Cloning the HP3325A Option 002 - HV Output - Page 1
Forum section: electronics / testgear

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: April 07, 2019, 02:37:20 am
content: Hi,This thread is dedicated to cloning the high voltage option board A8 used in the HP3325A option 002 HV Output.I have successfully cloned this board in the past, but I have lost the files.Here are pictures of my clone:I have attached the section from the manual.I remember entering the schematic from the manual and then placing the components in the same place and orientation as the HP original. I used the net list as a guide as where to route the tracks.I used MPS8099 (NPN) and MPS8599 (PNP) for all the small transistors. Q1 on the original is a dual transistor. I just used two MPS8099 glued together.I used MJE243 (NPN) and MJE172 (PNP) for the output transistors.Regards,Jay_Diddy_B

author: TERRA Operative
author_rank: Super Contributor
timestamp: April 07, 2019, 04:00:46 am
content: I think I'll do a similar thing re. placing the components to replicate the HP layout, with maybe a few little alterations as I find along the way to neaten the routing etc.I have been having a look at cross referencing of the silicon so far.So far I have this (Subject to change):(Part numbers from Digikey)Dual NPN Transistor 1854-0475 (supersedes to 1854-1030 and 1854-0688) - MAT01GHZ + heatsink 323005B00000GAll PNP transistors - 2N390615V Zener 1902-3205 - 1N524530V Zener 1902-0244 - 1N4751Switching Diode 30V 1901-0040 - 1N4148Switching Diode 80V 1901-0050 - 1N4150Other parts so far:RCA Socket - RCJ-021TO-220 Heatsink - V2109B3-Pin Connector - Molex KK5273 Series - 0009652038Bridge Rectifier MDA202 - KPB204GJay_Diddy_B, what did you use for the board interconnects? I am looking for short pre-made 90oRCA cables but I haven't turned up anything with a quick search yet..Also, what are the dimensions of your board?

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: April 07, 2019, 09:59:50 am
content: Quote from: TERRA Operative on April 07, 2019, 04:00:46 amI measured the board that I made:The holes are 0.250 inches in from the sides. The board is 4.600 x 2.350 inches. (too big for the 100mm x 100mm cheap boards)Regards,Jay_Diddy_B

author: TERRA Operative
author_rank: Super Contributor
timestamp: April 07, 2019, 12:40:25 pm
content: Awesome, thanks.Yeah, I thought it would be too big for the cheap boards..Ah well, it's still not tooooo expensive anyway. I wonder if there is anywhere that will do gold plating and also clear or no solder mask to match the old HP style PCB?

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: April 07, 2019, 02:34:05 pm
content: Hi,I have put together an LTspice model for the amplifier. I have picked some transistors that I am familiar with in the LTspice library. This is the same as the original HP circuit. I haven't done any tweaks.I haven't compared these results to the hardware.I have attached the model.Regards,Jay_Diddy_B

author: TERRA Operative
author_rank: Super Contributor
timestamp: April 08, 2019, 02:27:44 am
content: Nice work. I haven't used LTspice before, I should learn it some day..Is there a spice model for the MAT01GHZ for the dual transistor? I wonder how much of a difference it would make.Also, that square wave looks a bit nasty, how does it look on a scope from your physical unit?

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: April 08, 2019, 03:37:05 am
content: Hi,I am not sure why the LTspice waveform is distorted.I would not use the MAT01. It is not recommended for new designs (NRND). I think that it is because it is in a metal can.The main property of the MAT01, matching is not needed in this high voltage amplifier. The voltage gain of the circuit is only 2.I have good news!!I have anoriginaloption 002 that I was able to compare with my clone.OriginalCloneNot a lot of difference.Regards,Jay_Diddy_B

author: TERRA Operative
author_rank: Super Contributor
timestamp: April 08, 2019, 04:25:27 am
content: Well, that's good news that the MAT01 isn't needed, that will certainly save a good few $$$ and make future builds easier too.Can you post a few photos of the original HP option board? I want to see it all close up.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: April 08, 2019, 04:30:55 am
content: Quote from: TERRA Operative on April 08, 2019, 04:25:27 amI will do tomorrow, it is very late here in Toronto.Regards,Jay_Diddy_B

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: April 08, 2019, 11:24:22 am
content: Hi group,I have taken some photographs of the original board.The board is slightly smaller than the one I made. The dimensions are 4.500 x 2.25 Inches. The fixing holes are the same.I did notice a few differences:All the mounting holes are grounded on the original.There are ferrite beads on the base leads of Q4 and Q5.Here are the pictures:Regards,Jay_Diddy_B

author: TERRA Operative
author_rank: Super Contributor
timestamp: April 10, 2019, 01:16:31 am
content: I just finished drawing up the schematic in DipTrace.Next step is to start laying out the PCB.[Edit: Fixed schematic]

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: April 10, 2019, 02:43:41 am
content: Hi,I have had a quick look at the schematic.1) R10 should be 3.62) Q14 should be a NPN power transistor MJE182 or similarHP used MJE2233) Q15 should be a PNP power transistor MJE172 or similarHP used MJE2334) C9 should be 22uF 50V Electrolytic capacitor5) Most of the small signal transistors need to be more than 40V1853-0036 was selected from 2N3906 (probably for Vceo >60V)1853-0042 is a 50V PNP transistor1853-0020 is a 25V PNP transistorI used MPS8099 and MPS8599 on the board I built.Regards,Jay_Diddy_B

author: TERRA Operative
author_rank: Super Contributor
timestamp: April 10, 2019, 03:52:59 am
content: That'll teach me for doing it at 3am...I'll make a revision tonight, maybe before midnight this time.

author: TERRA Operative
author_rank: Super Contributor
timestamp: April 10, 2019, 12:24:08 pm
content: Ok, I fixed up the schematic and reuploaded it in my post above, except I still am looking at easy to source transistors.The MJE243 and MJE172 are easy, but Digikey doesn't have MPS8099 and MPS8599 as they are marked as obsolete, Mouser has them though, so it should be ok.I wonder if the KSC945 (NPN) and KSA733 (PNP) would be ok substitutes?

author: vindoline
author_rank: Unknown
timestamp: April 10, 2019, 12:27:33 pm
content: Looks like a great project! I have an HP3325B - I suspect it would use the same board. I'll have to check.

author: LazyJack
author_rank: Frequent Contributor
timestamp: April 10, 2019, 01:01:00 pm
content: Yes, the B version uses exactly the same board. It has the same part number.

author: Rollin Hand
author_rank: Regular Contributor
timestamp: April 11, 2019, 07:17:21 pm
content: Are this boards for sale?Thanks

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: April 12, 2019, 12:30:28 am
content: On the topic of the MAT01: even if this 'supermatch pair' is not really needed, a double transistor might be beneficial to the application. Some that are a bit easier to source: MD8002 (Mot),2N4045, 2N2915, BFY83, SL301L, although I haven't checked their respective suitability yet.

author: TERRA Operative
author_rank: Super Contributor
timestamp: April 12, 2019, 01:03:17 am
content: Quote from: Rollin Hand on April 11, 2019, 07:17:21 pmI'll release the gerbers and source files (if anyone else uses DipTrace) when they are finished and I'm sure I'll end up with a few spare boards when I get mine made that I could send to people who want one.Maybe I can order a few extra sets of parts too and send them out as a kit for people to solder together themselves?Quote from: Neomys Sapiens on April 12, 2019, 12:30:28 amCool, I'll take a look at thoise suggestions and see what matches up.Failing that, using superglue to marry a somewhat matched pair of transistors could work in a pinch.

author: VK5RC
author_rank: Unknown
timestamp: April 12, 2019, 01:17:59 am
content: Thanks for the post, @Terra if you are ordering boards and components and can easily add another set - I would put my hand up for one set of both parts and pcb.RobVK5RC

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: April 12, 2019, 02:35:20 am
content: Hi,The mismatch in the input transistors Vbe, multiplied by the gain of the amplifier (x2) will appear as offset on the output voltage.I will measure the offset voltage on my clone versus the original board.I have been playing with the amplifier in LTspice. I believe that it can be made to be better than original design.It is still a work in progress, but I have attached my latest LTspice model. I have removed the protection circuit for now. I will put it back at the end.This version has a slew rate of 1600V/us.I have made the input stage symmetrical and changed the output transistors. C2 and C3 are trimmers used to optimize the waveform.This circuit could be used with other function generators to boost the output voltage.I have attached the LTspice model.Regards,Jay_Diddy_B

author: TERRA Operative
author_rank: Super Contributor
timestamp: April 12, 2019, 05:27:17 am
content: Quote from: VK5RC on April 12, 2019, 01:17:59 amYeah, I'll probably make a batch of 10 or so to start.Whichever design we end up making, I'll put together a bunch of kits. I'll wait a bit to see how Jay_Diddy_B's design goes and with his permission, I'll get something put together unless he wants to sort it out for his design.

author: TERRA Operative
author_rank: Super Contributor
timestamp: April 17, 2019, 02:25:27 pm
content: PCB layout V1.0 so far....I went 4-layer as it greatly simplified layout and I have never tried 4-layer before so I figured why not?The components are laid out pretty much the same as the original, the traces are adjusted as needed.It'll change a little when I finalize which transistors will be used, but it's mostly there.Let me know if you see any obvious mistakes or tweaks I should do.

author: TERRA Operative
author_rank: Super Contributor
timestamp: April 19, 2019, 01:55:00 pm
content: Latest picture.Lots of little tweaks and stuff to make sure stuff fits. 99% done now.

author: SilverSolder
author_rank: Super Contributor
timestamp: April 20, 2019, 01:13:54 pm
content: Quote from: TERRA Operative on April 08, 2019, 02:27:44 amApparently there is no spice model for MAT-01. Analog has in the past recommended using the model for SSM2212 instead, which is available.https://www.analog.com/en/license/spice-models?mediaPath=media/en/simulation-models/spice-models/SSM2212.cir&modelType=spice-modelsLTSPICE does have the MAT-02 in its standard library, it may be close enough (or an alternative).

author: TERRA Operative
author_rank: Super Contributor
timestamp: April 28, 2019, 01:40:18 pm
content: Ok, time for some small updates.I recently ordered a bunch of PCB's, so they should arrive soon.I also just won another 3325A on Yahoo Auctions, with opt 001 (ovenised oscillator) and 002 so I can more easily compare performance between an original board and mine.Updates to come soonish.

author: SilverSolder
author_rank: Super Contributor
timestamp: April 28, 2019, 07:24:48 pm
content: Building @Jay_Diddy_B's improved board could also be interesting!

author: TERRA Operative
author_rank: Super Contributor
timestamp: April 29, 2019, 06:44:47 am
content: Yeah, I'll have to get my hands on one when they are done to do a 3-way comparison.Would be awesome if his could be used beyond the 1Mhz limit of the HP one, but I'm not sure if that'll require reflashing of the ROM on the 3325A motherboard or not?

author: LazyJack
author_rank: Frequent Contributor
timestamp: April 29, 2019, 07:50:33 am
content: It should not require a new ROM. My 3325B is happy to provide any frequency, even is Opt002 is enabled. It seems like that the only change is that id adjusts the output amplitude display, but does not limit the upper frequency.

author: TERRA Operative
author_rank: Super Contributor
timestamp: May 03, 2019, 03:42:23 pm
content: Alrighty, I got my hands on an original option 002 board.Here are some high quality photos of the thing for those who are interested.Interestingly, there was a shield on this one which I didn't realise was part of the upgrade. It wouldn't be very difficult to make one at all.

author: TERRA Operative
author_rank: Super Contributor
timestamp: May 03, 2019, 03:43:11 pm
content: Some more shots.

author: TERRA Operative
author_rank: Super Contributor
timestamp: May 03, 2019, 03:43:52 pm
content: And a few more, showing the shield.Someone might find these pics useful.

author: TERRA Operative
author_rank: Super Contributor
timestamp: May 07, 2019, 12:57:04 pm
content: PCB's have finally arrived!They are basically a 4 layer copy of the original board. Component placement is as close to the original board as possible, traces are different as needed.Next step is to solder it together and test that it actually works........If anyone is interested in one of these, let me know. I have 20 PCB's and I'll supply them as a full kit of parts, with all parts needed to complete one board, including parts to make interconnect wires and screws to mount it in the machine etc.If I get an idea of who is interested, I'll be able to price up what they are worth for a kit.

author: TERRA Operative
author_rank: Super Contributor
timestamp: May 16, 2019, 02:12:55 am
content: Pow! Got the first one assembled.A few things of note so far:You may notice a few smaller resistors in the mix, I accidentally purchased 0.25W instead of 0.6W...No big deal, just looks weird, I'll fix that with my next Digikey order.Also, I noticed only after I installed them that the two 10K resistors are specified as 0.1%, 0+-25 Temp Coefficient types... I used 1%, +-50 TC types.. These must be a little critical to stability, but the ones I have will be fine until the next order.All the rest of the resistors are 1%, +-50 TC types (I can get most of the values for 3yen a piece in Akihabara so yay), which is WELL under the specs in the parts list. Most are specified at 1% 0+-100 or 5% -400/+500.All the ceramic capacitors I used are C0G/NP0 types too, so good for performance there.The two axial tantalums have been substituted with axial electrolytics.For the final version, what do people think of this:https://www.digikey.com/product-detail/en/kemet/T110B335K035AT/399-11296-ND/4552792(Rated ESR of 4)Compared to this:https://www.digikey.com/product-detail/en/nichicon/TVX1H3R3MAD/493-16279-ND/2539907(Measured ESR of 2.6)It's a difference of $2.95 vs $0.55..... I think the electrolytic would be fine, no need to use the tant?Transistors are 2N3904 and 2N3906, output drive transistors are MJE243G and MJE172G in place of MJE223 and MJE233 respectively.- MJE223 NPN, 80V, 10MHz- MJE243G NPN, 100V, 40MHz- MJE233 PNP, 80V, 10MHz- MJE172G 80V, 50MHzWill be interesting to see how they compare at the higher frequencies...For the dual transistor on the input (The heat sinked can to the right, I replaced the HP part 1854-0475 with two 2N3904's superglued together that I hfe and Vf matched with my ebay component tester.And finally, I used all 1N4150 diodes (80V) in place of both the 1N4150 and 1N4148 (30V) diodes to simplify things. Diodes are cheap and I ain't penny pinchingthatmuch....Now to wait a few days for some time to start testing. Got family arriving from overseas, so it's time to relax, do some sight-seeing and heat up the barbeque.

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: May 17, 2019, 05:18:12 pm
content: Quote from: TERRA Operative on May 16, 2019, 02:12:55 amI would use the Kemet. Being of hermetic construction, it will keep it's parameters for a long time. Those are not the failure prone Tants! Also Kemet specs are reliable and conservative.

author: TERRA Operative
author_rank: Super Contributor
timestamp: May 18, 2019, 12:50:11 am
content: Quote from: mopa94500 on May 16, 2019, 07:50:18 pmIf you take a look at my boards, you'll see they are gold plated with no soldermask on the top to match the HP boards. They look more brown only due to the internal copper layers from the 4 layer construction.Quote from: Neomys Sapiens on May 17, 2019, 05:18:12 pmYeah, the lifetime of the tants is impressive compared to the electros. The electrolytics I used are only rated to 2000 hours or so.What about squeezing a poly or ceramic cap in, seeing as these are only 3.3uf?

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: May 18, 2019, 05:05:13 am
content: Hi,I used a tantalum bead. The capacitor has about 3.7V applied. The current is low, about 1mA peak, during square wave transitions. The current is lower with a sinewave. The value is not critical. A 4.7uF 10V (or greater) will be okay.I used something like this:https://www.digikey.com/product-detail/en/avx-corporation/TAP475K035SRW/478-8986-1-ND/4561852Regards,Jay_Diddy_B

author: TERRA Operative
author_rank: Super Contributor
timestamp: May 28, 2019, 01:14:04 am
content: Alrighty. Got it working finally.Turns out that after a bit of head scratching, Diptrace have the Emitter and Collector pins swapped on some of their footprints, or the part I used is swapped from the normal footprint...The usual story....So that means I have a heap of gold plated 4-layer boards to feed the bin.Anyway, it's all figured out and ready for a new PCB order, plus I made a few tweaks to placement for clearances and stuff, just minor stuff, a nudge here and a bump there.Here's the output shown in the pics below.In order:- 1MHz Sine (The device seems to attenuate above 1MHz)- 1Mhz Square- 100KHz Square- Close up of the 100KHz square rising edgeThings might need to be poked a bit to reduce that overshoot? Any suggestions?The overshoot seems to stay the same regardless of frequency setting, until it distorts like in the 1MHz image, which starts around 500KHz, where the period becomes the same width as the overshoot ripple.(The 1MHz square wave shape is showing just a portion of the overshoot ripple, hence the distorted shape for example).The triangle and ramp are perfect and boring, so I won't bother with pics.

author: TERRA Operative
author_rank: Super Contributor
timestamp: May 31, 2019, 02:12:24 am
content: Moar updates.It turns out that the Original HP Option 002 board I have wasn't working, but I traced it down to a faulty transistor Q8, it seemed to test ok in my ebay component tester, but it was nonfunctional enough to bring the whole thing to a grinding halt. Replacing it got the board working perfectly.So, seeing as it works fine with no overshoot, and I need to order another revision of PCB anyway, I ended up just copying the PCB layout with a few tiny tweaks here and there (stuff like neatening up things, 45degree corners, etc).The added benefit of no longer using a 4 layer board is that PCB's will be cheaper.I am thinking that the large ground and supply planes were adding capacitance and causing ringing, maybe. Thoughts?I could play with pulling the ground planes back a bit, but I figured 'why bother' when I am holding a working design to copy in my hand....Anyway, the linked images are the new PCB design, and the output from the repaired original Option 002 board.Once I get this set of PCB's back and the thing tested, I'll be able to start getting some kits made up for those who are interested.

author: TERRA Operative
author_rank: Super Contributor
timestamp: June 29, 2019, 12:31:54 pm
content: New PCB's arrived!I ended up with two batches, first one they ignored the keepout on the top solder mask, so I have a set of 10 boards with and without top solder mask.Since the original HP part has no top solder mask, I wanted the same to make it look the same.Original on the top (already had the electrolytics replaced) and new on the bottom. The traces are a 90% match to the original, and all modern parts are used and substituted and the passives have better specs than the original.Next step, start testing this to make sure my component values and substitutions all work.

author: VK5RC
author_rank: Unknown
timestamp: June 29, 2019, 01:10:15 pm
content: That is looking lovely, when you are happy, I will put my hand up for one.RobVK5RC

author: hnjmkl
author_rank: Regular Contributor
timestamp: May 16, 2020, 06:03:47 am
content: I'm late but I would also be interested in a PCB only board or whole kit, thanks

author: TERRA Operative
author_rank: Super Contributor
timestamp: May 16, 2020, 06:58:43 am
content: No worries, I'm sorting out the kits etc at the moment for a big run.It will be delayed for a while, as Japan Post has basically shut down international shipping due to the corona virus, but as soon as restrictions are lifted, I'll get things organised.

author: hnjmkl
author_rank: Regular Contributor
timestamp: May 17, 2020, 08:36:34 am
content: With reference to the dual input NPN (1854-0475), resulting obsolete, expensive, nowhere to be found, I would propose to focus on AS194, improved device of the AS394, components produced by a company from Riga in Latvia, they seem to be devices seriously built with vision of datasheets. Regards, Franco

author: VK5RC
author_rank: Unknown
timestamp: May 17, 2020, 09:08:51 am
content: I am still interested, but no rush.Thanks, Rob

author: Tazz
author_rank: Contributor
timestamp: May 17, 2020, 10:00:02 am
content: Quoting some 2015 post on group.io:QuoteCob is way to high on LM194 based clone in general. It is not specified on the AS version.They are generally slow too, as the Hp one so with high Vce/Ic polarisation and high Pd : The Hp one even rated at 750mW is mounted with a dissipator.

author: Tazz
author_rank: Contributor
timestamp: May 17, 2020, 12:34:10 pm
content: 2N2920AHR seems to be a good replacement. Active product but difficult to find (ST space qualified portfolio).Microsemi 2N2920(L) is only 350mw max an very expensive.2915A/2920A from Solid Sate Inc/Texas Instruments, 2N2920 from Thoshiba 2920A from central semi should be good but hard to find or obsolete.Why not simply MAT01 ? Available anywhere at not foolish price. Ok perhaps a little but expensive for the HV option, but as a general 1854-0475 replacement ?2920A From Solid State cost only 2$ less than a MAT01GHZ (~17 vs ~19)

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: May 18, 2020, 03:53:55 am
content: Quote from: Tazz on May 17, 2020, 12:34:10 pmThe circuit will work quite well with two ordinary MPS8099 transistors glued together.When I built mine it worked fine, without selecting or matching the transistors.In simulation a miss-match of HFE one transistor 250 and the other 300 results in about 20mV of offset on the output.I would try ordinary transistors before going chasing after special parts.Total Power dissipation for both transistors is around 180mW.The HV Option 002 amplifier schematic is similar to the normal output. Look at the schematics in the service manual. I am guessing the dual transistor was copied from there.Regards,Jay_Diddy_B

author: Tazz
author_rank: Contributor
timestamp: May 18, 2020, 06:09:48 am
content: Yes going back in the thread show me that I should have reread all first instead of going through all reference catalogs ...

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: May 18, 2020, 01:28:20 pm
content: Tazz,You can buy a *lot* of general purpose transistors for the price of the MAT01 or equivalent. You may even have someThe transistor in the input stage have 45V VCE. (+/- 30V minus the 15V Zener)So you need 60V parts.I used 80V parts.Jay_Diddy_B

author: hnjmkl
author_rank: Regular Contributor
timestamp: August 04, 2020, 06:22:09 pm
content: I would always be interested in the clone of the HVO option of the 3324A, I ask the current status of this project by the interested parties seen in this forum. Greetings Franco

author: TERRA Operative
author_rank: Super Contributor
timestamp: August 05, 2020, 02:36:29 am
content: Outbound international shipping from Japan isstillshut down, still waiting for things to start moving again. Will make more updates when I have new news.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: August 05, 2020, 02:51:28 am
content: Quote from: hnjmkl on August 04, 2020, 06:22:09 pmHi,I haven't seen the HV Option for the HP3324A. Is it the same as the HV option for the HP3325A?Regards,Jay_Diddy_B

author: hnjmkl
author_rank: Regular Contributor
timestamp: September 20, 2020, 07:45:06 pm
content: I wired the proposed improved circuit on breadboard, redesigned with kicad, but it doesn't work, Q3-Q9-Q13 warm up slightly, in the absence of signal the output has no important offset. is there any error in the wiring?Immagine 2020-09-20 211101.png(23.31 kB. 951x585 - viewed 386 times.)

author: AlfBaz
author_rank: Super Contributor
timestamp: September 23, 2020, 08:40:22 am
content: Did you end up finding the problem?It simulates properly with ltspice and is quite tolerant to model variations for the various transistors.Given that you have "breadboarded" the circuit it is most likely an issue with your physical wiring.I've just finished a quick laying out a surface mount version of that circuit and currently verifying transistor selections.I'm doing it on a 4 layer pcb for no other reason than to check out JLPCB's 4 layer serviceP.S.Hope you don't mind Jay

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: September 23, 2020, 01:44:06 pm
content: Hi,I see that you have copied the circuit from this post:https://www.eevblog.com/forum/testgear/cloning-the-hp3325a-option-002-hv-output/msg2337558/#msg2337558It is still a work in progress, but I have attached my latest LTspice model.I have removed the protection circuit for now. I will put it back at the end.I have never taken this beyond the LTspice model.I used 2n3904 and 2n3906 transistors in the LTspice model, these are 40V transistors. I can do this in SPICE because SPICE doesn't model the breakdown voltage.Q4, Q5, Q11 and Q12 should be 80V transistors.So building this circuit is risky.ProtectionI have highlighted the parts that need to be added to implement protection for the output devices.4 Layer BoardTerra Operative used the original HP schematic and built it on a 4-layer board. It did not work as well the original 2 layer design. This is documented in this message:https://www.eevblog.com/forum/testgear/cloning-the-hp3325a-option-002-hv-output/msg2450364/#msg2450364I think there may be similar issues building the amplifier I designed on a 4-layer board.Regards,Jay_Diddy_B

author: AlfBaz
author_rank: Super Contributor
timestamp: September 23, 2020, 03:23:01 pm
content: Hi Jay, thank you for the clarification.I mentioned that I was in the process of "verifying transistor selection".In actual fact all I have done is drawn up the schematic with generic components and pushed their generic foot prints to the PCB, followed by a quick route.The only thing that's complete is the size of the board and the position of the BNC's to suit the Hammond case I've chosenI had noted you removed the protection circuits but decided to go without to simply see how it performed compared to the simulation and to the data you and Terra Operative collected.I'll just have to be extra careful when testing.Thanks for pointing out the 4 layer issue, I had missed that.I originally went 2 layer but didn't save that version when I changed to 4 layers. Just some extra vias really so no big deal to change it back.I have a different stack up so I might still go 4 layer just to see what happens as all my signals are on the top layer followed by Vcc, Vee and finally ground on the bottom.I'll order both the 4 and 2 layer boards at the same time and enough components to do both. I like making mistakes, it's how I learnLTspice shows current draw from the rails as less than 100mA so I may be able to use smaller regulators than the ones currently used for the final board. I'll leave it as is and test on the actual circuit first

author: SilverSolder
author_rank: Super Contributor
timestamp: September 23, 2020, 03:30:38 pm
content: I'm not sure I totally understand why the 4 layer board is a problem - does it introduce extra capacitance that rounds the edges of the signal, or something like that?

author: AlfBaz
author_rank: Super Contributor
timestamp: September 23, 2020, 03:48:49 pm
content: I believe the problem was overshoot as shown in the post just before the one linked by Jay_Diddy_B. There may be some signals coupling via the planes

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: September 23, 2020, 05:04:40 pm
content: Quote from: AlfBaz on September 23, 2020, 08:40:22 amI don't mind at all. I encourage it.AlfBaz,I would add some copper to the collector connections on the output transistors Q7 and Q8. There is no concern with capacitance to the ground plane, because these are essentially at dc potentials. You look at the LTspice model for the dissipations.I suspect that the issue with the four layer board is capacitance to the ground plane. This is a high speed circuit running at relatively small currents.All we really know is that the original circuit, my layout and Terra Operative's second layout all work better than the Terra Operative's 4-layer version.Regards,Jay_Diddy_B

author: hnjmkl
author_rank: Regular Contributor
timestamp: September 23, 2020, 07:44:53 pm
content: After seeing the smd PCB I threw the breadboard in the trash, congratulations to the designer, I wait for developments.

author: TERRA Operative
author_rank: Super Contributor
timestamp: October 07, 2020, 05:00:37 pm
content: Works well I think.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: October 07, 2020, 05:16:01 pm
content: Hi TERRA Operative,It looks great!It looks and works just like the original.Regards,Jay_Diddy_B

author: TERRA Operative
author_rank: Super Contributor
timestamp: October 10, 2020, 05:28:05 pm
content: Made a video about my Option 002 PCB, some may find it a little less than dead boring.Link to all the files, BOM, gerbers etc:https://drive.google.com/drive/folders/1l8sT5sR7wLVCqZOov9T9yXTmKLvo_4Qv

author: AlfBaz
author_rank: Super Contributor
timestamp: November 05, 2020, 04:09:20 pm
content: Nice work TERRA OperativeHad a rainy weekend and some spare time.I added the protection circuit and sent the gerbers off to be madeOrdered the parts but due to back order Ive held the order until it's all ready so it will be a couple of weeks before the components arriveIn the mean time I'm looking at using newer current feedback opamps, in particular theTHS3491, 900MHz 500mA output.I'll see if I can get it to 100MHz without getting too fancy with the board

author: SilverSolder
author_rank: Super Contributor
timestamp: November 05, 2020, 06:53:43 pm
content: Quote from: AlfBaz on November 05, 2020, 04:09:20 pmThat might make a good basis for a "hot rod" high voltage option board!

author: AlfBaz
author_rank: Super Contributor
timestamp: November 06, 2020, 02:20:53 am
content: Quote from: SilverSolder on November 05, 2020, 06:53:43 pmThat's the idea. Given one of the applications the datasheet mentions is high voltage arb gen output.I'm going for 2 in parallel as it supposed to reduce harmonic distortionI will have to be serious with the board layout on this oneI'll create a new thread when I make some progress and post a link to it here

author: SilverSolder
author_rank: Super Contributor
timestamp: November 06, 2020, 04:17:11 am
content: Quote from: AlfBaz on November 06, 2020, 02:20:53 amsounds like fun!

author: Klaus Butzmann
author_rank: Newbie
timestamp: January 16, 2021, 03:17:24 pm
content: Quote from: TERRA Operative on August 05, 2020, 02:36:29 amGreat project, I have two 3325 but both without HV-Option.Are the PCBs or Kit still available?Is it expensive to ship to Europe / Germany?It seems China --> Germany is almost "free",PCBs, items, modules and shipping for free or 1-2 Euro.Thank youKlaus

author: TERRA Operative
author_rank: Super Contributor
timestamp: January 16, 2021, 07:53:18 pm
content: I haven't made any kits etc yet as Covid hit right as I was about to do so, which severely limited international shipping from Japan.I have a bunch of files so you can order PCB's and parts and make one yourself though:https://drive.google.com/folderview?id=1l8sT5sR7wLVCqZOov9T9yXTmKLvo_4Qv

author: PaulAm
author_rank: Frequent Contributor
timestamp: January 16, 2021, 08:18:40 pm
content: Thanks for posting that. I have a 3325 that I'd like to add that option to.

author: SilverSolder
author_rank: Super Contributor
timestamp: January 16, 2021, 08:30:02 pm
content: Is it the same card for 3325A and B models?

author: vindoline
author_rank: Unknown
timestamp: January 17, 2021, 04:49:15 pm
content: Quote from: SilverSolder on January 16, 2021, 08:30:02 pmYes, see reply #15.

author: MauriceS
author_rank: Contributor
timestamp: April 09, 2021, 06:26:44 pm
content: Has anyone found a source for the RCA style (but not RCA) connectors to make a cable ? I bought Option one - but it didn't come with the cable to connect it to the jack - and ePay prices are a bit steep, so is 4GT's...

author: TERRA Operative
author_rank: Super Contributor
timestamp: April 10, 2021, 09:31:59 am
content: In Japan I can get these, you might be able to find them around the web on the usual sites:https://www.sengoku.co.jp/mod/sgk_cart/detail.php?code=4A2W-CGLN

author: jcline01
author_rank: Newbie
timestamp: August 23, 2021, 09:29:54 pm
content: Hi Jared,Thanks for providing all the work and for the PCB fab information,I tried to have a company (Pad2Pad) make the board using your gerber files from google drive, but they said it would not work.Here are their words:"The top silkscreen is usable, however, the top masking layer provided encompasses the entire board profile and is not usable. We will require a new top masking layer to proceed."Do you have any insight on a solution?Also, is there another fab company that can make this happen?I'm new to PCB fab, so sorry for the questions.Thanks again,Joe Cline, KN5U

author: TERRA Operative
author_rank: Super Contributor
timestamp: August 24, 2021, 12:12:10 am
content: There is no top solder mask on this PCB to keep it more accurate to the original HP design, hence the top masking layer to exclude it.You can tell your fab that they can delete the top mask entirely and only apply solder mask to the bottom layer.

author: jcline01
author_rank: Newbie
timestamp: August 24, 2021, 02:04:20 am
content: Awesome - Thanks!

author: TERRA Operative
author_rank: Super Contributor
timestamp: August 24, 2021, 10:02:34 am
content: No worries.If you look back a little bit in the thread, or in the google drive link, you'll see photos of how it should look with the bare top.All nice and gooollldddd!

author: AVO8user
author_rank: Newbie
timestamp: June 01, 2022, 09:33:35 am
content: Hi there, interested in building this, hope you still look at this after all this time.My query is about the BOM in the Google drive as there seem to be a couple of questions and comments in the forum which differ from the BOM you have put up.1 Member P diddy refers to values for R10 and C19 but neither the HP service manual or your BOM have values or have them in the circuit schematic.2 The next query is using 2N3904/06 transistors, again P diddy refers to the need to use 80v transistors in some locations which you agree with but the BOM lists 3904/06 throughout.3 And finally in the blog you mention the 10k resistor should be 0.1% and say that you used 1% for the first build and will correct that in the next build, unfiortunatley the BOM still lists 1% parts.Hoping you can help, is there a newer version of the BOM ?

author: TERRA Operative
author_rank: Super Contributor
timestamp: June 01, 2022, 02:06:07 pm
content: Hi,Yep still here.1. If there's no R10 or C19 in my BOM or schematic, then they don't exist. J_Diddy_P was playing with his own version so he would have probably had his own part numbering, mine follows the HP design, so to make mine you don't need those two parts.2. Probably an alright idea to use higher voltage rated transistors, I used the 2N3904/2N3906 as it worked ok, but some headroom is a good idea.Maybe MPSA06 and MPSA56 transistors can be used. I might try it out myself soon actually.3. R12 and R13 are the 0.1% +/-0.25 Temperature Coefficient resistors. I still haven't replaced mine (I forgot!) but I'd put them in as they must be there for a reason. HP wouldn't have spent the extra money if it wasn't worthwhile.Hope that helps. MPSA06 and MPSA56 transistors work. There is a bit of overshoot on the square wave (all other waveforms look perfect on the scope), but I'll have to dig out my other 3325A with the original HP option board to compare.

author: AVO8user
author_rank: Newbie
timestamp: June 06, 2022, 09:33:59 pm
content: Hi there thanks for clearing that up.I was thinking of using MPS8099 and MPS8599 as Mouser are stocking those and they appear to have a slightly better gain /bandwidth product than the MPSA06 and MPSA56. Perhaps I need to make it up with transistors sockets so I can experiment further.Lots of thes parts are being discontinued now, really frustrating when you look up the specs for a part and it looks really good and then you cannot buy it anymore.Thanks for putting in the hard work of creating the board files as I know the theroy but don't have the expeience with the software to come up with a board like this. JLPCB have just sent my order to me and they look great.LTspice looks very useful too-another bit of software to learn!!

author: TERRA Operative
author_rank: Super Contributor
timestamp: June 06, 2022, 11:00:21 pm
content: Yeah, all sorts of stuff is getting discontinued revently, seems I get an email every second day almost...Let us know how your experiments go, it will be nice to have some options on substitute parts for future reference.

author: flanneltuba
author_rank: Contributor
timestamp: February 21, 2023, 11:54:59 pm
content: I went ahead and spun off a batch of 5 boards through PCWay using your gerber files, built up one of the boards, and shazam! if it didn't work perfectly on the first power up. I ordered some of the higher voltage transistors just in case the 2N390x transistors proved themselves underrated, but so far have not had to use them. It appears to work quite well with the lower voltage jellybeans. It was happy to deliver a full 40v, 10KHz signal into loads as low as ~68Ω (well over 100mA) without significant distortion. Very impressive, indeed.One trap for young players (I'm 59, but evidently somehow still a young player): Be sure to insulate the legs of the transistors that have the ferrite beads. The circuit will work great while the PCB is upright -- that is while the 3325 is upside down during installation -- but as soon as you smittenly button it all up and heft it back onto your equipment stack, and pile a few other heavy pieces of equipment on it for good measure, the ferrite beads, which are of course conductive (duh) will slide up the transistors and short one or another of the leads.One other thing I didn't see mentioned was removing the option jumper on the A6 logic board located between the configuration switch block S1 and U43 to let the logic know you've got the 002 HV Option installed.I do now have a three extra unpopulated PCBs that I probably will never use, if anyone's interested. PM me and I'll send you one. First come first served. Note that I did not opt for the gold plating, so they're just regular tin plated. So call me cheap. See pics.Anyhow, a huge thanks to TERRA Operative for the Gerbers and associated files and for all the work you put into them. Thanks also to the other contributors who's comments were quite helpful.- Scott

author: TERRA Operative
author_rank: Super Contributor
timestamp: February 22, 2023, 12:47:11 am
content: Ah yes, the ferrites. I must have forgotten to make a note of them. I coated them with a bit of clear nail polish to insulate them. I also formed the legs of the transistor to help provide clearance. By bending the centre leg straight back towards the rounded side, flat on the base of the transistor, then bending straight down at 90 degrees, I was able to getjustenough clearance to not have a problem.But good to hear you have it all working without too much trouble! And you even made the shield plate too, nice work.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 25, 2023, 03:29:49 pm
content: Quote from: flanneltuba on February 21, 2023, 11:54:59 pmThose boards look just the ticket! Very useful addition to a 3325A.

author: SCSKITS
author_rank: Regular Contributor
timestamp: March 04, 2025, 08:53:52 pm
content: Was checking the specs on the 3325A HV option and noticed that they list greater or equal to 500 ohms in parallel with less than or equal to 500pF.I added a 500pF capacitor across the load in the model and the circuit oscillated. Also note that the model of the original HP design also oscillates with 500pF, so maybe it is just an LT Spice artifact or an issue with the transistor models.

author: aarons
author_rank: Regular Contributor
timestamp: September 24, 2025, 03:02:02 am
content: I just received an order of 5 of these boards, and got one assembled. At 1MHz my amplitude is only 36.5V pk-pk, and goes down to 4.25V at 20MHz, but that is a problem with my amplitude flatness of the signal feeding the amplifier board, so I guess I'll dig into that tomorrow.But I have 3 of these boards available, and most of the parts, if anyone is interested. I've also attached my digikey cart for all the components, which has some subs from TERRA Operatives original BOM due to availability and price.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: September 25, 2025, 02:11:52 am
content: Hi aarons,The original specification for option 002 in the HP3325A is from 1uHz to 1 MHz.Regards,Jay_Diddy_B

author: aarons
author_rank: Regular Contributor
timestamp: September 25, 2025, 03:24:27 am
content: Yeah, I ended up finding that today while going through the adjustments of the unit. My amplitude flatness is out spec and can't be adjusted into spec via the standard procedure, so I need deal with that, but the HV option is working great and I got the noise shield fitted as well.