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Re: TDS460A Will not turn on?
I¡¯m kind of surprised they handed out ¡°seconds¡± to JA folks. In ¡®79 I was a JA advisor at Opto div, at that time if JA needed it JA got it. We did an electronics project and our division PCB designer laid it out, the manufacturing div made the PCB and our div controller certified the books, HP really went all out for JA.
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At the time I was there were several amazing things I found, the 7 segment displays for Cadillac were color/intensity matched an order of magnitude better than the eye could resolve. We started building transistors for one of the instrument divisions because our Fab Dept had better quality control. This is why I never understood the problem, the Opto-couplers worked fine they just seemed to break more often additionally the push to use in-house parts that were waaay cheaper than brand ¡°X¡± was high. Regards, Stephen Hanselman Datagate Systems, LLC 3107 North Deer Run Road #24 Carson City, Nevada, 89701 (775) 882-5117 office (775) 720-6020 mobile s.hanselman@... www.datagatesystems.com a Service Disabled, Veteran Owned Small Business DISCLAIMER: This e-mail and any attachments are intended only for use by the addressee(s) named herein and may contain legally privileged and/or proprietary information. If you are not the intended recipient, any dissemination, distribution or copying of this e-mail and any attachments is strictly prohibited. If you have received this e-mail in error, please immediately notify me and permanently delete the original and all copies and printouts of this e-mail and any attachments. On Aug 20, 2019, at 02:16, Dave Seiter <d.seiter@...> wrote: |
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Re: 2467B focus/astigmatism anomaly...
Chuck Harris
I tested the cap's leakage at 1KV, and it was 0.3uA.
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1uA is 1V on 1M. And here we have impedances around 10M. It is concerning, especially since the cap has 1.4kV across it. -Chuck Harris satbeginner wrote: Maybe the cap IS leaking, and heated some of the resistors on the right hand side of the schematic up? |
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Re: TDS754A
I would suggest you open it up remove the proc board and PS cover. Then blow out the dust. We have found any ¡°new¡± unit to our facility was fairly dirty. The split wall between the PS and HVPS is perforated but with small holes which clog easily.
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Regards, Stephen Hanselman Datagate Systems, LLC 3107 North Deer Run Road #24 Carson City, Nevada, 89701 (775) 882-5117 office (775) 720-6020 mobile s.hanselman@... www.datagatesystems.com a Service Disabled, Veteran Owned Small Business DISCLAIMER: This e-mail and any attachments are intended only for use by the addressee(s) named herein and may contain legally privileged and/or proprietary information. If you are not the intended recipient, any dissemination, distribution or copying of this e-mail and any attachments is strictly prohibited. If you have received this e-mail in error, please immediately notify me and permanently delete the original and all copies and printouts of this e-mail and any attachments. On Aug 20, 2019, at 07:37, Siggi <siggi@...> wrote: |
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Re: TDS460A Will not turn on?
Chuck Harris
I am duly chastened.
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You all have argued, to the internet's satisfaction, no doubt, that every opto coupler in every circuit should be replaced on sight... ;-) ...And yet, in the hundreds of switchers I have repaired over the years, I have never needed to replace even one optocoupler. How can that be??? The internet clearly knows them to be highly unreliable, and recommends that they be shot on sight. I suppose it is possible that some supplies that I didn't fix had bad optocouplers, but I would think they would have shown open loop regulation failures, since most of the optocouplers (in switchers) are used to isolate the PWM voltage regulator's feedback loop. Which, I am pretty sure isn't happening here with supplies that won't turn on. The overwhelming majority of the failures I have seen have been capacitor related. The overwhelming majority of the completely dead switchers I have seen have had bootstrap problems. I guess we will never know if I have been not fixing optocoupler failures in switching supplies all this time.... Still, I stand by my less than 1% statement. [If I were an IEEE member, I might check out the papers referenced... But, like most of my colleagues, I gave up my IEEE membership many years ago as it just had no tangible value to practicing USA EE's. Where IEEE could have earned our membership dollars is if they did anything at all to help prevent USA engineering jobs from being exported to the third world over the internet. Or, did anything to prevent H1B Visa holders from taking our jobs, and depressing our wages. But IEEE, being an international organization, considered those to be highly desirable things.] I didn't, but, if I did check out the papers, I bet I would find that the authors are panicking over a failure rate that is 4 or 5 sigma, rather than the 6 sigma usually considered human perfection by the semiconductor industry. (Note: 1 sigma= 31% good, 2 sigma= 69% good, 3 sigma= 99.3% good, 4 sigma= 99.4% good, 5 sigma= 99.97% good, 6 sigma= 99.999997% good ) At 4 or 5 sigma, with two optocouplers per switching supply, I would have to fix a lot more than a few hundred switchers to see any significant failure problem in optocouplers. So might you... How many supplies are we fixing again? -Chuck Harris Glenn Little wrote: Where I used to work, we used optocouplers to Isolate TELCO ring from our circuit and |
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Re: TDS754A
Hey Dana,
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IIRC the standby power supply that allows soft-power on is also responsible for powering the main switcher. Maybe the standby supply needs recapping. The TDS5/6/7As are also well documented to suffer from capacitor plaque. There are SMD electrolytic capacitors all over the acquisition, CPU and front panel boards. If yours hasn't been re-capped, then that's also a possible explanation for what you're seeing. Siggi On Tue, Aug 20, 2019 at 10:25 AM danadak <danaaknight@...> wrote:
This scope has been excellent to date. Now when turned on it |
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Re: TDS460A Will not turn on?
The HP optoelectronics handbook contained data on designing for aging of LEDs in optocouplers so they saw this as a real phenomenon.
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Bruce On 21 August 2019 at 01:35 Adrian <Adrian@...> wrote: |
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Re: TDS460A Will not turn on?
I would echo Chuck's thoughts about opto-couplers, they are pretty reliable but I would also remind you that a meaningful test (especially on old devices) must include checking the CTR (Current Transfer Ratio) of the device. I recently fixed a 1970s HP 8" drive and one problem was caused by an opto-coupler.
The LED side measured like a LED, the photodiode side measured like a diode but with the correct LED drive current the diode was not sinking sufficient current for the next stage to turn fully on. As you will have noticed I'm sure, some panel LEDs from the 70s & 80s have 'aged' and are very dim today and I would speculate that the same thing can happen to the LED in opto-couplers and there is just a lack of photons internally? Adrian |
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Re: Need Help Troubleshooting Tektronix PS280
Hello,
On Aug 16, 2019, at 9:27 PM, John Crighton <john.crighton@...> wrote:I¡¯ve ben doing this for three days. on my E3630A HP power supply. Still no luck. I don¡¯ have the schematic for the daughter board meter section of the supply. Further, there are NO TEST POINTS! But, I¡¯ll continue working. larry |
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Re: 7000 series carrying handles - how strong are they?
Craig Sawyers
Even with the 500 series scopes, which weighed much more, and had handles that were covered inIt was not leather, but leatherette - a plastic faux leather. Which is why it degrades over the decades (probably because the plasticiser leaches out), cracks and falls to pieces. As does the piece of fibreboard underneath it without the leatherette to protect it - and that leaves only the metal strap inside, often rusty. Craig |
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Re: 2440 cal errors
Hi,
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Yes, definitely. The FPP error is 99% because of the nvram battery failed an lost the calibration. All other fails are likely a result of it. You can verify it by going into the extended diagnostics and check the detailed result of the FPP fail. Then you'll need to replace the battery (older models) or the nvram on newer models (or hack them for external battery). But first you shoul try self cal and ext cal, without powering down the scope and see if the errors go away. They should. If not, you should still try the full calibration as desvribed in the adjustments section of the service man. Mandatory warning: don't run the scope without cover without external cooling, you risk damaging the CCDmodules. Szabolcs Robert Simpson via Groups.Io <go_boating_fast@...> ezt ¨ªrta (id?pont: 2019. aug. 19., H¨¦t 19:46): Well I guess you get what you pay for. At $50 for a 2440 should have been |
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Re: Thoughts on TDS744A
Hey Mark,
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The early TDS5/6/7 suffered terribly from capacitor plague. I have a TDS684A in parts that will probably never be anything but a parts donor. All the electrolytics on the acquisition board had leaked and caused damage to the PCB. It is possible that the scope in question has been serviced already, but in your shoes, I¡¯d want to know for sure. If the seller doesn¡¯t know, you¡¯d have to open it up and inspect the acquisition, processor and front panel boards. You¡¯ll want the scope to pass all self tests as well as signal path compensation (SPC). Another thing to watch for is the state of the CRT. The color version of these scopes use an LCD color filter over the CRT, and triple scan the raster - once for each color. Because of the color filter, the CRT is driven hard, and they tend to fade early. I have a TDS784D, which is a powerful scope. Not my favorite or first go to, though, as it¡¯s loud and slow, and has a fairly unintuitive UI. I view it as my ¡°truck¡±, reserved for heavy lifting. The TDS5/6/7Ds were largely immune to capacitor plague, as Tek had switched to SMD tantalum caps for decoupling by then. Good luck, Siggi On Tue, Aug 20, 2019 at 03:33 Mark Schoonover <mark@...> wrote:
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Re: Fan direction on TEK485
The 485 has the wonderful temp controlled Siemens motor and impeller design
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fan. It draws the air in through the enclosure and expels it at the back of the scope. On Mon, Aug 19, 2019 at 20:28 Kevin Oconnor <kjo@...> wrote:
Did the TEK factory have the fan suck air in or blow it out the back? |
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Re: Thoughts on TDS744A
Hi, I have had one for a couple of years and I'm very pleased with it.
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The fan is a bit loud for a home environment and my wife complains if my project takes over the dining room, but I can tolerate that :-) It's a bit heavy so a truly portable it is not IMHO. Dave On 16/08/2019 03:31, Mark Schoonover wrote:
Hello, |
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Re: TOPIC CHANGE: Pro's and Con's of the 576 and 577 Curve Tracers. WAS: 5xx 'Scopes
Hi Dennis,
On Tue, Aug 20, 2019 at 09:41 AM, Dennis Tillman W7PF wrote: You're right, we strayed. This is how we got here: While discussing the modular construction of the 577 curve tracer and the possibility of changing a 577D2 into a 577D1, this happened: Hi Dave,Very relevant historically, interesting and significant but you're right, not ideal for posterity unless searching for content, not topic. Raymond |
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Re: TDS460A Will not turn on?
In the late 70's I was in a Junior Achievement program sponsored by a couple of guys from HP optical (Page Mill); they took us on tours, told us lots of stories (some rather racy), and gave some of us who were interested lots of "samples" that were mostly seconds (wrong tints, poorly filled molds, loose specs, etc) from single LEDs to laser modules, but never any optocouplers.? When I asked for some, I was eventually given "real" samples because the "failure rate was so low".? At least on the types I was interested in.
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-Dave On Monday, August 19, 2019, 02:33:24 PM PDT, Chuck Harris <cfharris@...> wrote:
Steve, As a life long EE, I would not have put up with that for a minute.? Either the circuit would get redesigned, or the vendor of defective parts get banned. But, I have always been a bit of a hard-ass about stuff like that. -Chuck Harris Stephen Hanselman wrote: Chuck, |
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Re: 7000 series carrying handles - how strong are they?
I've had 2 500 series handles break on me- one should have been obvious, it was rusted badly and only the metal was left, but the other one still had remnants of it's covering on it but was also rusted badly, maybe even worse than the first one.? The inside of the second scope also showed a lot of corrosion on the aluminum and steel parts.? My guess was that it spent a lot of time near the ocean in Santa Cruz (where I picked it up). Both didn't fall far, but were pretty used up anyway- only the good parts remain...somewhere.
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-Dave On Tuesday, August 20, 2019, 01:42:43 AM PDT, Dennis Tillman W7PF <dennis@...> wrote:
Ni Nenad, Not silly. I have been carrying 7000 series scopes around for almost 50 years and I have never given the handle a second thought because I have removed so many of them from instruments I have scrapped. Every one of them is as solid as the day it was made. This applies to the outer plastic cover, the inner spring steel, the way they are attached to the instrument, and the way the rigid aluminum chassis handles all that weight. It is beautiful integration of all those parts into a very sophisticated mechanical design. Even with the 500 series scopes, which weighed much more, and had handles that were covered in leather, I never saw a handle break.? The leather might dry out and crumble in some climates but the steel hidden inside was still more than strong enough to continue doing its job of making it possible to safely lift a scope (provided you had a couple of helpers with strong backs to provide assistance). Dennis Tillman W7PF -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Nenad Filipovic Sent: Sunday, August 18, 2019 2:41 AM Well I suppose this sounds silly, but I just can't get over it. This thin metal sheet inside the handle is surely tough, high tensile strength steel, but somehow subjectively it doesn't nearly impress as the rugged 465 handle, for example. In my head thin metal sheets tear and crack. Every 7000 handle end I inspected showed some minor bending around the hole where it pulls against the main screw. So my question is, has anyone ever had that handle crack or snap? 7000s are no longer costly lab instruments handled with utmost care, today we use them in our homes, shops... They get transported probably a lot more frequently than they were intended to, possibly against some rules which were in power back then, now forgotten or never even known. Should the instrument be supported by your other hand from below? I don't use my 7104 often, but when I do I need to carry and lift it on the table. And every time I get shivers in my feet. Some reassurance would help. Best Regards, Nenad F. -- Dennis Tillman W7PF TekScopes Moderator |
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