[volt-nuts] OT: ExpressPCB
Sorry if I'm behind the times, just did a new project that required a pcb, and ExpressPCB is my go-to vendor for one-off boards. I just noticed they now provide the low-cost boards (fixed size, 3x5, quantity 3) that I've always ordered with silk screen and solder mask for $71. I got my latest boards that way and they're beautiful. No relationship to them, just a happy customer. You can still get the barebones boards for $51. The hack I used to use was to put the component id and such on the top copper layer as tiny text, but that was a bit of a pain for layout. (Oops, can't put that label there, it's copper and there's a trace there also) Really nice to be able to get real boards, even if it does end up being ~$23/board. -- Bill Ezell -- The day Microsoft makes something that doesn't suck will be the day they make vacuum cleaners. Or maybe Windows 10. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Replacement displays for Solartron 70x1 meters
The FG209 VFDs came in about 6 or so variants, mostly having to do with whether or not it had decimal points, +/- signs, etc. The M2 variant is the exact replacement for 7081's, 71's and 61's, and that's the one on EBay. I've also used the C2 variant in my 7081. I was looking for my Noritake datasheet to find out the differences, but I apparently didn't save it and now it seems impossible to find. Sigh. -- I was just pointed to eBay listing 271905098924 (thank you Peter) which has some of the Noritake FG209 VFDs that I am pretty sure fit the Solartron 70x1 meters, should anyone need one. -- Bill Ezell -- The day Microsoft makes something that doesn't suck will be the day they make vacuum cleaners. Or maybe Windows 10. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Solartron 7081 randomly reinitializes
C2 certainly holds off the reset, not sure if it's just for pwdn, or also startup. If you can check voltages around the reset logic, might give you some more clues. Not much else I can think of that could be causing this, although I suppose if you have enough ripple on the +5v to the microprocessor, that could be triggering its own shutdown/restart. But, you've already checked that. PS - my comment about the nvram was for the 'cal constant' thread. I just combined them. Guess I should have pointed that out. :) BTW, my 7081 that usually holds calibration very well was off by 10 ppm when I turned it on a few days ago even after 24h warmup. Hope this isn't a sign of something bad coming. I have an HP 3458 ref, maybe I'll try that mod to use it in my 7081. Interestingly, my 7061 has held calibration impressively, off by only 3 ppm, and it's been a year since I calibrated it. (I use a pair of Datron 4910's for calibration. I had one calibrated by Fluke, and I do differential comparisons between the two to track drift. They are amazingly stable. Of course, they have been in continuous operation for about 12 years in my lab, and who knows how long before I got them.) -Original Message- Hi Bill, C2 is a hermetic tantalum, and doesn't appear leaky. +5V appeared on the mark and stable but C60 (220uF 10V in +5V supply) looked a bit crusty, so I replaced it on general principle with a 220uF 10V tant. I think that C2 is used to hold off of the reset signal for a period of time after PWDN- is asserted to allow the processor to save stuff to RAM. The ROMS appear all good and were all written pretty recently. Dave -- Bill Ezell -- The day Microsoft makes something that doesn't suck will be the day they make vacuum cleaners. Or maybe Windows 10. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
[volt-nuts] Yet another sub-nanosecond pulse generator thread
(cross-posting to time-nuts) After paying only limited attention to this topic, I suddenly have a need for a pulse generator that has <150 ps risetime and a pulse width of at least 2 ns. I've looked at the classic Jim Williams avalanche generator, but I don't want to have to deal with the (relatively) high voltage source needed. I've done microwave design using Gunn diodes, so I'm drawn to using a step-recovery diode. The topology seems very straightforward, and I can build it right onto a BNC connector, no PCB. I'm thinking using an SMD835 diode, biased at ~1ma. The (sketchy) datasheet claims a T of 20 nsecs and a Tr of 85 ps, Cj of 0.4 to 0.8 pf. Questions: The obvious, is it reasonable? Is the bias current reasonable? I'm assuming the bias current is actually dependent on the repetition rate, you need enough current to replenish the charge within one pulse cycle. I suppose I could compute it from the stated junction capacitance, but I'm not sure that's the only factor Will the stored charge actually give me the desired transition rate into 50 ohms? Hmm, again I should be able to compute this, but any other factors ignoring the non-diode ones like cap inductance? How should I compute the coupling cap from the diode to the load? Use the impedance at the pulse rep rate? Seems reasonable. BTW, I don't care about droop in the pulse, just the risetime. (measuring overshoot in an HF amp). Again, just want to verify that the obvious answer is the correct one. I clearly need to be very careful about the inductance. Thanks, Bill -- Bill Ezell -- The day Microsoft makes something that doesn't suck will be the day they make vacuum cleaners. Or maybe Windows 10. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Design Spark PCB Design Package
On 1/6/2015 12:00 PM, volt-nuts-requ...@febo.com wrote: Re: Design Spark PCB Design Package It depends on what you need PCBs for. I've used ExpressPCB for years. They have proprietary layout software, all very manual, no routing, and free. It will also do multilayer, vias, fills, etc. The reason I use them is that you can get 3 3x5 boards from them for $60 if you use their app. They also have a schematic capture app that works with the layout app and does some basic netlist checking. I find them very convenient for one-off projects that will fit. -- Bill Ezell -- The day Microsoft makes something that doesn't suck will be the day they make vacuum cleaners. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] 7071 noise
Mickle writes: Solartron 7071/7081 manuals don't have official information about the Only one of the docs - Instruments Test Specification - have a 10 V noise limits: 10 V noise - The rms noise of 10 readings at 10 V is measured. It must be less than 3 uV. This is roughly equal to 12 uV p-p (with p=0.998, f=10). My old measurements (7.5-digits, short, 5-10 minutes): 0.1 V = 0.2 uV 10 V = 5 uV Correct, not quite sure what I was thinking there. Re-reading what the OP said, looked like he was measuring the p-p reading over 10 mins. The posted values I gave were 'transfer standard' worst-case stability values at full scale, which of course isn't noise, but is a passable average over the specified transfer time limit. An averaged measurement over 10 mins should be pretty close to within those values, and of course you wouldn't make a precision measurement without averaging multiple samples. I actually have a 7081, but that shouldn't matter for the noise measurement (except possibly for a selected zener). My measured 7.5 digit p-p over 5 mins was 3uv (+2, -1). I've noticed that the average reading variation is usually in that range, but looking at a histogram of a few hundred readings, there are certainly occasional significant glitches of multiple microvolts. It's really hard to determine the source of those kinds of glitches, which is why when I'm trying to make the best measurements I can, I capture the samples and process them myself, throwing our any outliers. I also decided to check calibration, because I haven't recalibrated in over a year. I use dual Datron 4910's that I compare to each other, sending one out for Fluke calibration if they disagree by more than 2 ppm. I used to pay for hot-shipping, but Fluke said not to bother. Anyway, my 7081 has only drifted by 5ppm. I'm impressed. Question - did you find the switch to the LTC1052 to make a significant difference? That's an easy one to do, and I always have some on hand. I've considered making the LTZ1000 replacement you did, since I have a spare ref board from a 3458A, but given the stability of my meter, not sure if this is really worth the effort. Any opinion? -- Bill Ezell -- The day Microsoft makes something that doesn't suck will be the day they make vacuum cleaners. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Solartron 7071 noisy
That's a little high, a bit worse that what I remember mine being. According to the specs, you should expect about 0.1/0.6/4 uV for those ranges. So, your 10V seems a bit noisy. Question, what was your warmup time? These really take about 24 hours to fully stabilize. Do you have the service guide? There are several internal adjustments that affect the total noise, might just need tweaking. But, don't try to recalibrate the actual reference voltage unless you have a very good standard, of which a single Weston cell is not one of. I'll give mine a check. On 7/23/2014 12:00 PM, volt-nuts-requ...@febo.com wrote: Hi Everyone, I have a problem. I bought a Solartron 7071 on Ebay. That Voltmeter seems working properly but I think it's too noisy. It passes Self Test and Initialize and the reading is consistent against a Weston Cell to the µV. But, when left with a short circuit as input the noise (maximum during 5 min) is: 0.2µV for 0.1V scale 0.4µV for 1V scale 8µV for 10V scale Is it acceptable? Thanks for your help. Bye, Jean-Louis -- Bill Ezell -- The day Microsoft makes something that doesn't suck will be the day they make vacuum cleaners. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] AC Voltage Measurement Standards
I also have a Ballentine 1605A. These are quite accurate, reasonably fast, wide frequency response instruments. They're microprocessor controlled and will do automatic measurements so you don't have to do manual nulling. It can also be calibrated against a DC standard, but that doesn't correct for frequency non linearity, of course. The manual is still available from Ballentine (for a silly amount of money). I don't see many of these on FleaBay, though. -- Bill Ezell -- The day Microsoft makes something that doesn't suck will be the day they make vacuum cleaners. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
[volt-nuts] Valhalla 2720GS
I've been searching far and wide trying to find out what the calibration password is and how to use the hidden cal button. I know there was some discussion of 2720's and calibration a few years ago here, but I haven't found anything covering the above. If anyone knows, or has a link to the info, please let me know. Thanks, Bill -- Bill Ezell They said 'Windows or better' so I used Linux. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] PWM voltage divider / now Voltage divider
A PWM divider was used in the excellent Datron 4910 voltage standard, sub-ppm accuracy (and stability). It included a multi-pole active LPF (5? 7? don't remember) to eliminate switching noise in the output. The reference/divider topology they used pretty much eliminated any temp drift from any component other than the voltage ref itself (LTZ1000). There are schematics online in various places. I have two of them, I used to send them out alternatley for cal (by Fluke) whenever the out-of-cal one had an average diff from the calibrated one of more than 1uv. I haven't had to send either out for a few years now. Going long distances down the aging curve is a wonderful thing. Of course, they could both be aging at exactly the same rate now. :) They're both on continuously, and have been for the 8 years I've had them. I have no idea how many thousands of hours they had on them before I got them. -- Bill Ezell They said 'Windows or better' so I used Linux. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Old Weston cells
pa4...@gmail.com writes: I have 4 weston cells in a guildline cabinet with oven. I have the cal data for the first 10 years they have been used. After this time the oven was turned off , the lab was closed but all gear stayed put on that same place over 30 years (the lab was turned into a server room but all the gear just stayed unused ) I made a graph from the data. Took a ruler and extended the lines. After a few months I had a change to measure them with a calibrated 6,5 digit meter and a year later a 7,5 digit meter and the values I found where plus/min a few uV on the lines. But more important the difference between the individual cells was spot on with my graph. I have that same unit myself. For some years I kept it on and would periodically compare the cells to my (calibrated) Datron 4910's. I kept logs of the voltage sampled weekly using an 8.5 digit meter for differential comparison for 2 or 3 years. I was surprised at how stable and predictable they were. But, I stopped doing that probably 5 years ago. Nostalgia strikes, I'll plug it back in and see what's changed. Unfortunately, it takes weeks for the voltage to stabilize from a cold start. -- Bill Ezell They said 'Windows or better' so I used Linux. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Improving Solartron 7071 and 7081 (m k)
As far as I can determine this appears to be caused by a big spike as IC403 (74LS02 on the earthy processor board) switches. You can see the spike at TP 3 on the earthy processor board. This spike goes below ground by about 1.4V every 0.66uS. This is interesting. I don't see this at all. I just probed the tp and it's a very clean TTL signal, no undershoot at all. I'm using a 300 Mhz scope (Tek 2465A). Not only is the tp clean, the +5 is also clean. I'm using the ground point very near the tp. Silly question - have you checked your probe compensation? There is a very small rf burst every 0.66 uS I can see on the floating board, but it's not on the digital power line, I checked that on one of the ICs on the floating board. I'm seeing about 20 mv bursts at the AC buffer test point you mentioned before, the burst is quite short, and the burst frequency is much higher than any of the clocks in the meter, so something is ringing, but it's not getting coupled out very far. I'll probe around some more. -- Bill Ezell They said 'Windows or better' so I used Linux. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Solartron 7071 beeping about twice a second
Joe, Looks like you win the prize for remote diagnosis! Disconnecting PL2 which goes to the keyboard, and it all comes up nicely. What I can do about that though I am not at all sure ... That is a remarkable catch. You can disassemble the front panel quite easily. It could be as simple as a bad bypass cap, an intermittent short, or, yes, a sticky switch. If the last, you do have a bit of problem. It might be possible to just work it a bit and get it to unstick. I don't remember the construction of the switches, but I have a vague recollection that the flexible silk-screen button is separate from the actual switch. If so, you can probably find something that will work. Note also that there are a number of ICs on the front panel PCB. You could have a bad IC. If, for example, interrupt is being continually asserted, that could certainly keep the self-test from completing. (happened to me on a 7061) -- Bill Ezell They said 'Windows or better' so I used Linux. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] volt-nuts Digest, Vol 41, Issue 11
On 01/19/2013 7:00 AM, David C. Partridge wrote: The zener token value is written on the lower right PCB in the rear right hand corner. I should have remembered that. Thanks for the reminder. BTW, anyone looking for cal keys, the switch is still made and you can order one from several of the online suppliers; I got mine from Digikey. The part number on the switch is current. (or was last time I checked) It wasn't particularly expensive, either. One note - the switch has 32 (or so) possible keys. Solartron always used the same key. But, if you order a switch, it's possible that its key won't be compatible with other Solartrons. You can specify the key, but Digikey didn't stock the one Solartron used. Personally, I didn't worry about it. -- Bill Ezell They said 'Windows or better' so I used Linux. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] vSolartron7081 rom reading (m k)
BTW, make absolutely sure you save the Zener current token value somewhere safe. The rest of the cal constants can be recovered with some good calibration standards, but the Zener value takes some pretty specialized calibration. I think the performance of the 7081 is really phenomenal given that the reference is a non-ovenized Zener. It gets this by individually setting the Zener current to the value that gives the minimal voltage change for temperature change, then injecting a 2nd-order correction factor. The moral of this story is that the current token setting is specific to the Zener, and you'd need a good temperature-controlled chamber and a lot of time to replicate. -- Bill Ezell -- They said 'Windows or better' so I used Linux. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] vSolartron7081 rom reading
Going from memory, no, you have to pull the roms and read them. At least, that's what a few of us in the group have done. You can access ram and nvram, though. -- Bill Ezell -- They said 'Windows or better' so I used Linux. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
