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KGSSHV Carbon Build Thread


mwl168
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  • 1 month later...
On 7/19/2021 at 9:36 AM, JoaMat said:

Has been in service for a few months now. Sounds alright.

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So, another quarter has elapsed. Raised the current through output stage from 11 mA to 17 mA ...and, it all sounded shitty bitty.

Fired up the desoldering gun. Removed FJPF2145 and replaced them with 2SC4686.

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Wow, what an upgrade and I’m happy again.

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  • 1 month later...

After several years layoff  I have built a KGSShv Carbon which uses boards I had in and 4 Cree sicfets from several years back (luckily).   The power supply is KGSShv v8 and the amps Carbon v6.

It has been one of the easiest builds because of a different way of making the cases which I have described in Making diy cases,

 https://www.head-case.org/forums/topic/18892-making-diy-cases/

It is set for 400v supplies and 17mA output stage currents.  It does not get particularly hot in a 20o C room, the heatsinks run a max of 40o at the centre.  The power supply pass transistors are bolted to the bottom of the case and the case runs pleasantly warm to the touch.

The size is 335 W x 314 D x 155 H inc feet.  Weight 8.5Kg. (13in x 12.4in x 6.1in, 18.8lb.)

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P1090547.JPG

Edited by headinclouds
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  • 1 month later...

I've ran into an issue building Carbon.

I'm using split PS boards + separate GRLV.

When I connect PS boards to transformer (without AMP boards) everything is fine, and voltage is +405/-406VDC (bias is a bit low at 563 but that's non-relevant issue and a matter of zener tolerances).

But as soon as I connect AMP boards, transformer starts to heat up a lot (I didn't risk to leave it connected for more that 15 sec). Maybe it will start melting.

Here is my connection:

+400 goes to each AMP's B+ terminal, -400 goes to each AMP's B- terminal (obviously). However GND from each PS from goes to nearest AMP board only and are not tied together or by a sort of star terminal, therefore GNDs are not shorted.

Am I missing a point here? Should connecting GNDs of each split boards remedy the transformer heating problem?

Easy to check by yourself, one must say, but one of my DN2540N5 went bad and I cannot check it right now.

This is my transformer spec (must be plenty of power, so insufficient VA rating must not be a reason?):

1 x AUDIO GRADE WITH EPOXY FILL INTERIOR
PRI:230V SEC:
> 2x 330V under load (350mA) (separate windings)
> 2x 18V under load (500mA) (separate windings)
- VA rating around 300VA

IMG_20220123_161107_2.jpg

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If your transformer is heating up that quickly you've got a short somewhere, or something wired seriously wrong.  I'd recommend posting up some pictures of the entire build if you can folks can look for at least the obvious faults.  I don't know the project well enough to start talking specifics but i don't think and under-rated trafo would behave that badly, that quickly, unless it was way undersized.  

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1 hour ago, Helium said:

I've ran into an issue building Carbon.

I'm using split PS boards + separate GRLV.

When I connect PS boards to transformer (without AMP boards) everything is fine, and voltage is +405/-406VDC (bias is a bit low at 563 but that's non-relevant issue and a matter of zener tolerances).

But as soon as I connect AMP boards, transformer starts to heat up a lot (I didn't risk to leave it connected for more that 15 sec). Maybe it will start melting.

I would suggest 

0. make sure there is continuity between the grounds on the amp boards, hv psu and low voltage psu. HV psu ground -> amp ground       LV psu ground to -> another amp board with no ground connection between the LV and HV boards is not going to work. All 4 pcbs needs to share a common ground.

1. check nothing is shorting to the case on the amp boards e.g. metal tabs on transistors

2. check the amp boards for solder bridges.

3. did you check each transistor before soldering in? did you get the transistors from known reliable sources? i.e. could any of the transistors be fake?

4. did you see any burn marks on the amp pcbs, discoloured components etc.

5. check the orientation of transistors, diodes, zeners.
6. try each channel  powered up separately - to see if you can isolate the problem to a single channel or if its both channels and quickly measure the psu voltages on the amp board. Whichever rail has a short will almost certainly show much lower voltage than expected... This might narrow it down to one channel and or a particular voltage rail.

7. power up the amp boards with just the low voltages to see if its a short in the low voltage part of the amp boards.

9 post some detailed photos

 

 

 

Edited by jamesmking
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11 hours ago, Helium said:

+400 goes to each AMP's B+ terminal, -400 goes to each AMP's B- terminal (obviously). However GND from each PS from goes to nearest AMP board only and are not tied together or by a sort of star terminal, therefore GNDs are not shorted.

This is no good!
Connect all grounds (LV, HV+, HV-, all amp boards) together to a single (star) point.

From there you connect to chassis (best is through a circuit breaker if not 2nd best is through a 10 ohm R, 3rd best is directly). 

 

Edited by audiostar
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Thank you folks.

4 hours ago, jamesmking said:

0. make sure there is continuity between the grounds on the amp boards, hv psu and low voltage psu. HV psu ground -> amp ground       LV psu ground to -> another amp board with no ground connection between the LV and HV boards is not going to work. All 4 pcbs needs to share a common ground.

 

2 hours ago, audiostar said:

This is no good!
Connect all grounds (LV, HV+, HV-, all amp boards) together to a single (star) point.

Yes, currently GRLV has no ground connection with HV ground.

Didn't know that non-tying LV and HV grounds is so critical. Usually it ends up with hum/noise, such sort of things.

I will fix that and see.

I the mean time I adjusted CSS with GRLV 15VDC to 18mA, so AMP boards are presumably good. Currently amp is almost done, need to replace DN2540N5 on +400 PS.

 

IMG_20220123_220415_2.jpg

IMG_20220123_220354_2.jpg

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since the grlv and grhv have separate transformer windings they are floating with respect to each other.

with only one amp being grounded through the grhv that amp board is tied to that psu but would have no idea what the LV voltage is since the LV floating with respect to the hv psu and not referenced to it. The other amp board being grounded through the LV only would have no idea what the hv voltage is in relation to the lv voltage....

you would see this by measuring the voltages on one amp board with the multimeter neg on that amps ground and then measure the voltages on the that amp board with the multimeter neg on that amp boards ground.

Another way to think of it is electricity flows in a circle, for the amp connected to the hv board the electricity comes out of the hv board goes into the amp board and returns to the hv board through the ground wire, The Lv electricity enters the amp board BUT has no return path direct or indirect to the LV board... and visa versa for the amp board connected to the lv ground only....

This is why I check the psu voltages of a fully built amp at the amp board using the amp boards ground and not at the psu using the psu ground....

 

 

 

 

Edited by jamesmking
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9 minutes ago, jamesmking said:

since the grlv and grhv have separate transformer windings they are floating with respect to each other.

with only one amp being grounded through the grhv that amp board is tied to that psu but would have no idea what the LV voltage is since the LV floating with respect to the hv psu and nto referenced to it. The other amp board being grounded through the LV only would have no idea what the hv voltage is in relation to the lv voltage....

you would see this by measuring the voltages on one amp board with the multimeter neg on that amps ground and then measure the voltages on the that amp board with the multimeter neg on that amp boards ground.

Another way to think of it is electricity flows in a circle, for the amp connected to the hv board the electricity comes out of the hv board goes into the amp board and returns to the hv board through the ground wire, The Lv electricity enters the amp board BUT has no return path direct or indirect to the LV board... and visa versa for the amp board connected to the lv ground only....

This is why I check the psu voltages of a fully built amp at the amp board using the amp boards ground and not at the psu using the psu ground....

 

 

 

 

Wait a minute please. I see what you mean.

Is the transfotmer up to the task? That's most unfortunate if it's not. Is Star ground of everything a cure?

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Would the phase of the transformer secondary windings be an issue here? There doesn't seem to be anything indicating the start of a winding, both wires of each winding are the same color.

I know that getting the phase wrong can cause issues when tying windings together to create your own centre tap.

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21 minutes ago, Helium said:

Wait a minute please. I see what you mean.

Is the transfotmer up to the task? That's most unfortunate if it's not. Is Star ground of everything a cure?

star ground just makes sure the grounds don't for a loop

for my builds my grounds go

 

GRHV --ground -----------amp Left ground

             |  |

             |   +-------------amp right ground

            +----------------GRLV ground

you can of course swap the grhv and grlv in the above and it will still work the same. The makes one psu the master for ground reference and everything else is in a tree from that with zero loops.

A longer tree will also work e.g.

GRHV --ground ----------- GRLV ground ---------------- amp Left ground

                                                              |

                                                              +-------------amp right ground

so everything has a ground wire from one psu board and no loops.

 

What may cause hum is ground loops. For example if both the grlv and hv are ground connected together and you also run grounds from both the grlv and grhv to both amp boards. You now have multiple return paths. e.g. +15V can go directly to grlv or can go grhv -> grlv and visa versa for the high voltages. In addition +15V on left channel could go grhv -> right channel -> grlv or even worse left channel +15V could go grhv -> right channel -> left channel -> grlv etc etc... i.e. multiple ground loops:

GRHV --ground -----------amp Left ground---------+-----+

             |            |                                                                         |

              |           + -----------amp right ground ------- +        |

              |                                                                           |         |

              +----------------GRLV ground --------------+-----+

 

Edited by jamesmking
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9 minutes ago, Beefy said:

Would the phase of the transformer secondary windings be an issue here? There doesn't seem to be anything indicating the start of a winding, both wires of each winding are the same color.

I know that getting the phase wrong can cause issues when tying windings together to create your own centre tap.

his grlv seems to have separate windings for + and - (and they are using two diode bridges in the lv) and I don't think the grhv  offers a centre tapped option at all - all the grhv I have seen have separate diode bridges for + and - 

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1 minute ago, jamesmking said:

his grlv seems to have separate windings for + and - (and they are using two diode bridges in the lv) and I don't think the grhv  offers a centre tapped option at all - all the grhv I have seen have separate diode bridges for + and - 

Check check!

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34 minutes ago, Helium said:

Wait a minute please. I see what you mean.

Is the transfotmer up to the task? That's most unfortunate if it's not. Is Star ground of everything a cure?

can I ask a possibly dumb question, I see the grlv with fully populated + and - sections,

the board attached to the side wall seems to be a grhv but it only looks like a single rail grhv which would mean its either +400V or -400V but not both! it does not look like a dual output grhv board to me..... ??? I also cant see a bias supply. Or do you have another single rail grhv with the bias hiding somewhere else????

I also don't see the outputs of the single channel grhv being connected to anything...

 

Edited by jamesmking
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17 minutes ago, Beefy said:

Would the phase of the transformer secondary windings be an issue here? There doesn't seem to be anything indicating the start of a winding, both wires of each winding are the same color.

I know that getting the phase wrong can cause issues when tying windings together to create your own centre tap.

I checked phase of all windings prior to connecting. Yes, they are not marked, I marked them by myself. And connected both HVs in phase.

4 minutes ago, jamesmking said:

can I ask a possibly dumb question, I see the grlv with fully populated + and - sections,

the board attached to the side wall seems to be a grhv but it only looks like a single rail grhv which would mean its either +400V or -400V i does not look like a dual output board to me..... ???

 

Yes, it's single -400 board. The other one (+400) is dismounted ATM and waiting for a part for replacement.

Edited by Helium
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22 minutes ago, Helium said:

I checked phase of all windings prior to connecting. Yes, they are not marked, I marked them by myself. And connected both HVs in phase.

Yes, it's single -400 board. The other one (+400) is dismounted ATM and waiting for a part for replacement.

cool, I guess thats why the grhv on the side wall does not have the output connected to anything.

dont forget the two separate grhv boards will also need a common ground with everything else.... since the grlv has two ground terminals, it can make a convenient centre point for the grounds:

 GRLV--ground -----------amp Left ground

           |  |  |

           |  |   +-------------amp right ground

           | +----------------one GRHV ground

          +---------- other grhv ground

(the two rails of the grlv already share a common ground on the grlv pcb)

Edited by jamesmking
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8 hours ago, Helium said:

However GND from each PS from goes to nearest AMP board only and are not tied together or by a sort of star terminal, therefore GNDs are not shorted.

Again, this is not good. As I said above, connect ground of all PCB together and to the chassis. Best in a star config, saves wiring as well.

He said above he is using split GRHV and the ground of one half goes to left amp board and the ground of 2nd half goes to right amp board with no connection in between.

Edited by audiostar
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10 hours ago, Helium said:

This is my transformer spec (must be plenty of power, so insufficient VA rating must not be a reason?):

1 x AUDIO GRADE WITH EPOXY FILL INTERIOR
PRI:230V SEC:
> 2x 330V under load (350mA) (separate windings)
> 2x 18V under load (500mA) (separate windings)
- VA rating around 300VA

Transformer specs more than enough for a Carbon.
The LV is way oversized if this is 500mA per 18V sec winding.

PS:
You can twist all AC lines. Includes the long + and - from pot to amp board inputs.

Edited by audiostar
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2 hours ago, audiostar said:

Again, this is not good. As I said above, connect ground of all PCB together and to the chassis. Best in a star config, saves wiring as well.

He said above he is using split GRHV and the ground of one half goes to left amp board and the ground of 2nd half goes to right amp board with no connection in between.

I don't think I would tie to the chassis at this point. Chassis should be grounded via the PE of the IEC inlet connector. Any connection from the PCB ground to chassis should be done thru a ground loop breaker.

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1 minute ago, Pars said:

I don't think I would tie to the chassis at this point. Chassis should be grounded via the PE of the IEC inlet connector. Any connection from the PCB ground to chassis should be done thru a ground loop breaker.

This is what I have written in my first reply above, in detail... using 1) circuit breaker 2) a 10 ohm R or 3) directly. 

For the sake of this test it is not relevant. All signals GNDs together best in star. 

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Here even the most complete case with an external power supply. GND and PE should make contact first and break last (in connectors between PSU and Amp case).

Edit:
The image below shows single ended amp though, Carbon being balanced one would connect the - to the 2nd amp half and not to ground, but that was not the original question.

screenshot_05 2.jpg

Edited by audiostar
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Did anyone experience how vulnerable DN2540N5 are?

They are damaged so easily that I had to scratch my head.

E.g. desolder it from a donor known good GRHV, actually new (don't ask why, I had to get spares) and it's detected OK in circuit as N-Ch depletion mosfet.

I desolder it, test it and BAM it's no longer depletion mosfet, it turns into kind of Voltage regulator. And doesn't work of course. I spoiled 4 pcs already, despite the fact that I know how to desolder and handle components. And only one out of 5 was OK after desoldering.

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