Well we should never have to rely on the solder resist for insulation.  It's very thin on the boards Tran has made though

Should we cover the board with Kapton tape before populating it? 

The new ones?  Shouldn't be necessary with the increased tolerances. 

 

Edit:  Also won't help with this since it's trace to ground plane, not something that's on top of the board. 

Edited August 3, 201312 yr by spritzer

I must remember to leave some space between the parts and the boards for precaution measures in my next build.

It is a good idea to never rely on the insulation actually insulating.  As somebody on HF found out, the shell of the caps is connected to the negative terminal which is fine in a simple B+ setup (where the negative is always grounded) but here it is prolematic.  If the cap is sitting on the PCB then just the thin shrink wrap is all that sits between 650VDC and ground.  Even 1mm of clearance is enough for 1kV or more at high humidity so that makes sense. 

Wanted to thank all of you for the advice, but it turned out to not have anything to do with the grounding at all, which I think is why it took so long to discover what happened. I was undoing the left channel from the pot, first from the input side, and nothing changed. Then from the output side, and it went away, but if I moved the wire sometimes the hum would come back sometimes not, so I looked at what was changing as I moved the wire. It turned out that during shipping I guess, from GeorgeP to me, the positive wire connection came out of the terminal block from the pot. So I unscrewed it, put the wire back in, screwed it back down. And now no buzz, and also, the channel imbalance I had, is also gone...

 

anyways, now I'm getting beautiful music from my KGSSHV and Sr-307s

Congrats the problem solved!

Can anyone PM me the BOM? What is the cost to build this?

The servo has finally been tested and has a 15 volt range with the 10k resistor as labeled.

If you change the 10k resistor to a 5k resistor , it has a 30 volt range.

Edited August 4, 201312 yr by kevin gilmore

Wanted to thank all of you for the advice, but it turned out to not have anything to do with the grounding at all, which I think is why it took so long to discover what happened. I was undoing the left channel from the pot, first from the input side, and nothing changed. Then from the output side, and it went away, but if I moved the wire sometimes the hum would come back sometimes not, so I looked at what was changing as I moved the wire. It turned out that during shipping I guess, from GeorgeP to me, the positive wire connection came out of the terminal block from the pot. So I unscrewed it, put the wire back in, screwed it back down. And now no buzz, and also, the channel imbalance I had, is also gone...

 

anyways, now I'm getting beautiful music from my KGSSHV and Sr-307s

 

Chase and I had also been trying to figure this one out off-line as well. Never thought it was the grounding scheme as it was dead silent for me for several months while I used it. Sounds like a combination of me not tightening the little terminal screw down enough (always afraid of overtightening) and UPS using their patented "super-vibration-crash'em-bang'em" delivery system from Canada to the States. Glad it was such an easy fix (albeit tricky to locate!).

Finally received my power transformer, I can keep working on.

 

It's [email protected] x2 and 16V@1A x2 , order from a local PT factory.

Edited August 8, 201312 yr by palchiu

I'm on the quest to clean up some wiring, I was wondering- if I've got a twisted pair of conductors in a single sheath which is rated for 600v, can I use each of the wires inside for the hv rails or is that reading the rating wrong? the figure 600v/200c should be per enclosed wire right?

Yes that's how the rating works.  I believe Belden also rate their wires when you bundle them and then they are 1000V+ for the 600V PTFE. 

Edited August 9, 201312 yr by spritzer

Making progress...

 

I just got the amp boards in.  Here's the front & back.

 

 

 

Here's one of the PS boards with a voltage doubler on top for the bias voltage.

 

 

 

Parts will be in on Monday

Edited August 10, 201312 yr by Kerry

Making progress...

...Parts will be in on Monday

 

The board's color also caught my eyes.

 

Well done! Thanks Kerry!

I used OSHPARK for the prototypes.  It's $5 / inch for 3 boards (color standard).  Expensive for larger boards, but works OK when checking the board.

Those boards look really nice, Kerry. 

can anyone tell me off the top of their head if you need to upgrade the transformer to turn up the output current of the last stage? i was under the impression it was more of a no strings attached mod.

Thanks!

The transformer is a beefier 150VA model, it uses a screen and the 420 V windings are now capable of continuous current @ 250mA.

The psu is standard 450V, for the amp boards I changed R8 and 9 from 180ohm to 113ohm, simply by parallelling 300ohm over the existing 180ohm resistors which saved lifting the amp boards of the heat sinks. I was going to dabble with the third stage, but chose to leave it, I was concerned about not being able to get the boards to balance. As it is I can get both boards under 1 V, but cannot get down to the ~ 0 V where I was before, not that is matters, just worth mentioning. As for heat, there’s not much difference, runs slightly warmer overall.

Listening I found higher frequencies have opened up, sounded really good to my ears and definitely worth the effort.

Hey all,  running into some problems with a new kg build (450v w/ a1968).    PSU works fine, but both amp boards are showing strange behavior and I haven't been able to figure it out.  (amp boards are revision .5) 

 

When I apply power to the amp boards, only 3 leds light up (the led by the balance pot doesn't come on)  However, as the power turns off the 3 lights power down and then the balance led comes on.  here is a youtube showing the symptom.  http://www.youtube.com/watch?v=LcVCWShWCHc&feature=youtu.be  (sorry about the quality)   

 

I am sure there is a short but I am not sure where.    Any thoughts on what might be wrong?       Thanks for any help!

What's the power supply board size dimensions? What's the length between the edge of the board to the heatsink mounts (measured from the edge of the board to the contact point between the heatsink and IC)?

I have a heatsink that is 7.625" width by 2.25" length. Before ordering the chassis, I need measurements.

The new HVk PSU board?  It is 6.92" by 6.56 and the distance from the back of the transistor to the edge is 0.563014" give or take... 

 

Hey all,  running into some problems with a new kg build (450v w/ a1968).    PSU works fine, but both amp boards are showing strange behavior and I haven't been able to figure it out.  (amp boards are revision .5) 

 

When I apply power to the amp boards, only 3 leds light up (the led by the balance pot doesn't come on)  However, as the power turns off the 3 lights power down and then the balance led comes on.  here is a youtube showing the symptom.  http://www.youtube.com/watch?v=LcVCWShWCHc&feature=youtu.be  (sorry about the quality)   

 

I am sure there is a short but I am not sure where.    Any thoughts on what might be wrong?       Thanks for any help!

 

So both boards are like this? 

yea both boards exhibit the same behavior with the leds.

Have you quadruple checked all the parts?  Same fault on both boards is either PSU related or the wrong part on both boards. 

Make sure that no resistors are installed backwards. (I keed, I keed!)

Still one should check for things that may have been reversed, or wrong part in the wrong place.

I did that with the exstata build. It was a real pain but a good experience being my first build.

A guy whose name starts with s and ends with u at the other site volunteered to help at a price. I sent him my boards but he sent them back untouched :0

It is weird that you have a problem with both boards. If you are using Lil Knight boards, is not the boards.