Can't "calibrate" one channel of a 7A26
I have a 7A26 (in a 7704A) whose channel 1 will calibrate nicely using the front adjustment versus 25 MHz signal set at 0 dBm; 640 mV P-P. Channel 2 shows about 800 mV P-P but the adjustment is at minimum. Same for the internal gain adjustment for channel 2 which is at minimum.
Thanks in advance.
--
William, k6whp
"A friend told me to cheer up, things could be worse.
So I cheered up and, sure enough, things got worse!"
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Martin,
I looked at that part number too. I believe that the difference is the position of the 1k and 10K modules. In 311-1411-00 the 1K is the outer concentric and the 10 K is the inner.
The "coarse" and "fine" adjust would be reversed as compared to 311-1759-00.
Functional but confusing, especially if only one pot is changed...
BTW, I did change R45/145 to 10 turn trimpots, makes the 20.2 volt setup adjustment much easier (and perhaps more stable).
gwerl
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Hi all,
thanks for all the tips in finding the right pot.
- I checked QService, they don't have one in stock.
@JimAdeny:
I, too, looked for "mod pot" on Ebay. Actually, I found a Bourns 1k/10k concentric pot (article #133006820204, Tek Part n¡ã 311-1411-00).
In the Tek Service Manual the part number is 311-1759-00, and its from Allen-Bradley (not Bourns). Do you think they are interchangeable?
@ghwerl:
I checked the catalogue of potentiometers.com. They seem to have all sort of mod pots, but probably very expensive if I only need one.
I'm looking into the listing, did ask them about shipping. Let's see...
cheers
Martin
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Re: 576 arrived with bad CRT... total dead end?
I am not even sure 1's of Mhz are reached on the 576 and 577. At least on the 576 the collector sweeps are locked to mains frequencies. Though rectified but not filtered. So the collector pulses are running at 120 Hz max 100Hz in places. When set to DC mode the corrector output is lightly filtered just to keep DC. 1/3 of the weight on a 576 is a massive transformer in the center of the unit this is the base of the collector supply. Removed from the unit the collector supply is 20 odd lbs by its self.
Zen
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-----Original Message----- From: [email protected] < [email protected]> On Behalf Of Jim Ford Sent: Thursday, May 5, 2022 9:23 AM To: [email protected]Subject: Re: [TekScopes] 576 arrived with bad CRT... total dead end? The 1-2 MHz theory is supported by the fact that the 577 uses the CRT from the 5110. Maybe the horizontal and/or vertical drive circuitry, too?Jim Ford Sent from my T-Mobile 4G LTE Device -------- Original message --------From: Jeff Dutky <jeff.dutky@...> Date: 5/5/22 2:06 AM (GMT-08:00) To: [email protected] Subject: Re: [TekScopes] 576 arrived with bad CRT... total dead end? Is two channels enough, or do you need Z-axis modulation too?I'm still betting that even the lowest end Picoscope (at 10 MHz) is vastly more bandwidth than this application requires. I'd be surprised if this needed more than 1 or 2 MHz.-- Jeff Dutky
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Re: 576 arrived with bad CRT... total dead end?
The 1-2 MHz theory is supported by the fact that the 577 uses the CRT from the 5110.? Maybe the horizontal and/or vertical drive circuitry, too?Jim Ford?Sent from my T-Mobile 4G LTE Device
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-------- Original message --------From: Jeff Dutky <jeff.dutky@...> Date: 5/5/22 2:06 AM (GMT-08:00) To: [email protected] Subject: Re: [TekScopes] 576 arrived with bad CRT... total dead end? Is two channels enough, or do you need Z-axis modulation too?I'm still betting that even the lowest end Picoscope (at 10 MHz) is vastly more bandwidth than this application requires. I'd be surprised if this needed more than 1 or 2 MHz.-- Jeff Dutky
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Re: 2465 Calibration Completed but boot still fails
Yeah, I recalibrated the vertical, but this time I checked all of the calibration voltages of the PSG9080 waveform generator first on my Hantek portable scope and wrote the values down to get the proper voltages. Then the vertical calibration breezed through with no limit errors and when I checked them after calibration, they all looked good.
HOWEVER - the uncalibrated dots still returned. This time I noticed that they returned when I changed the sweep rate. So I guess I need to redo the horizontal cal now. Sigh. The horizontal is tough to do accurately on the slow sweep cal. It's hard to see what's happening when the dot is moving slowly across the screen. Also the highest sweep rate gets difficult to see. But I'm determined to get this thing all working, so I will persist. I'm so close now. Then I can move on to something else. I have a friend that inherited his engineer neighbor's house. His neighbor was a horder and his house is totally packed with electronic gear. I was told I could have anything in it that I wanted, for free. That's how I got the 2465.
I really don't understand how the 2465 knows it is uncalibrated. Is it comparing its sweep rate to some internal clock? If so, I wonder why it can't just do the whole calibration itself, using its internal clock.
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Re: Proper Way to Pull Single-Ended Connectors?
While these aren't the ones I need to remove, these are the type to which I'm referring:
Thanks,
Barry - N4BUQ
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----- Original Message ----- From: "n4buq" <n4buq@...>
To: "tekscopes" <[email protected]>
Sent: Thursday, May 5, 2022 8:07:06 AM
Subject: Re: [TekScopes] Proper Way to Pull Single-Ended Connectors? Jon,
Yes, I'm familiar with the "harmonica" connectors. The 7704A uses them
extensively as well as the plugins and that makes taking the 7704A apart quite
a bit easier. The 7514 uses a half dozen of those to the Main Interface, but
there are many, many individual slide-on connectors that must be removed in
order to remove that board. The manual mentions those but I didn't realize
there'd be so many of them!
Yes, I could clean it with IPA and can remove sub-boards and clean them;
however, the plugin socket side covers are in very bad shape and I'd like to
have the Main Interface board out to better see what I can do about that. If I
had a complete set of covers, then that might not be necessary but if I have to
try and find a substitute method for those, then having that board out where I
can access it directly will be much better.
Thanks,
Barry - N4BUQ
----- Original Message -----
From: "Jean-Paul" <jonpaul@...>
To: "tekscopes" <[email protected]>
Sent: Thursday, May 5, 2022 7:35:03 AM
Subject: Re: [TekScopes] Proper Way to Pull Single-Ended Connectors? Barry I have no experience on 7514, but most 7000 mainframes use single or
double row inlune black Molex or AMP flat ribbon cable to PCB connectiors, one
name is "harmonica" style.
BEWARE!! over the decades the thin plastic deterioration causes breakage or
crumbling of the connectors plastic!
VERY haed to fix.
If gentle rocking does not release then the pins may he frozen to the
recipticles.
In fact removal may nit be needed, perhaps just a water or isopropyl alcohol
wash can clean up the PCB.
A photo of the dirty board and close-up of connector will be useful
Bon courage
Jon
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Re: Proper Way to Pull Single-Ended Connectors?
Jon,
Yes, I'm familiar with the "harmonica" connectors. The 7704A uses them extensively as well as the plugins and that makes taking the 7704A apart quite a bit easier. The 7514 uses a half dozen of those to the Main Interface, but there are many, many individual slide-on connectors that must be removed in order to remove that board. The manual mentions those but I didn't realize there'd be so many of them!
Yes, I could clean it with IPA and can remove sub-boards and clean them; however, the plugin socket side covers are in very bad shape and I'd like to have the Main Interface board out to better see what I can do about that. If I had a complete set of covers, then that might not be necessary but if I have to try and find a substitute method for those, then having that board out where I can access it directly will be much better.
Thanks,
Barry - N4BUQ
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----- Original Message ----- From: "Jean-Paul" <jonpaul@...>
To: "tekscopes" <[email protected]>
Sent: Thursday, May 5, 2022 7:35:03 AM
Subject: Re: [TekScopes] Proper Way to Pull Single-Ended Connectors? Barry I have no experience on 7514, but most 7000 mainframes use single or
double row inlune black Molex or AMP flat ribbon cable to PCB connectiors, one
name is "harmonica" style.
BEWARE!! over the decades the thin plastic deterioration causes breakage or
crumbling of the connectors plastic!
VERY haed to fix.
If gentle rocking does not release then the pins may he frozen to the
recipticles.
In fact removal may nit be needed, perhaps just a water or isopropyl alcohol
wash can clean up the PCB.
A photo of the dirty board and close-up of connector will be useful
Bon courage
Jon
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Re: Proper Way to Pull Single-Ended Connectors?
Barry I have no experience on 7514, but most 7000 mainframes use single or double row inlune black Molex or AMP flat ribbon cable to PCB connectiors, one name is "harmonica" style.
BEWARE!! over the decades the thin plastic deterioration causes breakage or crumbling of the connectors plastic!
VERY haed to fix.
If gentle rocking does not release then the pins may he frozen to the recipticles.
In fact removal may nit be needed, perhaps just a water or isopropyl alcohol wash can clean up the PCB.
A photo of the dirty board and close-up of connector will be useful
Bon courage
Jon
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Proper Way to Pull Single-Ended Connectors?
I'm in the process of cleaning up a very dirty 7514 (apparently belonged to Southern Railway at one time and was stored in a fairly dirty environment). As part of that, I want to remove the Main Interface board and that involves removing many, many of the single-ended push-on connectors (the type that attach to the small pins that typically interconnect individual boards).
I removed a couple of these with a small hooked tool but that doesn't seem to be the most effective way to remove them because uneven pressure on one side or the other doesn't let the connector pull straight up. I'd imagine a hooked tool with a slot in it to clear the pin and allow even pulling pressure but I don't exactly have such a tool.
Is there a better way to do this? Needle-nose pliers? Unfortunately, I need to remove about thirty of forty of these so am looking for a "best method".
Thanks,
Barry - N4BUQ
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Re: 576 arrived with bad CRT... total dead end?
On 2022-05-05 6:17 a.m., David Aurora wrote: I think 2 should be ok based on my tests so far. And yeah, the base model should do just fine, although I grabbed the 25MHz one just to have more bandwidth if I need it for something else.
The seller has come back to me and it sounds like he¡¯s going to do the right thing, apparently his kid packed it up for him trying to help out and left the foam out. Shit happens, but he genuinely seems to be trying to sort a replacement so I¡¯ve got to give him points for decency.
I hope you don't return the damaged unit. Most likely it would go to landfill and as someone else pointed out, it's full of irreplaceable stuff that could drive another display one day (per parallel thread).
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Re: 576 arrived with bad CRT... total dead end?
IMHO you should still open an eBay case for this within 30 days of receipt of the item. You may wish to wait until close to the end of the 30 day period if you want the buyer to have a chance to sort things out some other way. It does no harm and may do some good.
<>
David
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-----Original Message----- From: [email protected] < [email protected]> On Behalf Of David Aurora Sent: 05 May 2022 11:18 To: [email protected]Subject: Re: [TekScopes] 576 arrived with bad CRT... total dead end? I think 2 should be ok based on my tests so far. And yeah, the base model should do just fine, although I grabbed the 25MHz one just to have more bandwidth if I need it for something else. The seller has come back to me and it sounds like he¡¯s going to do the right thing, apparently his kid packed it up for him trying to help out and left the foam out. Shit happens, but he genuinely seems to be trying to sort a replacement so I¡¯ve got to give him points for decency.
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Re: 576 arrived with bad CRT... total dead end?
I think 2 should be ok based on my tests so far. And yeah, the base model should do just fine, although I grabbed the 25MHz one just to have more bandwidth if I need it for something else.
The seller has come back to me and it sounds like he¡¯s going to do the right thing, apparently his kid packed it up for him trying to help out and left the foam out. Shit happens, but he genuinely seems to be trying to sort a replacement so I¡¯ve got to give him points for decency.
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Re: 576 arrived with bad CRT... total dead end?
Is two channels enough, or do you need Z-axis modulation too?
I'm still betting that even the lowest end Picoscope (at 10 MHz) is vastly more bandwidth than this application requires. I'd be surprised if this needed more than 1 or 2 MHz.
-- Jeff Dutky
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Re: Alternate trace sweep length disparity 547
Thanks for the reply Ozan, I checked the values of the components in the multi and they are all in spec, also the square wave is there and opposite phase between sections as it should be thanks.
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Re: 576 arrived with bad CRT... total dead end?
I posted in the other thread that while looking for solutions I noticed that Picoscopes allow you to create probes with your own scaling, AND by default the grid is 10 x 10, so in theory once the scaling is set we should be able to get a 1:1 readout. I'll order one with my parts orders today and do some probing when it arrives to see what works best
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Re: Saving 576 plots (again)
Actually yeah, good point. I've got a nice clean display just probing in plain old XY. Appropriately scaled in software that's a super simple solution.
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Re: 576 arrived with bad CRT... total dead end?
This is why I was hoping to tap the amplifier signal Pre final amp. If I remember correctly from the last time I looked at the schematic (it has been a while) The pre tube driver stage is not differential. It is signal ended. Also the 200Vdc supply is only used in the tube driver stage. This being the case the HV transformer is no longer needed because you don¡¯t need the -4Kv supply or the 200 Vdc supply. This is not used in the collector supply for sure. This would also solve the failing HV transformer issues and would really set these units up for a long run. The low voltage supply is a pain to rebuild but it is just time consuming and not difficult.
Zen
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-----Original Message----- From: [email protected] < [email protected]> On Behalf Of David Aurora Sent: Wednesday, May 4, 2022 9:43 PM To: [email protected]Subject: Re: [TekScopes] 576 arrived with bad CRT... total dead end? It really seems to be that the dead simple solution is just to tap the deflection signals off through the necessary attenuation/diff to single ended conversion and plug the XY in a USB scope. I really don't see the need for doing your own A/D and writing software to drive it all?
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Re: 576 arrived with bad CRT... total dead end?
It really seems to be that the dead simple solution is just to tap the deflection signals off through the necessary attenuation/diff to single ended conversion and plug the XY in a USB scope. I really don't see the need for doing your own A/D and writing software to drive it all?
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Re: 576 arrived with bad CRT... total dead end?
From what I've seen, the problems revolve around getting the CRT (pretty? much unobtanium), and replacing the CRT with either an LCD display installed in place of the CRT, or using an external XY display as a readout.
One thing you could do (and I've seen it done) is to take an STMicro Disco board, add an op amp to scale the signal tapped off from the deflection amplifiers, digitize that with the processor's A/D converters (fast enough, perhaps), and then use the built in display (cell phone size) to display the curve data.? Once digitized, the virtual com port on the board could be used to transmit data over to a PC (USB interface), and then displayed on a PC.? No remote control, just remote display.
Another option would be to take a larger display and use it, but you're getting into problems with a round CRT bezel and a rectangular display.
another option would be to have some fast A/D converters driving a processor, which could store the data points, and then either drive a display or a CPU.
Note that any of these options involve programming at a minimum, or hardware.
A fourth option would be a pair of fast A/D converters driving an FPGA for memory, and then perhaps using that FPGA to drive an LCD display, although it would be easier to put a FIFO on the A/D converters (if needed) and then have the display controller in either the processor or a separate chip, all depends on the display.
All of the above are possible, all of the above require some effort, not inconsiderable.
Harvey
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On 5/4/2022 8:55 PM, David Aurora wrote: I'm definitely happy to collaborate (as long as I have a unit to work with haha, if this one goes back to the seller I don't know when I'll get another one). When I found this board and saw all the posts about the topic I thought there would be a solution in there somewhere but it seems like something people thought about but never followed through on. So if I can help get us to a concrete solution that everyone can benefit from I'm happy to help
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k6whp
Martin
Jean-Paul
David C. Partridge
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