i'm on a roll... the kgsshv

[blubliss]

I hope we have done something else wrong but we can't find it. We replaced all active parts and same problem. I can take pics later today for you. I don't think you will harm anything by turning it on briefly?? If you see 940v, just turn it off right away.

[Pars]

nm

Edited November 8, 2011 by Pars

[Horio]

Andy just out of curiosity, what were your measured output voltages (+/-) for your HV rails?

[luvdunhill]

Andy just out of curiosity, what were your measured output voltages (+/-) for your HV rails?

Also, is there an AC component on the rails?

[kevin gilmore]

The boards are designed the same as the T2 boards.

So if you mount the transistors from the top of the board,

you bend the pins back and stuff into the board.

If you mount the transistors on the bottom of the board, you

bend the pins forward and stick thru the board.

[Pars]

deleted

Edited November 8, 2011 by Pars

[ujamerstand]

Which ones? Could you mark them? I've checked the ones mounted against the heat sink, and they are in the correct orientation. (BCE)

Edited November 8, 2011 by ujamerstand

[Pars]

Ooops, was looking at a A1468 datasheet. These are correct and are BCE pinout. I'll go back to sleep now...

[stv1756]

Here are the pictures of Andy's board.

[kevin gilmore]

that is the correct orientation.

change out the 1.2k resistors in the current sources for

2k resistors which should lower the current enough so

that we can figure out what else may be wrong.

these current sources may have a broader cutoff voltage

range than the 10m90s.

[cobra_kai]

Are you looking at the layout, which is correct, or the schematic. I don't know how to read this stuff myself, going by someone else's opinion. It's possible we are wrong.

To my eyes, the schematic matches both the on-board and off-board layouts. I am certainly not as familiar with the circuit as some here so I might be missing something but I don't see anything wrong with the IXYS ccs.

[Pars]

I would agree, but only looked at the offboard and was only looking at the TO-220 devices.

[blubliss]

Andy just out of curiosity, what were your measured output voltages (+/-) for your HV rails?

Voltages on the PS for the 500v version are around +484 and -477, a bit different, but close.

Also, is there an AC component on the rails?

I will check.

[blubliss]

We put in the 2K resistor and now have balance between O +/-, but now the O +/- WRTG is pegged at ~+480 on both sides, and not adjustable with the offset pot. Also, D1 LED is not lit now.

[ujamerstand]

Is this the case with both boards? Or only the board with the flipped transistor? How does the board without the flipped transistor test out?

[blubliss]

It actually seems that the flipped transistor did not do any damage but this was with the board where we un-flipped the transistor and did not change the active parts. I guess we should try it on the other one where we changed all the active parts too.

[Inu]

I want to see picture of your 2SC2705... and A970, C2240.

Edited November 9, 2011 by Inu

[blubliss]

I want to see picture of your 2SC2705... and A970, C2240.

Why?

So we also put a 2K in the other amp board, the one where we had replaced all of the active parts and we got the same result as before, pegged at -940. The O +/- WRTG were around -477 and + 480 and the D1 LED was lit.

Did you fire up Horio? We probably have done something stupid so don't use me as an example.

[deepak]

OK.

I´ve the onboard type and started with the ”1968 current source” and after a week I changed to ixys.

Both variants have worked without any problems for me.

But since you have the offboards I guess I won’t be much of help for you.

Probably a dumb question since audio memory is fleeting, but did you notice any difference in sound between the IXYS and a1968?

[Horio]

Did you fire up Horio? We probably have done something stupid so don't use me as an example.

I'm kind of nervous about firing mine up, until we get a better idea of what is going on with your build. I've been working on some of my wiring in the mean time.

I want to see picture of your 2SC2705... and A970, C2240.

I'm guessing he wants to make sure they are real?

[blubliss]

Pretty sure i got everything except the IXTP (from mouser) at bdent, so it should be fine.

[JoaMat]

Probably a dumb question since audio memory is fleeting, but did you notice any difference in sound between the IXYS and a1968?

No, I can´t say I noticed any difference between them two. I also changed the high voltage from +/- 450 to 500 volts so it isn´t really possible to compare them.

[kevin gilmore]

Need to test the current sources and adjust them to 2ma each.

Then the rest should be easy unless there is a major mistake

in the circuit board. (like flipped feedback) Need to check

more, maybe later today.

[kevin gilmore]

Sure enough, the feedback is flipped. Not sure how i missed that one.

Easiest way to fix it is to cross the 2 x 50k resistors. Or cross the 2 x 1n914 diodes.

Someone with fresh eyes needs to check this.

This is for the off board heatsink boards.

Edited November 9, 2011 by kevin gilmore

[blubliss]

We measured the current, seems fine. There is 2.7v across the 2K resistor, which equals 1.3mA, right? Back to the 1.2K resistor I guess.

So now on to the feedback thing. Seems like crossing the resistors would be easiest.