KGSSHV Carbon Build Thread

[judo]

I think my caps came from the group buy organized by @sorenb in 2015. 680u 550v from "FTcaps Germany". (These were overkill because my carbon was 400v). Maybe bad apples or any other cause, the bought  volume was enough for more than 10 carbons. I think I would replace the caps in your place in the positive supply too, less fuss.

[mattmatt]

Hi guys, 

I've had these boards for a few years now and want to build them now, I have a full folder of the golden reference and kgsshv carbon schematics and pcb layout prints. There are a lot and confuses me. Below are the boards that I have. I hope some can point me to the right file for the PSUs and amp section. Can someone verify if this is the proper schematic for the amp?

[Pars]

That looks like the correct schematic. The boards look fine I think, assuming that the one on the right, which is chopped off in the photo, is for -400V. Given the age of these boards, you might scan completely thru the thread to ensure there were no board errors found. I seem to recall one, which did not affect the boards that I used. Here is a schematic for the GRHV. The 900 board you have listed above is for something else (Megatron or something). Also note there is a separate GRHV thread now as well.

goldenreferencehvsic.PDF

[mattmatt]

4 hours ago, Pars said:

That looks like the correct schematic. The boards look fine I think, assuming that the one on the right, which is chopped off in the photo, is for -400V. Given the age of these boards, you might scan completely thru the thread to ensure there were no board errors found. I seem to recall one, which did not affect the boards that I used. Here is a schematic for the GRHV. The 900 board you have listed above is for something else (Megatron or something). Also note there is a separate GRHV thread now as well.

goldenreferencehvsic.PDF 24.61 kB · 6 downloads

Hi Pars, Thank you for your reply. I appreciate it. I was kinda worried that the thread is old and no one checks on it. Here are the photos of the PSU boards. Just want to ask for verification, the goldenreferencehvsic is the whole schematic for the 2 boards? Doesn't seem complete to me. Do we also have an existing BOM right now? Every link that I try to open are dead as of now sadly. I'm kind of embarrassed to ask here coz I may sound like an idiot. I've read the forum quite a lot repeatedly but still seems loss at some points. 

[MLA]

So, the golden rule for Kevin Gilmore boards seems to be to always follow the board. Schematics are sometimes earlier drafts rather than the finished design, which can be confusing. I have build both the 1.8 GRHVs and the .6 Carbon boards which you have with success.

If you go for +/-400V rather than 450V, SimmConn has a nice post on how to push the pzta42 back into a more linear region. 

The BOM excels and links to Mouser carts posted by mwl168 in the first post of this thread both open and download without issues for me. Should be a good place to start.  

[mattmatt]

1 hour ago, MLA said:

So, the golden rule for Kevin Gilmore boards seems to be to always follow the board. Schematics are sometimes earlier drafts rather than the finished design, which can be confusing. I have build both the 1.8 GRHVs and the .6 Carbon boards which you have with success.

If you go for +/-400V rather than 450V, SimmConn has a nice post on how to push the pzta42 back into a more linear region. 

The BOM excels and links to Mouser carts posted by mwl168 in the first post of this thread both open and download without issues for me. Should be a good place to start.  

Oh, you're right! I've been trying to download everything by clicking only. never thought of right click and save as. My stupid ass's mistake. 

Just wondering, I'm no expert with transformers and all, what does this mean?

 

For a 400V PSU:

• 2× 335VAC @200mA
• 16-0-16VCT (anywhere from 15-0-15VCT to 18-0-18VCT should work fine) @500-700mA (the higher amperage is way overkill)

Do I need 2 secondary windings for the 335VAC and 16VAC or 2 split leads will do? 

[Pars]

For the 335, you'll need dual (2x335 as shown). Are you planning on using a GRLV or the onboard +/-15V supply? For a GRLV, you can use either (depending on version of the GRLV). If your board has space for 3 bridges, you can use either a center tapped transformer, or dual secondaries. It it is only 2, then you need the dual 2x15V secondaries. You are pretty much always safe with dual secondaries vs. center tapped.

[mattmatt]

6 hours ago, Pars said:

For the 335, you'll need dual (2x335 as shown). Are you planning on using a GRLV or the onboard +/-15V supply? For a GRLV, you can use either (depending on version of the GRLV). If your board has space for 3 bridges, you can use either a center tapped transformer, or dual secondaries. It it is only 2, then you need the dual 2x15V secondaries. You are pretty much always safe with dual secondaries vs. center tapped.

I'm not planning to use any other boards other than the ones I have currently so i'll be using the +/-15V on board.

 

Stupid question. What's the reason to use dual secondary winding vs single winding and just splitting wires into 2? 

[insanity]

I just had one of the main capacitors blow in my Carbon which is a few years old and has been lightly used. I think its the input cap of the -400v board.

The Caps are from the Groupbuy a few years ago (2015 OMG). F&T Germany 550V 680uf. 

Toroid is 2x 117v (234V AC In) and for the HV 2x330V out. Resistors on the boards for 400v configuration. 

Any idea what could have caused this?? Usually caps only blow from overvoltage??

The music was still coming through flawlessly after the bang, but I turned it off right away and checked the internals. I hope the other components are ok. Maybe it would be worse if it was the output cap. 

I am not 100% sure if the other 3 Caps may be slightly bulged or if they came that way from the factory. 

I will replace all 4 for sure. 

Does anyone have a partnumber from mouser ready?

if I remember correctly a bit less capacitance would also work, right? What is reasonable?

Edit: I just read some of the previous post with a similar problem. Maybe these caps are really trash... 

 

Edit 2: Just found the datasheet from the group buy

 

I would probably order 4 of these (only 560uf, but should be enough) and hope everything still works after replacing...

https://www.mouser.ch/ProductDetail/KEMET/ALA7DA561EF550?qs=IS%2B4QmGtzzosEBZF0Z4Lbg%3D%3D

 

 

Edited October 31 by insanity

[jamesmking]

13 hours ago, insanity said:

 

 

Electrolytic caps are well known for being relatively fragile. Almost any reverse polarity voltage will damage them over time. They also degrade with temperature and time too. The input caps take the highest hammering because of the higher input AC voltage peaks compared to the output caps -  (which only have to handle well regulated DC).

Check if the diodes in the bridge rectifier are leaking, if one of the diodes starts to leak more than a couple of volts that would degrade your input cap. Also, when you have got the amp up and running again  it might be worth monitoring the temperatures close to the caps, a rough rule of thumb is every 10C degrees rise in temperature halves the cap life.

I have had good reliability experiences with kemet al10 series caps - although they can be expensive they are rated at around 15000 hours at 85C - significantly higher life expectancy than your caps and life expectancy. Part number ALC10A681EL550 is 550V 680uF. The ripple current of the kemet is 50% higher than your caps, but the esr of the kemets is higher, leakage current is the same. Unfortunately kemets tend to go in and out of stock again and the pricing can also be somewhat erratic.

note the ALc10 kemets tend to be tall rather than wide - the ALC10A681EL550 is 80mm tall and so you would have trouble fitting it into a 2U high case.

Edited November 1 by jamesmking

[judo]

Died by age not by usage I think. My carbon was rarely used. I have the same problem, same caps, all four are bad. Bad quality so who got these caps from the same group buy have to be cautious. My amp is taken apart on my workbench for  months I have more serious problems, illness in the family. I hope I can continue the repair in the near future.

[insanity]

8 hours ago, jamesmking said:

Electrolytic caps are well known for being relatively fragile. Almost any reverse polarity voltage will damage them over time. They also degrade with temperature and time too. The input caps take the highest hammering because of the higher input AC voltage peaks compared to the output caps -  (which only have to handle well regulated DC).

Check if the diodes in the bridge rectifier are leaking, if one of the diodes starts to leak more than a couple of volts that would degrade your input cap. Also, when you have got the amp up and running again  it might be worth monitoring the temperatures close to the caps, a rough rule of thumb is every 10C degrees rise in temperature halves the cap life.

I have had good reliability experiences with kemet al10 series caps - although they can be expensive they are rated at around 15000 hours at 85C - significantly higher life expectancy than your caps and life expectancy. Part number ALC10A681EL550 is 550V 680uF. The ripple current of the kemet is 50% higher than your caps, but the esr of the kemets is higher, leakage current is the same. Unfortunately kemets tend to go in and out of stock again and the pricing can also be somewhat erratic.

note the ALc10 kemets tend to be tall rather than wide - the ALC10A681EL550 is 80mm tall and so you would have trouble fitting it into a 2U high case.

Do you think this type would be fine aswell? 

https://www.mouser.ch/ProductDetail/KEMET/ALA7DA561EF550?qs=IS%2B4QmGtzzosEBZF0Z4Lbg%3D%3D

It is in stock at mouser, whereas the other have a very long lead time. 

My case is 3U because the old caps were quite high aswell. But if I use some with a bit less capacity, they will be small anyway. If I remember correctly 680uf was overkill anyway. 

Edited November 1 by insanity

[Pars]

Those would be fine. Some drop down to the 470uf in that cap as well, particularly if you are trying to get this in a 2U chassis. When I built the one I did for a French user, the 680uf were no longer stocked at mouser in the US.

Some discussion in the GRHV thread here:

 

[insanity]

I finally got all four caps out... This was such a big pain without a real desoldering station at hand. I had to cut all caps open to get them out without destroying at PCBs. 

When open all the remaining 3 had built up pressure in them. I guess it would have been a matter of time until the next one would have given up. 

I would therefore encourage anyone who has these caps in use to either replace them now, or keep a really close eye on them. 

Now gotta order the replacement ones. 

Edited November 2 by insanity

[insanity]

Just wanted to report that the amp is up and running again. Luckily nothing but the blown cap was damaged. 

Thank you for your support and help.

[judo]

Mine too. I had no no time and nerve so I replaced the big caps and all sands in the negative psu. I have to check yet which parts died. There was a few similar catastrophe so this may be interesting. Thanks the help too.