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goldenreference high voltage power supply (GRHV)


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  • 1 month later...
On 9/22/2022 at 5:23 PM, BadgerMcBadger said:

is 550 pulsed 475 continuous VDC  good enough for the big caps on the grhv?

This depends on what DC output voltage you are building for which depends on the input AC voltage to the GRHV which depends on the AC rms output of the transformer you are using...

for example if you are building for 400V DC output to power for example a blue hawaii then you need about 360VAC rms input to the golden reference. (360VAC rms is about 509 peak when full wave rectified by the diode bridge before the input cap (DC voltage * square root of 2) which is enough for the internal voltage drops inside the GRHV and gives you some margin so the GRHV can actually regulate). Mains voltage typically varies by about +-10% so that is factored in to. But if you mains voltage is high then the input filter cap will see additional voltage so 550 rated cap should be fine for 400VDC output... If you are going for 450VDC output (about the maximum a GRHV can do) then your cap is going to be marginal and a 600V rated cap would be better....

The output cap should only see the output DC voltage, so if your GRHV is outputting 400V DC a 450VDC or 500VDC rated output cap should be fine.

Dont forget many high voltage caps especially the 680uF are 80mm tall and so too tall to fit into a 2U case.... Kemet make some nice high voltage caps with life time ratings of around 15000 hours. 

https://www.mouser.co.uk/c/passive-components/capacitors/aluminum-electrolytic-capacitors/?q=kemet 550V&life=10000 Hour~~20000 Hour&voltage rating dc=550 VDC&rp=passive-components%2Fcapacitors%2Faluminum-electrolytic-capacitors|~Life

 

 

 

 

 

Edited by jamesmking
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  • 1 month later...
13 hours ago, BadgerMcBadger said:

is  the BU2508AF a good replacement for the ksc5026m on the grhv? 

It would probably work, but I wouldn't call it a 'good' replacement. You would have to deal with a different package, higher Cob and lower Hfe.

In theory any NPN with sufficient breakdown voltage can be used in that position, but since it is the only gain stage in the regulator (both the STN9360 and the SiC FET are followers) and consumes very little power, I tend to use lower current parts with potentially higher Hfe. The compensation cap value was designed for the KSC5026M, so if the replacement part has lower Cob, increasing that cap may be necessary for the stability of the circuit. 

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On 9/23/2022 at 11:45 AM, BadgerMcBadger said:

is there any benefit for going higher than 400v? (for the carbon)

I'm satisfied with 400V. Started with 500V ten years ago. Reduced to 450V a couple of years ago and now 400V for all my electrostatics, including DIY T2.

16 hours ago, BadgerMcBadger said:

is  the BU2508AF a good replacement for the ksc5026m on the grhv? 

You might try stn0214. It's surface mounted piece, but it can be soldered in standing on the ksc5026 pads.

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The GRHV is not particularly fault-tolerant. If any of the high-voltage part had a breakdown, it will likely cause a chain reaction and bring down other parts, including the expensive (if you didn’t buy from AliExpress) LT1021. So being able to test the breakdown voltage of the parts before putting them on the board helps a lot.

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18 hours ago, BadgerMcBadger said:

that was super helpful, thanks. i bought some ksc5026m off aliexpress but i couldnt find a transistor tester at the electronics store so i bought some BU2508AF as a replacment . if the ksc fail, could there be any harm done to the rest of the circuit?

I would be very wary of buying hard to get parts from aliexpress. In these high voltage applications, a fake part that breaks down can easily cause catastrophic and expensive failure.

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42 minutes ago, BadgerMcBadger said:

is powering the grhv without a heatsink for the c2m1000170d and 10m90s OK if there is no load connected?

yes, for short term testing, e.g. for checking output voltages, voltage regulation etc.

(P.S. its also possible to test the grlv with no heatsink with no load.)

 

Edited by jamesmking
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  • 2 weeks later...
2 minutes ago, BadgerMcBadger said:

Hey, i accidently created a solder bridge between the legs of the lower bc557b that i cant desolder no matter how hard i try. can the grhv function normally like that?

Put extra flux in there and solder again. The flux will separate the legs and resolve the bridge.

Edited by audiostar
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7 minutes ago, BadgerMcBadger said:

i tried, didnt work, its just a very thin and sticky layer of solder that wont go off

Then heat up and use a solder wick (or braid) to suck up everything around there. Then clean and solder again using enough flux. 

There is no such like you can not remove. 

Look here 

 

 

 

Edited by audiostar
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3 minutes ago, audiostar said:

Then heat up and use a solder wick (or braid) to suck up everything around there. Then clean and solder again using enough flux. 

There is no such like you can not remove. 

it isnt solder but rather parts of the rings around the legs that dissolved into each other, i have no idea how i managed to do it

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9 minutes ago, audiostar said:

Probably overheating, pulling around on the components and/or lower quality boards. In any case advisable to resolve this first before going further. Might be you best take out the component first and repair the tracks and board.

i was usually soldering with 320 celcius. could that be too much?

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  • 2 weeks later...

OK, finally getting around to testing the GRHVs I'm building for the Carbon. Using Soren's post on pre-testing, I had some variances.

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I marked up the schematic from James above.

  1. For the first test, using ~17Vdc thru an ammeter, I'm getting 0.5mA (not 2mA) (points A1-B1)
  2. For the second test, I'm getting ~1.3-1.4mA (points A2-B2), which matches Soren's figures.
  3. For the third test, I'm getting 10.5-10.9mA (points A3-B3). This may be referring to a Megatron HV900 PSU in Soren's notes below, and I'm not sure I'm looking at the correct points anyhow.

I have a 100K resistor paralleling the two 390Ks. Bringing the positive supply up on a variac until it regulates, it seems to be regulating at 55Vdc, which is about what I calculated. Boards are 1.8 version, single fat sw variants. The voltage appeared to be stable; raising the variac a bit didn't change the output.

Just checking because the first CCS test was considerably lower than what Soren saw. I did unsolder one end of the 100K resistor and rechecked, but no change.

Any thoughts, or just go for full voltage?

On 7/2/2017 at 10:28 AM, sorenb said:

I never had troubles with the HV900's, and haven't had any that blew, so the following is based on what I've found useful troubleshooting/checking the regular Golden Reference HV.
Often it can be helpful to work at lower voltages when trouble shooting. Paralleling the high resistor (is it 2x 450kohm in the HV900?) in the probe string to get the circuit in action at a lower output DC. If regulation doesn't work for some reason and things go bad it usually isn't really bad.
Parallel the R8(2x 450k) with one ~100k (one across both) will provide some ~100VDC.

Initial check:

  1. The CCS's
    Use a lab supply at some ~15-20V, through a DMM at mA: put the (+) at the drain (middle leg) of the 10m90, and the (-) at the bottom of the CSS where R2(100) and R1(4k5) meets ...you should get ~2mA ....if you see much more, try replace the DN2540.
    Do the same at the other CSS: (+) to drain (middle leg) at the 10m90, and (-) at the bottom (pin 6 at the voltage reference) ...you should get ~1.3mA ...if not the 10m90 is probably damaged. 
    Check the current limiting CSS you added (your drawing) the same way (Kevin suggested 50mA for this)

When powering up the supply, hold the variac when you reach some ~40-50VDC output, and check: 

  1. the pin6 of lt1021 against "ground" (pin4) ....you should see 10V ...if not, the lt1021 has probably gone south
    Before raising the VARIAC further:
  2. Attach a DMM across the 2k at the bottom of the cascoded CSS ... you should see ~0V (when at ~50VDC output) and only before regulation kicks in, the voltage jumps to some ~4V; it happens just before you reach the desired output voltage
  3. Attach a DMM across the 3k at the source leg of the output CSS (right most leg) ...should be some steady ~4V
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