Re: Sick TG501 Main 1Mhz ref not running.
Dave,
I had thought that I had seen a video by either Jared Cabot (NFM) or Zen (Zenwizard) showing the addition of Option 01 to a TG 501, but I can't seem to find it now. I may have been thinking of Jared's video about adding a similar option to a DC503A.
The TG 501 Option 01 seems to consist of basically two components: U50 (a 7490 TTL decade counter) and Y50 (a 5MHz crystal oscillator, possibly ovenized?). The part numbers for Y50 are either Electronic Research Co. EROS-600-TK-9 (SN below B034510) or Bliley Electric Co. T15B141 (SN B034510 and above). I imagine that any 5 MHz TXCO or OCXO can be made to work, with effort.
The service manual has this to say about Option 1:
The TG 501 Option 01 is equipped with a temperature-compensated, 5 MHz crystal oscillator for a highly stable and precise internal clock. U50 provides countdown circuitry for the 5 MHz crystal.
Remove U100 and disconnect pin 3 of U350 before using external clocks. To disconnect pin 3 remove U350, bend pin 3 out then insert U350 back in tcurciut board.
The main circuit board jumpers that must be installed for Option 01 are: J3 and J7 (see. Fig. 5-2 for jumper location).
-- Jeff Dutky
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Re: TG501 2ns & 1ns operation
If it comes to precision and ceramic tools for electronics I have always been fond of "Bernstein", a company based at Remscheid, Germany. Never cheap but well made. Somewhat bigger tools? I do prefer HAZET, again based at Remscheid. I have been fixing old cars for over 40 years now and some spanners have been in use from the first day up to now. And for coarse jobs I'd suggest "Ridgid" from Ridge tool company, Elyria, Ohio.
Not all the fine tools are European made! But well, I am old fashioned and really avoid buying from Asia as far as possible.
Regards, Joe
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Re: Sick TG501 Main 1Mhz ref not running.
On Mon, Nov 29, 2021 at 11:39 AM, Michael W. Lynch wrote:
Zen,
I converted all of my TG501s over to "Option 1" Units with the 5Mhz
Oscillator. This might be a solution as well.
--
Michael Lynch
Dardanelle, AR
Michael, I'd like to consider making this conversion. My TG501 timing is doing fine with its 1MHz oscillator, but my finicky nature would like to achieve the +/- 5x10^-7 option 1 seems to give. I would think this would directly bear on the accuracy of the 1ns timing marks? Do you have something of a BOM for the conversion? Feel free to reply off list if you prefer. Thanks, Dave
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Re: TG501 2ns & 1ns operation
Jared Cabot wrote:
(I also have cheap ebay ceramic screwdrivers that work great)
I said that they got the job done. I would not say that the "work great." The set I have was $13 (US) for 8 pieces, but several of the shafts are not straight in the plastic handle, and the swivels on the back do not turn smoothly, so you can't really use them like you would a proper jeweler's screwdriver. The work, but not great. I will have to invest in some quality Japanese tools, but the Vessel screwdrivers cost more for a single screwdriver than I paid for all eight cheap Chinese ones. -- Jeff Dutky
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Re: TG501 2ns & 1ns operation
On Fri, Dec 3, 2021 at 11:44 AM, Jared Cabot wrote:
Even when I was living in Australia, I would seek out Japanese and German
tools.
When working on Japanese motorcycles, a set of JIS screwdrivers is a must,
they have parallel flutes (like a Pozidriv minus the extra little flutes
between the larger ones), so if you try to use a Philips driver with its
tapered flutes, you'll very quickly damage or destroy the screws.
I only buy tools from Germany, Japan, USA and Taiwan (ROC), (in no particular order). I have Snap-On tools that are in excess of 50 years old and still being used daily. Tools from China, India and Pakistan (among others) are at the very bottom of my list, except where I know that the tool will only be used once, is to be modified or needs to be disposable. -- Michael Lynch Dardanelle, AR
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non-conductive tools (was: TG501 2ns & 1ns operation)
I found a seller that combines shipping, so the total for three ceramic drivers was $5.10
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Re: TG501 2ns & 1ns operation
On Sat, Dec 4, 2021 at 12:05 AM, Michael W. Lynch wrote: Jared,
I was able to find these two brands on AMAZON. Vessel makes a great set of JIS
Screwdrivers as well, invaluable when working on Japanese equipment. I also
found some very high quality, German made Pozi-Drive screwdrivers there. As a
professional motorcycle mechanic, I was exposed early on to high quality
Japanese tools. HONDA used many KOWA SEIKI brand tools. I have owned and
used these for 40+ years.
There is definitely a difference in the quality of the Japanese tools.
--
Michael Lynch
Dardanelle, AR
I'm lucky in this regard that I live in Japan, so obtaining Japanese tools is somewhat unavoidable. :) Even when I was living in Australia, I would seek out Japanese and German tools. When working on Japanese motorcycles, a set of JIS screwdrivers is a must, they have parallel flutes (like a Pozidriv minus the extra little flutes between the larger ones), so if you try to use a Philips driver with its tapered flutes, you'll very quickly damage or destroy the screws. On Sat, Dec 4, 2021 at 12:40 AM, Dave Peterson wrote: Jared,
So does your TG501A have a small amount of 500MHz signal on MARKER OUT in 1ns
mode?
Here is what I see, just random noise and junk. I guess Tek engineers assumed users wouldn't care much what was on the unused outputs when the others were in use maybe?
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Re: TG501 2ns & 1ns operation
On Fri, Dec 3, 2021 at 04:40 PM, Dave Peterson wrote:
I've been looking them up. I like the ceramic solutions, but am disappointed
that they tend to be the stubby type that don't have a lot of reach. I'm
currently fashioning an FR4 tip for the trimmer I made out of a hard
toothbrush handle.
I like my trimming screwdrivers as stubby as possible, because of their small rotational elasticity. It helps overcome the trimmer's friction, providing higher precision control. A ceramic stem works much better than materials like plastic and even FR4. Raymond
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Re: TG501 2ns & 1ns operation
Jared,
Thanks for the pics. I suspect at some point I'll pick up a modern DSO that can handle frequencies above 500MHz, just so I can capture such signals.
The "signal" that was causing me concern was the MARKER OUT output in 1ns mode. I know that the 1ns signal is on the "1ns ONLY" output. The question in my mind that I was trying to understand was what was MARKER OUT supposed to do while in 1ns mode? It seemed that the 2ns output might remain on the MARKER OUT. Raymond corrected my understanding pointing out that K450 shuts off the 2ns Filter output from MARKER OUT, which unloads it enabling a somewhat larger 1ns ONLY output. But in 2ns mode, there is still a fair level out on 1ns ONLY. I was a bit concerned about the low 1ns level, but I knew I was in BW limit territory. Feedback from the group reinforces that suspicion.
So does your TG501A have a small amount of 500MHz signal on MARKER OUT in 1ns mode?
Regarding trimmer tools: I'm sure you're all well aware of the variety of trimmer pots, caps, and inductors we encounter in Tek equipment. Not only are there a variety of cross sections (philips, flat, torx, hex, ...) there are also a variety of depths and diameters to contend with. This is why I'm trying homemade solutions first. I'm perfectly happy to spend a little, or even a lot, for a tool that works. I have, and have had, a number of trimmers that work well in some situations and not others. Have we all had the situation where you can't get the trimmer through the access hole in the cover plate? Or the pot/cap is just out of reach? It surprises me how many available trimmers have a small shaft that would fit through a small access hole, but have hardly any length so the pot/cap remains just out of reach of the tool. Alternatively there are long slender trimmers that are too weak to turn old frozen pots/caps because of their thin plastic construction. But if one uses metal there's shorting risk and/or capacitive impact.
I do appreciate the recommendations. I've been looking them up. I like the ceramic solutions, but am disappointed that they tend to be the stubby type that don't have a lot of reach. I'm currently fashioning an FR4 tip for the trimmer I made out of a hard toothbrush handle. The epoxy is setting as we speak. I tried the shaped tip on C515 to see if it could stand up to the torque required. Worked like a charm. Now I need to test my craftsmanship. I suspect I'll make a few types, and based on what works I'll buy something online once I know the dimensions I need.
Thanks all!Dave
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On Friday, December 3, 2021, 06:15:09 AM PST, Jared Cabot via groups.io <jaredcabot@...> wrote:
Both Vessel and Engineer brands are very good Japanese brands I have a bunch of tools from both brands. You can find them everywhere here in Japan, not sure about other countries though..
For reference, here is the output on my somewhat adjusted TG501A measured on my 1GHz TDS784C scope.
1ns -
2ns -
5ns -
Marker Output @ 0.1us -
+Trig Output @ 0.1us -
I found that my usual plastic adjustment screwdriver with the little metal tip would affect the adjustments for the 2ns and 1ns trimmer capacitors, making accurate adjustment almost impossible.
I guess the little metal tip was changing the capacitance just enough to alter the rather touchy adjustments. Switching to a ceramic screwdriver made it a breeze (I also have cheap ebay ceramic screwdrivers that work great).
Also, I found that putting the side cover on made a small impact to the output amplitude, probably due to the close proximity of the grounded cover plate to the trimmer capacitors.
Luckily the cover plate on the TG501A is a perforated style, so I could juuussstt squeeze the screwdriver in through the holes (sometimes at an angle) with the cover plate in place to tweak the trimmer pots for the best output.
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Re: TG501 2ns & 1ns operation
On Fri, Dec 3, 2021 at 08:15 AM, Jared Cabot wrote:
Both Vessel and Engineer brands are very good Japanese brands I have a bunch
of tools from both brands. You can find them everywhere here in Japan, not
sure about other countries though..
Jared, I was able to find these two brands on AMAZON. Vessel makes a great set of JIS Screwdrivers as well, invaluable when working on Japanese equipment. I also found some very high quality, German made Pozi-Drive screwdrivers there. As a professional motorcycle mechanic, I was exposed early on to high quality Japanese tools. HONDA used many KOWA SEIKI brand tools. I have owned and used these for 40+ years. There is definitely a difference in the quality of the Japanese tools. -- Michael Lynch Dardanelle, AR
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On Fri, Dec 3, 2021 at 12:15 AM, Mike Merigliano wrote:
There is an excellent document on fixing the older analog scopes called
"Troubleshooting Your Oscilloscope: getting down to basics" (I can send this
too). It really stresses diagnostics, many of which involve the front-panel
(switches, etc.), and discourages taking the cover off until you have a fair
idea of what part of the scope is faulty.
Mike, Great advice that needs to be repeated. "Troubleshooting Your Oscilloscope: Getting Down to Basics" is a cornerstone of the repair process. I was fortunate to find this early on, when entering this hobby. This technique is just good basic diagnosis, and a system which can be applied to any piece of complex equipment. I would encourage anyone who is getting into (or back into) this hobby/profession; to follow the procedures outline in that work. This will eliminate many a "wild goose chase" or "rabbit hole exploring". I understand that it is tempting to rip into the scope (been there, done that). Along with the troubleshooting guide, a study of the Service and Operators manual in general and the Theory of Operation or Circuit Description in particular; will be most helpful. . -- Michael Lynch Dardanelle, AR
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Re: TG501 2ns & 1ns operation
Both Vessel and Engineer brands are very good Japanese brands I have a bunch of tools from both brands. You can find them everywhere here in Japan, not sure about other countries though..
For reference, here is the output on my somewhat adjusted TG501A measured on my 1GHz TDS784C scope.
1ns -
2ns -
5ns -
Marker Output @ 0.1us -
+Trig Output @ 0.1us -
I found that my usual plastic adjustment screwdriver with the little metal tip would affect the adjustments for the 2ns and 1ns trimmer capacitors, making accurate adjustment almost impossible.
I guess the little metal tip was changing the capacitance just enough to alter the rather touchy adjustments. Switching to a ceramic screwdriver made it a breeze (I also have cheap ebay ceramic screwdrivers that work great).
Also, I found that putting the side cover on made a small impact to the output amplitude, probably due to the close proximity of the grounded cover plate to the trimmer capacitors.
Luckily the cover plate on the TG501A is a perforated style, so I could juuussstt squeeze the screwdriver in through the holes (sometimes at an angle) with the cover plate in place to tweak the trimmer pots for the best output.
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Re: Tektronix 1900 NTSC test signal generator - basically dead
Toby -
Do you collect and restore analog TV equipment?
--
Dale H. Cook, GR/HP/Tek Collector, Roanoke/Lynchburg, VA
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WTB(US): 2x tektronix 7s11 & 1x tektronix 7t11
I posted this wanted ad on the eevblog forum, but someone recommended I might have more luck here. I hope this kind of post is allowed in this group.
As the title suggests, I want to purchase two 7s11 and one 7t11(a) modules for the 7000 series oscilloscope. I can't bring myself to pay the imo ridiculous ebay prices for the 7t11, and the 7s11's listed there aren't much better. I just purchased a 7904a and two s-3a sampling heads, and I'm eager to get them working. Looking to pay 200 (or more, or less, preferably less lol) + shipping for a set of these 3 modules. I'm located in USA 55033 and would drive 2 hours to meet, or just ship them. Thanks.
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Hello,
The TekScopes articles mentioned earlier are a great place to start. If you lost track of them or cannot find them, contact me at <mmerigATsilverstarDOTcom> and I will send you pdf's.
If I remember correctly, your 453 does not trigger on any channel, nor A or B. Does it have a sweep?
There is an excellent document on fixing the older analog scopes called "Troubleshooting Your Oscilloscope: getting down to basics" (I can send this too). It really stresses diagnostics, many of which involve the front-panel (switches, etc.), and discourages taking the cover off until you have a fair idea of what part of the scope is faulty. You may be lucky and surprised that the scope is basically okay except for a bad switch or something like that. Do you have another scope to check the 453 with?
Although it's tempting to just dive in and replace parts and see what happens, there are of course hundreds of them. Read the documents, think about where the fault(s) could be, take good notes on your diagnoses and any parts testing or repairs. If you get stuck after this, that's when the experts on this group will really shine.
The 453 I have hardly worked when I got it (just a dot, and only on one channel unless I used the beam finder).? There were two bad transistors (leads broken) and another that was put in its socket wrong. Fixing these restored nearly everything to normal.
I think these 453's (and similar) are industrial marvels, and the build quality is amazing. They are also pretty easy to work on, and more fun than a Rubik's Cube.
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On 11/30/2021 10:03 AM, quadzillatech@... wrote: any idea where to start checking then?,is there any common components can cause this?
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Re: TG501 2ns & 1ns operation
Or Vessel ceramic screwdrivers from Japan.? I used them in the early 2000's to adjust inductors in an oscillator.? Way easier than using a regular metal screwdriver; the oscillator drifted off frequency when I pulled it away.? Really annoying!? ? ? ? ?Jim Ford?Sent from my Verizon, Samsung Galaxy smartphone
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-------- Original message --------From: Tom Lee <tomlee@...> Date: 12/2/21 6:02 PM (GMT-08:00) To: [email protected] Subject: Re: [TekScopes] TG501 2ns & 1ns operation Re: non-conductive toolsI often make my own from cast-off bits of FR4. A little filing action, and you've got your tool. Works great.--Tom-- Prof. Thomas H. LeeAllen Ctr., Rm. 205350 Jane Stanford WayStanford UniversityStanford, CA 94305-4070 12/2/2021 17:47, Dave Peterson via groups.io wrote:>?? The schematic depiction of switches in Tek schematics isn't always clear to me.>> Yes, I was clear on the 5, 2, and 1 ns circuits - really the 5ns and 1/2ns circuits, and that K450 switches between them. Thus my confusion regarding K450 DE-activating in 1ns mode. I further missed that in NOT 5ns mode the base of Q460 is pulled up by the disconnection of the 5ns pushbutton (S450A) and R451. And checking the 2ns and 5ns output I now understand why the 5ns mode jumps up in DC offset compared to the 2ns output. Incremental understanding.>> So the 2ns Filter output is disconnected from MARKER OUT, Q460 is off, anode of CR468 is pulled down by R465, and MARKER OUT is floating. That explains is susceptibility to noise. Recall I'm the guy who has Sutro Tower looming over my house blasting me with 100MHz broadcast frequencies. Still, the proximity of the 500MHz/2ns signal out of the 2ns Filter is plenty to appear on the MARKER OUT.>> I had (in the pictures) the 2ns level C515 set for a large output. Adjusting it to a minimum 2ns level results in a significantly smaller "noise" level on MARKER OUT in 1ns mode. No surprise. There also seems to be a balance between maximum 2ns level and maximum 1ns level. As this is all a tuned resonant type circuit, I'm not surprised. I'm working on rebuilding my small signal analysis chops. And again, I'll say I'm closer to full understanding. But it's always a closer approximation - never quite fully there.>> As an aside, since you brought it up: I've been looking for a suitable non-capacitive trimming screwdriver. I just tried making one out of hard plastic, but these aged devices tend to be kind of sticky. It can't stand up to the torque needed to turn some of the caps. So I have to resort to a metal trimmer to get the caps turned. I can do incremental adjustments and get the effects I need.>> I've been wary of buying plastic non-capacitive trimmers online. I suspect they'll be no better than I've been able to make myself. You mentioned ceramic. Do you have a particular brand or source for such? An Amazon link perhaps?>> Thanks.Dave>>>????? On Thursday, December 2, 2021, 04:18:29 PM PST, Raymond Domp Frank <hewpatek@...> wrote:>?? >?? On Fri, Dec? 3, 2021 at 12:41 AM, Dave Peterson wrote:>>> Nope, not intended nor expected. But I don't expect to see the MARKER OUT>> output to be putting out anything while in 1ns mode. The 1ns output on the 1ns>> ONLY BNC is otherwise fine - as good as my equipment can make out.>> The MARKER OUT should be pulled up by Q460, and I'm seeing a crappy 40mV ~2ns>> (500MHz) sine wave. I've taken a look at Q460. It's not socketed, so I'm not>> going to pull it at this point to check on a curve tracer. Not yet anyway. I>> would like to know what is expected. Am I right that it should be near +5v>> (minus a diode drop?)?>>> I'm not sure if you realize that 2ns and 1ns aren't generated by the 5ns+ circuits; they are separated by K450-S1, which selects either all 5ns+ signals or both the 1ns and 2ns signals. The fact that you can see 1,2 ns and 5ns+ signals indicates that K450-S1 does its selection job. For 1ns and 2ns, everything "above" K450-S1, i.e. from P468, doesn't count.>> The 2ns signal is the bandwidth-filtered result of a dirty signal going into the 2ns filter (CL510, C/L511, C/L512, CL513).> CR515 "sharpens" that signal, creating harmonics, which are then bandwidth-filtered out by C/L517, C/L518, C/L519 and C/L5120. the result is a "soft" signal with a frequency of 1GHz, presented at the "1ns only" BNC socket.>> The irregular 2ns signal in your picture looks like the result of mixing, caused by leakage: Bad screening by the aluminium cage covering the 1ns and 2ns etc. circuits may cause this. It should be a pretty tight and complete fit. Just the screws holding it in place and making contact isn't enough.> If you can make a setup where you can put pressure on the cage with power on, I wouldn't be surprised if the signal shape of 1ns and 2ns signals visibly varies, depending on pressure exerted on the cage cover.> If that is so, you may want to remove the cage lid and bend its sides together, even to a slightly smaller than 90 degree angle. Use some tool to fit the lid on and put in the screws.> Next, perform the adjustment for the 2ns and 1ns signals (C/L510 ...C/L520), unless everything looks perfect already. Preferably use a ceramic screwdriver, definitely not one with a metal tip. Simple peaking of the signal and watching for a regular signal on your scope will do the job; first 2ns, then 1ns, and repeat until no more changes. This usually is enough to achieve excellent results. The BW of your 'scope is only important in so far as it is able to show and trigger on the signal. Correct amplitude is not important.>> Raymond>>>>>>??? >>> >>
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Re: TG501 2ns & 1ns operation
Dave,
I bought a set of ceramic screwdrivers about a year ago, from Amazon. The best thing I can say about them is that they were inexpensive. They are also very cheap. They do, however, get the job done, and I don't worry about breaking or losing them (as I said: inexpensive).
Somewhere, in my mess of a lab, I should have some ceramic screwdrivers that I bought back in the early 90s, and those were, if my memory is not betraying me, much better made than the ones I bought recently.
I also have a couple of sets of TV trimmer tools, some old, some new. They are all quite cheaply made, but they also do the job for which they were intended.
I like Tom's suggestion to construct your own from bits of FR4. I think I even have a couple of old non-conductive screwdrivers that are basically that; the shafts are made from fiberglass rod. Making your own is probably a good plan, as the ones I have seem to have aged poorly (maybe I need to reshape the tips, which appear to have lost their corners with use).
-- Jeff Dutky
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Re: TG501 2ns & 1ns operation
Re: non-conductive tools
I often make my own from cast-off bits of FR4. A little filing action, and you've got your tool. Works great.
--Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
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On 12/2/2021 17:47, Dave Peterson via groups.io wrote: The schematic depiction of switches in Tek schematics isn't always clear to me.
Yes, I was clear on the 5, 2, and 1 ns circuits - really the 5ns and 1/2ns circuits, and that K450 switches between them. Thus my confusion regarding K450 DE-activating in 1ns mode. I further missed that in NOT 5ns mode the base of Q460 is pulled up by the disconnection of the 5ns pushbutton (S450A) and R451. And checking the 2ns and 5ns output I now understand why the 5ns mode jumps up in DC offset compared to the 2ns output. Incremental understanding.
So the 2ns Filter output is disconnected from MARKER OUT, Q460 is off, anode of CR468 is pulled down by R465, and MARKER OUT is floating. That explains is susceptibility to noise. Recall I'm the guy who has Sutro Tower looming over my house blasting me with 100MHz broadcast frequencies. Still, the proximity of the 500MHz/2ns signal out of the 2ns Filter is plenty to appear on the MARKER OUT.
I had (in the pictures) the 2ns level C515 set for a large output. Adjusting it to a minimum 2ns level results in a significantly smaller "noise" level on MARKER OUT in 1ns mode. No surprise. There also seems to be a balance between maximum 2ns level and maximum 1ns level. As this is all a tuned resonant type circuit, I'm not surprised. I'm working on rebuilding my small signal analysis chops. And again, I'll say I'm closer to full understanding. But it's always a closer approximation - never quite fully there.
As an aside, since you brought it up: I've been looking for a suitable non-capacitive trimming screwdriver. I just tried making one out of hard plastic, but these aged devices tend to be kind of sticky. It can't stand up to the torque needed to turn some of the caps. So I have to resort to a metal trimmer to get the caps turned. I can do incremental adjustments and get the effects I need.
I've been wary of buying plastic non-capacitive trimmers online. I suspect they'll be no better than I've been able to make myself. You mentioned ceramic. Do you have a particular brand or source for such? An Amazon link perhaps?
Thanks.Dave
On Thursday, December 2, 2021, 04:18:29 PM PST, Raymond Domp Frank <hewpatek@...> wrote:
On Fri, Dec? 3, 2021 at 12:41 AM, Dave Peterson wrote:
Nope, not intended nor expected. But I don't expect to see the MARKER OUT
output to be putting out anything while in 1ns mode. The 1ns output on the 1ns
ONLY BNC is otherwise fine - as good as my equipment can make out.
The MARKER OUT should be pulled up by Q460, and I'm seeing a crappy 40mV ~2ns
(500MHz) sine wave. I've taken a look at Q460. It's not socketed, so I'm not
going to pull it at this point to check on a curve tracer. Not yet anyway. I
would like to know what is expected. Am I right that it should be near +5v
(minus a diode drop?)?
I'm not sure if you realize that 2ns and 1ns aren't generated by the 5ns+ circuits; they are separated by K450-S1, which selects either all 5ns+ signals or both the 1ns and 2ns signals. The fact that you can see 1,2 ns and 5ns+ signals indicates that K450-S1 does its selection job. For 1ns and 2ns, everything "above" K450-S1, i.e. from P468, doesn't count.
The 2ns signal is the bandwidth-filtered result of a dirty signal going into the 2ns filter (CL510, C/L511, C/L512, CL513).
CR515 "sharpens" that signal, creating harmonics, which are then bandwidth-filtered out by C/L517, C/L518, C/L519 and C/L5120. the result is a "soft" signal with a frequency of 1GHz, presented at the "1ns only" BNC socket.
The irregular 2ns signal in your picture looks like the result of mixing, caused by leakage: Bad screening by the aluminium cage covering the 1ns and 2ns etc. circuits may cause this. It should be a pretty tight and complete fit. Just the screws holding it in place and making contact isn't enough.
If you can make a setup where you can put pressure on the cage with power on, I wouldn't be surprised if the signal shape of 1ns and 2ns signals visibly varies, depending on pressure exerted on the cage cover.
If that is so, you may want to remove the cage lid and bend its sides together, even to a slightly smaller than 90 degree angle. Use some tool to fit the lid on and put in the screws.
Next, perform the adjustment for the 2ns and 1ns signals (C/L510 ...C/L520), unless everything looks perfect already. Preferably use a ceramic screwdriver, definitely not one with a metal tip. Simple peaking of the signal and watching for a regular signal on your scope will do the job; first 2ns, then 1ns, and repeat until no more changes. This usually is enough to achieve excellent results. The BW of your 'scope is only important in so far as it is able to show and trigger on the signal. Correct amplitude is not important.
Raymond
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Re: TG501 2ns & 1ns operation
The schematic depiction of switches in Tek schematics isn't always clear to me.
Yes, I was clear on the 5, 2, and 1 ns circuits - really the 5ns and 1/2ns circuits, and that K450 switches between them. Thus my confusion regarding K450 DE-activating in 1ns mode. I further missed that in NOT 5ns mode the base of Q460 is pulled up by the disconnection of the 5ns pushbutton (S450A) and R451. And checking the 2ns and 5ns output I now understand why the 5ns mode jumps up in DC offset compared to the 2ns output. Incremental understanding.
So the 2ns Filter output is disconnected from MARKER OUT, Q460 is off, anode of CR468 is pulled down by R465, and MARKER OUT is floating. That explains is susceptibility to noise. Recall I'm the guy who has Sutro Tower looming over my house blasting me with 100MHz broadcast frequencies. Still, the proximity of the 500MHz/2ns signal out of the 2ns Filter is plenty to appear on the MARKER OUT.
I had (in the pictures) the 2ns level C515 set for a large output. Adjusting it to a minimum 2ns level results in a significantly smaller "noise" level on MARKER OUT in 1ns mode. No surprise. There also seems to be a balance between maximum 2ns level and maximum 1ns level. As this is all a tuned resonant type circuit, I'm not surprised. I'm working on rebuilding my small signal analysis chops. And again, I'll say I'm closer to full understanding. But it's always a closer approximation - never quite fully there.
As an aside, since you brought it up: I've been looking for a suitable non-capacitive trimming screwdriver. I just tried making one out of hard plastic, but these aged devices tend to be kind of sticky. It can't stand up to the torque needed to turn some of the caps. So I have to resort to a metal trimmer to get the caps turned. I can do incremental adjustments and get the effects I need.
I've been wary of buying plastic non-capacitive trimmers online. I suspect they'll be no better than I've been able to make myself. You mentioned ceramic. Do you have a particular brand or source for such? An Amazon link perhaps?
Thanks.Dave
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On Thursday, December 2, 2021, 04:18:29 PM PST, Raymond Domp Frank <hewpatek@...> wrote: On Fri, Dec? 3, 2021 at 12:41 AM, Dave Peterson wrote:
Nope, not intended nor expected. But I don't expect to see the MARKER OUT
output to be putting out anything while in 1ns mode. The 1ns output on the 1ns
ONLY BNC is otherwise fine - as good as my equipment can make out.
The MARKER OUT should be pulled up by Q460, and I'm seeing a crappy 40mV ~2ns
(500MHz) sine wave. I've taken a look at Q460. It's not socketed, so I'm not
going to pull it at this point to check on a curve tracer. Not yet anyway. I
would like to know what is expected. Am I right that it should be near +5v
(minus a diode drop?)?
I'm not sure if you realize that 2ns and 1ns aren't generated by the 5ns+ circuits; they are separated by K450-S1, which selects either all 5ns+ signals or both the 1ns and 2ns signals. The fact that you can see 1,2 ns and 5ns+ signals indicates that K450-S1 does its selection job. For 1ns and 2ns, everything "above" K450-S1, i.e. from P468, doesn't count. The 2ns signal is the bandwidth-filtered result of a dirty signal going into the 2ns filter (CL510, C/L511, C/L512, CL513). CR515 "sharpens" that signal, creating harmonics, which are then bandwidth-filtered out by C/L517, C/L518, C/L519 and C/L5120. the result is a "soft" signal with a frequency of 1GHz, presented at the "1ns only" BNC socket. The irregular 2ns signal in your picture looks like the result of mixing, caused by leakage: Bad screening by the aluminium cage covering the 1ns and 2ns etc. circuits may cause this. It should be a pretty tight and complete fit. Just the screws holding it in place and making contact isn't enough. If you can make a setup where you can put pressure on the cage with power on, I wouldn't be surprised if the signal shape of 1ns and 2ns signals visibly varies, depending on pressure exerted on the cage cover. If that is so, you may want to remove the cage lid and bend its sides together, even to a slightly smaller than 90 degree angle. Use some tool to fit the lid on and put in the screws. Next, perform the adjustment for the 2ns and 1ns signals (C/L510 ...C/L520), unless everything looks perfect already. Preferably use a ceramic screwdriver, definitely not one with a metal tip. Simple peaking of the signal and watching for a regular signal on your scope will do the job; first 2ns, then 1ns, and repeat until no more changes. This usually is enough to achieve excellent results. The BW of your 'scope is only important in so far as it is able to show and trigger on the signal. Correct amplitude is not important. Raymond
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Re: TG501 2ns & 1ns operation
On Fri, Dec 3, 2021 at 01:18 AM, Raymond Domp Frank wrote:
I'm not sure if you realize that 2ns and 1ns aren't generated by the 5ns+
circuits;
Of course, all signals have a common frequency source (variable timing out is a special case). Raymond
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Joe
Dave Peterson
Michael W. Lynch
Jared Cabot
Raymond Domp Frank
Dale H. Cook