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Re: Looking for data on 9-pin Vacuum time delay relays used in old Tek-scopes
A few years ago the time delay relay in my 555 died and lacking a replacement I had to cobble up a substitute. I repurposed an old device I had made to trigger a super 8 movie camera (remember them?) for time lapse. That device was designed to work form a 9 volt battery. I started by rectifying the 6.3 volt supply for the time delay relay using a half wave voltage doubler with the input capacitor deliberately kept to a small value to allow the output voltage across the storage cap to rise slowly. When it got to a suitable level it triggered a SCR through a zener diode to discharge the output cap through the coil of a little relay to close the main scope relay. Once the scope relay pulls in the 6.3 supply is disconnected from the voltage doubler. A reverse biased diode from the storage cap to the +100 volt line removes any residual charge as soon as the scope is switched off so the time delay will function properly next time it's switched on.
There's plenty of room in the 555 power supply for small proto board with the circuit on it. All the parts were in my junque box so the whole thing cost nothing and provided a bit of fun. In retrospect it would have been even simpler to slowly charge a cap from the raw +100 supply which is about +165 volts according to the manual, and use that to trigger the SCR.. Morris |
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Re: 2712 SA with display (and normalization) issues
#photo-notice
On Mon, Jul 19, 2021 at 03:27 PM, Colin Herbert wrote:
OCR'ed version added. Raymond |
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Re: ++Processor error on TDS 754D on startup
Thanks for the response. If endeavoring to do this (rtc + ram), there are already a number of folks that claim to have working solutions, so I would search out their progress and find the flaws and try to find elegant workarounds. The easiest way is to find compatible no-batt rtc, and add logic around that to extend the ram. Maybe easiest is to used the latest version of the original MC148616 and i/f logic and add an fram if the are any parallel i/f available - the original has muxed a/d so that would have to be demuxed. Goal would be to try to get away with a bunch of glue logic in an XC9536 or 72. To try to recreate the ds1486 from scratch would take a tremendous verification/validation effort with no payback. Seems like a lot of nuances present. Mot's original MC14xx had battery discharge bugs which was one of the Dallas popularities. Mot fixed it in the b version.
Most modern designs use an i2c rtc and an fram. So, other than legacy sockets, not much market. pmoyle |
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Re: ++Processor error on TDS 754D on startup
Yes the 754s are really good scopes. I've got two, an A and a D. I am dreading the day when I need to get after this problem. I've already backed up the contents of the NVRAM via the floppy drive method, so I'm ready if I need to do it, but not looking forward to it.--EricSent from my Galaxy
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-------- Original message --------From: BobH <wanderingmetalhead@...> Date: 7/19/21 9:03 AM (GMT-06:00) To: [email protected] Subject: Re: [TekScopes] ++Processor error on TDS 754D on startup Thanks for the information. The reason that I was asking is that I have been working on a replacement for the battery backed SRAMs. I currently have an 8Kx8 board design that I am testing. It does not support timekeeping right now. Backup power is supplied by a socketed coin cell on top of the board.I looked at the two part numbers you supplied, the DS1486 has RAM and a clock on board, and is obsolete with 0 stock at Mouser. The DS1250Y is a 512Kx8 SRAM which would be more approachable for a homebrew fix, but they are still available with Mouser having them in stock. They are expensive though.On the boards that I am working on, they are using the DIP package. I have been looking at adding timekeeping to my design, but that is going to get a lot more complex, as it will require an FPGA to allow formatting the data to emulate the various module part numbers. Also, 5V tolerant FPGAs are getting scarce.Good Luck with your 754D, those are nice scopes!BobH
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Re: 7904A compress sweep
Tom,
Use 91% IPA for the coax inputs and socketed transistors. I use a small artist brush to apply the IPA then move then move them up and down in their sockets a few times to clean them. You do this to the neck pins and sockets also. Dirty contact(s) would be the most likely cause of your trouble. I think you mean the hot transistors are the 900 numbers. I have three two fin Thermalloy 2225C heatsinks on three of them. There is not enough room for all four to have this type of heatsink on them. The heatsinks on mine are on Q900, Q930 and Q940. I used MX-4 compound. In mine, I replaced C100 with a film type and the two 22mfd with ULD 47mfd 25V. R921 and R954 are now, in mine, 1W 1% and R900, R941 and R960 are 2w 1% types. I had these parts in stock. These resistors are off the board to allow air all around the bodies of the resistors. I did add compound on the two pars if transistors with the metal band around them to further aid in thermal coupling. You do what you want with your piece. I did what I wanted to in my piece. Mine works fine. My B time base socket on the main board had bad/no solder on the two coax output from the time base. This was a factory defect. No one had worked on this after it was originally bought. The spring tension wire was off its pin. I took these off, repaired the problems then put back in. Now it works. The two plastic covers were carefully removed to do the work. I know what I had is a rare defect. Mark |
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Re: 7904A compress sweep
If the trace can center, then the circuit is in balance as far as the + section and - section are concerned, putting the same voltage on the plates.
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There is, however, no guarantee that it's the *right* voltage. I'd center the trace, or duplicate the test conditions in the manual, then go through and check the static voltages on each transistor.? Running each output at, say, twice the current will still give you deflection, but it will bottom out, for instance. Did you check the emitter supply resistor (and bypass capacitor) for the emitter supply circuits of the balanced pairs? Harvey On 7/19/2021 8:46 AM, Tom Phillips wrote:
Thanks for suggestions |
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Re: ++Processor error on TDS 754D on startup
Thanks for the information. The reason that I was asking is that I have been working on a replacement for the battery backed SRAMs. I currently have an 8Kx8 board design that I am testing. It does not support timekeeping right now. B
ackup power is supplied by a socketed coin cell on top of the board. I looked at the two part numbers you supplied, the DS1486 has RAM and a clock on board, and is obsolete with 0 stock at Mouser. The DS1250Y is a 512Kx8 SRAM which would be more approachable for a homebrew fix, but they are still available with Mouser having them in stock. They are expensive though. On the boards that I am working on, they are using the DIP package. I have been looking at adding timekeeping to my design, but that is going to get a lot more complex, as it will require an FPGA to allow formatting the data to emulate the various module part numbers. Also, 5V tolerant FPGAs are getting scarce. Good Luck with your 754D, those are nice scopes! BobH |
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Re: Looking for data on 9-pin Vacuum time delay relays used in old Tek-scopes
" If you were building a replacement for one of these delay relays
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(hypothetically speaking, maybe for a 533A), would it be enough to have a timer that cut a relay in after a fixed time? Is that really all that the delay relay is doing?" If its filaments are in the heater chain, something would need to be done to replace the filament of the time tube. Also, if it is in the heater chain in a serial fashion (I don't think they are, eh? I have to study the schematics again), that is a safety factor if one tube's filaments open, that power does not get applied. I am probably overthinking it. a 555 and a S202SE2 SS Relay would probably suffice. Dave On Sun, Jul 18, 2021 at 11:06 PM Jeff Dutky <jeff.dutky@...> wrote:
Bruce, |
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Re: Looking for data on 9-pin Vacuum time delay relays used in old Tek-scopes
" For instance .
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Albert" Albert; thank you; I had been thinking of this too. In industrial controls, we would use on-shot (Time Delayed) relays too, but they are much larger and bulkier than that tube. I guess someone could design a tiny 555 timer and relay to replace it if needed. An extra aggravating (LOL) step, but yaa got ta do what yaa gotta do. Dave On Sun, Jul 18, 2021 at 4:02 PM Albert Otten <aodiversen@...> wrote:
For instance . |
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Re: Binding Post Thumb/Head Nut Replacements
Jeff -
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which are the originals and which are "new"? ¸é±ð²Ô¨¦±ð On 7/19/21 4:53 AM, Jeff Dutky wrote:
I have added a photo album with pictures of the two replacements I have found compared to two sizes of thumb nuts from Tek instruments: /g/TekScopes/album?id=266234 |
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Re: 2712 SA with display (and normalization) issues
#photo-notice
Have you looked here?
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Not OCR, but probably useful. Failing that, try Artek Manuals (). They don't have it listed but they might be able to help. Colin. -----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Ronan Sent: 18 July 2021 22:59 To: [email protected] Subject: Re: [TekScopes] 2712 SA with display (and normalization) issues #photo-notice Just one more tidbit (before I decide if I'm going to dig deep into it). Enabling debug diagnostics and re-running the Frequency Normalization indicates this: ¡°ERROR in MAIN DAC OFFSET: Cannot center start spur¡± Explanation: "Beginning at 10 MHz/div span, the start spur was located and centered, then span was reduced. In 1 MHz/div span, the signal could not be centered within 30 horizontal storage bits." I have a ¡°oddity¡±, a +30dB rise of about 70MHz width: 1486 MHz 1498 MHz 1558MHz Does anyone have an OCR of the 2712 Service Manual? Thank you Ronan |
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Re: ++Processor error on TDS 754D on startup
I believe the they are DS1486, and DS1250Y (from memory of reading recently) I guess maybe I should hunt the data sheets and re-familiarize myself with the beasts - I used to know something about everything Dallas had- but that was mid '90's. I started hoping I could find someone I could pay to do it and just outsource the problem, but it looks like I'm going to end up diving into the swamp.
I don't know which is the culprit but if one is replaced so should the other due to battery age, and pulling the board out and reworking one is not much less than reworking both. I have seen on some threads, someone has designed a workalike using a non battery Dallas part allowing using an external battery But at the moment I'm looking for assistance with how diagnose the problem further to prove that is the problem I am getting in a Prologix IEE488 to usb adaptor in a week or so and I would like to get some instruction on how to download/upload the content If it's one of those I should be able to clear the error at least long enough to do a self test to verify the hypothesis. I have a file someone posted for the DS1486 - I suppose that is where the error is Anyhow just looking for some diagnostic steps I can go thru using 488 I/F. I have seen some using the floppy, but I don't have any of those and I guess you could find them online somewhere, but I think the 488 I/F will just be better, more user friendly, more robust |
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Re: 7904A compress sweep
Thanks for suggestions
I moved the gain pot slightly but it has little effect. The power supply voltages are very close to spot on and stable but the four metal output transistors Q610, 20 30 and Q640 are definitely hot. I'm in the middle of a long distance move and don't have another scope handy at the moment to check stage waveforms but if needed are equivalents for motorola ST919/ST7394 available? Casual web search not turning up much. |
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Re: Binding Post Thumb/Head Nut Replacements
I have added a photo album with pictures of the two replacements I have found compared to two sizes of thumb nuts from Tek instruments: /g/TekScopes/album?id=266234
I have also found another candidate in this item on eBay: I will post pictures when the parts arrive. -- Jeff Dutky |
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Re: Power transformer 453A
Mark,
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Thank you for the effort to inform me about the secundary voltages. I expected this already. If I decide to use a 454 transformer, which is identical to a 453 transformer, I have to do some cable dressing, as these transformers are horizontally arranged, with respect to the 453a transformer which is vertically arranged. Anyway thanks again for your info. Fred On 18 jul. 2021, at 18:20, Mark Vincent <orangeglowaudio@...> wrote: |
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Re: Looking for data on 9-pin Vacuum time delay relays used in old Tek-scopes
Bruce,
If you were building a replacement for one of these delay relays (hypothetically speaking, maybe for a 533A), would it be enough to have a timer that cut a relay in after a fixed time? Is that really all that the delay relay is doing? Might there be another way to determine when the heaters are at temperature, like by monitoring the current through the heaters, or even by directly sensing the temperature of the tubes themselves? Just curious (though I am in the process of refurbing a 533A, and this may be useful information when I get to the point of applying power to the instrument) -- Jeff Dutky |
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Computer interface to 576
I know folks have been talking about this for a while and it looks like
someone actually did it. Description is a bit on the thin side and if you're going to go to all that trouble it seems that you should calculate the parameters instead of making you calculate them off the screen grid. Apparently you do get cursors, meh. Disclaimer: no connection to whoever did it -- Paul Amaranth, GCIH | Manchester MI, USA Aurora Group of Michigan, LLC | Security, Systems & Software paul@... | Unix/Linux - We don't do windows |
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Re: 2712 SA with display (and normalization) issues
#photo-notice
just one more thing...yeah, right. It is pretty warm in my lab in Calif. today -- I attempted a full normalization just now, it succeeded. Perhaps this is more proof I need to do the real work now from great posts such as Mike/WZ5Q, Randy/AB9GO, Marcus/PP5MS (et al). Now I'm thoroughly convinced I need to check PS voltages/ripple, and to order two batteries -- check the caps and do the due diligence. I am headed to the copy/print store to make printouts of the 11x17 schematics. Appears surprisingly "normal": Thanks for your virtual patience, R |
Raymond Domp Frank
Fred Schumacher
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