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i'm on a roll... the kgsshv


kevin gilmore
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PSU is finally done.... positive is stable at 505V, negative at -505V, and bias at 396V. I didn't use the Fluke 113 due to the low impedance input, so the measurement might be off by one percent; however, as long as they are matching I'm satisfied.

My friend made a LTspice file for the positive and negatic rail. If anyone is interested, just send me a PM with email.

Congrats! What was or were the earlier problem? Can you post pictures? This is where many would like to know what the potantial problem(s) is/are so that we can keep them in mind when doing our future builds. Grateful if you can share.

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Congrats! What was or were the earlier problem? Can you post pictures? This is where many would like to know what the potantial problem(s) is/are so that we can keep them in mind when doing our future builds. Grateful if you can share.

For positive, I don't really know what fried the LT1021-10, because all the other parts are good. All I did was replacing the chip, and it started to work again.

For negative, it's just common sense not being so common.... Cap's metal container got too close to the trace; silkscreen got blown away and there was a short via the container.. fixed with some kapton tape.

There was actually another minor problem with the Bias.... Apparently testing on wooden floor with 8mm stand-off is not a good idea... Somehow it shorted via the floor and completely blew out one trace (the one that connects the bias to the input cap) and left a pretty big burn mark on the floor. Fixed with a jumper..

Hopefully this is the end of all explosions... I'll get some pics later. it ain't pretty though, considering what it has been through.

Edited by jwzhan
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Any suggestions on how to check if the LT1021 is real and if it is, whether it is working to spec.before plugging it and letting charred parts tell us that it is bad?

For positive, I don't really know what fried the LT1021-10, because all the other parts are good. All I did was replacing the chip, and it started to work again.

From my understanding a fried LT1021 was replaced, the positive rail then functioned correctly, the defective LT1021 did not damage any other parts.

The negative rail shorted from an arc between the metal case of a cap and trace.

I’m sure this is the second time I’ve seen the LT1021 give a builder good headache.

Congrats on psu jwzhan!

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From my understanding a fried LT1021 was replaced, the positive rail then functioned correctly, the defective LT1021 did not damage any other parts.

The negative rail shorted from an arc between the metal case of a cap and trace.

yep, that's the gist of it. It seems that the LT1021 was not completely fried(open). It somehow acted like a diode with a strange breakdown voltage value that prevented the frying of every component. I got lucky on this one.

I am on a ship somewhere of the coast of Alaska using a very expensive internet connection, yet can't help myself but wasting valuable minutes following jwzhan's saga smile.png

You are making me feel bad.

Now here is the photo that I promisedevil.gif

7989170562_c32bb5bdcb.jpg

haven't gotten a chance to do a proper cleaning. Everything that happened is quite visible. This is a very educational experience.

Edited by jwzhan
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I am on a ship somewhere of the coast of Alaska using a very expensive internet connection, yet can't help myself but wasting valuable minutes following jwzhan's saga smile.png

True love is forever, in heart and in soul. Enjoy your trip our friend.

Jwzhan, your perseverance has paid off although earlier on you had doubts as to whether you could get this PSU to function. Keep us posted of the balance of your journey.

Edited by Victor Chew
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I did some research on parts that I need to buy since there are tons of BOMs, and looking at the schematics and the jpg and found that the resistor before the Pro Bias in pdf uses 5M and in jpg 4.7M... Which one is the right one? Or this don't make any difference? Should I trust more in the pdf schematic or the jpg?

JPG: http://gilmore.chem.northwestern.edu/kgsshvps8e.jpg

PDF: http://gilmore.chem.northwestern.edu/kgsshvps8e.pdf

I'm going to build IXYS since A1968 is unobtainable nowadays... using IXYS, If I'm using a 450v supply, R6 and R16 stay as 20k right? The resistance on these is dependent only of the supply and not if it's ixys or a1968, is it correct?

Thanks for your help

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I did some research on parts that I need to buy since there are tons of BOMs, and looking at the schematics and the jpg and found that the resistor before the Pro Bias in pdf uses 5M and in jpg 4.7M... Which one is the right one? Or this don't make any difference? Should I trust more in the pdf schematic or the jpg?

no diff

JPG: http://gilmore.chem..../kgsshvps8e.jpg

PDF: http://gilmore.chem..../kgsshvps8e.pdf

I'm going to build IXYS since A1968 is unobtainable nowadays... using IXYS, If I'm using a 450v supply, R6 and R16 stay as 20k right? The resistance on these is dependent only of the supply and not if it's ixys or a1968, is it correct?

Thanks for your help

yes

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yes

Thanks livewire

4M7 or 5M, it doesn't matter but do use one which is rated for 600V.

I was using the Lil Knight BOM and the 4.7M listed is the 293-4.7M-RC (xicon) which is rated only 350v...

The KOA Speer, although listed as 700v voltage rating at mouser, if you look at the data sheet, the absolute maximum working voltage is only 350v too.

The best I could get was the CMF-60 from Vishay/Dale, absolute maximum working voltage of 500v. Do you have any model that is rated at 600v spritzer? Looked at mouser and couldn't find any that kept the 50ppm/C and 1/2watt power rating

Thanks

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Thanks livewire

I was using the Lil Knight BOM and the 4.7M listed is the 293-4.7M-RC (xicon) which is rated only 350v...

The KOA Speer, although listed as 700v voltage rating at mouser, if you look at the data sheet, the absolute maximum working voltage is only 350v too.

The best I could get was the CMF-60 from Vishay/Dale, absolute maximum working voltage of 500v. Do you have any model that is rated at 600v spritzer? Looked at mouser and couldn't find any that kept the 50ppm/C and 1/2watt power rating

Thanks

why not use something like this http://www.mouser.com/ProductDetail/Vishay/VR37000004704JR500/?qs=%2fha2pyFaduiU7nw9S7xDMMvHHBNPX2%252b3%2fjJQVocKE2r89FMTyeG1R5W5Hn7RFMSD thats what i ordered. Though i guess it doesnt have the tolerance of the units you're looking at, but its not like you're matching it to anything, so thats not really of the utmost importance

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  • 2 weeks later...

If you have lots of heatsinking you can increase the third stage current.

Which increases the high end frequency response a bit.

Its the output stage current you want to bump up. You can bump up the 3rd stage a bit, but no reason

to go crazy on that one.

Kevin, what value did you have in mind when you said “You can bump up the 3rd stage a bit”?

... in my case I have Modushop 3U 400mm sinking with the output current stage targeted for 10mA with A1968’s parts.

If you have a formula for the 3 stage source resistors that would be helpful. smile.png

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^where I got mine. Shipping was fast for me, but the company is in the same state as I, so I don't know about other states.

My amp boards are up (somewhat,) now I'm just waiting for the case to come back from Cam-Expert, which might take a week or two.

At the first start-up, I think I saw some white somke from one amp board, but there weren't any during the second, third and many after (they are all very short though, around 1 mintues or so, because the only heatsink the transistors have are the angled aluminum bars.) Will do more extensive testing after the panels and heatsinks come back.

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