EEVblog #709 - EDC 4601 AC Voltage Standard Teardown - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: January 28, 2015, 04:46:01 am
content: Dave does some performance checks and then tears down a Krohn Hite EDC 4601 0.05% 6 decade 1ppm resolution 0-1000V AC voltage standard.Service Manual with schematics:http://www.eevblog.com/files/4601ServiceManual.pdfUser manual:http://www.krohn-hite.com/htm/ServiceSupport/PDF/Manuals/4601%20Manual.pdfMV106 DC Voltage Standard:Datasheets:Vactrol:http://www.excelitas.com/downloads/dts_vtl5c3c4.pdfXR2228 Multiplier/Decoder:http://html.alldatasheet.com/html-pdf/119347/EXAR/XR-2228/96/1/XR-2228.htmlEpson SPG8640 oscillator/divider:http://www5.epsondevice.com/en/quartz/tech/discon/epsondiscon/2000catalog/spg_8640series_e.pdf

author: scopeman
author_rank: Frequent Contributor
timestamp: January 28, 2015, 05:15:34 am
content: Hi Dave,Nice teardown. Maybe you can get KH to send you a PDF of the manual with the schematics in them.Anytime you get tired of this piece "old school" electronics I would be happy to take it off of your hands!SamW3OHM

author: pickle9000
author_rank: Super Contributor
timestamp: January 28, 2015, 05:23:10 am
content: LM3914 is an awesome chip, super useful.

author: coppice
author_rank: Super Contributor
timestamp: January 28, 2015, 06:40:14 am
content: From the way the meter reading jumps around the output of this thing appears quite noisy. That's going the make the bandwidth of the meter a significant factor in the reading. Its not exactly the most sophisticated reference ever made.

author: EEVblog
author_rank: Unknown
timestamp: January 28, 2015, 07:14:00 am
content: Quote from: coppice on January 28, 2015, 06:40:14 amIt's also not a DC reference.I don't have another AC reference to compare noise performance to.

author: electronics man
author_rank: Frequent Contributor
timestamp: January 28, 2015, 08:17:56 am
content: it would have been nice if you could have hooked the scope across the output

author: Dr. Frank
author_rank: Super Contributor
timestamp: January 28, 2015, 08:30:33 am
content: Dave,on all of these multi-dial calibrators, you better use full scale output, instead of 10% f.s. only.Only then, you get full accuracy and stability out of it.The 10V range (f.s.) is the most stable also.You can easily see that in the datasheet:accuracy, 10V: 0.05% of setting + 0.005% of rangestability, 8hrs.: 0.0075% of setting + 0.001% of rangeThat ..(x% of range) doubles your in-accuracy and instability, if you set these instruments to 10% only.Therefore, always dial to "10" on the first digit: .(10) 0 0 0 0 0 V or to .9 9 9 9 9 (10) instead of 1. 0 0 0 0 0 VIf you repeat that A.C. stability (noise) measurement on your 34461A with 10V f.s., you would see a much better performance, about ten times better short term stability, I bet.These AC standards usually convert a programmable D.C. reference to an A.C. output by comparing the D.C. setting to the precision rectified A.C. signal..Therefore, it's a pity, that the DC to AC comparator / rectifier is not explained in the manual, as the Theory of Operation chapter is missing.Maybe, that's done by the XR-2228, although its squaring accuracy is normally too bad for that.That means, that this instrument also contains a D.C. reference standard in first instance.You may measure the DC reference of 0.. 10.00000V, or so, somewhere inside the circuit.I bet this D.C. reference part of the circuitry is very similar to the DC standard you also own from KH /EDC.Concerning the muddy corner of the instrument, that may be caused by high voltages present there.If you open such HV calibrators, DC or AC, you will always find an accumulation of dust, something like carbon black, at and around all parts, which carry the HV, due to electrostatic attraction.This one looks a little bit odd, anyhow.Frank

author: Fungus
author_rank: Super Contributor
timestamp: January 28, 2015, 11:01:23 am
content: I've used LM3914s to get a simple constant current sink for LEDs. Just tie the 'input' pin high and you can connect 10 LEDs to it without worrying about resistor values. Using one for only 3 LEDs seems weird, but whatever...PS: You can also do it withAN6884sif you only need 5 LEDs. They're dirt cheap if you buy packs of 50. They're also SIP packages and don't take up much space on a PCB.Edit: "SIP packages" as defined by the department of redundancy department...

author: EEVblog
author_rank: Unknown
timestamp: January 28, 2015, 12:21:14 pm
content: Quote from: Dr. Frank on January 28, 2015, 08:30:33 amYes, I mentioned that, almost certainly the same zener reference and circuit as in the MV106 DC standard.QuoteYes, but in this case that's not the high voltage side, it's just the mains side, the high voltage is right over on the other side of the chassis.

author: max_torque
author_rank: Super Contributor
timestamp: January 28, 2015, 03:30:08 pm
content: Quote from: EEVblog on January 28, 2015, 12:21:14 pmIt does look to me that some time ago, rather like something has "gone bang" in that back LHS of the device and left some sooty remnants!

author: station240
author_rank: Unknown
timestamp: January 28, 2015, 04:25:34 pm
content: Quote from: max_torque on January 28, 2015, 03:30:08 pmMaybe there was a MOV or filter capacitor across the mains input, that exploded and was removed. Might explain why that area has heatshink on it, if the wiring had to be renewed anyway.

author: JackOfVA
author_rank: Unknown
timestamp: January 28, 2015, 05:13:46 pm
content: Looks like the power transformer has been roughly handled as well - look at the lamination stack near the front by the trim pot module -- laminations are bent out, almost like someone forced a screwdriver into the corner. How that passed QC is interesting as well.

author: cj555
author_rank: Contributor
timestamp: January 28, 2015, 05:51:04 pm
content: Dave, you find the most interesting stuff to tear down! Thanks, learned something again.But.......was I the only one who noticed that 18 kg is not 50 lb?? It's more like 40 (OK, closer to 39 lb 10 oz). No matter what the manual says!...also, every time you say "that's a bit how ya doin!"...now I think of "that crazy Kiwi" Doug Jones.

author: dentaku
author_rank: Frequent Contributor
timestamp: January 28, 2015, 06:28:03 pm
content: Vactrols are mostly being used in audio applications these days. You can still buy modern ones for things like analog synths and effects boxes.I once built one with an LED and an LDR taped together.

author: SeanB
author_rank: Super Contributor
timestamp: January 28, 2015, 06:39:34 pm
content: A few thoughts. The main board likely dates from the late 1970's, probably they made a batch of them, partially populated them with the reference soldered in, and probably they originally used SFC2741 opamps as original spec, as they have been selected for low offset and low popcorn noise. They then just put them in storage until needed. Shows in the composition resistors on the board, and the 1970's style capacitors and the precision resistors ( the Vishay glass film resistor has been around since the 1970's, it just was a very expensive part then) along with the roller tinned board. When needed they likely unsoldered the original IC's and installed sockets to use more modern parts with a better spec, but left the original reference untouched ( and probably were careful not to solder near it to keep the tempco stable) as an aged reference.The relay being used without a base is simple, you cannot bolt the base down with the single bolt, but have to use 2 bolts at the ends of the socket, then use a spring clip to hold the relay down. No room on the board for that, and likely the original relay type was no longer available, so they used the best that fitted the restricted space.The output stage was also likely an upgrade, as the original probably used 2 TO3 power transistors and the driver stage on the main board, the mosfet upgrade being easy to do with a bias change ( some of those new resistors and cut traces and new holes) and a protection/mounting board for the leads.Dirt on the mains side is easy, they used a Schaeffner mains filter, and it did the usual flaming exit after a few years. Clean up the board a little with a brush, new inlet ( unfiltered) and away it went.the oscillator board is likely the only new design, as the original board would have used all discrete parts in the most case, and some specialist IC's that went obsolete in the 1980's, like so many small low volume specialist semiconductors do. So a new board design to do the same job, using as many of the original parts as possible. Thus the Vactrol, and on the main board is likely an even older one, that uses an incandescent lamp inside as a light source instead of the new fangled LED, though it will be run at a current that at best warms the filament to a dull red.

author: Dr. Frank
author_rank: Super Contributor
timestamp: January 28, 2015, 08:27:29 pm
content: Comparing to the MV106 video, the 1N829 reference diode again is soldered onto these standoffs, in this muddy compartment.These diodes where Dave was pointing at in this actual video, were simply the anti-parallel diodes to protect the inverting inputs of the three/four OpAmps nearby.I assume, that reference diodes were mostly housed in plastic or painted glass cases, as if they were housed in simple glass diode case, any light onto the chip would affect the zener voltage.The trim pots around probably set the offsets of the OpAmps only.As there's all that dirt around, which looks like it would be conducting stuff, (the idea of an exploded AC filter cap seems to be striking), I'd like to propose to clean that compartment thoroughly, to maintain the accuracy.Frank

author: EEVblog
author_rank: Unknown
timestamp: January 29, 2015, 12:08:11 am
content: Got the service manual:http://www.eevblog.com/files/4601ServiceManual.pdf

author: EEVblog
author_rank: Unknown
timestamp: January 29, 2015, 12:10:04 am
content: Quote from: mojo-chan on January 28, 2015, 08:48:29 pmTechnically, a lower bitrate per frame. 28Mbps 50fps (maximum of camera) vs 17Mbps 25fps (not maximum of camera, I could have 28Mbps 25fps).But I don't see the difference.

author: EEVblog
author_rank: Unknown
timestamp: January 29, 2015, 12:11:29 am
content: Quote from: SeanB on January 28, 2015, 06:39:34 pmService manual schematic dates the design to 1986.

author: plexus
author_rank: Contributor
timestamp: January 29, 2015, 01:50:20 am
content: Im watching as I type so you may have addressed this: What does THAT smell like??? I can almost smell it from here (Canada). want to know if Im right?Just so y'all know, if you question Dave's apparent obsession with gear smell, I totally get it. For example some years ago a friend gave me a roadcase for a music synthesizer. I am an electronic musician. I opened the case and said, "Was a Roland in here?". Sure enough it was! I explained that different synth manufacturers have different smells especially the older synths from the 70s and 80s which were made more.from organic compounds .That AC standard LOOKS like its pungent??

author: boffin
author_rank: Unknown
timestamp: January 29, 2015, 04:33:53 am
content: Dave; when you were trying to date the thing, you missed the fact that all of those multi-turn trimmers (and the relays) also had date codes on them

author: IshtarTor
author_rank: Newbie
timestamp: January 29, 2015, 04:56:31 am
content: I think the effect of the blowing was interesting, and I would like to see how it looks like with the FLIR, and what is the stability effect of using a hair drier or something like that on different areas of the instrument. Maybe there is something to learn here on the design of precision instruments ?

author: EEVblog
author_rank: Unknown
timestamp: January 29, 2015, 05:22:39 am
content: Quote from: boffin on January 29, 2015, 04:33:53 amYep. When you are yapping into a camera whilst trying to subconsciously think what to say, and what to say next, and looking at the LCD screen, and thinking about the shot etc, it's surprisingly easy to miss stuff.

author: boffin
author_rank: Unknown
timestamp: January 29, 2015, 05:47:00 am
content: Quote from: EEVblog on January 29, 2015, 05:22:39 amWasn't trying to criticize, just help. Not everyone looks for date codes on the passives.

author: ludek
author_rank: Newbie
timestamp: January 29, 2015, 03:04:39 pm
content: Dave said "...sort of "HP 200" oldschool, used in a light bulb, as the main stability element in your oscillator." - what device do you mean?I'm very interested in unusual sollutions. Please more info about this stability elemnt (which EEV Blog number(?) or something).Very nice video BTW I like "rare" gear tearing down.?//edit: ok i found:https://en.wikipedia.org/wiki/HP_200A

author: tchicago
author_rank: Regular Contributor
timestamp: January 29, 2015, 04:50:54 pm
content: Looked at the power amp schematic. Wow, the output is weird: it is actually the central point of the power supply. Whereas the push-pull MOSFETS "drive the ground", so that the central point of the power supply will fly up and downWhy is it made this way? I think this alone may deserve a whiteboard video episode.

author: djQUAN
author_rank: Frequent Contributor
timestamp: January 29, 2015, 05:00:08 pm
content: Regarding the caps on one of the output mosfets,Rod Elliott's P101 mosfet amp design (http://sound.westhost.com/project101.htm) uses the same devices and also used the capacitor trick. It was done to compensate for the gate capacitance as the P channel part has a much larger capacitance than the N channel complement.The capacitor will be in around a couple hundred pF in value and when added in parallel with the N channel gate capacitance, the total will be close to the P channel gate capacitance.The output stage is similar to the old QSC amplifiers (see attachment) The main filter capacitors are also used as a sort of DC blocking capacitor so that a failure of an output device will not result to a huge DC voltage on the speaker output (output transformer primary in this case). This also lessens the need for a very low DC offset power amplifier stage as the output is AC coupled and will not introduce a small DC voltage across the output transformer primary.

author: Smokey
author_rank: Super Contributor
timestamp: January 30, 2015, 05:35:40 am
content: Quote from: ludek on January 29, 2015, 03:04:39 pmhttp://cds.linear.com/docs/en/application-note/an43f.pdfPage 32. Jim Williams replaced the bulb with a VACTEC VTL5C10 in his wien bridge

author: EEVblog
author_rank: Unknown
timestamp: January 30, 2015, 05:51:26 am
content: Quote from: mojo-chan on January 29, 2015, 10:06:14 pmI see no noticeable difference between detail in my original rendered video file, and Youtube at 50fps 1080p (shift print screen capture).I used the Agilent meter front panel shot as a test.When I flick between them it's very hard to see any detail difference. Slight brightness difference because not exactly the same frame, but no real loss of detail.Had to convert from PNG to JPG to upload

author: EEVblog
author_rank: Unknown
timestamp: January 30, 2015, 05:53:36 am
content: Quote from: mojo-chan on January 29, 2015, 10:06:14 pmSorry, but I think it's a problem at your end somehow. As just demoed, at my end I cannot see the difference. Youtube is not losing detail from my original at 50fps as captured on my machine.

author: EEVblog
author_rank: Unknown
timestamp: January 30, 2015, 06:12:47 am
content: And the original capture from inside Sony editor.Essentially no difference in detail at all. if you can spot anything serious you have better eyes than I do.

author: allikat
author_rank: Contributor
timestamp: January 30, 2015, 07:05:04 am
content: Never ask an engineer to check something unless you want a complete answerNice work looking at the YT renders Dave. Youtube render differences may be caused by YT going for full on HTML5 recently, which would mean it's now not using that *insert technical engineering curse here* Adobe Flash. A thread on Reddit (https://www.reddit.com/r/chrome/comments/2bmxpp/youtube_html5_vs_flash_player_performance_cpu_and/ ) has looked into the change, and found that the current YT player may not use the GPU for acceleration, since the GPU will often do some colour tweaking as part of that render, and a CPU based system won't usually, you may well notice some differences depending on your precise setup.

author: hikariuk
author_rank: Unknown
timestamp: January 30, 2015, 08:03:17 am
content: Quote from: allikat on January 30, 2015, 07:05:04 amIf you right click on the video in Chrome you get an option for "Stats for nerds" which will tell you what acceleration it's using, if any.

author: ludek
author_rank: Newbie
timestamp: January 30, 2015, 09:08:22 am
content: Quote from: Smokey on January 30, 2015, 05:35:40 amThanxPage 28 shows also configuration, that's interesting solution.I have one more question about what Dave said. What is this HP200 thing? Is this a device model? Or electronic part number?BTW I've watched this episode in 1080p quality and 25(or 30?) FPS mode and the quality is more than good. No compared to other framerates.

author: EEVblog
author_rank: Unknown
timestamp: January 30, 2015, 09:11:58 am
content: Quote from: hikariuk on January 30, 2015, 08:03:17 amMine just showed 37Mbps bandwidth for one of my 1080p50 videos!

author: EEVblog
author_rank: Unknown
timestamp: January 30, 2015, 09:12:59 am
content: Quote from: ludek on January 30, 2015, 09:08:22 amThe product that started HP:http://www.hp.com/hpinfo/abouthp/histnfacts/museum/earlyinstruments/0002/

author: hikariuk
author_rank: Unknown
timestamp: January 30, 2015, 01:39:32 pm
content: Quote from: EEVblog on January 30, 2015, 09:11:58 amI think DASH uses as much bandwidth as it can - it dynamically adjusts the quality of the video based on the throughput it's getting. That may be why some people are perceiving lower quality videos: their connections aren't up to snuff.(http://en.wikipedia.org/wiki/Dynamic_Adaptive_Streaming_over_HTTP)Just noticed the HTML5 player doesn't actually show you the acceleration info either; that only comes up for the old Flash videos.

author: EEVblog
author_rank: Unknown
timestamp: January 30, 2015, 01:50:43 pm
content: Quote from: hikariuk on January 30, 2015, 01:39:32 pmThat makes sense. Nothing wrong at my end at all.It wouldn't be sensible for me to go back because of a few complaints. Youtube is always changing it's compression and delivery of content, always has, always will it seems. Content producers shouldn't go chasing the Youtube tail, you'll never win.

author: hikariuk
author_rank: Unknown
timestamp: January 30, 2015, 02:30:36 pm
content: Quote from: mojo-chan on January 30, 2015, 02:17:38 pmErm, I actually can't see any difference between those two images.

author: Andy Watson
author_rank: Super Contributor
timestamp: January 30, 2015, 02:47:36 pm
content: Quote from: hikariuk on January 30, 2015, 02:30:36 pmNeither can I

author: c4757p
author_rank: Super Contributor
timestamp: January 30, 2015, 02:51:59 pm
content: They look slightlydifferentto me, but neither looksbetter.

author: Fungus
author_rank: Super Contributor
timestamp: January 30, 2015, 02:57:48 pm
content: Quote from: mojo-chan on January 30, 2015, 02:23:00 pmUmmmm...no.

author: hikariuk
author_rank: Unknown
timestamp: January 30, 2015, 02:58:31 pm
content: Quote from: Fungus on January 30, 2015, 02:57:48 pmYeah. Wrong way around.

author: elgonzo
author_rank: Unknown
timestamp: January 30, 2015, 04:18:40 pm
content: Quote from: mojo-chan on January 30, 2015, 03:34:56 pmYes, and noJEDEC kilobyte = 1024SI kilobyte = 1000kibibyte= 1024

author: Quarlo Klobrigney
author_rank: Super Contributor
timestamp: February 01, 2015, 03:43:06 pm
content: Dave, please wash your hands. Here in Florida, I am all to well acquainted with those splotches in the power supply. They look to me to be all of the residue of cockroach shit. They like the warmest part of a piece of electronics, i.e. the power supply, output sections, resistors and displays. I not saying that is what you have there, but it sure looks like it. Wear some gloves as cockroaches carry disease, and clean that crap out of there.Otherwise good video and nice piece of kit from the old days with engineering that was good enough. "We don't need no stinking software. Why in my day, everything was analog and will still be analog. This digital stuff is just a fad." Apparently what the engineers say at that company that built that thing.BTW, I always thought that Vactrols were a linear analog pot. Some of the uses I put them to were in audio limiters and compressors. Of course now that can all be done in silicon and software.

author: funkyant
author_rank: Unknown
timestamp: February 03, 2015, 12:24:54 am
content: Quote from: mojo-chan on January 30, 2015, 02:23:00 pmThe streaming encoder only updates blocks of pixels where there is a change detected between frames. A still image at 10 billion fps will use pretty much the same bandwidth as a still image at 25 fps. This is how VBR works.However, when there is motion involved such as panning, other vector algorithms come into play. For example in a slow panning image, the codec will extrapolate groups of pixels moving linearly in a particular direction and simply use vectoring to move them, and only redraw new information coming into the frame. Again, higher framerates don't really affect bitrate, because although there are more frames, each frame introduces less information, and this ratio is directly proportionate (however there is some overhead in front/ back porch and the like).Even on a cut frame between two completely different frames of high complexity, the bandwidth required is a factor of resolution, not so much framerate. The only time this is not true, is if the cuts are happening faster than the base framerate (25fps in your example). An instance this might happen is if you shot 60fps random noise on a scope screen compared to 25fps - then you would eat into bandwidth and resolution would most likely be compromised.BTW this is what they mean when you hear temporal algorithms mentioned with regards to video codecs. The encoder is looking ahead and comparing frames and subdivisions of frames (referred to as blocks) classifying their 'behavior' and then going back and marking the blocks accordingly as they are drawn so they can be handled in the most efficient manner. These days the algorithms are so complex that they are nesting blocks within blocks, so you can have a large block with vector movement, which then has a sub section which is being refreshed with new information as it's parent block is vectored across the screen. Ah, my head hurts now...Watch your software when it's rendering (or encoding) and see how quickly it smashes through still images and slow pans, compared to cuts and very fast pans. The codec only updates what it needs to. The look ahead is also a part of the reason why the progress bar gets to the end before the render is actually complete.Uncompressed formats update every frame in its entirety, every time, even if two adjacent frames are identical.

author: EEVblog
author_rank: Unknown
timestamp: February 03, 2015, 01:13:03 am
content: Quote from: mojo-chan on January 30, 2015, 02:17:38 pmNope, I can't see any difference at all.

author: EEVblog
author_rank: Unknown
timestamp: February 03, 2015, 01:15:47 am
content: Quote from: mojo-chan on January 30, 2015, 02:14:09 pmLet me see if I get this straight. Your complain is only that the 25fps video youtube is delivery (from my 50fps source) is worse than my original 25fps uploaded content?BTW, how can you know this when you don't have a the exact same clip uploaded in 25fps, and 50fps?

author: EEVblog
author_rank: Unknown
timestamp: February 03, 2015, 01:16:52 am
content: Quote from: mojo-chan on January 30, 2015, 03:40:53 pmYou're kidding right?This is your example of the quality difference you are complaining about? Seriously?

author: EEVblog
author_rank: Unknown
timestamp: February 03, 2015, 01:19:07 am
content: Quote from: mojo-chan on January 30, 2015, 03:33:15 pmOf course it will be recompressed! This is what Youtube does, it re-encodes everything that gets uploaded, and it's always re-encoding and changing the compression and quality of content in the background without anyone knowing, based on what new wizz-bang technology Youtube has this week.

author: funkyant
author_rank: Unknown
timestamp: February 03, 2015, 09:44:51 am
content: Quote from: EEVblog on February 03, 2015, 01:16:52 amloooooool

author: TheRuler8510
author_rank: Regular Contributor
timestamp: March 27, 2015, 01:36:50 am
content: Anybody know what the 4601 AC voltage standard is worth?I picked one up recently cheap and I'm wondering if it is worth selling or if I should keep it. None have appeared on eBay in a while.Regards,

author: BrianHG
author_rank: Super Contributor
timestamp: January 03, 2017, 04:06:50 am
content: Correction on vactrol datasheet, this is the actual part used in the EDC 4601 AC Voltage Standard:http://www.excelitas.com/downloads/dts_vtl5c2232.pdfThat center tap is crucial if you want to correct for the ageing of the led, photocell & if you want to perfectly match multiple vactrols.I used to use these for an stereo audio pre-amp electronic volume control. The LED current to output resistance generated a nice clean curve. The photo resistor element responds exactly like a clean noise free, 2 matched variable resistors pots with a center tap. The slow response of the photocell filtered out all higher frequency electronic noise from the led. Though obsolete today, it was still useful around the early 2000s for some niche applications.