VARIABLE HV POWER SUPPLY 0-4000VDC, 0-200mA, 0-200W

[Moonage]

Hello to everyone,

Recently, I bought an electrophoresis power supply. It is EC600 by E-C Apparatus,made around 1987 but there are also units made by Fisher Biotech.
Supply is able to deliver up to 200W and can be limited, and voltage is adjustable up to 4000V. Current is also adjustable up to  200mA.
Voltage, current, and power can be adjusted prior to turning the output on.
Supply also has ground leakage indicator that allows only 120 microamps ground leakage.
As a safety feature, the supply will not deliver voltage to the output if it does not see the load, and the load must have resistive component.(I tried to shoot some capacitors with high voltage to see how far can they go, but would not turn the output on. It worked after adding resistor in parallel with the cap.)
Paid $36 on ebay.
That would be positive things...

Negative....
It is not a lab power supply, and there is quite some ripple in the output. I measured voltage at 150 V,  with about 2.76 VAC RMS, or measured on the scope, about 10.8 Vp-p wich is about 7.2%.
If voltage is preset, once the output turns on, there is an overshoot. I measured 24V overshoot at 160V preset value, supply briefly went to 184V
It is HEAWYYY!

I would like to correct ripple, and overshooting problem.
Anybody with schematic?
Any ideas?

Supply is rather complex, and you can see that from the pics

[HotBluePlates]

... I bought an electrophoresis power supply ... able to deliver ... voltage ... up to 4000V. ...
...
It is not a lab power supply, and there is quite some ripple in the output. I measured voltage at 150 V,  with about 2.76 VAC RMS ...

I would like to correct ripple ...

It is a lab power supply, by definition, because it's intended for electrophoresis processes in a lab environment.

The manuals I found online are for users and don't dig into the engineering specs of this supply. I don't think it's fair to the supply to view the 2.76v RMS ripple (~1.8% of 150vdc) in terms of peak-to-peak volts (resulting in your 7.2%) when thinking about the regulation.

The 150vdc test point is also less than 4% of the full voltage output capability. It's unclear whether the supply will have the same 2.76v RMS ripple at the top of the voltage range... If it did, that would be vanishingly-low ripple. Food for thought.

If voltage is preset, once the output turns on, there is an overshoot. I measured 24V overshoot at 160V preset value, supply briefly went to 184V.

I would like to correct ... overshooting problem.

Why is the overshoot a problem?

With any bench power supply, the user should still have a power supply rail for the circuit under test with filter caps and series decoupling resistors. Amplifier stages need that filtering & decoupling to avoid feedback due to shared power supply impedance. And since you're going to build a power supply rail anyway in light of this, you should appropriately rate the filter cap voltage to allow for your power supply's overshoot (which really isn't that big anyway).

FWIW, guitar amps have similar "overshoot" but due to the fact power supply voltage will drop when the tubes pull current because of the series impedance of a guitar amp's power supply. So it's a standard practice to rate filter caps for the maximum possible supply voltage, rather than the operating voltage.

... I would like to correct ripple, and overshooting problem.

... Supply is rather complex, and you can see that from the pics

The little bit I can gather from online information is this supply is microprocessor-regulated. So unless you can establish with certainty that the <3v RMS ripple exceeds the design ripple for this supply (again, <1/1,000^th of full output voltage), there may not be a "problem to fix." And if there is a problem, it's not gonna be a simple part-swap.

It might be harder to find help on power supplies which aren't simpler linear-regulated supplies. I have a couple that are more complex than that, and I hope nothing major fails in them because they'll probably be beyond my ability to repair.

[pompeiisneaks]

Agree 100% with HBP, especially if you plan on it to replicate our play with amp circuits.  Assume the power you get is right outside the rectifier, and expect the filter caps to clean the ripple.  That's what they're there for in the first place.

~Phil

[Moonage]

Tested power supply again, this time on higher voltage.
Output voltage  1017VDC
Ripple voltage   6.5VACrms/23.36Vp-p (0.64% / 2.29%)
Output current  16.4mA
Load 62kohm

Much better!

HotBluePlates thanks for reply, absoulutely agree with all you wrote.

For tube amp testing purposes, that is more than needed...but trying to improve something, should not be bad thing.
Also, I checked ICs inside the supply, no microprocessor, here is the list of ICs used
MC14066 - Quad Analog Switch/Quad Multiplexer
MC1458 - Dual Operational Amplifier
TL082 - Wide Bandwidth Dual JFET Input Operational Amplifier
H11B1 - Photodarlington Optocoupler
SCL4020BE - Asynchronous Binary 14-Bit Up Counter
SCL4071BE - Quad 2-input OR gate
MC1494 - Linear Four-Quadrant Multiplier

I was just looking for some simple solution, like adding a NTC Thermistor at the output, and adding additional smoothing filter, or modifying existing one.

[HotBluePlates]

... Also, I checked ICs inside the supply, no microprocessor, here is the list of ICs used ...

Fair enough; I was using terminology I thought I saw in the EC600-90 manual, but I might have confused it with something else. I still think it's fair to call it a digitally-controlled regulator given the functions you noted. Then again, maybe that stuff is mostly for timing/counter. Either way, I won't be much help in modifying it.

I was just looking for some simple solution, like adding a NTC Thermistor at the output, and adding additional smoothing filter, or modifying existing one.

You can do that stuff, but will it make the supply any better than it is? You've got a very nice $36 lily already... 

My personal take on a bench power supply is that it should replace the power transformer and rectifier of an amp circuit, hopefully adding a convenient means of stable voltage adjustment. Current limiting for a fault condition would be nice. So I still expect to have the full supply rail of filter caps, decoupling resistors and possibly a choke.

All those other bits will add the additional smoothing. They're needed anyway while you're designing, because the complete independent circuit will need them.

[pompeiisneaks]

I have been thinking of getting a bench power supply and due to your find, I just bought one for 45$ as well.  Thanks for the tip :)

~Phil

[Moonage]

Did you get the same model?

[pompeiisneaks]

Pretty sure I did.  There is another newer model with a digital display, but it goes for a bit more. 

Mine looks just like yours, with analog meters. 

Thanks for the tip :)

~Phil

[Moonage]

Get ready for heavy lifting 
That is realllly heavy...

[pompeiisneaks]

Yeah shipping is equal to the cost of it, and its coming from the next state :)  (I'm in WA and the seller is in Oregon, a 5 hr drive away).

~Phil

[Moonage]

Yeah shipping is equal to the cost of it, and its coming from the next state :)  (I'm in WA and the seller is in Oregon, a 5 hr drive away).

~Phil

Listen to the fan first time you power up, and tell me your impressions.....

[pompeiisneaks]

Lol will do, should arrive either today or tomorrow.  (shipping from the next state so should be soon). 

I've got to think through how I can do some of the same tests you've done with my scope, see what kind of overshoot etc.

~Phil

[Moonage]

Lol will do, should arrive either today or tomorrow.  (shipping from the next state so should be soon). 

I've got to think through how I can do some of the same tests you've done with my scope, see what kind of overshoot etc.

~Phil

I used my Fluke 189  Fast Min/Max
I will see if I can do that with oscilloscope too, and maybe post some pics.

[pompeiisneaks]

It arrived tonight, I won't have time to set it up on the 'scope and play, but I wanted to ensure it worked, and I've set it up on my fluke and it overshoots BAD :)  I had it set at 500V and it went to OL (600v over limit) not even sure how high, so I set it at 100 V and it still goes OL.  I guess it may be that the caps might need replacement, but it drops right down almost perfectly to the right range after that overshoot.  I'll get some time this weekend to setup some caps and see how it goes.

~Phil

[PRR]

An auto-range DVM will start from 0.2V. And of course show OL until the auto-range catches-up. I think mine does it on a wall-outlet, which sure isn't going to "overshoot" the exact moment I stick the probes in.

[Moonage]

Fluke 189 when set for FAST MN MX can capture transient signal events as short
as 250 µs, but with decreased accuracy; only 3-1/2 display
digits are allowed.

If you set meter to manual range, should not show OL, and good meters should show actual value without "hunting".

[pompeiisneaks]

Oh thanks to you both, makes sense, the meter is in tens of volts mode when it jumps to hundred rage and it takes a second to switch.  I'll give that a go.

Phil

[pompeiisneaks]

Set at 398 it went to 473.8 so that's 19% overshoot

Tried again at 352.5 and got 420.5, same 19%.  Guess you could set it lower than needed, then let it come up, and slowly dial in the right voltage after the overshoot is done.  This weekend I'll try some experiments with caps in the circuit.

Phil

[Moonage]

That is close to what I had, but, I measured at lover voltage, 160/184V, or 15%

[PRR]

100 Ohms and 100uFd would probably damp that transient.

Don't think it is a Problem which needs fixing.

[pompeiisneaks]

Thanks prr, good to hear. 

Phil

[Paul1453]

This is very nice for those higher voltage amp circuits.

My bench supply won't go over +440 for B+, but it does have some things this doesn't.
It has a 10A 6.6VAC and a negative 0-300 VDC supply for bias voltage all in one unit.
Mine is an old tube controlled model from an Oak Ridge TN Govt lab.
Not likely to find many of these available now, and I had to make a 4-5 hour roundtrip drive to get it.

I Thank HBP for explaining to me that I still had to build my power rail as designed.
I thought that since this was putting out nice clean DC I just needed the resistors to drop to the lower voltages.

I am finding that I prefer to work on circuits with around +400VDC B+ or less, better than a higher B+.
I feel a little safer, and haven't had any unexpected arcing happen.

+4000VDC able to supply 200mA of current scares the crap out of me.
I know that we can feel static electricity shocks of around that voltage, and those have minimal current.
I'm getting too old to have that kind of HV able to jump up and bite me for getting too close and not even touching it. 

But for those of you, that like to run Big Bottle tubes near their upper voltage limits this PS seems like a good deal at that price.   

[Moonage]

This is very nice for those higher voltage amp circuits.

My bench supply won't go over +440 for B+, but it does have some things this doesn't.
It has a 10A 6.6VAC and a negative 0-300 VDC supply for bias voltage all in one unit.
Mine is an old tube controlled model from an Oak Ridge TN Govt lab.
Not likely to find many of these available now, and I had to make a 4-5 hour roundtrip drive to get it.

I Thank HBP for explaining to me that I still had to build my power rail as designed.
I thought that since this was putting out nice clean DC I just needed the resistors to drop to the lower voltages.

I am finding that I prefer to work on circuits with around +400VDC B+ or less, better than a higher B+.
I feel a little safer, and haven't had any unexpected arcing happen.

+4000VDC able to supply 200mA of current scares the crap out of me.
I know that we can feel static electricity shocks of around that voltage, and those have minimal current.
I'm getting too old to have that kind of HV able to jump up and bite me for getting too close and not even touching it. 

But for those of you, that like to run Big Bottle tubes near their upper voltage limits this PS seems like a good deal at that price.   

I was looking to get something like that, but could not find anything that would not cost a lot of $$$.
And yes, it is scary having 4000 V PS on your bench. Good thing with this one is that you can select voltage, current and power ranges with selector switches, and two safety features: ground leakage detection, and no load detection. In both cases, the output would shut down.

[HotBluePlates]

... I was looking to get something like that, but could not find anything that would not cost a lot of $$$. ...

On rare occasions, the bigger hamfests will have something like that at reasonable cost. If it were still the 90's you coulda found people throwing them away.

But there are just enough people tinkering tube electronics that the word is out, and there are eBay sellers willing to ask (ordinarily) ridiculous money while letting the thing sit for years until it sells at the price they want.

Same with how some eBay vendors want $300+ for a variac (and it sits for years), while others sell them for $40-60 and move them along quickly.

[jjasilli]

This thread caused me to blunder into www.tubelab.com


An industrial control transformer is another alternative.  Generally used to convert a 480vac supply to 120 or 240vac.  Swap primary for secondary.  I.e., 120  > 480.  Use a variac to hit desired voltage (SS voltage doubler for really high voltage if needed).