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Re: 2465 blower
On Wed, Apr 7, 2021 at 07:39 PM, <adesilva_1999@...> wrote:
Never tried. I might still do that, motors still in a box, I think. Thanks for the suggestion! Raymond |
Re: Fast probe prices?
I didn't use the 50 ohm terminator when plugging directly into the 1S1 because I thought that would be too much load, since the 1S1 already provides 50 ohms of load. However, I tried to replicate the setup as best I could by adding in an equivalent number of SMA adapters, including the tee (with an open end where the 50 ohm terminator was). SMA adapters don't seem to change the waveform noticeably. So I don't think the setup itself is causing the ringing, unless the 0.25 inch unshielded line running from the SMA socket to the solder pad of the probe's input is the culprit.
I already wanted a NanoVNA, but now I feel compelled to also own an TinySA. I need more gift-giving holidays in the calendar. |
Re: Early 465 CRT "mesh" or "Post Accelerator Grid".
I finally realized a couple months ago that the colors on multicolored ribbon cable actually meant something other than just identifying separate wires. Standard resistor color code, duh. Start with brown on pin 1 and you're golden.
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The color coding on Tek wiring is very useful, particularly if you have to pull a board for some reason. Inventory must have been a headache though. I've had some equipment where all the wires are black and, if you're lucky, there may be an ID printed in 2 point type in white ink that may or may not be readable. Paul On Wed, Apr 07, 2021 at 12:27:08PM -0400, n4buq wrote:
I agree with Michael. I always looked at the striping as just a means of identifying a wire from one end of a cable to the other and hadn't thought about the color codes indicating a pin number, etc. --
Paul Amaranth, GCIH | Manchester MI, USA Aurora Group of Michigan, LLC | Security, Systems & Software paul@... | Unix/Linux - We don't do windows |
Re: Early 465 CRT "mesh" or "Post Accelerator Grid".
I agree with Michael. I always looked at the striping as just a means of identifying a wire from one end of a cable to the other and hadn't thought about the color codes indicating a pin number, etc.
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I know HP usually notated the stripes on the schematics and that also helps troubleshooting but not sure if any of those correspond to anything such as a pin number, etc., on the boards. I'll have to remember to take a closer look at that the next time I have one of them open and see if I can determine any correlation. Thanks, Barry - N4BUQ Time to give away another secret:Raymond, |
Re: Early 465 CRT "mesh" or "Post Accelerator Grid".
On Tue, Apr 6, 2021 at 05:25 PM, Raymond Domp Frank wrote:
Raymond, When I read your comments, such as above, I realize just how little I actually know. Thank you for sharing your knowledge with us. I will never look at those wires and stripes the same way, going forward. Sincerely, -- Michael Lynch Dardanelle, AR |
Re: Fast probe prices?
That's a lot of ringing (and it persists for a long time, too)!
For the "direct" test, did you also have the tee with the 50 ohm terminator attached? (Is the ringing from the probe itself or from the setup)? I may still buy one and tinker with it... I have sine-wave sources up to 920 MHz, and of course my 300-ish ps avalanche pulser. |
Re: Early 465 CRT "mesh" or "Post Accelerator Grid".
On Wed, Apr 7, 2021 at 05:00 PM, Raymond Domp Frank wrote:
Correction: The background color is not *printed*, so a straight white wire would indicate pin 9. Tek avoided this by not using pin 9 on the 465's CRT -;). Raymond |
Re: Early 465 CRT "mesh" or "Post Accelerator Grid".
On Wed, Apr 7, 2021 at 04:43 PM, Jim Adney wrote:
Using the resistor color code, brown-white would translate to 19. The brown-red combination on a white background indicates 12 - or 21. The CRT socket however only has 14 pins. The background color is not used and yes, below 10 only one color is printed on the (white) background.Because, using the resistor color code, brown-white translates to 12, the CRT Yes, this was standard Tek. Often, the harmonica connectors (the linear ones, pushed onto rows of pins on a PCB) are molded in colors indicating the last digit of the socket number. HP (Agilent) had a similar habit, using color codes for the PCB ejectors. Raymond |
Re: 0.25R resistor in calibrator ground
On Wed, Apr 7, 2021 at 3:35 PM Albert Otten <aodiversen@...> wrote:
Thank you for confirming this, Albert. My previous message got somewhat mangled in transit so I'll try to post the text again here: Further to this discussion on the 0.25R anti-ground-loop resistor on tube-era calibrator outputs, I looked further in to why my 127's calibrator output ground seemed to be open-circuit. It turned out that there was actually a manufacturing error. There's an arrangement of plastic bushes and fibre washers to keep the calibrator socket's outer from being in contact with the front panel. In my 127, one of the fibre washers was in the wrong place, so the bottom of the volts/millivolts divider chain was connected to chassis ground, and both ends of the 0.25R resistor R898 were also connected to chassis ground. The calibrator socket outer wasn't connected to anything at all. It was completely floating. The paint seals on the screws were still intact, so it must have left the factory that way in 1960. The only reason I noticed is that in my office the power sockets have no ground connection, so when by chance I powered the 127 from a different outlet to the scope I was testing it with, they had no common ground connection via their power cables. Trying to view the calibrator output it seemed to be imposed on about 100V of mains hum, which I blamed on a faulty cable. But the cable was blameless. It was an actual Tek assembly error! I guess nobody had ever noticed due to never having tried to connect the calibrator to an ungrounded device. I've moved the offending washer now and the wiring matches the schematic diagram. It all works as it should now. Chris |
Re: Early 465 CRT "mesh" or "Post Accelerator Grid".
On Tue, Apr 6, 2021 at 05:25 PM, Raymond Domp Frank wrote:
The wire actually is white, with a brown and a red stripe. Guess why?Because, using the resistor color code, brown-white translates to 12, the CRT pin number it goes to. And for pins 1-9, I'll bet there will be only one stripe. Nice catch, I wouldn't have gotten it without your hint. Was this standard Tek practice? |
Re: 0.25R resistor in calibrator ground
On Thu, Mar 25, 2021 at 05:17 PM, cmjones01 wrote:
561B (mentioned by keantoken) manual page 3-5 bottom left: "R183, which is about ten times the resistance of the braid of a 42-inch coax cable, cancels any ground loop current that may exist between the CAL OUT connector and some other instrument chassis." I didn't look in other manuals. Albert |
Re: 0.25R resistor in calibrator ground
Further to this discussion on the 0.25R anti-ground-loop resistor on
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tube-era calibrator outputs, I looked further in to why my 127's calibrator output ground seemed to be open-circuit. It turned out that there was actually a manufacturing error. There's an arrangement of plastic bushes and fibre washers to keep the calibrator socket's outer from being in contact with the front panel. In my 127, one of the fibre washers was in the wrong place, so the bottom of the volts/millivolts divider chain was connected to chassis ground, and both ends of the 0.25R resistor R898 were also connected to chassis ground. The calibrator socket outer wasn't connected to anything at all. It was completely floating. The paint seals on the screws were still intact, so it must have left the factory that way in 1960. The only reason I noticed is that in my office the power sockets have no ground connection, so when by chance I powered the 127 from a different outlet to the scope I was testing it with, they had no common ground connection via their power cables. Trying to view the calibrator output it seemed to be imposed on about 100V of mains hum, which I blamed on a faulty cable. But the cable was blameless. It was an actual Tek assembly error! I guess nobody had ever noticed due to never having tried to connect the calibrator to an ungrounded device. I've moved the offending washer now and the wiring matches the schematic diagram. It all works as it should now. Chris On Thu, Mar 25, 2021 at 6:49 PM Dave Wise <david_wise@...> wrote:
|
454 Fireworks Followup to the Followup
Well,
I finally got me some 2N3442s from mouser. Good news: the HV sparking problem was definitely cause by the 75V regulator going short. Bad news: there appears to be no vertical deflection. But, there's a caveat to that. I'm pretty certain the problem lies downstream of the front end amplifiers because the channel 1 out signal is present and responds to vertical position control when viewed on another oscilloscope. Another symptom is that the spot is about 1 cm long in the X dimension when the time base is slowed down. I'm hoping the 75V rail going high didn't take out a bunch of stuff! Sean |
Re: Fast probe prices?
That dang Jeff Dutky keeps making me spend money on test equipment!
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LOL. Last I'd checked there wasn't any availability. R&L has them now! Get 'em while their hot! Dave On Tuesday, April 6, 2021, 09:00:11 PM PDT, Jeff Dutky <jeff.dutky@...> wrote:
Jonathan Pyle wrote: Good News! You can remedy both deficits by the acquisition of a TinaSA: The TinySA is a spectrum analyzer that can operate on signals between 100 KHz and 960 MHz (in two ranges), it can generate sine waves up to 350 MHz, and square waves up to 960 MHz, and it fits in the palm of your hand. Make sure you buy from one of the reliable sources: When I bought mine, earlier this year, I paid less than $60. I bought through the Zeenko store on AliExpress. It did take more than a month or the item to arrive, as I did not pay or expedited shipping. -- Jeff Dutky |
Re: Fast probe prices?
Jonathan Pyle wrote:
Good News! You can remedy both deficits by the acquisition of a TinaSA: The TinySA is a spectrum analyzer that can operate on signals between 100 KHz and 960 MHz (in two ranges), it can generate sine waves up to 350 MHz, and square waves up to 960 MHz, and it fits in the palm of your hand. Make sure you buy from one of the reliable sources: When I bought mine, earlier this year, I paid less than $60. I bought through the Zeenko store on AliExpress. It did take more than a month or the item to arrive, as I did not pay or expedited shipping. -- Jeff Dutky |
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