltage across the storage cap to rise slowly. When it got to a suitable level it triggered a SCR through a zener diode to discharge the output cap through the coil of a little relay to close the main scope relay. Once the scope relay pulls in the 6.3 supply is disconnected from the voltage doubler. A reverse biased diode from the storage cap to the +100 volt line removes any residual charge as soon as the scope is switched off so the time delay will function properly next time it's switched on.
There's plenty of room in the 555 power supply for small proto board with the circuit on it. All the parts were in my junque box so the whole thing cost nothing and provided a bit of fun. In retrospect it would have been even simpler to slowly charge a cap from the raw +100 supply which is about +165 volts according to the manual, and use that to trigger the SCR.. Morris |
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Re: 2712 SA with display (and normalization) issues
#photo-notice
On Mon, Jul 19, 2021 at 03:27 PM, Colin Herbert wrote:
OCR'ed version added. Raymond |
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Re: ++Processor error on TDS 754D on startup
Thanks for the response. If endeavoring to do this (rtc + ram), there are already a number of folks that claim to have working solutions, so I would search out their progress and find the flaws and try to find elegant workarounds. The easiest way is to find compatible no-batt rtc, and add logic around that to extend the ram. Maybe easiest is to used the latest version of the original MC148616 and i/f logic and add an fram if the are any parallel i/f available - the original has muxed a/d so that would have to be demuxed. Goal would be to try to get away with a bunch of glue logic in an XC9536 or 72. To try to recreate the ds1486 from scratch would take a tremendous verification/validation effort with no payback. Seems like a lot of nuances present. Mot's original MC14xx had battery discharge bugs which was one of the Dallas popularities. Mot fixed it in the b version.
Most modern designs use an i2c rtc and an fram. So, other than legacy sockets, not much market. pmoyle |
Raymond Domp Frank
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