HP410C late version - Page 1
Forum section: electronics / testgear

author: Ovi4
author_rank: Contributor
timestamp: July 12, 2023, 09:39:55 pm
content: Hi, everyone. I recently purchased a HP410C (E-bay) with no AC Probe and in my mind and according to what I've seen so far (On YouTube and other places) it is a hybrid meter that has tubes and solid state components as well.Well, ... to my big surprise the item that I received is nothing like I thought It would be, simply because it has no tubes, no stereo (audio style jack for the AC probe) but has a BNC style socket instead. Further on inside, there is no optic chopper to be seen but there is some sort of newer revision PCB that no longer uses a chopper component but some FET transistors and some op-amps (I think).So, after searching high and low... For the life of me !!! I just simply could not find a full manual for this version other that the 1 page solid state module schematic diagram only the one that seems to have replaced the chopper version found on BAMA site.I've attached some relevant pictures below.I really need the full manual since I really need to know what kind of newer version AC probe it has and how it is built since it no longer uses the tube style oneNow, if anyone has or knows where I could get a full service manual from, would be of a great help.Any links or pointers are much appreciated.Thank you

author: TimFox
author_rank: Super Contributor
timestamp: July 12, 2023, 09:42:31 pm
content: I can't tell in your attached photo:Is the AC probe connector a BNC or a triaxial connector?

author: Ovi4
author_rank: Contributor
timestamp: July 12, 2023, 09:50:18 pm
content: Hi, it is shown at picture number 7 as you count from the top down, and yes is a normal BNC style socket.

author: factory
author_rank: Super Contributor
timestamp: July 13, 2023, 06:00:09 pm
content: Not mine, but serial number very close to your 410C, the BNC is definitely not original.Can't comment about the later A3 board, you could check component date codes to determine if it's original, or a replacement done by HP or someone else.This service manual covers both the older & later versions, it's two manuals combined into one (crappy scan) pdf.https://www.keysight.com/us/en/support/410C/multi-func-meter.htmlDavid

author: TimFox
author_rank: Super Contributor
timestamp: July 13, 2023, 06:40:42 pm
content: The meter shown in factory's post above uses a vacuum diode in the probe, and a BNC would not have enough contacts.The original diode used in the early 410s was an Eimac 2-01C, which might have been replaced later by an EA53.

author: Ovi4
author_rank: Contributor
timestamp: July 13, 2023, 07:32:22 pm
content: Tnx for the comment and info + the manual link. Meanwhile I found that there must be an original individual service manual just for the later models (like mine) that have no tubes inside whatsoever so... apparently is full solid state. The manual HP PART NUMBER: 00410-90009 and it came out for the first time in March 1981 (so it is definitely a new manual for the late models) and it covers models created as from the serial number 982A and above.Actually Artekmedia website has that manual for $10 but could not buy it because they want you to pay via a PayPal account and I do not have one. Lather I found that they also sell on E-Bay so....I purchased it via E-Bay. Is in the form of a CD so, I'm gonna have to wait a few days for it to arrive.Now....regarding to the AC probe socket I really don't know what to think or say but to my eyes it looks to be original. Mind you sometimes the looks can be deceivingthe unit is kind of dusty in the inside and at first gallant (without detaching the front panel as of yet) the soldering seems factory to me ( again, I could be wrong ) but...the manual will reveal the trues (when I get it) If someone has artificially planted a BNC instead of that old style 3 pin telephone socket must have done it for a reason. Maybe to adapt or make his own kind of probe who knows.So again, say the BNC socket is original ? it only means that HP got rid of the vacuum tube diode and made a passive probe with solid state components instead. That way you wont need a third wire in the cable to feed the filament anymore (I guess) Who knows

author: bdunham7
author_rank: Super Contributor
timestamp: July 13, 2023, 10:52:41 pm
content: Quote from: Ovi4 on July 13, 2023, 07:32:22 pmI have a Keithley 414A Picoammeter with a BNC connector on the front and it looks completely factory, except it isn't. Somebody bodged it in there because using the old PL259 connector on the back didn't suit them. I converted it to an scope-out function. It would be virtually impossible to tell good workmanship (even mine) from factory in these old instruments.I don't see how this instrument would work correctly unless the peak-detection diode was right in the probe. I suppose it is possible someone made a different probe-end for it and you just don't have it anymore. The input on this instrument needs to see DC, so even if someone (even HP) did make a solid-state probe, why would HP change the connector? I doubt HP would do all that anyway without changing the model number, but I suppose anything is possible.Whilst you wait for Artek, here is a lower-quality compressed version of the manual. It still shows the TRS jack and an EA53 tube with a 6V filament in the probe.

author: TimFox
author_rank: Super Contributor
timestamp: July 13, 2023, 11:29:01 pm
content: The TRS jack and the BNC jack would both fit in a 3/8 inch diameter hole.My older 410A had the probe cable hardwired to the meter case, but my similar Hickock 1605M has the EA53 tube probe on a TRS plug (the rest of the meter is solid-state).The front panel of the 410A (much larger than the 410C) has a hinged door to hold the probe, with the point connected to front binding posts for AC measurements at not-so-high frequency.

author: Ovi4
author_rank: Contributor
timestamp: July 14, 2023, 08:26:28 am
content: Well, I had a closer look on the inside of the front panel and up close you can indeed see that the BNC is a mod done by someone but long time ago since it is all dusty in there. Further on the power transformer has a 6V winding that is used (on the older units) to power up the filament inside the AC probe so. ....yeah!!!!. What a F..K bummer.Now, I'm gonna have to hunt (god knows where) for a pair of male/female 3 pin/contacts socket and plug for my AC probe.Ah... by the way, lucky me !!!I already own one of those AC probes, 3 pictures attached (that was given to me a few years back) but without the male plug on it. So at the moment is just the bear black triaxial cable. It has the 2-01C diode tube inside and it came with an original specs/instructions paper that states it is made as a probe replacement for the (the older version) HP410 B as from the serial 024-31434 onward. So this should work perhaps with some minor adaptation (I suppose) Shouldn't it

author: Ovi4
author_rank: Contributor
timestamp: July 14, 2023, 08:40:24 am
content: @ bdunham7 tnx. for the manual and info. You are perfectly right in what you.re saying. Well the mod has been done so, I'm going to try to have it restored back to the original since I already own one of those old HP 41B AC probes that has no plug at the end of the triaxial cable. So I'm gonna have to hunt for a pair of TRS male/female combination and hopefullyI wouldn't find other major mods insideFingers crossed.:-

author: factory
author_rank: Super Contributor
timestamp: July 15, 2023, 07:55:40 am
content: You would need to find an EA53 tube & spring to use that probe, some 410B probes only fit one type of tube too.The EA53 has a 6.3V heater, 2-01C has a 5V heater, the 410C has no adjustment for this.If the 410C was mine I would look for the correct probe and save that NOS probe for a 410B, both types of VTVM in good working order are quite pricy these days.Did you compare component date codes with the A3 board & the rest of the 410C, to determine if it is original, or a repair replacement due to failed neon photo chopper assembly?It isn't clear from the two manuals in the Keysight (Agilent) pdf, at which serial number the change was made, note the A3 tube heater was fed from the +6V dc supply.I do have pictures of one with the optical chopper board, that otherwise looks the same as yours, but the serial number plate had been removed, quite strange as it looked in almost new condition.David

author: Ovi4
author_rank: Contributor
timestamp: July 18, 2023, 01:15:41 pm
content: @Factory, I had a closer look at the modules and found the following :1. the A3 module is made by HP (so original) has 00410-66502 REV D is identical with the one presented in the manual2. the A6 module is made by HP (so original) has 410-65B REV C is again identical with the one presented in the manualBoth boards appear to have the factory components on them and the right component values (precisely) as the manual statesEven the PSU part appears to be untouched since it still has the original filtering capacitors, Original diode bridge rectifier and the Power transformer as wellNow the bad part: I couldn't say the same for the TRS Jack (socket) that has been exchanged for an ordinary BNC connector with a bit of white coax cable soldered to it. Now the person who did this mod was nice enough simply leave the original jack wiring alone and just had the ends insulated with some light gray electrical tape. wiring colors are white, black and gray. See pictures attached. Now I'm still to follow each wire and bell them out to see if they're really for that AC probe's jack.Now regarding the AC probe you are right, it is wise to leave the HP410B probe (2-01C tube) that I have alone and search to an original HP410C probe (EA 52 tube)Well, at the moment there aren't any for sale on E-Bay other than the ones sold via E-Bay by the kiss-electronics.com but quite pricey !!!!Now, I wonder where am I suppose to find one to buy here over the net since where I live there isn't such thing as swap-meets or anything like that.Perhaps one of the people here on this forum might have something like that for sale.Any clues or perhaps links are highly appreciated.Thank you all.

author: Renaud F5ZR
author_rank: Contributor
timestamp: February 26, 2024, 11:56:46 am
content: Hi,I just bought an HP410C too but unlike yours it is the vacuum kind.It's probably an early model as the mains plug is not IEC but one I didn't know.SN is also unusual I think:G605-01163The G (hence german made) beeing first not in the middle in HP fashion. 1966?I'm also looking for the EA53 probe I don' have.Renaud

author: factory
author_rank: Super Contributor
timestamp: February 26, 2024, 06:16:27 pm
content: 605 isnotthe date of manufacture, it's the date of the last design revision, in this case the design revision is week 5 of 1966.The 410C was available with or without the AC probe, hence why many don't have one with them.David

author: trackersoft
author_rank: Contributor
timestamp: February 26, 2024, 06:55:30 pm
content: Ashley at Kiss Electronicshttp://www.kiss-electronics.com/index.htmis a great resource for parts and service.

author: Ovi4
author_rank: Contributor
timestamp: February 27, 2024, 11:01:54 am
content: I'm (sadly) still looking for a probe for my own (newer solid state version) HP410C even though I've purchased it almost 3 years ago and, all this time I was unable to find a suitable probe for it. The probe I need is : the one with an (EA 52 tube). So my meter has become just a "Shelf Queen" that gathers dust !

author: factory
author_rank: Super Contributor
timestamp: March 01, 2024, 10:38:50 am
content: One for sale.https://www.ebay.co.uk/itm/305425665246David