i'm on a roll... the kgsshv

[Pars]

Those that were following my BOM need to make sure to use an isolation pad on the +/-15V regulators. Or substitute the units with 511-L7815CP and 511-L7915CP. On the negative rail, the tab is connected to the input pin, so the input could potentially short to the ground if isolation pads are not used... Really sorry about this.

I would not use ST Micro regulators... I've had problems with them in the past, mostly the negative, Use Fairchild or National or ON instead.

[kevin gilmore]

I'll second that one. Never figured it out either, i don't know how they can continue to sell those things, every time i try

one even in a simple circuit i have trouble.

[ujamerstand]

Hrm. Is it because of bad regulation? Or are they very likely to fail?

[Pars]

^ the one I recall was in a circuit (don't remember what it was exactly) that wouldn't draw enough current for the negative regulator to go into regulation. Increased the load and it would regulate. Replaced with a Fairchild (and then an ON) and both worked perfectly.

EDIT: remembered what it was in: a dynahi board (+/- 15V regs for the servo opamps). 1 opamp would not pull enough current to convince the STM neg regulator that it should, umm, regulate. No problems with the other brands mentioned.

Edited May 23, 2012 by Pars

[spritzer]

I could take two of those PCB's.

Cool. The price comes to 2.71$ each and the shipping should be 2-4$ depending on location. Btw. Here is a pic:

[jantze]

Those PCB's are still looking good

PM sent.

[vvs_75]

I just trashed four STMs (511- L7915CV). They all gave me between -18 to 19v output.

I am going to try OnSemi (863-MC7915BTG), it has output noise only 90uV vs. others 250 - 350uV.

[justin]

put a load on it before you throw it away...

[guzziguy]

Yeah, send them to Birgir. I'm sure that he'd be happy to step on them.

[luvdunhill]

put a load on it before you throw it away...

Don't we have an emoticon for that here?

[Pars]

^ Yes, we do....

Edited May 22, 2012 by Pars

[eggil]

Spritzer, I'll take 4 if you still have a few to spare

Edited May 23, 2012 by eggil

[vvs_75]

put a load on it before you throw it away...

I know about the load and was absolutely sure that I tested it under the load. As you can see it’s the original KGBH board and not KGSSHV but the + 15/-15v sections are almost identical so it should not matter really in my case.

To make long story short I was having problems with the amp board which eventually lead to problems with PSU. My old 7915 regulator, do not even remember which manufacturer, was working fine there before I screw it up. So after trying STMs I thought that my input voltage a bit high for this particular regulator. I am really glad to look dumb stupid now , if not this thread I would put the project on hold again. Now everything looks like working right, all I need is to find time to powder coat my panels and put this beast together.

Edited May 23, 2012 by vvs_75

[spritzer]

Spritzer, I'll take 4 if you still have a few to spare

I have dozens and dozens of them so just drop me a PM with your address so I can figure out the shipping.

[ujamerstand]

Tested the power supply today. Low voltage rails test out okay, regulated at +/-14.97V. Fuse blown when I tested the -500V rail. Let troubleshooting begin.

[livewire]

Ugh.

Let us know what you find.

[eggil]

I finished the wiring today. Balance and Offset are within 1 V on both sides.

Problem is, there is volume only on the right side even with the volume down to zero, then it sounds equal on both sides as the pot is increased to about 12 o'clock

Because there is eventually sound on both sides I figure the connections are fine; since the balance and offset are fine, sound like the amp is fine too.

I did not ground the Pot.

Checked all the connections, I flipped the O- and O+ because of the flipped feedback.

I am thinking is the Khozmo. Not sure yet.

Edited May 29, 2012 by eggil

[johnwmclean]

Sounds to me like left and right channels are mixed.

I’d check the resistances over the amp board +/- inputs and +/-XLR inputs.

If the resistance changes when adjusting the attenuator that’s confirmation for that channel.

Just check it’s wired correctly.

[eggil]

One side of the pot is not working though. I get on open line (OL) in my DMM.

John, I have the same pot you have.

Edited May 29, 2012 by eggil

[johnwmclean]

Arghh yeah ok.

The only other thing could be where Arek has joined the wires together, I asked for 400mm length wires, thinking that it would be one piece of wire directly from inside the attenuator, instead he just extended it by soldering and heat shrinking a new piece of wire.

So maybe the join is cold?

[eggil]

is one single wire. I opened it and all are soldered to the boards. I am stumped and will have to return it.

We'll see how good their customer service is.

I now get OL on all the stacks, but when I measure the In and Out on the same stack get 51K (I have the 50K pot).

[Victor Chew]

How are you measuring them eggil?

I believe 2 wafers control one channel (either right or left). Each XLR channel has hot and cold. Hot to one wafer and cold to the other wafer. One wafer will have "in", "out" and "ground". "In" will connected to the XLR and "out" to amp input. To check if the wafer/attenuator is working correctly measure the "in" and "out".

Edited May 29, 2012 by Victor Chew

[eggil]

That's how I am measuring them; I get an open line (OL) from all of them now, when measuring In from one wafer to Out to the other wafer.

If unable to fix I think I may try the Goldpoint instead. Too bad it has only 23 steps, but I have found myself using the share screen in another computer to fiddle with the iTunes volume anyway.

Edited May 29, 2012 by eggil

[ujamerstand]

Threw in a 3A fuse. No problem. regulates at 506V. Very Solid.

Edit: Tested the negative postive rail separately. No problem. Solid regulation at +506V. Bias is very stable at 480V. Today is a happy day.

Edited June 1, 2012 by ujamerstand

[Victor Chew]

Bias ought to be 580v instead of 480v.

A need to use at least 3A fuse for the PS alone looks like it is pulling quite a lot of current. I am using a 2A with amp connected to the PS and source playing through the amps. Nevertheless, congratulations on get the PS up.

Edited June 1, 2012 by Victor Chew