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Re: Curve Tracer CRTs
I assume that the newer 57x curve tracers use cam switches for selecting voltage and current ranges, and I think I understand how Tek piggybacked readout onto those cam switches (by reading the position of the cams from the opposite side). I've never worked with older style wafer switches (though I've got a type A plug-in that needs it's waver switches repaired, but it's far down on the list of projects), so I don't know how difficult it would be to add readout detection to one of them.
While you are collecting X and Y data it would be useful to know the setting of the other front-panel controls. The pots could be sampled directly (I think) but sampling the positions of the selector switches will require some mechanical retrofitting. -- Jeff Dutky |
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Re: Curve Tracer CRTs
Oops... apologies:
( .... before I get flamed !! (yikes ! ). The obvious place to tap-in to the CRT signals would likely be at the low voltage H & V deflection amps, as suggested in the original 576 - USB thread. see those details. It would not be advisable to tap into the actual HV 576 CRT signals for this project ! |
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Re: Curve Tracer CRTs
Would still need to differentiate between graticule pixels and curve pixels.
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Just a thought -----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Jeff Dutky Sent: Tuesday, November 2, 2021 11:57 AM To: [email protected] Subject: Re: [TekScopes] Curve Tracer CRTs I would not bother with the queue; I would simply map the ADC values (X and Y) into a 2D pixel array, accumulating a "bright" pixel value to the existing value at the pixel location, and periodically decimate the pixel values (e.g. divide all pixel values by 2 every 1/10th of a second) which should give you a nice emulation of phosphor decay. You can tune the decimation schedule to get a pleasing decay period according to your pixel bit depth, and the update rate of your output device. -- Jeff Dutky |
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Re: Curve Tracer CRTs
Once it gets into the FPGA, it's all digital, so with access to that memory, you can get the screen dots out (I'd be very tempted to use two memory planes) and scale them with a processor.? Going from there, the data is available through the microprocessor.
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Harvey On 11/2/2021 11:42 AM, Zentronics42@... wrote:
Harvey, |
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Re: Curve Tracer CRTs
On 2021-11-02 11:42 a.m., Zentronics42@... wrote:
Harvey,Just gonna throw this out there: GPIB? --T Zen |
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Re: Curve Tracer CRTs
I would not bother with the queue; I would simply map the ADC values (X and Y) into a 2D pixel array, accumulating a "bright" pixel value to the existing value at the pixel location, and periodically decimate the pixel values (e.g. divide all pixel values by 2 every 1/10th of a second) which should give you a nice emulation of phosphor decay. You can tune the decimation schedule to get a pleasing decay period according to your pixel bit depth, and the update rate of your output device.
-- Jeff Dutky |
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Re: Curve Tracer CRTs
Harvey,
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Also if all the data is digital as well it would be a nice to have to be able to dump out a screen cap to flash somewhere. The good news is there quite a bit of space available once the tube is gone. To add a few boards. Zen -----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Harvey White Sent: Tuesday, November 2, 2021 10:51 AM To: [email protected] Subject: Re: [TekScopes] Curve Tracer CRTs If I were to try that, I'd first look at flash a/d converters, at least 8 bits if not more. That gives you a digital output of the X and Y channels (scale input first!). For an FPGA, I'd suggest (for experiments) getting one that fits the FPGA tools you already have (XILINX OR ALTERA), and one that has about 50K or more gates, the more the better. The X and Y inputs specify which dot on the screen to set, and if you have that in a delayed queue, which dot to erase if you want persistence on the screen to be variable. You'd want a microprocessor to talk to the display to set up scale factors and draw gridworks or whatever you decide to do, and an overall control of the display. At this point, it would be a color display. Harvey On 11/2/2021 10:35 AM, garp66 wrote: hi Walter, |
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Re: Curve Tracer CRTs
Rick,
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I would not mind putting effort behind a project like this. I have a perfect test chassis here in the lab as well. A fully complete 576 with no tube and a dead HV transformer. Moving to a LCD display would be fantastic possibly as well working on a digital read out. A possible modern replacement for the fiber optic readout. I have a readout board in the lab that has some of the dead custom tech IC's so it is a door stop at the moment without a good deal of effort. In my mind it would be cool to have a CRT delete HV transformer as well this could be a matched transformer to the original with the 4KV winding removed. This way we will only need to handle about 200 Vdc I am not totally sure if the 200 Vdc supply is even necessary as this might only be used around the tube. So if the CRT is removed it would be convenient if the HV supply could be totally deleted but I am not sure about that yet. I have a calibration fixture available to me in the lab so I can also test a full calibration on the test frame. 067-599-00 I am getting very interested in this one. Zen -----Original Message-----
From: [email protected] <[email protected]> On Behalf Of garp66 Sent: Tuesday, November 2, 2021 10:35 AM To: [email protected] Subject: Re: [TekScopes] Curve Tracer CRTs hi Walter, I have been thinking about a possible replacement video display panel for the Tek 576 CRT : It would require some cpu or processor ( A/D, logic, etc.) to translate, format and communicate the Tek 576 info to the LED or LCD display. Perhaps an FPGA or other ( Arduino, or Rasp Pi with A/D shields, etc. ) ?? I am trying to look at, and understand some of the possible video processor IC's that might have some functionality that could be tapped to aid in this sort of a ' converter" but am not familiar with modern ones. Anyone have any ideas ? A] I am aware of the NEC 7220 IC, and am just starting to look at that for a possible shoe-horn type of use ( ? ) B] Epiphan has some interesting video frame grabber converters ( typically converts VGA, etc. ) that might be of use, but how to kludge them into the Tek 576 CRT signals ( ? ). .... but does not seem to have any input for an x-y O-scope type of signal set ( ? ) Perhaps some hidden function in an Epiphan VGA2USB LR or other unit ? C] It would be nice to have a table or list of all of the Tek 576 CRT signals, and their voltage ranges that are applied to the Tek 576 CRT, -- if anyone has such ? { >>> if so, can they post it in the Tek 576 file page, ... perhaps labelled CRT display specs ?? }. D] Some time ago, I had posted the finding about the eBay Seller of the USB-Tek 576 contraption: { ** below } That USB- Tek 576 post developed ~ 80 posts by the members of this group, .... and had some good tips, descent ( ! ) and other info. ** /g/TekScopes/message/162844?p=%2C%2C%2C20%2C0%2C0%2C0%3A%3ACreated%2C%2CTek+576+USB%2C20%2C1%2C0%2C69490299 Clearly, tapping into the Tek 576 and display, via USB into a laptop *might* be a good solution to failing CRT's in Tek 576 units, to extend their life. I still think this would be a valuable asset for a Tek 576, with an ailing CRT, and would provide the ability to save, massage ( via MaLab, or other math programs ) and compare Tek 576 CT data files. Must be some way to tap into the 576 CRT signals !! rick |
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Re: Curve Tracer CRTs
If I were to try that, I'd first look at flash a/d converters, at least 8 bits if not more.? That gives you a digital output of the X and Y channels (scale input first!).? For an FPGA, I'd suggest (for experiments) getting one that fits the FPGA tools you already have (XILINX OR ALTERA), and one that has about 50K or more gates, the more the better.? The X and Y inputs specify which dot on the screen to set, and if you have that in a delayed queue, which dot to erase if you want persistence on the screen to be variable. You'd want a microprocessor to talk to the display to set up scale factors and draw gridworks or whatever you decide to do, and an overall control of the display.
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At this point, it would be a color display. Harvey On 11/2/2021 10:35 AM, garp66 wrote:
hi Walter, |
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Re: Curve Tracer CRTs
hi Walter,
I have been thinking about a possible replacement video display panel for the Tek 576 CRT : It would require some cpu or processor ( A/D, logic, etc.) to translate, format and communicate the Tek 576 info to the LED or LCD display. Perhaps an FPGA or other ( Arduino, or Rasp Pi with A/D shields, etc. ) ?? I am trying to look at, and understand some of the possible video processor IC's that might have some functionality that could be tapped to aid in this sort of a ' converter" but am not familiar with modern ones. Anyone have any ideas ? A] I am aware of the NEC 7220 IC, and am just starting to look at that for a possible shoe-horn type of use ( ? ) B] Epiphan has some interesting video frame grabber converters ( typically converts VGA, etc. ) that might be of use, but how to kludge them into the Tek 576 CRT signals ( ? ). .... but does not seem to have any input for an x-y O-scope type of signal set ( ? ) Perhaps some hidden function in an Epiphan VGA2USB LR or other unit ? C] It would be nice to have a table or list of all of the Tek 576 CRT signals, and their voltage ranges that are applied to the Tek 576 CRT, -- if anyone has such ? { >>> if so, can they post it in the Tek 576 file page, ... perhaps labelled CRT display specs ?? }. D] Some time ago, I had posted the finding about the eBay Seller of the USB-Tek 576 contraption: { ** below } That USB- Tek 576 post developed ~ 80 posts by the members of this group, .... and had some good tips, descent ( ! ) and other info. ** /g/TekScopes/message/162844?p=%2C%2C%2C20%2C0%2C0%2C0%3A%3ACreated%2C%2CTek+576+USB%2C20%2C1%2C0%2C69490299 Clearly, tapping into the Tek 576 and display, via USB into a laptop *might* be a good solution to failing CRT's in Tek 576 units, to extend their life. I still think this would be a valuable asset for a Tek 576, with an ailing CRT, and would provide the ability to save, massage ( via MaLab, or other math programs ) and compare Tek 576 CT data files. Must be some way to tap into the 576 CRT signals !! rick |
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Re: 7B53A Schematic Question
Okay - I see that in the parts list now. It isn't shown on the pictorial diagram and I don't see it on at least one of the boards I have either. It's listed as "NOMINAL, INSTALLED, TEST SELECTED" so, perhaps, it wasn't needed on all the boards.
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Thanks, Barry - N4BUQ ----- Original Message -----
From: "mc1648pp" <mc1648pp@...> it is a ferrite core which prevents high frequency oscillations, I believe. |
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7B53A Schematic Question
In the manual for the 7B53A/7B53AN, the #2 schematic for the Main Trigger Generator (for SN B209999 & Below on page 124 of the version of that manual I'm viewing) shows a small rotated rectangle labeled E376 across the output of U350D. I've not found references to that symbol nor have I seen this before. Could someone please fill me in on what that represents?
Thanks, Barry - N4BUQ |
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Re: Looking for fasteners in EU
You linked to the black one which only goes up to 16mm. It doesn't
matter. It proves nothing. The fact that some fly by night corner shop in China doesn't have a specific screw doesn't mean someone else won't have them. I posted here because people are helpful here, so take a hint from others and stop being negative. On Mon, Nov 1, 2021 at 12:10 AM snapdiode via groups.io <snapdiode@...> wrote:
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Re: tek 2215 trace position issues
The usual rule for fault finding is 'first check all low voltage DC supplies for correct voltage and ripple'. Particularly relevant in this case!
It is not clear why you have two spots. Are you displaying Ch1, Ch2 or both? What input do you have to the active channel? What have you selected for the horizontal display options? Where are the spots on the screen? Regards, Roger |
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Re: 7B92 with no repeating sweep
Mark,
Thanks for the rundown. I have not tried again to address the TIME/DIV issues on the new 7B92, concentrating instead on diagnosing the old 7B92 by swapping boards (I will get to the new 7B92 in due course, so your advice is invaluable. Also, the trigger lamp on the old 7B92 may also need to be replaced, so good advice all around). I've also gotten some encouragement from Dave Peterson for disassembling and maintaining Tek cam switches, including a wonderful set of photographs of disassembled cam switches from (I believe) a 465. It looks much more doable than the dire warnings in the Tek service manuals would lead you to believe. I swapped the sweep and main trigger boards between the two 7B92s and I think I found out the following things: 1. swapping the sweep boards makes no difference in the behavior of either unit, which rules out the sweep board, and any of its components as faulty. 2. swapping the main trigger boards between the two units did not fix the old 7B92, but it did make the new 7B92 unable to get a stable trigger on a signal, which means that the main trigger board from the old 7B92 has a fault, but it is not the fault that is causing the lack of free running sweep in the old unit. With these two conclusions in hand I proceeded to examine components on the main interface board that were directly related to the sweep IC: Q102, Q104, Q106, Q108, Q144, Q146, and Q148. All of those checked out as "good" on my cheap Chinese component checker, but while I was doing that I noticed two more bits of damage to the main interface board: R238 had one leg sheared off at the solder pad, and CR205 was blown open. I reattached the left of R238 at the pad easily, but I'm having trouble finding a proper replacement for CR205. The Tek part number is 152-0322-00, which maps to an HP part number of 5082-2672 and a JEDEC number of ND4973. The CDPC indicates (on page 12-4, 2nd row) that it is a "General Purpose, 15V" Schottky diode with a maximum junction capacitance of 1.2 pF. For most of the specs it looks like I can use a 1N4148 as a substitute, but the maximum junction capacitance on the 1N4148 is specced as 4 pF (yes, it's a maximum value, I know, so the typical may be much lower, and may in fact meet the Tek spec for CR205). It occurs to me that the same Schottky diodes that I am using for the 7S14 samplers may work here too. CR205 is in the AUX Z-AXIS signal chain. It occurs to me that if the Z-axis signal were clamped in the "off" state then I might see something that looks like a lack of free running sweep (because the beam is always blanked). Also, why is it always a Z-axis fault with me? -- Jeff Dutky |
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Re: Curve Tracer CRTs
Roy,
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I will have to respectfully disagree with the statement that the 57X units have been replaced and usurped. However to establish my personal bias I will have to admin that I have more than one of the 57X units in both types I have a couple 576¡¯s and a few 577¡¯s. Despite having to do major overhalls and calibrations. Even going so far as to get the calibration fixture. 067-0599-00. I can say that these units have been an incredibly addition to my lab and I wish that everyone especially students have access to them and knowledge as to how to use them. I have even made a few videos on the topic of rebuilding and tuning these for the channel. Having a Vc up to 1600 Vdc and a current capacity of 200 amps is incredibly useful for testing power silicon especially power silicon in HV application that tends to only about ? way fail like in the case of my fluke 5200A There was a power transistor that went some what leaky and was over loading the -190V supply. Also my 577 was instrumental in repairing and testing my 284¡¯s as it was used to test the tunnel diode that was an irreplaceable part so I was skittish about even testing it on a 57X. The current modern equivalent from Tek/Keithly is a transistor characterizer and those concise of a special computer with 4 built in SMU¡¯s and a starting price tag non-upgraded at $26,000. Even a single SMU at the LOW end new in the 24XX series will run you $6,000 at the high end it is $10,000. To test 3 pin devices you need 2 of those and a computer to script it. In my mind there is not anything that is a ¡°modern¡± equivalent as the current SMU¡¯s top out at 1100 VDC. Don¡¯t get me wrong I have some SMU¡¯s on the acquisition list for the lab but the price is steep. And in the lab I also have a 178 for the 577 and a 176 for the 576. I have not repaired and tested the 176 quite yet. But this turns them in to incredibly capable units even measuring currents as low as 2na/div up to 200 A/div I find my self using the 577 more often but this is to save the tubes on the 576¡¯s till I need them. I would also love to add the 570 to the lab but owners are holding on to those tightly right now. I would not even mind having to rebuild one but I will see what time will tell. I have no personal experience with the 3xx series but from a bench space perspective I will stick with the 57X even given the weight. Zen -----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Roy Thistle Sent: Monday, November 1, 2021 4:53 PM To: [email protected] Subject: Re: [TekScopes] Curve Tracer CRTs On Sun, Oct 31, 2021 at 11:17 AM, Andy Warner wrote: Well... given the prices that some people pay for these... and unless its on one end of a chain... and sometimes on the bottom of the pond (just cause you can afford it)... I just don't see why, if it isn't for the analog display. (Perhaps not the unit's own CRT... but, a CRT never the less.) Getting/designing a "device" to generate a set of I-V curves (especially in a box the size of the 57x big boys) isn't rocket science, anymore. Probably however, I'm missing something... because I know people who have them holding down the basement floor... and are working on finding the perfect transistors?... to get that "perfect" audio experience. Others covet them, I reckon, for speculation. I remember there were some of the 57x series, in the graduate lab(s)... and the students in the groups working on BJTs didn't even know what they were. -- Roy Thistle |
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Re: Replacement 7000 Plugin Guides
Albert,
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I had been looking at it with the side cover removed; however, I just went out and turned the scope on its left side and that gave me a slightly better view. While it's a bit hard to see, I can now see that H?kan is indeed correct and that protrusion does not give an initial lift like I thought. Apologies. I'm not really sure why this one plugin is being difficult; however, given that the plastic guide on it is broken like it is, then perhaps it's just an overall slight misalignment. As I say, none of the other plugins exhibit this problem. If anything, it would help if the bottom plastic guide rails were raised a mm or two so that the slanted guide surfaces would not have as much work to do but I don't want to modify the scope that way so, for now, I'll chalk this up to the broken plastic guide on the back of the plugin. Thanks, Barry - N4BUQ ----- Original Message -----
From: "Albert Otten" <aodiversen@...> Barry, |
David C. Partridge
G?ran Krusell
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