Datron 1030D RMS Voltmeter

[telectric]

I've been working on a Datron 1030D RMS voltmeter for a while now and am getting no where trying to trace out the design.  I have looked high and low for a service manual for this model but have not found one.  While the 1041 has some similar circuits the assembly drawing with the component reference designation is completely different.
So if someone has a 1030 manual and would like to make a  copy or sell the manual I'd be willing to pay a reasonable price plus shipping.  Or better yet if someone knows where to find a scanned copy and can point me to the download location I'd be one grateful & happy camper.

Thanks

[Gyro]

Damn, I can't keep my head down any longer.

I have a bunch of vintage Datron kit, a 1041, 45, 51, and a 1030A. I was the one who scanned the 1041 and 1051 manuals on KO4BB... with the help of a fellow 1051 owning member, who stiched the schematics and straightened the pages for me.

I have the 1030 Manual, the component layout matches my 1030A (the original 1030 was a slightly less polished layout). I have no idea what the differences are with the 1030D (or presumably 1030C), presumably they are later tweaked versions.

The A/D / display PCB is identical to the one on the 1041, just depopulated for the lesser requirement (in fact, add one ttl counter chip and cut a link and you get the enhanced resolution 4 1/2 digit option.

The problem is that the 1030 is very well documented, ie. a lot of pages, schematics larger than A4 etc. I knew ought to scan and upload it at some point but wasn't looking forward to it. You'll probably need to give me a couple of weeks to do it.

Is there anything specific that you're looking for immediately, or a specific fault? I can take a couple of snaps with the camera if so.

[telectric]

Chris,

Thanks for the reply.  I came across most all your posts in the EEVblog but not much on the 1030x.  A couple of discussions, one with some one generous enough offering to give two away and another discussions but no mention of where to get a manual for the 1030 series. I did download the 1041/1051 manual from KO4BB boat anchor site.  Thanks to you and the person who helped you for all the effort to get it out there.

Right now all that's displayed is a decimal point which will follow the selected range.  Occasionally all decimal points show up and even less frequent I'll have some digits when first turned on. Either of these two will stay until a range button change. Then back to one decimal.  I disconnected the input wires from the back of the front binding post so I could check that the flat cable connector was OK.  Lucky I did this because I found a pin folded over. Correcting this didn't help fix the other problem(s).

I have checked the power supplies and have done some input tracing through the front end of the AC board, checked that the relays are switching and contact is being made in each of the positions. I've not done any verification if there's any voltage drop across the contacts but I'm don't think this matters to much at this time. If needed I'll clean the contacts once I have the unit working. This is about as far as I've gotten.

I'll get back to it one night this coming week and use the 1041/1051 schematic and hope the test points match the 1030D.  If they do then this will help considerably.

A photo of the 1030D AC board is below so if it comes close to matching that in the 1030 manual you have then I'd appreciate a quick snapshot showing the component reference designations.  I am in no hurry for a complete manual but would like to have one sometime if you do get around to scanning it in. I'd be happy to contribute to the effort in any way that would help.

Thanks again for responding and your offer to help. It's really appreciated.

Tracy

"And your name is..."

[Gyro]

Hi Tracy,

Glad to be of help.

That looks in very nice condition internally. It looks like one of the later "Datron Instruments Limited" front panel Logo ones (earlier ones just said "Datron"). From the size of the grey capacitors and the manual, I've figured out the 1030D bit. The D refers to the filter combinations. The 'D' configuration has minimum frequency of 10Hz (normal) and 0.1Hz (LF mode). You will probably want to change it to the Default 'A' configuration at some point (40Hz/1Hz) as it significantly improves settling time (the options are all in the manual anyway). Despite their age, these meters have really good specs and are very useful. Nice Panaplex displays too.

Firstly, treat all Tant bead capacitors (particularly the ones near the regulators on the A/D board) with extreme caution, I've had several fail. Replace with higher voltage ones at the first opportunity. Failed tants can also cause all sorts of fault symptoms if they pull down the +/-15V rails (or leak too much), finger check the temperatures of the relevant strip metal heatsinks.

The other thing to remember is that with these Datrons, overload is denoted by the display blanking, so apparent display problems can be nothing more than out of range input (particularly with the DC high impedance models). I worked out an easy mod for this, to give the more common +/- leading 1 on overrange. Just add a diode (1N4148 is fine) between  M9, pin 6 (anode), and M15, pin 8 (cathode), no track cuts needed. It might just be worth adding this as a diagnostic measure anyway. The 'sig'  pin on the A/D board is expecting a 1V scaled input voltage (max 1.999V), so if that isn't happening, the display will blank otherwise.

I've attached photos of the board idents and schematics, hopefully readable enough to get you going. The decimal point issue ought to be fairly trivial to trace, as you found, issues with the ribbon cable can cause issues. The switches are normally very reliable and actual functions on the board are JFET switched rather than relying on contact resistances. You'll see that the A/D board is a part loaded 1041 (and 1045) board - it doesn't need to handle negative inputs, no autoranging etc.

I hope this gets you started. I've just remembered that the manual is ring bound which will make scanning a bit easier.

Chris.


P.S. I've had to compress the images a bit to fit. They still look readable but if you want the full res ones, I've uploaded them to uploadfiles.io https://ufile.io/i3wq2onk available for 30 days. No need to create an account, just use the free download option. 

[telectric]

Chris,

Perfect!!  That's exactly what I needed.  I did download the high res shots and then cleaned them up with some changes in brightness and contrast using GIMP.  They came out fantastic once printed. Even on letter size paper I can see everything clearly. Nice job of taking the photographs.

I'll start t-shooting again in the next day or so and feel pretty confident (famous last words) that I can get this 1030 back in good health.  I have read a lot of good things about the Datron meters and that's why I picked this one up.  Plus I just don't have enough meters as it is, ha ha.

I'll implement your tips and mods once I have it working.  They seem very worthwhile. BTW do you work or did you work for Datron?  You appear to be at guru if not wizard status with all that you know about these meters.  Just curious!

Not only is it clean on the inside the outside it in really excellent condition as well. It's going to be a nice addition to one of my benches.

I'll post what I come across and what the root cause was as I go along.

Thanks again for your help.

Tracy

[Gyro]

You're welcome Tracy,

Yes, the images did look a bit dark when I uploaded them, I'm glad they responded to a bit of manipulation.

No, I never worked for Datron (who were bought out by Wavetek. I think they retained the name on some of their high end meters and calibrators though). I wish I had, they were very good at attention to detail and extracting the maximum performance from the semiconductors of the day.

I don't know about the wizard status! I got interested when I found an early 1045 DC voltmeter,very cheap, in the bargain section of my local surplus store, a good 30 years ago. With 0.01% +/- 1 digit basic accuracy, 1uV resolution and high impedance input it was a big step up from anything else I had. I just started picking them up occasionally after that, so it's really just having spent decades playing around with them (sorry, no magic).

With the 1030, 104x and 105x series, there's pretty much nothing in them that can't be fixed or maintained. Compared to the 106x family that followed then (and retain many of the same analogue bits) they are much easier to work on... Panaplex displays, but standard rather than the custom one, all discrete logic, signal transformer galvanic isolation rather than commonly troublesome optos, no micro, eproms, batteries etc. to worry about, built like tanks (especially the mil spec ones) and more compact too (There's no way I could fit the depth of a 106x on my shelves).

A link to my current good ones... https://www.eevblog.com/forum/chat/show-your-multimeter!/msg793266/#msg793266

Good luck with the repair, all of the logic is socketed so watch out for the occasionally bad pin connection. Shout if you run into a problem. I'll hopefully have the manual scanned by the time you need to tweak any calibration.

Chris.

[Gyro]

As promised, I have finally finished scanning the Datron 1030 combined Operator and Service manual. It's a pretty comprehensive manual with plenty of circuit description, full parts list and all of the options. Importantly, It also contains the component value tables for the various low frequency cut-off  filter combination options. I've had to split the A3 sheet size diagrams but there is plenty of overlap.

The manual is a nice reminder of the days when decent handwriting was an important skill for an engineer!

I've uploaded the manual to KO4BB, but as manuals sometimes takes a little while to go live, I've also uploaded it to Uploadfiles.io (link valid for 30 days, use the free download button)...  https://ufile.io/huar3sba


EDIT: Now available on KO4BB...  http://www.ko4bb.com/getsimple/index.php?id=manuals&dir=06_Misc_Test_Equipment/Datron/Datron_1030_True_RMS_Voltmeter

[telectric]

Chris,

Sorry I fell radio silent for a while.  I was able to confirm the pre-amp and RMS converter were functioning with the first set of schematics you supplied.  I then moved onto the A-D and display digital section.  Feeling confident that the analog parts were likely working on this board I started looking at the the display section first.
Also I could understand the digital much better than the analog.  After spending a fair amount of time I figured out that no pulse was coming out of M7 to clock the 74L75's. It was here that I became really puzzled and turned off the o-scope and took a break.  I checked back to this topic and found that you had scanned the entire manual and made it available.  So I down loaded it and started reading the design descriptions.   It was what I needed to intelligently continue t-shooting.  Thanks a lot for going to the extra effort to supply the manual. So I finally figured out where the problem was, the integrater M33 was not functioning.  I found that resistor R134 was open from C48 shorting.  These two components are on the negative fifteen supply to M33.  So replaced both parts and turned the 1030 on and got a measurement display finally.  However it lasted about two seconds and R134 started smoking.  So, turned it off and checked that I didn't get C48 in backwards which I didn't. Checked R134 and C48 and they were still good.  So I took a chance & turned the power back on....got nothing but a decimal point on the display and R134 stayed cool.  Back to where I started.  I suspected M33 had an internal short that pulled a lot of current and caused the resistor to get hot.  The internal short must have cleared when I first turned it on and -15V was once again supplied to the IC.  Anyway I have confirmed that M33 is dead and have ordered some replacement LM101A's. Should see them by the end of this week.

One question I have is why is there  R134 (10 ohms) & C48 (22uF tant.)  on the negative fifteen supply of M33? Is this for supply sequencing so the op amp comes up properly? None of the other LM101A's have the resistor and capacitor on their -15V rails.  It's a curiosity that I am not sure about so I thought you might know.

This is the first piece of test equipment I've worked on that has so much transistor and diode logic implemented with discrete components.  It's taken my back 45 years when I actually worked with transistors and diodes to do logical functions.  Long forgotten knowledge though so it was very interesting and thought provoking and I have enjoyed working on this project immensely. I'm also looking forward to having the 1030 functioning properly. I'll do the calibration steps and then hopefully I'll be able to supply a picture showing it along side the 3458A with it's four and a half digits matching the 3458A's with both attached to the Datron 4200 AC Standard I have.

Thanks again Chris for the documentation and your help.

Regards,  Tracy

[Gyro]

Hi Tracy,

You're welcome, I'm glad all that scanning helped.

No, I don't know why they added the extra R134/C48 RC filter to the -ve supply of M33. As you say, it's not there on the other opamps. All I can think is that they felt the need for a bit of extra filtering for noise rejection on the integrator by AC referencing the supply it to signal ground. I checked the 1041 and 1045 and they are both the same, so it's nothing to do with the 1030 being positive polarity only (they have nothing equivalent on the +15V). I don't think it's for supply sequencing though, the converter is pretty latch proof err, it might be to guarantee a comparator pulse at startup now you come to mention it. 

As you say, the obvious reason for R134 smoking would be a shorted C48 Tant (I think I've had that), but you replaced that That shouldn't take out the opamp though. It's pretty unusual for one of those metal can opamps to die. There's no particularly heavy load possible on the output, unless it is shorted, maybe an idea to double check for solder whiskers.

Btw, this is one of the areas where Datron cheaped-out on the 1030 A/D versus the other ones (presumably because of the lower accuracy spec). The 1041 and 1045 both use a larger cased Wima 470nF 400V Polypropylene capacitor for the integration capacitor C35. This has lower dielectric absorption to improve linearity. On the 1030, they stuck in a cheaper, lower voltage polyester! The other place they saved money was to use a 1N821 reference rather than a 1N827A. I suppose together, they did save a bit of money. The +5V reference opamp is also depopulated down to a resistive divider, which is reasonable as it will never be required to read negative values, just avoid it latching up. One amusing cost saving is the instruction, on the board layout, to remove (salvage) M13 and M10 after test for the 3 1/2 digit version. Luckily they didn't change to a 2 digit Panaplex too.

I agree, it's nice to see so much of it implemented in very basic discrete logic, it's part of the 'charm' (and repairability) of these meters, by the time they got to the 106x it was all cheap analogue switches and fudging in s/w.  I'm looking forward to seeing it working.


P.S. if you have a spare LM101, you can substitute M34 (LM741), as long as you add the required compensation cap on the bottom of board. This gives useful zero settling time improvement during warm up - it's more noticeable on the 104x though. You can find the 1041 manual on KO4BB too.

[theHWcave]

Hi Gyro, just bought a Datron 1030a from eBay, "for spares, not working". I hope I can get it working with the manual you so kindly provided.
Cheers

[Gyro]

Good luck 


Edit: Keep an eye out for hot 16V Tantalum bead caps on 15V supply rails - particularly the ones right next to the mains transformer, between the 15V regulators, on the A/D board. They always seem to go first!

[theHWcave]

Hi Gyro,
my 1030a arrived in mint condition but the display did not do much apart from lighting the V mv lights when switching range. I checked the rails and -15V was missing. Disconnecting the lower (RMS) board from the upper (AD) one, the problem was clearly on the RMS board and there appears to be just one Tantalum cap across the -15V to 0 rails. Not wanting to go through the hassle of removing the RMS board, I simply snipped one leg of the cap of and the short was gone. I have not done an exhaustive test yet but I checked 0.5V and 1V in the 1V and 10V range and the meter was spot on. 

In trying to prepare a shopping list for this and other Tantalum caps, I noticed that my meter is noticeably different from the parts lists, PCB layouts and schematics in the 1030 manual. The manual is not even consistent in itself.    For the AD board, the manual's part list list and schematic show for example the Tantalum cap for the 5V smoothing as C3 but the PCB layout diagram doesn't have a C3, instead it shows a C9 in that place.  Since you mentioned the similarities between the 1030 and 1041, I downloaded that manual as well and indeed the PCB layout for the AD board there shows a C3. So it looks as if the PCB layout in the 1030 manual is for previous revision and slightly different from part list and schematic.  Careful comparison of my actual AD PCB layout shows that it matches (or at least is closer to) the one in the 1030 manual.
For the RMS board there isn't an easy compare with the 1041 manual. All I can say is that my board layout is quite different from the one in the 1030 manual. Check the photo below and compare the locations of the big yellow 1KV cap and the two relays

Don't get me wrong. I am very grateful that you made the 1030 and 1041 manuals available  I can figure out the cap values from the schematic but I just wanted to mention that Datron left some inconsistencies in the manual in case other folks have the same problem.

One more question, if I may: Did you replace the Tantalum caps with new Tantalum caps or used electrolytic ones?  I am very tempted to use good quality electrolytic ones.

[Gyro]

Hi,

I'm glad you managed to get the unit working so quickly - yes, snipping Tant legs is by far the quickest way of debugging and doesn't seem to have sigificant material effect, maybe a bit more supply noise. I replaced with Tants because I had some, but there's no reason not to use modern electrolytics now.

Looking back over ebay listings, is yours item 325289589635 with the silver front panel? If so, I think it is a very early example (S/N 423!). I can't really tell from the photos, but it looks to have an LED display rather than panaplex. That would mean differences in the display drivers on the A/D board - I've never seen one of these in the flesh, in fact I didn't realise there was an LED model(?) until I saw the ebay photos.

I do know that Datron went through at least one (maybe 2 now) PCB layouts for the RMS board before the one in the manual, that probably explains the confusion.

It's great that you got it running so easily anyway. They're good meters, particularly on the10mV range (they are capable of measuring their own input noise (which can be subtracted from the reading) rather than dropping to zero reading below a certain level, like Agilent 34401A for instance. You also get AC or AC+DC RMS reading and different filter options and decent bandwidth.

[theHWcave]

Yes, that's the one and it has a LED 7-segment display. It is in an amazing condition. Practically new. No property tags or calibration stickers of any kind which is very unusual for a vintage meter (I have quite a lot, too many in fact). I  don't think it was ever opened before I did.

I had not even noticed that the display board is not the one in the manual, but I did wonder about your statement on how easy it is to convert to 4.5 digit display when I saw all the extra anode/cathode? resistors that need to be added. Both the AD-PCB and the display PCB are prepared for that but its quite a bit more work. Maybe I'll look into it when I extract the boards to replace the caps properly....

Thanks again

[Gyro]

It looks as if you have a piece of Datron history there. As I say, I've been into their earlier products for a long time now and I've never seen a hint of one like that, and the serial number is really low.

I'd appreciate some photos of the top side of the A/D board (preferably showing the rear of the display board too) when you next have it open.

BTW, if you're looking at enabling the extra digit, the simplest way of getting to the front of the display board (if you need to) is to unbolt the input terminal solder tags, remove the 4 screws holding the front panel and slide it forward over the buttons and away. That saves you having to mess with the fiddly wiring of the screened mains lead to the power switch and lets you keep the boards in situ. If you need to add a few discretes to the A/D board you can pre-form the leads, cut them short enough that they won't get close to the RMS board, insert and solder from the top side. I've done it several times when changing resistors and Tants.


P.S. I see that your RMS board is S/N 00006! It must have been from the very first batch of PCBs.

I've attached a photo of the older of my two 1030s, RMS board S/N 347, unit S/N 3164. It shares the same front-end and general layout as yours although it was clearly after they adopted solder resist and emptied the rear corner. I was curious about the way they had laid it out with that empty space, I wonder what the unpopulated section of yours would have done? I guess we'll never know. I notice that yours is before they lengthened the case too.

[theHWcave]

Hi Chris, thanks for that image and the info how the 1030 evolved. I attach an image of the AD board with the resistors for the LED 7-segment displays.
I noticed that on you image of the older AD board, Q4 also has a solder blob on top. Any idea why they did that? Testing them for temperature drift?

Regards
Heinz

[Gyro]

Hi Heinz,

Thanks for the A/D photo. Remembering now, I had a 1045 (DC voltmeter) in the same case format and the board looks very familiar (aside from the LED drivers). It is non-multiplexed so it has the same arrangement for the extra digit, 1 latch and 1 driver IC missing with associated resistors. The difference from the later ones is that they didn't solder in the sockets, test with the ICs populated, and then pull them out again on non-option models! A bit of a shame as it means that you do need access to the bottom of the board to fit them. First, you would need to check that the display board actually has the extra digit or at least the footprint and you can find a compatible display (not an issue on the panaplex ones because they were dual digit packages).

Yes, there is a Select-On-Test 'Factory Select Value' resistor trim for Q4 thermal matching (it's the dual JFET input stage), it's referenced on page 52 of the manual. The procedure includes a quick dab with a hot soldering iron on the package! Datron used a lot of 'SOT' 'FSV' resistor trimming during oven cycling and burn-in. The relevant resistors are raised on metal pin sockets to allow easy swapping and then soldered on completion. Being the 6th production board, it probably had the privilege of being performed, or supervised, by the designer, so is probably a rather well trimmed example.

I don't know if you noticed, but on my photo there is a second vertical brass screening strip, soldered further towards the rear of the RMS board, between the 3 SOT FSV resistors and the single trimmer cap (C24). It might be worth cutting something suitable and adding this (obviously being careful that it doesn't short the SOT FSV resistor pin sockets). They must have added it to improve performance (I think the circuit flow wraps back on itself in that area).

Regards,
Chris