Formally that is called the transformer regulation - the percent difference between fully loaded and no load. For your numbers (490 cf 450) that is 9%, and is typical of a 120VA transformer. That percentage also takes into account that when loaded the transformer will heat up - typically to 50 - 60C, and the copper windings will increase in resistance.

Yes indeed, my spec sheet shows off load at 480.7v and 16.3v but my actual reading is 490v and 18v x 2 = 36v hence my slight concern. Will test it again when loaded. In anycase, thank you all for the replies.

It's probably off due to small differences in manufacture and different line voltages. I believe those SumR numbers are calculated and not measured though...

Some progress. My custom casing made from 3mm thick 4 inch and 5 inch plates. Bones are half inch. Its 15 x 11 x 4 in dimension. It was hard work tapping and drilling all the holes to precision. Took me about 4 days to get this case up from scratch. Need another for the amp portion. Good thing is that it costs US50 for both the casings and the tools (drill bits and taps). With all the metal it weighs close to 4 kg per box.

^^ Nice! What are you going to do for ventilation?

Some holes for the bottom and plenty more on top arranged in the form of some design, a bit like the BHSE perhaps.

Looks like a Pass Labs case. (Aleph P, etc.).. nice job

Here are my stuffed boards.

I used PEEK screws, but not sure if nylon washers with metal nuts are OK.

The heat sinks are a pain to solder. Will try to fix that tomorrow.

Edited February 19, 201214 yr by eggil

The nut is more isolated than the heat sink so I can't imagine how it'd be a problem.

The heat sinks are a pain to solder.

That is because --- they are heatsinks

So they are always a pain to solder - needs a really hot and high power iron for those joints.

Craig

No kidding! I have a Hakko 936. Even at 800F is hard. I spent a lot of time today going over all the solder points with a magnifying glass. Will double check and triple check the components tomorrow.

Edited February 20, 201214 yr by eggil

No kidding! I have a Hakko 936. Even at 800F is hard. I spent a lot of time today going over all the solder points with a magnifying glass. Will double check and triple check the components tomorrow.

Get a wider chisel tip as well if you haven't switched out to one to solder the heatsinks.

I used a 3.6 mm chisel tip for the heatsinks.

No kidding! I have a Hakko 936. Even at 800F is hard.

I’m gonna need a bigger iron.

Real men know how to solder

Edited February 20, 201214 yr by eggil

Hah! I've sweated miles of copper pipe! It's not relative at all, trust me.

I used PEEK screws, but not sure if nylon washers with metal nuts are OK.

I did the exact same thing on my build with no issues.

One word of advice, make sure your solder joints for the HV transistors (the heatsink mounted parts in particular) are nice a clean. I learned the hard way that a little spec of solder sticking out near the ground plane can lead to a short.

Thanks Horio. I did pay attention to your post on the "help me build my kgsshv" thread on hf. Interesting thread to say the least.

Did you apply the Conformal coating spray to yours?

Edited February 20, 201214 yr by eggil

That thread was a train wreck waiting to happen. I'm glad Nate shut it down.

Conformal coating is a great idea if you have plans to send your amp into space

or if it is to be used in a corrosive environment. Beware that it is a major pain in the ass

to remove if you ever need to replace any parts during rework or repair.

I didn't use any conformal coating and didn't have any kind of shorting or arcing problems. I think like Horio said if the joints are neat and solder isn't all over the place you should be fine. Although if jcx were here I imagine he would not agree.

That thread was a disaster - someone who doesn't know one end of a diode from the other, and worse yet the difference between a resistor and a diode on a layout should not be building a KGSSHV.

I think of it less as a disaster and more like a Nascar wreck. As many times as I posted to deter the guy from building it, I secretly wanted him to try it anyways and post 3 months from now about how his life flashed before his eyes upon his first attempt to power it up. An extra bonus would have been attached photos of small housefires it may have caused.

I was waiting for the first hf Darwin award nominee...

But he swore it was perfectly safe! He had a professional with 20yrs of experience ready and waiting to look over his work!

I thought it was a nice touch when he cursed at people that were warning him about the safety implications.

Well he specifically said they weren't allowed to warn him off doing it, so they must've been real big dhiks to do it anyways.

Conformal coating is a great idea if you have plans to send your amp into space or if it is to be used in a corrosive environment.

Couldn't help myself.

On a serious note, it does not sound like a good idea.

Edited February 20, 201214 yr by eggil