Analog newbie, requesting help recomissioning a tiny and obscure scope! - Page 1
Forum section: electronics / repair

author: Riverturtle
author_rank: Newbie
timestamp: May 04, 2020, 03:09:46 am
content: Hello all, I recently picked up a neat old oscilloscope from an eBay thrift shop. It's a VU-Data model MS210A, and I've had a hard time finding *any* information about this scope online. Basically all I know about it is what I can glean from looking at it and pictures of others on the internet. It looks like this unit came out of a large rack mount case which held several of these individual scopes in the case. I don't have this case.What I do have is one individual unit which *appears* to me to include most of the oscilloscope circuit except for the power supply. Given that I know very little about this scope (and am a beginner to analog scopes in general), I'd like to ask the EEVBlog community for some help pointing me in the right direction to build/assemble/acquire a power supply which should work for this thing and how exactly to hook it up.The scope attaches to the power supply through the 18-pin plug on the back of the unit. There are markings on the bottom which give some information about what each pin is for but I'm unfamiliar with the nomenclature and general layout of this thing so not all the markings make sense to me. What I have figured out is that pin "7" on my photo goes directly to pin 8 on the crt (through the white-blue wire) and pin "15" leads to pin pin 3 on the crt through the red wire. Other than that I assume some of the markings are voltages (0, 5.5 etc) and some markings describe the pin on the crt connected (3 and 8 at the bottom of the pcb). Otherwise, I'm clueless!Can anyone help lead me in the right direction or does anyone possibly have information/documentation on this scope or the tube? Again I am very much a beginner to the old analog electronics so a lot of this doesn't make much sense to me. Any and all help would be much appreciated! Would love to get this little guy up and running without letting the magic smoke out. Thanks! Photos of my board and the unit it came out of are attached.

author: Riverturtle
author_rank: Newbie
timestamp: May 04, 2020, 03:11:25 am
content: Close-up photo of underside of connector, since it didn't get attached before.

author: bob91343
author_rank: Super Contributor
timestamp: May 04, 2020, 06:35:59 am
content: Well the 6.3 is the heater voltage for the CRT. I think the 190 is a voltage input.However, this is very old technology and I suspect the bandwidth of the unit is rather limited. Plus, the controls are so abbreviated that it's probably only useful for a monitoring station and not intended for general purpose.I remember the brand but never used one. Did you Google it? There may be some info online. I believe they sold their gear through distributors and probably were listed in the EEM or Radio's Master catalogs. I would guess it goes back to around the 1960s. Are there any date codes on the components? Maybe even germanium transistors.

author: Riverturtle
author_rank: Newbie
timestamp: May 04, 2020, 08:46:24 am
content: Thanks, I appreciate the info. I have done a fair bit of googling, both for the scope and the crt, but haven’t found any luck. I’ll try looking for those catalogs, although I don’t imagine they’ll be much help in getting it running.Definitely of limited utility but I have a DSO for things that require a real scope. Just hoping to make this, like you said, a monitor for testing audio equipment etc. I believe the tube has a date code from 1976 on it so older, but not as old as you were guessing.

author: oPossum
author_rank: Super Contributor
timestamp: May 04, 2020, 10:22:40 am
content: Based on the marking on the PCB the pinout seems to be...1 Rec vertical input signal2 Rep vertical input signal3 +190 VDC (focus)4 Gnd5 +5.5 VDC6 NC7 6.3 to 8 V (heater)8 NC9 Gnd10 Rec vertical input ground11 Rep vertical input ground12 +40 VDC (brightness)13 -5.5 VDC14 External trigger15 -1970 VDC (anode)16 NC17 NCSo you would need 6 different voltages to power it up.

author: PaulAm
author_rank: Frequent Contributor
timestamp: May 04, 2020, 01:30:03 pm
content: VU-Data seems to have existed in the late 70s, early 80s.This looks like a special purpose signal monitor with basic H and V amps on the board. I'm not sure I would classify it as an oscilloscope.What could you want to monitor with 7 channels? Maybe an audio session?

author: CaptDon
author_rank: Super Contributor
timestamp: May 04, 2020, 03:50:57 pm
content: What is the number on the CRT?? Do you own just one scopeor the whole 7 unit assembly? If you have the whole assemblythe power supply is right there. The other posters have providedprobably enough info to get just one module running if that isthe only piece you own. I have seen these complete units showup on Ebay from time to time. Even seen them show up bothwhole and in pieces at the Dayton/Xenia hamfest.

author: Riverturtle
author_rank: Newbie
timestamp: May 04, 2020, 05:01:31 pm
content: QuoteHey, thanks for the help! Pins 8 and 16 are both definitely connected though, looks like they both wind up at the intensity pot. Could those be -2000 and -2045 VDC like it seems to be marked?QuoteQuoteThanks, I appreciate the background info. I don't have the whole assembly, just the one unit which is why I'm trying to reverse engineer the power supply requirements. No idea what the original use was for one of these either, but if anyone knows I'd be interested to learn. I just picked it up for a little fun since it was cheap. If I get it running I may get another unit and have each monitoring a channel of my stereo system.I did fail to mention that the crt number is 5960-00-126-3429. There's another number, 3E34P31 that seems relevant. Made (or at least sold) by Thomas Electronics Inc in New York. I googled the best I can and wasn't able to find any sort of specifications on the tube but maybe someone will have some experience with it.

author: CaptDon
author_rank: Super Contributor
timestamp: May 04, 2020, 05:38:07 pm
content: Several things, The -2000 is not the anode, but the cathode of the crt.The CRT filament supply 6.3v should in some way be coupled to the cathodesupply voltage so that you don't have a large difference of voltage betweenthe cathode and filament. Typical scope power supply transformers includea crt filament winding that is specially insulated to withstand the high voltageand often one side of the filament supply, or its center tap is connecteddirectly to the cathode. the +190 probably supplies the anode as well as thedeflection circuits. I have seen these Vu-Data units used with telemetryrecording and the REC/REP was live data to the recorders (REC) and playbackdata from the recorders (REP). Telemetry data was often audio frequencycarriers that were FM or PSK modulated. Data could come from Radiosondes,test aircraft, target drones, satellites and even buoys. These units were kindof popular in the technology corridor of Rockville/Frederick/SilverSpring Marylandas well as Wallops Island Virginia.

author: bob91343
author_rank: Super Contributor
timestamp: May 04, 2020, 06:42:35 pm
content: 3E34P31 is the industry standard number for the CRT. Maybe you can get lucky and find the specs on it. The P31 is phosphor number 31, a common one for oscilloscopes and radar. The initial 3 is the size group, 3 inches. The 34 is the specific part.You might consider sending email to these guys:https://www.thomaselectronics.com/manufacturers/

author: Riverturtle
author_rank: Newbie
timestamp: May 04, 2020, 10:49:25 pm
content: QuoteThanks! At the very least I now know what color it will beQuoteSorry, I'm a little confused by what you said about the filament (same thing as "heater", correct?) and cathode voltages. The filament voltage (6.3 V) and cathode voltage (-2000 V) should be "coupled". Do you mean that they should just be fed from the same transformer basically and not isolated? I don't see how this would make it so that there isn't a large difference of voltage between them. Do you mind clarifying?

author: CaptDon
author_rank: Super Contributor
timestamp: May 05, 2020, 02:48:27 am
content: Generally on small general purpose scopes they use a rectifier to get the high negativevoltage. -2kv is actually typical even up to the 5 inch crt's. The filament gets 6.3vacapplied to it. Often the cathode connection and one side of the filament (heater) aretied together. You should google up the schematic for one of the old Heathkit scopeslike OS-8 or similar and familiarize yourself with how heathkit built their old scopesfrom the 60's and 70's. Maybe look up the good old Eico 460 scope. The schematicswill be similar. Look at how they do the high negative voltages on the back end of thecrt and only moderate positive voltage on the anode +300 to maybe +400. Typical onthe old scopes would be -2000 on grid 1, -1940 on the cathode which makes the grid 1appear more negative than the cathode and that is correct to control brightness. The lessof a difference between cathode and G1 the brighter the spot will be. The focus will bearound -1850 to -1750 adjustable by the focus control. The deflection plates will usuallybe around +180, the astigmatism grid if it has one will be also around +180 and thepost accelerator anode if it has one can be anywhere from +300 to +2kv. These are typicalvoltages for an electrostatic focus - electrostatic deflection CRT. Google up a 5CP1 forexamples. I wonder if your scope is magnetically deflected with a yoke on the neck??If so it is a whole different ball game!!!! I don't seem to see enough leads coming outof your CRT to have electrostatic deflection. Can you see a yoke (coils of wire) on theneck of your CRT?? It would sit right where the neck begins to flare out.

author: bob91343
author_rank: Super Contributor
timestamp: May 05, 2020, 05:22:58 am
content: I would vote for it being electrostatic. Otherwise one would need a complicated yoke driver for each axis. Little CRTs were never magnetic deflection.

author: Riverturtle
author_rank: Newbie
timestamp: May 05, 2020, 06:30:14 am
content: OK, beginning to understand better. I haven't looked at the schematics for the scopes mentioned yet but I did tear this one apart a bit and what you're saying seems to align with what I'm seeing on the tube and from what I've gathered by tracing back the connections on the PCB.Fairly certain this is indeed electrostatic. There is a coil around the neck but pretty sure that is for angle adjustment..? The tube is 8 pins. I actually did a little more google sleuthing and came across one old document from Thomas electronics detailing a CRT that looks *very* similar to the tube in my unit, with a different model number, 3ASP. I'll attach the PDF. Interestingly the part number in the PDF is nowhere to be found on my tube but they are the same size/shape, same number of pins, and (from what I can see looking at my tube) same pinout. So maybe mine is at least functionally compatible with the 3ASP, which was also manufactured by Sylvania. Not sure why they would have done this butGoing to start working on assembling a little power supply for this guy. Anyone know of a decent kit that will do it all?

author: Gyro
author_rank: Super Contributor
timestamp: May 05, 2020, 09:08:23 am
content: Just in case you haven't realised, the tube on that one is dead - the two white getters indicate compromised vacuum. It also makes it a good candidate for reverse engineering the PCB though.

author: CaptDon
author_rank: Super Contributor
timestamp: May 05, 2020, 02:05:43 pm
content: Yes indeed, the 3asp1, 3asp7 and so forth. They were usedin many things for the military. The other poster is very very correct,Your CRT is toast!!! It has a crack somewhere and as they say"Went to air". I see a black lead and a little cup for the anodeconnection and it looks like the anode was run at a voltagethat was at or near zero ground potential. The coil on the neckis for 'rotation' alignment as you suspect. I have a little CRT hereon my shelf pulled from a wrecked Tektronix 212 or 214 I forgetwhich. I keep it as a spare for my SC501 which uses the sameexact tube. It has 11 pins (Tektronix CRT's had extra grids whichmade them superior is sensitivity and small spot size) and arotation coil like yours. I ruined one of these CRT's years agoby putting 6.3 volts on the filament. It actually has a .6 voltfilament and I didn't see the decimal when I looked at the schematic!!!Oh well, this is how we learn!! Just hope our mistakes costless than a supper at Red Lobster!!!Cheers Mate!!

author: rsjsouza
author_rank: Super Contributor
timestamp: May 05, 2020, 03:34:48 pm
content: Quote from: Riverturtle on May 04, 2020, 03:09:46 amAh, then that was you... I was eyeing this little scope and, for the same reason as you, I couldn't find any information about it. I am sorry to hear it is toasted.

author: Riverturtle
author_rank: Newbie
timestamp: May 05, 2020, 04:40:24 pm
content: lack of experience strikes again! I was thinking those getter spots looked pretty crusty.QuoteI guess you're lucky I pulled the trigger firstOh well, learning a lot from this adventure for the price of a couple movie tickets. time to see if I can track down a replacement crt. Thanks everyone for the help!

author: james_s
author_rank: Super Contributor
timestamp: May 05, 2020, 09:39:21 pm
content: Quote from: bob91343 on May 05, 2020, 05:22:58 amI have several CRTs ranging from 0.5" to 2" that are magnetic deflection. These are video CRTs from viewfinders though, not oscilloscope CRTs. Scope tubes were always electrostatic until DSOs.

author: Riverturtle
author_rank: Newbie
timestamp: May 22, 2020, 09:01:25 pm
content: Update! I managed to score another complete MS210A unit. It was again a gamble but the CRT on this one appears to be intact!I also purchased a couple of HV power supply kits from an eBay seller (who may even be on these forums somewhere?)Charge pump multiplier:https://www.ebay.com/itm/Charge-Pump-Multiplier-Kit-HV-for-CRT-Photomultiplier-PCB-Parts-MP01/153915975308HV Power supply:https://www.ebay.com/itm/HV-Power-Supply-12V-In-45-to-190V-Out-5-5W-Nixie-Old-Radio-US-Seller/153938534422?hash=item23d773a016:g:eiEAAOSwAyJc7s~0With the combination of these two boards I should be able to generate at the lowest -1520 volts, which is ~500 volts higher than the -2045 volts the scope seems to have been designed for. Does anyone know if it can be run "undervolted" so heavily? Or will there be serious side effects? If it's inadvisable to try I'll just purchase another HV power supply capable of closer to 250v.

author: bob91343
author_rank: Super Contributor
timestamp: May 22, 2020, 09:09:57 pm
content: When you reduce the high voltage the trace becomes dimmer, goes a bit out of focus, and the deflection sensitivity increases. So you get a bigger display that isn't as bright or sharp.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: May 22, 2020, 10:51:19 pm
content: I repaired a VU DATA scope several years ago. It was an old portable TV repair scope. Maybe 15 MHz, don't remember exactly. I could not find any useful manuals but I found that the scope was a knock off of a Tektronix scope.The Tek schematics seemed to match the scope.It was a much different scope than you are repairing but maybe there is a Tek equivalent.Wally

author: CaptDon
author_rank: Super Contributor
timestamp: May 23, 2020, 05:48:01 pm
content: -1500 instead of -2000 should barely make a difference. Look up the typical voltageson the 3asp1. With these older CRT's it is basically a ratio thing. It looks like they ranthe final anode (the cap connection on the side) close to ground or maybe around +200or so. The cathode, G1, and Focus grid are negative referenced to ground, but measuring fromthe cathode, each element farther forward in the gun structure is also more positivelycharged than the element behind it. Although the anode is usually run at a high positivevoltage it can in many cases be only slightly more positive than the voltages on the deflectingplates. Some CRT's run the final anode and accelerator grid together on the same pinand same voltage. 5UP1 and 5DEP1 are examples. My PPI display with a 5CP7A has -1500at the back end of the tube and +3000 at the front end. They did this to get a very brightflash of the echo (blue flash) which excites the 'glow in the dark'...afterglow of the yellowishphosphor so the target appears to remain lit. There is an orange filter in front of the tubeto remove the bright blue flash. If you shine a flashlight on this CRT in the dark it will afterglowfor about 30 seconds, typical of the P7 radar phosphor. Have fun with your project!!