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Re: Strange Tek2440 issue
Szabolcs, from here (TekScopes) posted a method of accessing the internal battery of the Dallas NVRAM modules using a heat gun and a scraper. The difference in these modules was that there were two batteries that were visible. Anyway I scraped down to pin 7 of the DS1210 and soldered a wire to it on each module. I ran those to a small circuit board where I had a battery holder and two diodes on it. The diodes fed the voltage to each of the modules.
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When I put it back together it didn't work. Then I noticed I forgot to plug in one of the ribbon cables! Anyway, the subject for the post I mentioned above is: Easy method for NVRAM battery replacement Vince. On 08/30/2020 05:53 PM, Bob Albert via groups.io wrote:
Not your current problem but I replaced the NVRAM chips in my 2440 and the scope doesn't work. I switched one of them back and still no joy. I will try the other one. --
K8ZW |
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Re: Strange Tek2440 issue
Bob Albert
Not your current problem but I replaced the NVRAM chips in my 2440 and the scope doesn't work.? I switched one of them back and still no joy.? I will try the other one.
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I probably got some counterfeit modules from China.? I am hoping it will be fixed when I put the old one back.? ?How did you fix yours? Bob On Sunday, August 30, 2020, 02:37:52 PM PDT, Vince Vielhaber <vev@...> wrote:
I picked up a 2440 on ebay that had the dead nvram battery problem.? Got that fixed up with an external battery.? Ran thru the self cal and ext cal and all seems fine, except when the sweep rate is turned above 100 or 200 ns. In trying to research this a bit, the only thing I could find was on one of the Tek forums back in 2017 but there were zero responses.? Here is how the other person described the problem: --------------------------------------------------------------------- The 5 volt regulated rail is getting crowbared when the scope Sec/Div is set to 100ns or faster. If save is pressed at a slower setting the Sec/Div can then be set to any value without the 5 Volt rail getting pulled down. It appears the issue only occurs during an active acquisition cycle at 100ns Sec/Div or faster. ---------------------------------------------------------------------- While I didn't measure the 5v rail, the screen shrinks a couple of times as the waveform changes, the inputs get switched to GND and the display goes blank.? Sometimes, if I'm quick enough, I can turn the sweep back down (1us or slower) and it'll recover, but I still have to go to the input coupling and switch the inputs off of GND. Anyone seen this or have any ideas what's going on? Thanks! Vince. -- ? K8ZW? ? |
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Strange Tek2440 issue
I picked up a 2440 on ebay that had the dead nvram battery problem. Got that fixed up with an external battery. Ran thru the self cal and ext cal and all seems fine, except when the sweep rate is turned above 100 or 200 ns.
In trying to research this a bit, the only thing I could find was on one of the Tek forums back in 2017 but there were zero responses. Here is how the other person described the problem: --------------------------------------------------------------------- The 5 volt regulated rail is getting crowbared when the scope Sec/Div is set to 100ns or faster. If save is pressed at a slower setting the Sec/Div can then be set to any value without the 5 Volt rail getting pulled down. It appears the issue only occurs during an active acquisition cycle at 100ns Sec/Div or faster. ---------------------------------------------------------------------- While I didn't measure the 5v rail, the screen shrinks a couple of times as the waveform changes, the inputs get switched to GND and the display goes blank. Sometimes, if I'm quick enough, I can turn the sweep back down (1us or slower) and it'll recover, but I still have to go to the input coupling and switch the inputs off of GND. Anyone seen this or have any ideas what's going on? Thanks! Vince. -- K8ZW |
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Re: Tek 4654M; No Trace, No +5V, No +95V; Help
Slight correction. From the manual, it appears TP60 (et. al.) has a 28uS period making that about 38kHz instead of 30kHz.
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Thanks, Barry - N4BUQ ----- Original Message -----
From: "Barry" <n4buq@...> |
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Re: TDS3054 Replacement of DALLAS DS1742W (U640), data content in NV-RAM
you can just throw in a completely blank chip in there, no problem
reading the old chip and writing in the new one doesn't do much and doesn't do any harm either as I have learned...specially now that the # of hours is messed up the number of hours are stored in minutes (in HEX) at 07E0-07E3 and also at 07E8-07EB (the same number repeated) that's probably the only thing you need |
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Re: Free 6 pin lemo cable and THS720 question
As far as I know, there is no menu accessible way to see the battery condition on the THS720. I think that got added to the THS730, but that may be wishful recollection on my part.
One usability issue on the THS720 that is worth keeping in mind is that the two input channels do not share a ground. For low speed stuff with other scopes, I commonly just ground an unused input channel to the board under test and then wrap the ground lead of the probe that I am using arount the probe cable to keep it out ot the way. That does not work on the THS720! Each input channel must have it's own ground connection. The THS720 is a really handy little scope! I like mine a lot. Thanks for the article on building the battery packs! BobH |
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TDS3054 Replacement of DALLAS DS1742W (U640), data content in NV-RAM
Hello all,
a TDS3054 (built in year 2001) shows the following symptoms when connected to power: - 'A system error has occured', Error Count =11, 'display error', goes away after short power off/on - Unrealistic high 'total operation time' (16350105 hours) - Impossible time setting (e.g. '11:80:21') Topic #157465 also deals with this issue, the problem is data corruption inside U640 DALLAS DS1742W, exhausted lithium battery, date code on the package is '0029'. I ordered replacement DS1742W via Amazon in China (the chips I received seem fully functional when tested on a programmer), date code on the package is '0945'. How should I prepare the new DS1742W I am going to install in the scope? Simply read out the (most probably) rubbish of the old DS1742W and copy it to the new one? Is a memory map available somewhere which shows the addresses of the relevant memory locations and their expected content in a working scope? (the address locations 0x7F8...0x7FF are described in the DS1742W data sheet) I cannot believe that appr. 2k of memory are fully used to store internal scope status data. Thanks for any help! Best regards -Roland |
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Re: Tek 4654M; No Trace, No +5V, No +95V; Help
Harrison,
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If you suspect the multiplier is bad, you can disconnect its input by unsoldering the wire to the transformer. You can see that in the the picture of the HV board that I added just now here: /g/TekScopes/album?id=252850 If I remember correctly, you have to be somewhat careful that the wire is not close enough to arc back to the transformer. I remember that happening and had to move it a bit further away so that I could have the rest of the HV circuit operating but not engage the multiplier. If you have a meter that can measure the output of the transformer (I forget the output value but it would theoretically be 1/3 of the anode voltage and it's at around 30kHz as I recall), then you might could establish that everything else works up to that point. Thanks, Barry - N4BUQ ----- Original Message -----
From: "n4buq" <n4buq@...> |
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Re: DEC PDP11/05 on a 202D cart - did one survive?
From Tim P (UK)
I don't know if you have seen the P7001 section on TekWiki - it's under 7000 series, as it uses the 7704A. Lots of pictures of the 'guts' of the P7001 and some stuff on the interfacing. I would be interested in how many were sold, and who bought them. (Chuck, do you know??). Tim On Sun, 30 Aug 2020 at 16:17, Holger L¨¹bben <tekscopesinput@...> wrote: Hi! |
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Re: Tek 4654M; No Trace, No +5V, No +95V; Help
Hi Harrison,
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Yes, the 3x multiplier is U550. For mine, even after I replaced it, I did some testing on it and, at lower voltages, it would triple the input voltage; however, it appeared that at operating voltage, it would arc internally thus blowing the fuse. If I'm not mistaken, this is a common failure for that module after all these years. There's a thread on/around October 7, 2017, where the messages for that can be found. Thanks, Barry - N4BUQ ----- Original Message -----
From: "Harrison" <buma7@...> |
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DEC PDP11/05 on a 202D cart - did one survive?
Hi!
I've added an old picture of a Tektronix DPO/DEC PDP 11/05 combination on a 202D cart to the photo section: /g/TekScopes/photo/252847/0 Has one of these machines survived? I'm looking for some detailed pictures of this combination. Holger |
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Re: Reverse part lockups
On Sun, Aug 30, 2020 at 04:02 PM, Lawrance A. Schneider wrote:
I have -151 ready, just waiting for "permission"(?) to upload. Good OCR and size reduced to 196MB with little quality degradation. Non-reduced is also available, almost same size as before. Raymond |
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Re: Tek 4654M; No Trace, No +5V, No +95V; Help
In circuit tests of these components will be quite meaningless because of
the low impedance components connected to them and the other semiconductors connected across them, such as CR556 across Q556 b-e junction. The only accurate way to test is to remove them and test out of circuit. Before you start removing parts, have you replaced the fuse and checked for 55v across C558? Q552 and Q556 comprise a blocking oscillator which provides primary excitation for T550. This oscillator cannot function without the 50 volt bias at T550 pin 4 (or across C558). Q554 and Q548 are control circuits which regulate the blocking oscillator output to provide a stable +95volts. The voltages across C721, C741 and C761 all look good, so they are not the problem. Dave On Sat, Aug 29, 2020 at 07:38 PM, Harrison wrote: On Sat, Aug 29, 2020 at 10:28 PM, Harrison wrote:
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Re: Tek 4654M; No Trace, No +5V, No +95V; Help
Read out the voltages across C721. Also read out C741 and C761. Used the Beckman HD110 MM with the common to ground. C721; three of four pins read zero, both AC and DC. The fourth pin read 55.5V DC and 0.240V AC. C741; four of five pins read zero, both AC and DC. The fifth pin read 11.4V DC and 0.068V AC. C761; four of five pins read 11.3V DC and 0.078V AC. The fifth pin read zero, both AC and DC.
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Re: Tek 4654M; No Trace, No +5V, No +95V; Help
Hi Harrison,
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Back in 2017, I worked on my 465M. The following is from an email I sent outlining what I did. Perhaps that will help since it sounds very similar to what you're seeing with yours. ------------------------------------------------------------------------------------------------ And, so, to recap - after getting the scope on the cheap via a Craglist buy and finding it inoperative: 1. Filter capacitors were bad and restuffed them with new capacitors 2. Accidentally bumped L582 (in the +95V filter) damaging it beyond repaid so replaced it ("repaid" should have been "repair" - Barry) 3. Scope then worked for about 15 minutes and then pfffffft - F558 blew 4. Found Q552 was bad and replaced it but the HV oscillator was now drawing excessive current blowing F558 again 5. Multiplier was bad and replaced it and scope appears to be working again ------------------------------------------------------------------------------------------------ BTW, the 465M still works fine - at least the last time I used it several months ago. Thanks, Barry - N4BUQ ----- Original Message -----
From: "Harrison" <buma7@...> |
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Re: Tek 4654M; No Trace, No +5V, No +95V; Help
I will check out voltages across C721. Since my last posting I did some reading after which I decided to look closer at the HV Oscillator and HV Regulator circuits. I did an in circuit check of Q556, Q552, Q548, Q544, C548, and L554. I used my beckman DMM in the diode mode or the SZBJ BM4070 digital LCR tester. All seemed to check out okay except the Q552 (part of the HV Oscillator circuit). I plan on removing it, doing an out of circuit test and replace it regardless. But if I understand the manual correctly that circuit has a direct impact on the oscillation and output of T550.
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Raymond Domp Frank
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