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The board arrived with his instruction to contact him by his email address. It bounced back after I sent it.
I left him an Ebay message, he has always eventually responded so not a big deal at this point. Just thought someone might know a better email for him.

on ebay when you purchase an item and pay for it, then you can exchange email/phone etc...
it will not block it

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Greetings,

I just did a redesign of these myself - for the chopper I used a 1N5817 for the diode and BC109Cs for the transistors because I already had a drawer full - although 2N3904s would work just fine in that application.? I used two 1N4151s for the input limiting, a NZX18B for the zener, a 2N3971 for the FET and a 2N6428 for the output.? Everything seems to work at least as well? as the original but I have not taken the time to really dig in and to more detailed testing. The response is a couple of percent high in midscale but I don't know if that is from the converter or is something from the input stage (which is all original.) I'll swap boards around with other units over the holidays and see if I can track that down - may be well be something related to the FET but we'll see...?

On a somewhat related note, I just made new versions of the boards for the 5087A - and relearned yet again that transistor footprints are **NOT** to be taken as a given. Sigh. At least boards are cheap now-a-days...

Hal

Received my three boards from Michael Muller, the Ebay seller in Germany.

Does anyone have his email address? The one he gave me is bouncing back and Ebay does not allow exchanging contact info.

Michael enclosed a note with order telling me to send him an email for updated BOM and other info.

I've had a good look at the differences between the Rev C & D boards and the pdf manual I bought.

Errors I found in the manual;

Parts list,
R601 should be 105k (was 174k) and R604 should be 174k (was 105k).
The circuit diagram, component layout & boards are correct.

Circuit diagram;
C10, missing '+' symbol
R615, decimal point missing from 61.9R

Differences between A6 Rev C and Rev D;

R608 was 22.1k, now 21k
R609 was 22.1k, now 21k
R610 was 2k, now 1.87k
R611 was 2k, now 1.87k
R616 was 1.21k, now 1.02k
R625 was 1M, deleted
R627 was 1k, now 500R
R629 was 100k, deleted

U602 was 1826-0310, now 1826-1381 (LT1012)

I haven't been able to verify all the diodes & capacitors, CR601 is not readable and some tantalum capacitors are facing the wrong way (both on my Rev C and Hal's Rev D).

---

I've now completed the Rev D design in KiCAD, I used the Rev C board for location measurements, then adjusted the traces for the Rev D design.

Most parts should be obtainable, the 2N4384 transistors seem to be obsolete, but I do have some BCY59X low noise NPN in my spares to try instead, the 1901-0518 Schottky diode I need to find some data for, Molex test point pins have been salvaged from some scrap SA plug-ins.

David

On Mon, Nov 20, 2023 at 04:01 PM, factory wrote:

it confirms the 1826-1381 for U602

Which is an LT1012 - I was very surprised to see that they used such a precision amp on purpose - the precision is not needed there other than to possibly not have a negative output; even in the 3400B they used one section of a LM324. Doesn't hurt but just seems like an unnecessary expense and a departure from any other in the series.

Hal

On Mon, Nov 20, 2023 at 09:32 PM, Harold Foster wrote:

My board was a revision "D" and I uploaded pictures to the 3400A area of the files section.

Hal

Thank you Hal, those pictures should have all the missing information, I can see they removed a double thickness ground trace from the front and made a much wider trace on the back, it confirms the 1826-1381 for U602. I'll check the resistors another night, getting late tonight here in the UK.

And Artek did have the correct manual, very quick response to my email and I now have an excellent quality manual covering the 1982-84 versions.


David

My board was a revision "D" and I uploaded pictures to the 3400A area of the files section.

Hal

Below is a partial screengrab showing what the dropbox email from Artek contained, from this you should be able to make out the Agilent front page on the second file, I've sent a message, hopefully they still have the scan they did, also odd as I didn't buy the first manual.


David

Thanks to both Hal & David for info.

The 03400-60013 manual covers 03400-66512 Rev A (prefix 2225) & Rev C (prefix 2415).
As has been suggested elsewhere, it's most possible the Rev D was only covered in a service note, there is a low resolution picture of this board on the web with 2713 on the sticker (1987 date?).

I've added pictures of several A6 boards I own here; https://www.eevblog.com/forum/repair/hp-3400a-ldrs-replacement/msg5015905/#msg5015905

For my new board, I'm very much in design stage, about 75% done in KiCAD, using my Rev C board as a guide.
The Rev D has minor component differences (two removed) around the meter amp U602, plus minor differences I can see to the traces above the edge connector, I want to keep to through-hole parts.
Also wanted to confirm the U602 part number (think it's 1826-1381 aka LT1012, but not 100% sure from the low res picture), less critical at the moment is knowing any resistor value changes, this can be done afterwards.

Need to ask Artek about the correct manual, I ordered the 03400-60013 at $9.95, but for some odd reason the dropbox zipped file contained the 3400A-OSM-90008 (an excellent scan from Artek) and that Agilent branded 03400-90013 pdf of poor quality.

David

David - you mention you are doing your own replacement for this board - if you are still in the design stage i would suggest you look at the OPA182 for the chopper amp - I used it in one I did a while back along with a very-much-overkill OPA197 for the output/meter driver (I had several available) and have had flawless operation - it's my daily driver on the bench.? Pretty much just duplicated HP's design other than the new parts and of course deleting the offset adjustment pot / quiescent current resistor required for the original MC3476.

Hal

On Sun, Nov 19, 2023 at 06:24 AM, factory wrote:

Also I've found there was an 03400-66512 Rev D board, but the manual fails to cover that. Has anyone got a good picture of that board showing both sides? As I'm currently working on making my own version of this board.

David

I'm *think* that I have one that has this revision - I'll check this evening and post pictures if I do.

Hal

I have the 03400-90013 version from Artek and it is a very good and clear scan of the manual with full page schematics and bookmarks - typical Artek quality... maybe your copy was overwritten or something?? I've accidently deleted a file before and they cheerfully resent it to me.

Hal

Strange . Not listed as available. Must be sold out .?

On Sun, Nov 19, 2023 at 06:24 AM, factory wrote:

The original boards with edge connectors were nickel or gold plated, the ones I saw on ebay looked to be HASL, this could be a problem with the gold edge connector sockets, a warning from an ex-HP designer that they can get quite stuck here;

I prefer my HP TE to be original where possible, but I do have a 1976 prefix design Rev. that got modernized by HP with a 03400-66512 Rev C board from 1984.
I've got quite a few 3400As, can't remember the PSUs causing much trouble, except where an incorrect manual was used by a previous repairer & Ge/Si parts got mixed up, some diodes & resistors changed for biasing, all mine are using Ge power transistors, TO-3 parts are getting pretty much obsolete these days anyway, so finding genuine parts from reputable suppliers is a problem.

Wonder what people are doing with the old but still working A6 boards? Noting the large & small optical chopper assemblies were used in other HP analog meters & some DVMs.

One thing I've never found is a decent readable manual for the later serial prefix of the 3400A, I tried the manual bundle from Artek, the 03400-OSM-90008 is a decent scan of the 1972 manual (marked part no. 01768 on the pages), the 1972 03400-90008 is available for free download, but I haven't checked how much it differs. But the 03400-90013 is the exact same one available by download from Agilent/Keysight, the scan quality isn't great.

Has anyone got a decent scan covering the later variants? i.e. A6 with part no. 03400-66512 Rev A & C,
Also I've found there was an 03400-66512 Rev D board, but the manual fails to cover that. Has anyone got a good picture of that board showing both sides? As I'm currently working on making my own version of this board.

David

David,
I have a PDF of the 03400-90013 manual that I downloaded from Didier's manual site (serial prefix 2415), It contains a readable schematic & parts placement for the 03400-66512 A6 board.? Not sure if the A6 covered is the version you're looking for; I don't know how to identify the board version covered in the manual. Both of my 3400As have the optical chopper (and still working well), so I can't help with a picture of the board you want.

It's the best scan that I've found for the 03400-90013 manual.??
http://www.ko4bb.com/getsimple/index.php?id=download&file=HP_Agilent/HP_3400A_RMS_Voltmeter/HP_3400A_RMS_Voltmeter_Service_Manual.pdf

On the impedance converter; according to the circuit description in the manual, it's just a unity gain non-inverting amp with hi input impedance and low output impedance, so that stage should be pretty easy to replace with many of today's opamps.??

Cheers,
DaveM

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The board set is visible if you click on completed auctions.

John?? KK6IL

The original boards with edge connectors were nickel or gold plated, the ones I saw on ebay looked to be HASL, this could be a problem with the gold edge connector sockets, a warning from an ex-HP designer that they can get quite stuck here;

I prefer my HP TE to be original where possible, but I do have a 1976 prefix design Rev. that got modernized by HP with a 03400-66512 Rev C board from 1984.
I've got quite a few 3400As, can't remember the PSUs causing much trouble, except where an incorrect manual was used by a previous repairer & Ge/Si parts got mixed up, some diodes & resistors changed for biasing, all mine are using Ge power transistors, TO-3 parts are getting pretty much obsolete these days anyway, so finding genuine parts from reputable suppliers is a problem.

Wonder what people are doing with the old but still working A6 boards? Noting the large & small optical chopper assemblies were used in other HP analog meters & some DVMs.

One thing I've never found is a decent readable manual for the later serial prefix of the 3400A, I tried the manual bundle from Artek, the 03400-OSM-90008 is a decent scan of the 1972 manual (marked part no. 01768 on the pages), the 1972 03400-90008 is available for free download, but I haven't checked how much it differs. But the 03400-90013 is the exact same one available by download from Agilent/Keysight, the scan quality isn't great.

Has anyone got a decent scan covering the later variants? i.e. A6 with part no. 03400-66512 Rev A & C,
Also I've found there was an 03400-66512 Rev D board, but the manual fails to cover that. Has anyone got a good picture of that board showing both sides? As I'm currently working on making my own version of this board.

David

I contacted the seller who is currently out of stock. He replied that he will get new PCBs in about a week.
I asked him to offer it ?worldwide“ on eBay which should make it searchable on ebay.com as well.

vy 73 Heinz DH2FA, KM5VT

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