Author Topic: Cloning the HP3325A Option 002 - HV Output  (Read 6108 times)

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Offline hnjmkl

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Re: Cloning the HP3325A Option 002 - HV Output
« Reply #50 on: August 04, 2020, 06:22:09 pm »
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
 

Offline TERRA Operative

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Re: Cloning the HP3325A Option 002 - HV Output
« Reply #51 on: August 05, 2020, 02:36:29 am »
Outbound international shipping from Japan is still shut down, still waiting for things to start moving again. Will make more updates when I have new news.
Any circuit design must contain at least one part which is obsolete, two parts which are unobtainable, and three parts which are still under development.

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Online Jay_Diddy_B

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Re: Cloning the HP3325A Option 002 - HV Output
« Reply #52 on: August 05, 2020, 02:51:28 am »
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

Hi,

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
 

Offline hnjmkl

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Re: Cloning the HP3325A Option 002 - HV Output
« Reply #53 on: September 20, 2020, 07:45:06 pm »
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?[attachurl=1]
 

Offline AlfBaz

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Re: Cloning the HP3325A Option 002 - HV Output
« Reply #54 on: September 23, 2020, 08:40:22 am »
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 service

P.S.
Hope you don't mind Jay :)

 

Online Jay_Diddy_B

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Re: Cloning the HP3325A Option 002 - HV Output
« Reply #55 on: September 23, 2020, 01:44:06 pm »
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/#msg2337558



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.

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.

Protection

I have highlighted the parts that need to be added to implement protection for the output devices.

[attachimg=1]


4 Layer Board

Terra 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/#msg2450364

I think there may be similar issues building the amplifier I designed on a 4-layer board.

Regards,
Jay_Diddy_B

 
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Offline AlfBaz

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Re: Cloning the HP3325A Option 002 - HV Output
« Reply #56 on: September 23, 2020, 03:23:01 pm »
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 chosen
 
I 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 learn :)

LTspice 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
 

Online SilverSolder

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Re: Cloning the HP3325A Option 002 - HV Output
« Reply #57 on: September 23, 2020, 03:30:38 pm »

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?
 

Offline AlfBaz

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Re: Cloning the HP3325A Option 002 - HV Output
« Reply #58 on: September 23, 2020, 03:48:49 pm »
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 :-//
 
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Online Jay_Diddy_B

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Re: Cloning the HP3325A Option 002 - HV Output
« Reply #59 on: September 23, 2020, 05:04:40 pm »

P.S.
Hope you don't mind Jay :)

I 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
 
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Offline hnjmkl

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Re: Cloning the HP3325A Option 002 - HV Output
« Reply #60 on: September 23, 2020, 07:44:53 pm »
After seeing the smd PCB I threw the breadboard in the trash, congratulations to the designer, I wait for developments.
 
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Offline TERRA Operative

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Re: Cloning the HP3325A Option 002 - HV Output
« Reply #61 on: October 07, 2020, 05:00:37 pm »
Works well I think. :)
Any circuit design must contain at least one part which is obsolete, two parts which are unobtainable, and three parts which are still under development.

https://www.youtube.com/user/NearFarMedia/
 
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Online Jay_Diddy_B

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Re: Cloning the HP3325A Option 002 - HV Output
« Reply #62 on: October 07, 2020, 05:16:01 pm »
Hi TERRA Operative,

It looks great!

It looks and works just like the original.

Regards,
Jay_Diddy_B
 
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Offline TERRA Operative

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Re: Cloning the HP3325A Option 002 - HV Output
« Reply #63 on: October 10, 2020, 05:28:05 pm »
Made a video about my Option 002 PCB, some may find it a little less than dead boring. :D



Link to all the files, BOM, gerbers etc:
https://drive.google.com/drive/folders/1l8sT5sR7wLVCqZOov9T9yXTmKLvo_4Qv
Any circuit design must contain at least one part which is obsolete, two parts which are unobtainable, and three parts which are still under development.

https://www.youtube.com/user/NearFarMedia/
 
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