Re: Tek 2465b two probes showing slightly different voltages and phases
No, apparently, the nanosecond is out of favor this year (as of about 42 minutes ago) and the arcsecond is in. Go figure.
DaveD
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On Dec 31, 2020, at 19:37, Tom Lee <tomlee@...> wrote:
A nanosecond just isn't what it used to be... :)
--Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
On 12/31/2020 16:27, Tom Gardner wrote:
On 31/12/20 21:53, Tom Lee wrote:
Enjoy that scope, Mark -- it's an amazing instrument. Consider that it is so capable that the finite speed of light was the root cause of your delay problem! Nice to own a scope where you start complaining about light being too slow...
Here's a nice video of (Rear Admiral) Grace Hopper demonstrating the "size" of 1ns in vacuo: a piece of wire 11.8in long. In a cable it will be shorter, due to the reduced speed of light.
The 1972 portable Tek 1502 TDR is capable of resolving discontinuities 140ps apart, i.e. ~1.2in in a cable.
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Re: Grid Bias Adjustment on 475A
Trying to find R1375 & associated components on your earlier pictures, but I think from looking at my 465 that they're just out of frame.
Also using my 465 as proxy, it looks like the zener diode and 10k resistor node (don't have your schematics at hand for #'s) are accessible. I'm not advocating, and I wouldn't blame anyone for not being comfortable operating their scope with the shield off, but can you get a measurement off this output of the R1375 pot? Looks like it'd be possible to get a 10x scope probe on one of the leads of the cap maybe? Reassemble the shield and see if the value responds to turning the pot - again with the shield on. And this all depends on the 475A board layout, accessibility, clearance for the probe with shield, etc.
I'd be wary of trying to get a good R value in situ with the 50v supply being connected to the regulator divider feedback network.
Dave
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Re: I built a TM500 mainframe tester, and updated the design. Someone might find this useful?
Non-working TM500 modules appear on eBay from time to time at fair price and include top,? bottom and side panels and the all-important latch-release pull-tab. Shielding is not important for this tester and 3D printed parts might be adequate if made strong enough.LarrySent via the Samsung Galaxy S10
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-------- Original message --------From: Jeff Dutky <jeff.dutky@...> Date: 12/31/20 8:43 PM (GMT-08:00) To: [email protected] Subject: Re: [TekScopes] I built a TM500 mainframe tester, and updated the design. Someone might find this useful? Does anybody now if the aluminum plates are required? Would plastic plates (3D printed or otherwise fabricated) work just as well?My stable of TM500 modules is already pretty thin, and I don't have any unrepairable units lying about.-- Jeff Dutky
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Re: I built a TM500 mainframe tester, and updated the design. Someone might find this useful?
In my experience, the 3D printed plastic frame needs a thin gauge aluminum backing to give it rigidity.? If you had any machine shop capability (such as a decent drill press), you could make your own plates.? The idea of a bare PC board is not at all a bad one, your choice of whatever the board solder mask is.? However, I've seen no silver boards at all.? I'm going to experiment with a 3D printed overlay, possibly black, possibly blue, but it could be the same gray as the normal plastic backing.? YMMV on this.
The standard construction on the modules seems to be a thin aluminum plate, a plastic backing plate (screws go through these two), and a front plate that's silk screened and held on by control knobs.? Makes a clean appearance.? It's possible to do a transparency, either laser or inkjet, and perhaps put a thin layer of transparent plastic over it, that gives you photo art.? The advantage of an inexpensive board would be that all the machining is done for you.
Harvey
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On 12/31/2020 11:43 PM, Jeff Dutky wrote: Does anybody now if the aluminum plates are required? Would plastic plates (3D printed or otherwise fabricated) work just as well?
My stable of TM500 modules is already pretty thin, and I don't have any unrepairable units lying about.
-- Jeff Dutky
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Re: Spectrum analyzer Tektronix 7L13 on mainframe Tektronix 7603
Wow.. I just checked my 40 + year stash of normally useless crystals, and found
52.500000 CR-55A/U. Probably a 3d OT, but the spec should tell. HC-18 with
the hard pins, not flying leads. Yours for post and a coffee.
JimMc
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-----Original Message----- From: "Tom Lee" <tomlee@...> Sent: Thursday, December 31, 2020 7:20pm To: [email protected]Subject: Re: [TekScopes] Spectrum analyzer Tektronix 7L13 on mainframe Tektronix 7603 Yes, finding oddball crystals is a challenge. I very much doubt that you will find 52.5 (or 55, for that matter) MHz crystals as standard stock items, so your choices are limited. If you can't find them as off-the-shelf or surplus items from the usual sources (including ebay), you'll have to have them made. So, your next question would be: Who makes custom crystals? The number of good answers is unfortunately diminishing with time, as vendors disappear. About the best recent discussion I've seen is a couple of years old: Scroll down near the bottom of the first page. A poster "drussell" offers a comprehensive list of potential vendors. Warning: Custom crystals tend to be rather expensive. You may spend as much or more just for the crystal than for a nanoVNA. :) In discussions with potential vendors, let them know that you would be happy with a third-overtone crystal, if they ask. Fundamental-mode crystals for that frequency range exist, but are incredibly expensive. Plus, the TR50x gens already use third-overtone crystals. No need to pay a surcharge on top of a surcharge. Good luck! -- Tom -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 350 Jane Stanford Way Stanford University Stanford, CA 94305-4070 On 12/31/2020 12:16, Attilio wrote: Hi everybody,
where can i find the 52.5 MHz crystal? It is hard to find!
Thanks and happy new year
Attilio
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Re: I built a TM500 mainframe tester, and updated the design. Someone might find this useful?
Does anybody now if the aluminum plates are required? Would plastic plates (3D printed or otherwise fabricated) work just as well?
My stable of TM500 modules is already pretty thin, and I don't have any unrepairable units lying about.
-- Jeff Dutky
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Re: Grid Bias Adjustment on 475A
Okay, I've examined R1375 (with the power off, and I'm not sure where to probe for anything other than that center tap on the pot, so I can't really answer whether it's seeing the full +50 V at one of the outer terminals) but the pot seems (to my uneducated eye) to be acting strangely. I was able to find a pad that is connected to the center tap of the pot, so I measured its resistance between center tap and ground, and between center tap and the +50 V rail, as I turn the pot through its range. It starts a effectively zero ohms (0.001 K ohm), goes up to about 6 K ohms, then drops down again to around 2 K ohms. The schematic says this is a 25 K ohm pot, so shouldn't I expect it to go from 0 to 25 K ohms?
If it turns out that the pot is dead, I guess that's good, but I don't relish the idea of removing the main interface board to unsolder and replace this trim pot.
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Re: I built a TM500 mainframe tester, and updated the design. Someone might find this useful?
I ordered my rotary switch from Digikey, looks like there are 100 in stock with a little bit of a price break for multiple purchases.
Might be worth looking around for cheaper prices, I didn't ask the manufacturer for direct pricing, but that might be worth the time spent to send an email to see if cheaper pricing is a possibility.
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Re: I built a TM500 mainframe tester, and updated the design. Someone might find this useful?
Six list members have said they want to participate in a group buy of these board sets. Those are:
ML
PA
SM
DC
HB
GL
I've asked Jared for clarification on some points and for help ensuring the order is placed correctly. I'm waiting to hear from him.
I'm inclined to place the order with the same board house Jared used. I'm not willing to go into a lot of competitive bidding on board cost! I don't know the cost of a set of four boards but it can't be that much...
I live in Southern California and am retired so I can manage a group buy, with reimbursement via PayPal Friends and Family. There is a very special PWB-mount rotary switch required; I may buy a lot of those to ensure availability so that would likely be part of the board set purchase. Be aware this is a $25 switch! Many of us have other standard parts available so I'm not enthusiastic about buying other parts.
So, think about really wanting to build one of these testers and let's see if we can make a group purchase work.
I'm currently building a GPSDO into a TM500 proto module. But, any non-working TM module can be bought and stripped to provide the chassis structure for this tester. The PWB set makes is easy...
I welcome your constructive comments. Note the cost of the rotary switch stated above.
Larry
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On 12/31/2020 3:12 PM, Larry McDavid wrote: Anyone interested in buying sets of boards to share?
Larry
On 12/31/2020 11:27 AM, Jared Cabot via groups.io wrote:
Hi all,
I have been accumulating TM500 modules and mainframes for a little while, so I recently finished building an 067-1201-99 TM500 mainframe tester from the Tek construction notes floating around.
I updated the design somewhat and designed it for simplified construction (Not a single wire to strip and solder!) and I thought someone here might be interested in taking a look or even building one themselves.
Here's a link to the youtube video:
And here's a link to the google drive with all the gerbers and schematics and stuff. I went so far as to rewrite the manual with the alterations and corrections included.
Direct link to the new manual:
Let me know what you think, and let me know if you see any errors that need correcting. :)
Regards
Jared.
--
Best wishes,
Larry McDavid W6FUB
Anaheim, California (SE of Los Angeles, near Disneyland)
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Re: Grid Bias Adjustment on 475A
I have not examined the grid bias trim pot (R1375) yet, so I don't know what voltages it sees. Like I said, if it turns out that the trim pot has drifted out of spec that would explain a lot of what I'm seeing. I'll see what I can measure straight away.
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What do you mean by chip? 74LS logic and SRAMS can be tested with the TL866 II device programmer.
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Greetings,
Allow me to seek some owner/user comments as well as alternate suggestions.
I am considering acquiring an IC tester/identifier instrument. Currently, on-line I have found a very limited selection - actually just one unit - a Chinese built YBD868.
I have been unable to find any useful information regarding this thing. The very few on-line videos are rather worthless. They are either void of any operational demonstrations or show the unit as completely unresponsive.
Does anyone have personal experience with this unit and if ¡°yes¡± I would be very grateful for an accurate assessment.
Additionally, if there are other IC test and identification units available, which I have simply not discovered, I would greatly appreciate recommendations.
I wish all of us a much better 2021 than this year has been.
Wherever in the world you might live I hope 2021 becomes you best year thus far with many fantastic years to follow.
Regards and best wishes!
Ken
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Re: Grid Bias Adjustment on 475A
Sorry! that should be 50 volts. Not 150 volts!
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Re: Grid Bias Adjustment on 475A
On Thu, Dec 31, 2020 at 04:36 PM, Jeff Dutky wrote:
I also checked the voltage at the base of Q1332 which measured -1.75 V (as
indicated).
The diagrm I have for 475A has the Q1332 base grounded. I am not sure about the readings you have mentioned. I have not gone through the whole manual but just looking at the schematic only. Also, do you have the 150 volts on one leg of the R1375 trim pot?
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Re: Tek 2465b two probes showing slightly different voltages and phases
Yes, it works better in US units -- "1ns per foot". "3.3ns per meter" just doesn't quite have the same mnemonic quality.
--Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
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On 12/31/2020 18:41, Steve Hendrix wrote: At 2020-12-31 07:27 PM, you wrote:
Here's a nice video of (Rear Admiral) Grace Hopper demonstrating the "size" of 1ns in vacuo: a piece of wire 11.8in long. In a cable it will be shorter, due to the reduced speed of light. Wow, that brought back a memory - I attended her talk in person when I was a cadet at the USAF Academy, and that 11.8" has always stuck with me and been quite useful. That would have been about 1977.
Steve Hendrix
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Re: Tek 2465b two probes showing slightly different voltages and phases
At 2020-12-31 07:27 PM, you wrote: Here's a nice video of (Rear Admiral) Grace Hopper demonstrating the "size" of 1ns in vacuo: a piece of wire 11.8in long. In a cable it will be shorter, due to the reduced speed of light. Wow, that brought back a memory - I attended her talk in person when I was a cadet at the USAF Academy, and that 11.8" has always stuck with me and been quite useful. That would have been about 1977. Steve Hendrix
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Re: I built a TM500 mainframe tester, and updated the design. Someone might find this useful?
Me too.
Glenn
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On 12/31/2020 6:31 PM, Dale Chayes wrote: Yes,
-Dale
On Dec 31, 2020, at 18:12, Larry McDavid <lmcdavid@...> wrote:
?Anyone interested in buying sets of boards to share?
Larry
On 12/31/2020 11:27 AM, Jared Cabot via groups.io wrote:
Hi all,
I have been accumulating TM500 modules and mainframes for a little while, so I recently finished building an 067-1201-99 TM500 mainframe tester from the Tek construction notes floating around.
I updated the design somewhat and designed it for simplified construction (Not a single wire to strip and solder!) and I thought someone here might be interested in taking a look or even building one themselves.
Here's a link to the youtube video:
And here's a link to the google drive with all the gerbers and schematics and stuff. I went so far as to rewrite the manual with the alterations and corrections included.
Direct link to the new manual:
Let me know what you think, and let me know if you see any errors that need correcting. :)
Regards
Jared. --
Best wishes,
Larry McDavid W6FUB
Anaheim, California (SE of Los Angeles, near Disneyland)
--
-----------------------------------------------------------------------
Glenn Little ARRL Technical Specialist QCWA LM 28417
Amateur Callsign: WB4UIV wb4uiv@... AMSAT LM 2178
QTH: Goose Creek, SC USA (EM92xx) USSVI LM NRA LM SBE ARRL TAPR
"It is not the class of license that the Amateur holds but the class
of the Amateur that holds the license"
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Re: I built a TM500 mainframe tester, and updated the design. Someone might find this useful?
To answer a few other questions: I used a blank module kit to build this project, I lucked into one when buying a 'mainframe with modules fitted' at Yahoo Auctions so put it to good use. But I don't see why any old chassis from an otherwise unrepairable TM500 module couldn't be used. The front faceplate PCB needs to be made from 1mm PCB rather than the usual 1.6mm, black silkscreen on white solder mask, but this is easily done by any Chinese manufacturer. I know PCBWay and JLCPCB can do it as they both manufactured this sort of thing for me in the past. I can't comment on actual costs as such as the PCB's were sponsored, but matte black from PCBWay is rather expensive so the more standard colours (like green etc) will help save cost. The white for the front faceplate shouldn't raise costs much (or at all) though, so that shouldn't be much of a concern. The large PCB does raise the cost a little, but it's not too bad from the Chinese manufacturers, and when divided out to a group buy, the individual cost should be pretty manageable. I just uploaded the files to the files section here too, to make it easier to download for anyone having trouble with google drive (seems google groups isn't compatible with some of the URL's generated by Google Drive, who would have thought??) /g/TekScopes/files/Tek%20TM500%20Power%20Module%20Tester%20067-1201-99%20New%20Ver. Hopefully that link works, it's in the files section anyway. :)
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Re: I built a TM500 mainframe tester, and updated the design. Someone might find this useful?
Hi,
Wow, I didn't expect such a big response. :D haha
As for production of PCB's, I did use PCBWay as they are a sponsor of my Youtube channel, however, they are a slightly more 'premium' Chinese manufacturer.
Using JLCPCB or Seeed Studio (with 3 e's) will be cheaper and still have very good quality.
Gold plating is a good idea for the Main PCB, and a manufacturer that can chamfer the card edge connector is a good idea too. JLCPCB and PCBWay can do this (it's a minimal extra cost per PCB) but I think Seeed Studio couldn't last time I checked.
I have used JLCPCB extensively in the past, their prices and quality are quite good.
I'm not quite in a position to run a group buy myself as I live in Japan, so shipping and logistics would be more expensive and difficult than if someone in the USA did it instead. However, I am more than happy to provide 'technical support'.
Just let me performance check my unit first to make sure I have it all working 100%, I'm a bit paranoid that I might have a gremlin hiding somewhere. :D haha
Anyway, I'm glad you all like it. I have a few more ideas for some similar projects in the future so stay tuned. :)
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Re: Fun with the type S plugin
Thanks everyone for your comments. This plugin was an interesting mix of tube and transistor circuitry. I think it is one of Tek's first attempts to use transistors in their instruments wherever possible. It certainly uses some early Ge pnp transistors in less critical areas. The lowest 2N number in it is a 2N270 which is an emitter follower for the shift voltage applied to one side of the vacuum tube differential output amplifier. The multivibrator transistors were 2N1377's and the trigger amp is specified as a 2N1631 which had been replaced with a AC128 which is a lot slower but seems to work. All the tubes in the plugin were OK despite their age. The "magic" in this plugin is contained in the mercury wetted relay sealed inside the glass vial. I not so sure it is pressurized. It is pressurised and both the S and 109 manuals warn about the explosion risk. The 109 manual mentions the limited lifetime but not the S. I checked the Tek part numbers in the manuals to see if they used the same part and it was indeed the same one. It would have been an interesting challenge to try to make up a substitute fast rise pulser using modern parts if the reed was faulty. I switched on first time my "R type" plug in which measures transistor risetimes. I have one of these too. I last used it to check the transfer times of optocouplers I wanted to use to transfer video pulses to a CRT grid. Even though the unit seems to work well there are some glitches and I suspect some of the precision resistors in it have drifted over the years. Replacing them will not be easy and I might not do it at all. Where does one find a 43.4K or 69.5K precision resistor these days? Cheers, Morris
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Dave Peterson
Jared Cabot