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Re: Curve Tracer CRTs
The small HV transformer The drives the deflection plates and the -4Kv for the tube is not the transformer used in the collector supply testing. There is a second large transformer in the 57x that is about the size of the power transformer. This along with a varaic is how the collector supply is generated. So it would be safe to delete with out risk of loosing the upper voltage ranges.
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Zen -----Original Message-----
From: [email protected] <[email protected]> On Behalf Of David C. Partridge Sent: Tuesday, November 2, 2021 1:53 PM To: [email protected] Subject: Re: [TekScopes] Curve Tracer CRTs Except you want an HV supply for tracing HV devices. -----Original Message----- From: [email protected] <[email protected]> On Behalf Of Zentronics42@... Sent: 02 November 2021 17:30 To: [email protected] Subject: Re: [TekScopes] Curve Tracer CRTs Walter, Looks cool I will take a look tonight. I think the general conscience is to not use the 200V deflection circuits rather the drive amp for the 200 V amp. It would be awesome if we could delete the 200 V supply as well as the 4Kv supply especially in the 576 as this would permanently remove the need for the now failing HV transformers in the 576. Zen |
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Re: Curve Tracer CRTs
Except you want an HV supply for tracing HV devices.
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-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Zentronics42@... Sent: 02 November 2021 17:30 To: [email protected] Subject: Re: [TekScopes] Curve Tracer CRTs Walter, Looks cool I will take a look tonight. I think the general conscience is to not use the 200V deflection circuits rather the drive amp for the 200 V amp. It would be awesome if we could delete the 200 V supply as well as the 4Kv supply especially in the 576 as this would permanently remove the need for the now failing HV transformers in the 576. Zen |
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Re: Curve Tracer CRTs
Walter,
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Looks cool I will take a look tonight. I think the general conscience is to not use the 200V deflection circuits rather the drive amp for the 200 V amp. It would be awesome if we could delete the 200 V supply as well as the 4Kv supply especially in the 576 as this would permanently remove the need for the now failing HV transformers in the 576. Zen -----Original Message-----
From: [email protected] <[email protected]> On Behalf Of walter shawlee Sent: Tuesday, November 2, 2021 1:24 PM To: [email protected] Subject: Re: [TekScopes] Curve Tracer CRTs I see there is a nice XY lcd project already done, you can see it here, it has a pretty low cost: and another one here: it's clear you want to work from the low level XY signals in the cure tracer, not the deflection circuits. virtually nothing else is actually required. these articles may help somebody reach the goal line a bit quicker. for the round CRT 575, I think a CRT adaptation is maybe more appropriate and easier to accomplish. all the best, walter sphere research corp. |
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Re: Curve Tracer CRTs
walter shawlee
I see there is a nice XY lcd project already done, you can see it here, it has a pretty low cost:
and another one here: it's clear you want to work from the low level XY signals in the cure tracer, not the deflection circuits. virtually nothing else is actually required. these articles may help somebody reach the goal line a bit quicker. for the round CRT 575, I think a CRT adaptation is maybe more appropriate and easier to accomplish. all the best, walter sphere research corp. |
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Re: Curve Tracer CRTs
If I were undertaking a project of this sort, I would not attempt to digitize the analog display.
Instead, I would use a DAC to program the collector (drain) voltage and another to program the base (gate) current/(voltage) and an ADC to digitize the resulting collector (drain) current. An arduino (or other embedded processor) would drive the DACs and acquire the data (possibly using its internal analog-digital circuitry) and send the result via USB (or other) to an external PC for display, storage and further processing. The whole thing could be quite simple and small - the most difficult part being the replacement of the mains driven Collector voltage supply with a DAC controlled high voltage regulated supply. Basically, I am thinking of a modern curve tracer as a multiparameter data acquisition system. It wouldn't need blazing speed; so a flash ADC wouldn't be necessary to keep up with the legacy CRT display. Stephen Menasian |
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Re: Curve Tracer CRTs
WRT the horiz/vert signal pick-off for digitization, there is a nice clean
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demarcation point on the 577 RHS of schematic 6, where the outputs from U530 and U570 drive the output amplifiers. At this point, it is 500mV/division, and appears to be inverted, I am planning to buffer/invert these and convert to 100mV/div with an additional pair of op-amps. Looking at the 576, things are significantly more murky. Looking at the display amplifier schematic (#9 on the bama manual copy), it looks like we would need to pick off somewhere in that discrete signal chain. I want to pick the signal off after all the applicable front panel controls such as: magnification, inversion, positioning, etc If there is interest in doing this, I think there is value standardizing on pick off points for both the 576 and 577, preferably with maximum compatibility. On Tue, Nov 2, 2021 at 11:33 AM Jeff Dutky <jeff.dutky@...> wrote:
apply the graticule pixels to the final frame buffer on the display --
Andy |
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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. |
David C. Partridge
G?ran Krusell
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