UFN
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Posts posted by UFN
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I am struggling a bit to find a 787k high-voltage resistor for the bias-supply on my 450V PSU. The only thing I can find is Mouser p/n 594-HVR2500007873FR5. The voltage rating is fine (1.6 kV) but it is only rated 1/4W - is that enough?
//UFN
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Geoff, I can see you use the LSK389, can I ask how you got those? I looked at trendsetter but they want nearly $65 to send $80 worth of transistors to EU and I thought that was a bit steep - do you have another option maybe?
//UFN
Apologies for quoting myself, but in case anyone needs it: I ended up ordering LSKs from Micross in the UK. Postage was a bit steep at 15 pounds, but I ordered on Sunday and parts arrived Thursday, so no issues to report there at all
//UFN
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Yep, an all-black version would be great
Apart from that - obviously an outstanding job as usual Spritzer
//UFN
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Geoff, I can see you use the LSK389, can I ask how you got those? I looked at trendsetter but they want nearly $65 to send $80 worth of transistors to EU and I thought that was a bit steep - do you have another option maybe?
//UFN
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OK after some time I finally figured out why my caps were blowing. The Toroidy transformer that I have, although giving out a good 16V-0-16V, doesn't give me 450V. Instead, the output on the secondaries are 487V, both of them.
That sounds normal if there is no load on the transformer as the voltage for any transformer is specified at full load. At idle, you should expect 5-15% higher voltage (percentage depends on the size and core type of the transformer).
//UFN
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I believe the pins are a jumper to enable/disable the DC servo.
//UFN
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Looks good
Shown next to the new KGST boards, a smaller version of the group buy boards. The difference is not great but I had to shave off a few millimeters to get them into a chassis I bought.
Stop doing this to us - you know we always want the latest and greatest
//UFN
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2sa1831 is only an 800V part. So you would have to cut the power supply voltages down to +/-400
Ahh, yes of course. I'll just stick with the FETs then. Cheers Kevin!
//UFN
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Simple question really: I am gathring parts for a KGSSHV and would I be able to use 2SA1831 I already have instead of the 2SA1968 for the current sources - or would I be better off just buying the IXYS FETs from mouser instead?
//UFN
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Impressive work indeed.
//UFN
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Now that is cool
//UFN
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Typical tolerance for large electrolytics is +/-20%, so 600uF is well within spec.
//UFN
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Oh you gotta be fucking kidding me, that listing just ended all sold out before I could buy some. Ffs
More listed now.
//UFN
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anything over 20v is fine for the servo
Applies here as well I think...
//UFN
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Haven't bought anything in there a while so shipping may have made it prohibitively expensive, but http://www.conradheatsinks.com/welcome.htm would be on my list.
//UFN
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That's where I bought mine from (as shown in ) and I now have some more on the way. However, the batch numbers in the listing picture and the ones I got are (very) different and the available quantity keeps changing. Most likely this is a seller buying up various leftover components from manufacturers in China and so there is some risk that you don't get what you pay for. Also, in my naivity I bought some 2SK389s from the same seller and they were clearly fake (tested as BJTs and not FETs) but the listing very clearly said "genuine Toshiba" so I would not unconditionally recommend this seller.
//UFN
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1) Yes, that should be the only difference.
2) Looks that way.
//UFN
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I believe it should be 280V and around 140-150mA, so complete min. specs for a custom wound would be:
Pri: Whatever voltage(s) you need, power = 120VA or higher.
Sec. 1: 280V/min. 40VA
Sec. 2: 280V/min. 40VA
Sec. 3: 15V/min. 10VA
Sec. 4: 15V/min. 10VA
Sec. 5: 6.3V/min. 10VA
Sec. 6: 6.3V/min. 10VA
You can go higher power if you want of course. The 15V windings can be higher voltage (16-18V) if you want but it should not be necessary given the dropout voltage of the LM78xx/79xx regulators. It can also be 15-0-15 center-tapped instead of two discrete secondaries if you prefer.
//UFN
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Truly. I briefly entertained the idea of buying one of those, but it seems like it might be simpler to just make one from the start.
Same here, doesn't really seem worth the effort now.
//UFN
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I am in the process of gathering parts for a KGSSHV build and came across some 2SC4686a's at a reasonable price. Now, not the best picture in the world, but what do you think – are these genuine?
Pin connections are consistent with the data sheet and hfe seems to be in range as well. Unfortunately I have no way of measuring the breakdown voltage.
There’s no bar under the batch/lot number so either they are very old (pre-RoHS) or they have been remarked.
Thanks,
//UFN
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Looks very good - only annoying thing is that I already ordered a couple of boards of the older version and the KGST amps
I can see the amp board has been upgraded to v0.51 as well, can I ask what was changed?Oh, one minor error in the silkscreen by the way - one of the big caps is marked as 50V, not 500V.
//UFN
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Looks like they just gave you an extra core free of charge
How are Keen Ocean's prices (and quality) compared to the toroidy audio grade transformers?
//UFN
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Very impressive, but probably not really safe
//UFN
I can see the amp board has been upgraded to v0.51 as well, can I ask what was changed?
i'm on a roll... the kgsshv
in Do It Yourself
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Excellent, thanks!
//UFN