i'm on a roll... the kgsshv

[shipsupt]

Thanks everyone for the input, guidance, etc...  Glad to see my crap work brought a little life to the thread.  I'll be cleaning, testing, and fixing for a bit.

 

For sure I did not insulate the 78XX and 79XX as I misinterpreted earlier post on the topic and indeed thought that they were grounded and since the board didn't have the ample room for the ceramic (as it does on other parts) I made the bad assumption that it wasn't needed.  I'm straight on it now.

 

I'm afraid I'm with Eggil, I somehow doubt that the net result was only the arcing, the resistor didn't even actually blow.  I can't help but think I'll find some other damaged parts.  

 

Back to work.

[headinclouds]

I just searched for green nail varnish (!) Repair of photo resist might be possible using it. it dries in a few mins. I found a ref on nerdclub

http://nerdclub-uk.blogspot.co.uk/2013/04/nail-varnish-as-solder-resist.html

and the green varnish ;

http://www.barrym.com/products/nails/paint/all-nail-paints.html

Note it must not have metallic flakes in it!!

This could take our hobby in a whole new direction.

[kevin gilmore]

the 78xx and 79xx just need the regular thermasil or equivalent washers, they are low voltage.

and nylon screws.

the 10m90s current sources need the aluminum oxide washers and nylon or peek screws

[spritzer]

I use pink varnish as that's just how I roll but apply it in layers for a very good barrier. 

 

There are also insulated 78xx/79xx that we perhaps should put into the BOM.  Saves hassle but the new PSU board don't have any sinks for the LV section. 

[eggil]

So, what caused the arcing then?

Shipsut, let us know how the other components test

Edited June 10, 2013 by eggil

[shipsupt]

Will do.  It will be slow and steady at this point, so it make take a little time.

[Emooze]

Birgir, is anyone doing a run of the new PS boards in the short-term?

 

I think I missed a trace on my PS that caused my issues last night. I'll probably have to run some 600V wire across the board to fix this. Will report back.

[spritzer]

No but I have a spare one.  Might also have a spare of the bigger ones... 

 

I've been asked this a couple of times now but would people want a simpler power supply for the KGSSHV?  This one is a tour de force and there are ways of just bypassing the complicated stuff but perhaps it would be a good idea to have one that is simple and foolproof.  For instance, if the old Blue Hawaii power supply stopped working it was always the same fix, replace the mosfet. 

[headinclouds]

Yes please, I'd like to have the choice of the bells and whistles job or a simpler alternative. Assuming the low noise/transparency of the amp was not seriously compromised.

[kevin gilmore]

lil-knight has the latest smaller power supply version which has double the space around all the holes and circuit

lands to prevent arcing.  You have always been able to partially populate the board, setting the zeners for

the desired voltage and then putting a jumper in where the pass transistor is, driving the fets directly.

leaving in the current protectors for the fets if desired. then its almost identical to a higher voltage version of the

original BH power supply.

 

Newest version has a terminal block for directly measuring the bias voltage before the high resistance

resistors so you don't short it out and burn up circuit lands.

Edited June 11, 2013 by kevin gilmore

[Emooze]

I'm just looking for alternatives if I can't get mine working or trash it beyond repair. I'm learning the finer art of trouble-shooting high voltage in the process so I'm trying to enjoy it.

[eggil]

emooze, I have 2 or 3 PSU's from the first board run. You would have to PP lil-knight directly if you want one and I'd be happy to ship you one if you need it.

Enjoying troubleshooting?   

Edited June 11, 2013 by eggil

[headinclouds]

lil-knight has the latest smaller power supply version which has double the space around all the holes and circuit

lands to prevent arcing.  You have always been able to partially populate the board, setting the zeners for

the desired voltage and then putting a jumper in where the pass transistor is, driving the fets directly.

leaving in the current protectors for the fets if desired. then its almost identical to a higher voltage version of the

original BH power supply.

 

Newest version has a terminal block for directly measuring the bias voltage before the high resistance

resistors so you don't short it out and burn up circuit lands.

Thank you, that information about the extra space around the holes etc, and the bias test point. is very helpful.

And you are quite correct to remind me that we have always had the option of the alternative lesser parts on the pcb. That's all I need really.

I would like to try that out before too long.

Thanks

Edited June 11, 2013 by headinclouds

[spritzer]

We've also started on simplified PSU's, might even do two of them. 

 

I also drew this up on Sunday for my own use but some of you might be interested in it:

 

 

I'm tired of air wiring the power input so this takes care of that plus gives some inrush current protection and can power LED indication for amps with no easy low voltage supply to tap into.  I'll have some made ASAP and as always, I'm happy to share. 

[eggil]

Birgir, I am interested on this ^

[shipsupt]

Ditto emooze, I have a few spare boards, happy to share if you need one, but I'm in the UK so there would be some shipping involved...

[kevin gilmore]

finally for the first time I think in 3 years i'm back in the machine shop.

 

http://gilmore.chem.northwestern.edu/knobblanks.jpg

 

2 x ebony

2 x rosewood

1 x cocobolo

 

these will be inside knobs suitable for kgsshv

 

http://gilmore.chem.northwestern.edu/knobinsert.jpg

 

the aluminum piece is machined into and inserted upside down

into the wood for a complete blind look, with an extremely tiny

hole just barely big enough for the allen key.

 

Also on the newest version of the mini power supply there is a labeling error.

 

For the 450 volt version of the power supply the zener string needs to add to 500 volts.

For the 500 volt version of the power supply the zener string needs to add to 550 volts.

Edited June 11, 2013 by kevin gilmore

[eggil]

Beautiful knobs!

Kevin, would you mind posting the mini PSU schematics and board?

Also the new amp section with SMD's Spritzer mentioned.

Edited June 11, 2013 by eggil

[kevin gilmore]

The mini psu is the same schematic. Just a smaller board.

The all smd amp board is not ready yet.

[spritzer]

Yup, the mini PSU is just the same supply but the only thing that was added was a spot for a 270V zener.  It's there so you can use the KSA1156 instead of the 2SA1486 which is stock at Mouser and quite cheap. 

 

The simplified PSU will be polished over the next few days and then I'll order a prototype run.  It cuts out a lot of parts but should be similar enough in performance. 

[eggil]

Silly me. Missed the previous images you and Kevin had posted earlier in this thread.

Thanks

[kevin gilmore]

well its not really similar in performance over temperature. So for the 500v supply the

max really has to be a zener string of 480v which should result in an output voltage

of 475v which should drift up to say 490v with temperature.

[spritzer]

That is indeed true but it's still better than most of the commercial amps.   

[spritzer]

...and here is that PSU. 

 

 

As soon as we are both happy with the design then I'll have some proto's made. 

[s_r]

So there's one more working KGSSHV in the world.
 
Finally received the last parts I was waiting for to finish the replacement board, and it worked on the first try. Giving it longer on-time the side heatsinks reached ~40C. I got the balance & offset on both boards to zero as well. Not that warm at all considering it's running at 10mAx4. It also makes the SRM1/MK2 look tiny.
 
One thing though, if I turn the volume pot all the way to the left I can hear some ground hum. It's dead silent with a little turn to the right & up to max volume though. The grounding looks the same as I had it in my last internals pic (save for only one ground wire coming off the pot instead of two). This isn't just a quirk of the alpha quad is it?