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New-to-me 2445A - General Q&A, and where to start
Hi everyone!
I've had a 453A for a while now and recently a 150 Mhz 2445A (w/ Options 5 & 9) followed me home. Was hard to say no just for the measurement capabilities alone over my 453, I actually only found out about the options afterwards. I've already done a bit of repair (the usual broken knob) and the A/B sweep rate switch had dirty contacts and stayed O/C) I've been reading up and so far I've noted a few items I plan to do in the short term: 1. Replace the RIFA X2 firecrackers in the PSU, before they go. 2. Back up the calibration data from SRAM. (I'll do this with a video/Exer 02 first but I also have a GPIB addon on order for easier dump/restore). I believe the scope should warn me once SRAM battery voltage gets low in order to replace said battery as needed. 3. Look at sticking a heatsink on U800? 4. General cleaning, of course. Inside looks very good from what I've seen so far. Seems to have been well cared for. Also, print out the manuals for easier reference. I'd like to ask the hive mind what else I should consider adding to the list in terms of preventive maintenance, quality-of-life improvements and possible performance upgrades to get things running as best I can for a hobbyist workbench. (I don't have the gear/funds to do a full-service calibration, btw, or that would be the obvious answer). I've noticed a few things I wanted to ask folks more experienced with this model for thoughts/advice: - Occasionally there are "sparkles" on the display (random dots here and there). Not frequent, and they seem to go away if I turn down the readout intensity. I'm guessing an aged component that needs checking/replacing, or perhaps a crusty connector. - Despite adjusting the focus knob and spot-checking the astig control, the display seems a little fuzzy. Maybe the 453 has spoiled me and it's normal for this model, but if not, worth chasing down and fixing? Can try to provide a picture if it's helpful. Additionally, some (admittedly, probably very n00b) questions: - What are folks' recommendations on parts sources other than trawling ebay? I've already become acquainted with the gentleman in Greece but was wondering if there's a good supply stateside. I'm missing a few things like the front cover and word recognizer probe which, while not critical, are certainly nice to have. - Advice for flattening a curled graticule? The scope came with the stock + TV option ones, and the CCIR one has quite a curl to it. I'm guessing the usual plastic flattening methods of a heat gun on low + flat surfaces + weight would work, but did want to ask first. - Thoughts on retrofitting a DMM option (01)? Realize this might be a bit of a stretch as it requires case replacement too, but if I should find the parts, is it a worthwhile/practical add-on, or does even a typical DMM from today have more value/performance? Thanks all! -B |
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Re: 7603 Beam Sharpness
On Wed, Aug 21, 2019 at 01:59 PM, Jason A. wrote:
Hi Jason: You can also check out the downloadable Tek Concepts Series books by DeVere, on the TekWiki: Oscilloscope Cathode-Ray Tubes, 2nd ed. Storage Cathode-Ray Tubes and Circuits, 2nd ed. ¡ and with some trepidation, I can point you to a discussion thread on the forum entitled "7904 excessive shadow/flare"... there's a few other threads on the forum to about expansion meshes, in Tek CRTs... but the one I quoted is my fav. Best regards and wishes. Roy |
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Newly reworked Tektronix "XYZ of Oscilloscopes"... well new to me anyway.
Hi All:
Tek just talked me into downloading their new... well new to me anyway... their newly reworked "XYZ of Oscilloscopes. This one has a snazzy motif of a DSO screen, displaying multiple signals. There is no mention of analog oscilloscopes in the index anymore. (They are briefly discussed in the text as MSOs.) If you want to check it out, the link is at: (I tested it with copy and paste) Best regards and wishes all. P.S. Either Tek or... me and my Tek gear... are not in Kansas anymore. Ya, it's probably all me. |
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Re: 7603 Beam Sharpness
Wow. Thank you for the education on the expansion mesh. It makes complete sense why the 500-series tube-based equipment have such sharp traces - they were using much higher voltages on the deflection plates than the solid state gear, which made it a lot easier to "bend" the beam while keeping it focused. I also learned that the T2440 CRT had a different method of 'expanding' the deflection. I always love learning about the technology behind the equipment!
My quick education came from here, here and here: Considering what I just learned, it sounds like the 2430, 2440, 2445 and 2465 oscilloscopes should be the best compromise available given the considerations of modern analog convenience and sharpest traces. Thanks again for the enlightenment! |
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Re: Tek 576 chatters
Peter,
Here are some comments regarding the 576, 577, and TDS644A. Yes, the brown HV transformer is the bad kind, so it will likely crap out soon. The symptoms are about right. The 576 v. 577 discussion will likely never end, because they each have their pluses and minuses, and either is a fine CT for most uses. There is no consensus, except that it's nice to have both. The TDS series scopes, as far as I can tell, all use a similar PS topology, but unfortunately not identical in the details. I had to fix the standby PS in a TDS544A a while back. As I recall, the main supply/preregulator is a power factor correction (PFC) type. In its common form, it is a boost converter, so it is set up to make preregulated DC somewhat above the highest expected peak voltage of the power line - typically 350-375 V for 240 V operation, or doubled 120 V in a dual-range configuration. In a full-range, continuous coverage design, the input line can be anything between the lowest and highest line possible, in any country. I think the ones I have (TDS 544A, 754A, and 820) are full-range, but there may be some that use dual-range. Regardless of this detail, the highest expected rectified raw DC should be somewhat less than 400 V, so somewhere around there is what the PFC converter is designed to put out, and still provide regulation. All lower voltages are simply boosted up to this level, giving very wide coverage. It's been a while since I studied it, but I think that in standby, the PFC is actually running all the time too, and the standby supply runs from the PFC output. It isn't necessary for the PFC to be running all the time, since when it's off, the rectified DC from the line passes through, but would not be boosted or regulated. This would be OK too, since the standby supply should be able to operate over a wide input range too. Either arrangement can work, but controlling the on and off states would be different. The standby supply keeps it ready to go, and supplies power for scope-side circuits, including the one-bit memory (I think it's a latching relay) of its last power state. When the power button is pushed, the state is switched to the opposite of whatever it was. In the case of turning the scope on, the PFC converter is activated - if it's not always on anyway - then the main output chopper fires up, converting the 400 VDC to the low voltage secondaries. Anyway, in standby, you may see the input voltage to the standby converter be something similar to the peak of the input AC, or fixed near 400 V, depending on the implementation details. In the scope on state, this voltage should be around 400 V. Ed |
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Re: 7603 Beam Sharpness
Many photos of scopes in general have the intensity turned up so that the traces are easily visible, which makes the traces fatter.? That said, the 7603 when adjusted, will have nice traces, but because of the expansion mesh, will never have the razor thin lines of a 500 series scope.? (the 547 for example)? My T912 has really fat traces, but is still usable.
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-Dave On Wednesday, August 21, 2019, 12:18:37 PM PDT, Jason A. via Groups.Io <jagee228@...> wrote:
Hello All, Curiosity question for the group.? I've been contemplating trying to find a nice 7603.? I've looked online at the google images of traces and readouts on the screens of the 7603, however most of the traces I see online look fairly blurry.? I know a lot of these scopes put a plastic filter/implosion shield in front of the actual CRT face and those can eventually get a lot of scratches and the like on them, making everything behind them look out of focus.? I am guessing there are plenty of people on the forums that have a 7603 and can offer their opinions on it as a general purpose 7000 series scope, including commenting on the apparent blurriness I've seen on the online images as well as any potential pitfalls with them.? Other recommendations also welcomed. Thanks all and best regards, Jason |
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Re: 7603 Beam Sharpness
John Griessen
On 8/21/19 2:18 PM, Jason A. via Groups.Io wrote:
I am guessing there are plenty of people on the forums that have a 7603 and can offer their opinions on it as a general purpose 7000 series scope, including commenting on the apparent blurriness I've seen on the online images as well as any potential pitfalls with them.They're not like an old 564 for sharp traces. But 7854, 7844, 7603 is as good as 2230 and such and plenty usable. |
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7603 Beam Sharpness
Hello All,
Curiosity question for the group. I've been contemplating trying to find a nice 7603. I've looked online at the google images of traces and readouts on the screens of the 7603, however most of the traces I see online look fairly blurry. I know a lot of these scopes put a plastic filter/implosion shield in front of the actual CRT face and those can eventually get a lot of scratches and the like on them, making everything behind them look out of focus. I am guessing there are plenty of people on the forums that have a 7603 and can offer their opinions on it as a general purpose 7000 series scope, including commenting on the apparent blurriness I've seen on the online images as well as any potential pitfalls with them. Other recommendations also welcomed. Thanks all and best regards, Jason |
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Re: Tek 576 chatters
Bob Koller
I suspect that the problem you originally mentioned is a result of the 100V being loaded by the lossy HV transformer, the symptoms are classic. These transformers are difficult to find, as so many failed.
If your CRT is bright, and the balance of the instrument is in at least good condition, it is worth finding a later s/n unit for parts, or making one out of two if you find a later one with a poor CRT. The 577 is an option, they are much smaller and lighter, lower peak power, but better small current functionality. The storage version may appeal to some, but the storage CRT can be a problem if you get one with severe differential aging of the storage target, or weak flood guns. The writing gun may still be quite usable. Personally, I have and use the 576, I guess because I have bought, sold and serviced at least 100 of them. |
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Re: Tek 576 chatters
peter bunge
Thanks Bob and Chuck. Unfortunately my 576 has a brown HV transformer, I
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just looked. I also checked C759 in the 5v power supply and I replaced it a few years ago. My repair log shows how I adapted a more modern capacitor to the metal can mounting if anyone is interested. I continued with the Performance/Calibration steps without adjusting anything. When I got to p5-13 step 14 I could not see the display shown in Fig5-6 and realized this procedure was not going to be of any further help. I set the switches to look at an NPN 2N3565 at low current and curves flashed occasionally on the screen. Turning the Number of Steps knob and tapping it changed the steps but did not fix the problem. I took to tapping inside with an insulated rod and found U22 on the Step Gen board was really sensitive. Re-seating it in the (cheap) socket fixed the problem and now I get rock solid curves from 1 to 10 as selected. It has been running for over an hour without problems but I am concerned about the HV transformer. Are these HV transformers available anywhere? If it fails completely should I be looking at the newer 577? I saw someone started a thread about a comparison but it went nowhere. Is the 577 better than the 576? Now I still have the problem with the TDS 644A power supply on the other thread. I would love to hear comments on this one. Is there a parts list available that shows the correct transistor for the standby power supply? Why would a standby power supply run off 408V? I see there are good comments from Siggi. I will reply on that thread. On Wed, Aug 21, 2019 at 11:56 AM Chuck Harris <cfharris@...> wrote:
Yes, that is a consideration that I try not to think about. |
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Re: Will this capacitor fail?
Thanks for informing me C744 is a 170uF capacitor, I believe what happened I accidentally interpreted the u in uF as another zero and thought it was 1700uF, certainly made it easier finding a replacement capacitor. I am also replacing the insulator pads for U722 U732 Q788 Q766
- I think this thermal pad should work, bought it in a sheet so I can cut the pieces I want to fit. |
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Re: Tek 576 chatters
Chuck Harris
Yes, that is a consideration that I try not to think about.
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I guess I had better get my transformer business back in order this winter. -Chuck Harris Bob Koller via Groups.Io wrote: It may have a PSU problem as Chuck described. |
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Re: 7B15, 7B10 questions
Chuck Harris
Not an assertion I would make!
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I had one 7104 that had a permanently etched reverse image of a square wave and a triangle wave... obviously from a function generator. I know that there is a large contingent of folks that own these scopes, that have no real work for them, but seriously, how long could you stand to view a square wave and a triangle wave on your 7104's screen? It boggles the imagination.... well mine anyway... A more likely explanation is that the ebay seller had the function generator traces on the screen, really really bright because that is what 7104's are known for, and burned an image in the screen while preparing for, and taking a photograph... All staying within the protective timers very limited protection. The amber limited viewing LED comes on whenever the image is about what one would consider normal brightness for a 7904. You have to have a pretty dim environment to be able to run a 7104 comfortably, never activating that warning. The 2467B does a much better job of protecting the MCP. It never allows the readout to be on the screen continuously without a trace being on the screen, without putting the readout into flicker mode. It moves the readout around periodically to wear level the readout area of the MCP. It limits the trace intensity to a perceived value of screen brightness by strobing the intensity of the beam hitting the MCP. It leaves the MCP at its lowest amplification setting when the Intensity control is set to view low performance images, only raising it when the Intensity control is turned up near full... stuff like that.... In addition to the timers. -Chuck Harris Roy Thistle wrote: On Sun, Nov 19, 2017 at 10:12 AM, Dennis Tillman W7PF wrote:Hi Dennis: |
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Re: TDS 644A Power Supply problem
Hey Peter,
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I repaired one of those from a TDS684A which had failed in an interesting mode. The TVSes had become uni-directional, and so current was flowing through the TVSes, T3 and Q9 continuously. Out of circuit they measured as a diode in one direction, but as an open in the other (I didn't have any way to measure their threshold voltage). It seems only RT4/5 were limiting the current/damage at that point. I couldn't figure out why the TVSes had failed, but apparently it's not uncommon for them to do so. I suspect you'll find a very close schematic on H?kan's download page: . Looking at the schematic, it occurs to me that CR7 & C15 make a snubber, whereas the TVSen are clamps. If the snubber fails, I'd expect the TVSes and the switching transistor to suffer higher transients, so maybe that's one place to look. R21 is also perhaps suspect, as it will presumably discharge C15 between cycles. Good luck, Siggi On Tue, Aug 20, 2019 at 3:33 AM peter bunge <bunge.pjp@...> wrote:
A year ago I repaired a TDS 644A power supply.with overheated VR4 and VR5 |
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Re: Tek 576 chatters
Bob Koller
It may have a PSU problem as Chuck described.
However, if the 100V supply is being loaded, this sounds like the CRT HV transformer problem typical of the older brown encapsulated transformer design. Coupled with your comment of "However turning it off and on it ran for a few minutes then did the same thing" If your CRT HV transformer is the black silicone encapsulated type, you can disregard, but if not, that would be my very strong suspicion. |
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Re: Thoughts on TDS744A
Mark Schoonover
I got 0.07 USD for a class action lawsuit on bad motherboard capacitors
back in the day. Probably related to many different products. 73! Mark KA6WKE Website: Live Stream: YouTube Live!: Author: 4NEC2 The Definitive Guide EMail List:: [email protected] On Wed, Aug 21, 2019 at 4:27 AM greenboxmaven via Groups.Io <ka2ivy= [email protected]> wrote: The condensers you mention were a worldwide scourge. Many millions of |
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Re: 7B15, 7B10 questions
Roy,
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I got very lucky a couple weeks ago and scored a basically pristine 7104 and it's intended plugin complement at a .gov surplus auction for a very good price (all of the above for $125). It is obviously well cared for, as the crt is crisp, bright, with the only signs of any problems being around the readouts, which are a bit dim compared to the traces (which isn't unexpected I suppose). I've found it is very easy to get a perfectly usable trace for all but the fastest signals at very low brightness levels...low enough that the limited view circuit either isn't kicking in or it's in the 20 minute timeout region (beam current above 0.2 microamps, but less 2 microamps) than rather than 2 minutes (2 microamps or above). It's truly a tour de force for Tektronix analog scope engineering; beautifully crafted inside and out, with incredible performance. Sean On Wed, Aug 21, 2019 at 06:55 AM, Roy Thistle wrote:
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Jason A.
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