i'm on a roll... the kgsshv

[mwl168]

Is the input shorted to ground and the servo engaged when you adjust the offset?

[spritzer]

Does the offset pot adjust at all?  I mean if you can get a higher value by turning the pot the other way then you need to change the 2K series resistor.  Measure the resistance value of the pot + this resistor.  If it is just 2K then you need to go to say a 1.5K resistor.  If it is 4K then you need a higher value. 

[*high]

Sorry, false alarm. Offset trimpot does respond, it took a while to realize which channel is and make a few rotations.

So, Bias TP 488V (diff multimeter), bias 100V, balance and offset adjusted to zero. 

Thanks guys, very much appreciate your help!

PS Bass has improved, mainly after voltage corrections, I guess. The hum is less audible, almost silent unless you touch stax cable. It is not a riddle, a girls has no name, just shitty electricity.

[rol]

Hi all. Sorry for my bad english.

After 1 year working fine, something gave up in my KgssHv PSU. No smoke or anything blow and i still have sound in the output. But, when i measure the psu board, i get -495v / + 471v on +/- 450 rails. Bias TP 580v. I think positive rail is ok and problem is in negative rail. So, I measured everything from both side and found two difference. 

First is voltage between 270v zenner. In positive rail is 24v between 270v zenner (D11), voltage between 270v zenner in negative rail is 0v. 

Another difference is voltage of 8N80C. In postive rail, voltage between D / G legs is 70v, voltage of D leg to -450v output point is 534, volatage of G leg to GND output point is 475v. In neative rail is 39v / 534v / 497v. 

I had replaced all transitors but nothing changed, voltage is the same. All resistor is OK, no short in PCB on both side if i can see. Anyone have advice for me? 

After all, many thanks to Dr Kevin, Spiritzer and all contributors to for this wonderful amplifier. 

Thanks everyone. 

[spritzer]

If you've changed all the transistors, all the diodes and the voltage reference then it could be a short on the board.  I would also change the resistors which set the voltage too as if you used Xicon's they might age badly.  I always used the CMF60's due to their higher voltage rating. 

[rol]

5 hours ago, spritzer said:

If you've changed all the transistors, all the diodes and the voltage reference then it could be a short on the board.  I would also change the resistors which set the voltage too as if you used Xicon's they might age badly.  I always used the CMF60's due to their higher voltage rating. 

Thank you for advice. Yes, all diodes are ok. I have measured  3 diodes (150 + 150 + 200) 498v in postive rail and 510v in negative rail. Voltage between Lt1021 is 9v in both.
I will check the board again if it short in somewhere and replace 440k and 20k resistor tomorrow and see if it can solve the problem. Thanks again. 

[kevin gilmore]

lt1021 should be 10v

 

[rol]

11 hours ago, kevin gilmore said:

lt1021 should be 10v

 

Yes, it's 10v when i measured in 20v range  

Thank you spritzer, xicon resistor is problem, two resistor up to 490k instead 440k

[johnwmclean]

Rol can you confirm if these were the xicon 273’s?

[rol]

5 hours ago, johnwmclean said:

Rol can you confirm if these were the xicon 273’s?

John,

It's Xicon 273-442k ohm

[wokstarr26]

4 hours ago, rol said:

John,

It's Xicon 273-442k ohm

How come this resistor drift off value by such large amount?

[GeorgeP]

5 hours ago, rol said:

John,

It's Xicon 273-442k ohm

curious to know where you sourced them. I have bought fakes

[mwl168]

12 hours ago, rol said:

Yes, it's 10v when i measured in 20v range  

Thank you spritzer, xicon resistor is problem, two resistor up to 490k instead 440k

Were the resistance measured with the resistors on the PCB or off the PCB?

[rol]

1 hour ago, wokstarr26 said:

How come this resistor drift off value by such large amount?

I don't know why. It might be like Spritzer said.

1 hour ago, GeorgeP said:

curious to know where you sourced them. I have bought fakes

Bought from Mouser, i still have plastic bag from Mouser :))

43 minutes ago, mwl168 said:

Were the resistance measured with the resistors on the PCB or off the PCB?

I removed it out from pcb and measure. 

I have solved the problem of PSU today, connect to Amp board. Everything is fine, balance and offset ok. 5 minutes later, no smoke, pop or spark - 1 amp board have problem. I measured O+ / GND is 470v. O- /GND ~470v. Offset trimport didn't work. Balance trimport still work. Two C4686 near two 175k resistors quite hot.  3 led still lit up. Where do i should check?

[spritzer]

Something is wrong with the either of the last two stages.  Also look for shorts to the ground plane. 

[bui501]

Hello, everybody.  I just received my KGSSHV DIY Kit from Spritzer (and BOM from mouser) and am ready to start building my very first KGSSHV.  Would it be appropriate for a newbie to document and post his first build here in this forum?  It was because of all the discussions I saw here in this forum that inspired me to want to build my own electrostatic headphone amp.  I just want to share my excitement (and pick up some tips and advice along the way).  

-bui501 (in Bangkok, Thailand)

[johnwmclean]

Welcome bui501, I would start a new thread if you thinking of posting extensively, happy to help with any questions. Are you building an on board or off board?

John

Edited July 19, 2016 by johnwmclean

[bui501]

Thanks, John,

It's an offboard -- I got the boards and transformer from Spritzer.  I promise not to inundate you guys and will probably just put up several posts to show the start and result of my build (assuming I don't run into issues as I do this over the next few weeks).

Vinh (bui501)

 

[spritzer]

The boards are onboard.   

[bui501]

4 hours ago, spritzer said:

The boards are onboard.   

DOH!!!    Onboard = heatsinks ON the Board?  (I thought all along it had meant the power supply board was separate from the amp boards.)  

I just finished individually testing each and every passive component from mouser except for the high-voltage caps that my multimeter can't handle...  I'll definitely be building this weekend.

[chinsettawong]

Hi Vinh,

I'm also in Bangkok.  If you need any help, just let me know.  

Wachara C.

 

 

 

 

[insanity]

I am looking forward to seeing pictures of your build.

Yes, onboard means heat sinks on board. 

[mwl168]

One thing to consider if you have not already is to elevate the resistors and diodes slightly off the board by 3mm or so. It's a practice used by many (myself included) to prevent leakage or arcing due to the high voltage involved in this amp.

[Laowei]

2 hours ago, mwl168 said:

One thing to consider if you have not already is to elevate the resistors and diodes slightly off the board by 3mm or so. It's a practice used by many (myself included) to prevent leakage or arcing due to the high voltage involved in this amp.

Good advise.

I use those wooden coffee stirrers at Starbucks as spacers while soldering the resistors to the boards. When done, pull 'em out. Gives a nice uniform outcome.

Edited July 19, 2016 by Laowei

[gepardcv]

And don't forget to clean off the flux when you finish stuffing the boards... It's not supposed to be conductive, but not worth experimenting with at high voltage. I use 99% isopropyl, easily available from Amazon. Not are about availability outside the US.