Not sure if this has been discussed, but looks very interesting and I ordered a set:

"

Here you can buy a PCB-Set to modernize a HP 3400A to the latest 3400A Version.

It contains of the following PCBs: A6 Chopper Board from Defpom, A2 Impedance Converter Board

(no further need of the Nuvistor) and the A7 Power Supply Board. With the new A7 PS-Board you

can use silicon transistors not the old germanium types.

?

I'll add information about the new replacment parts and the new schematics to the boards."

Not finding the listing.

It is Germany. Seller chatted with me on Ebay messaging and said he will provide instructions in English. I asked for the BOM to see if anything unusual for US sourcing, which he promptly provided.

Search on Ebay "HP 3400A Board Set Modernization - PCB Set" and see if it comes up. I also used Google Translate for the resulting product page to go from German to English.

Seller is

Item number:186166001777

57 Euros, shipped to US

Michael may be out of stock which may be why it is not coming up. I sent him a message that members of the group are interested. Will let you all know.

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If the eBay seller has not enabled (at extra cost!) the ability to list outside the host eBay - .com, .de,.uk or whatever - a search by listing number from 'outside' will not find it.
I don't know if this is new but I just found this out trying to buy an item listed on eBay.com from the UK. Found it while on my .com account, tried to find it from .uk account it just came back with a "Sorry, sold out" message.
Talked to the seller and he told me the story (and changed his listings!)

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

Von meinem iPhone gesendet

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

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

John?? KK6IL

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

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

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

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

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

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

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

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

Hal