Krell KSA 50 PCB

[neychi]

Remove that R1 200 ohm resistor from the ground.

 

[henryve]

Hi, may be someone can help me out.

I have manage to get to pinkmouse boards working quite nice. But I'm having a strange problem that i can't figure it out.

As long as i have the input signal and ground shorted my amp stays stable with 250mV bias voltage over 0,47Ohm emmiter resistors. But as soon as I unshort the input signal and connect a dummy load or a speaker my ground starts to drift and i end up with a -72V rail and no middle ground (my posite railt end with ground potencial).
The strange thing is that is happening to both of the boards that I have build.


this is the PS configuration that I'm using



Please much appreciate if some one can help my out

Thanks Octavio

You have an issue with your Power GND I would think at first. EDIT: What he ^ said. Should have refreshed my page

 

[drmaftoon]

does any one have gerbers for any boards discussed in this thread?

I have gone through messages since 2005, but only found eagle files and I am not experienced enough to convert them.

EDIT- There was one gerber file as well but when I try to upload it to JLPCB it does not populate the size, if it is correct file then please tell me how to bypass this size issue?

Many Thanks

 

[octa]

Drmaftoon; right now I’m at work as soon as i get home I will try to upload the Gerber fails that I used for my boards.

 

[octa]

drmaftoon;

I have atached the files that I used to order the boards from JLC PCB.

Please let me know if they are what you are looking for.

 

[Mor7040]

Hello everyone . Sorry if I ask questions that you have already answered but it is really a lot to read everything. I also bought the pcb from ebay clone mkII. I would ask if the values ​​printed on the pcb are ok to realize? thanks

 

[henryve]

Hello everyone . Sorry if I ask questions that you have already answered but it is really a lot to read everything. I also bought the pcb from ebay clone mkII. I would ask if the values ​​printed on the pcb are ok to realize? thanks

Ask the seller on eBay that you bought the PCB from to send you the schematic from which the seller created the PCB layout from. We can't help you with that as there are various KSA50 variations, and we do not know which one the seller used.

 

[Mor7040]

it's this one pcb

 

[drmaftoon]

drmaftoon;

I have atached the files that I used to order the boards from JLC PCB.

Please let me know if they are what you are looking for.

Hi Octa
Thank you for your help, that is exactly what I was looking for.
Best Wishes

 

[chiily]

Bugger....these came through the post today...

 

[Mark Allen]

Pinkmouse used eagle to do his boards. Then he sent me the files and I had the boards produced through a company.in Canada. They were 2 oz copper and came out really nice. I built a half dozen klones for friends and never had issues with them.and all are still in.use. I likely have the same file sitting here as well. The KSA-100 boards were done by a chap in South Africa and I had the boards done the same way.

 

[chiily]

I've built a "forced air" KSA50 from a couple of ebay boards (they are excellent tbh) and I fancied building silent KSA50.

I assume the KSA-100 boards to just double up the drivers boards?

 

[Mark Allen]

I am actually thinking about a water cooled KSA-50. All the 50's I built (8) were forced air. There was one driver board before Pinkmouse did his and it worked ok, but had a couple of errors that had to be jumped before hand. It was also a PIA to mount the drivers... but it worked out well once I soldered them to the back of the board. That amp is still in use by a friend today.

Mark

 

[Stal]

I've built a "forced air" KSA50 from a couple of ebay boards (they are excellent tbh) and I fancied building silent KSA50.

I assume the KSA-100 boards to just double up the drivers boards?

Hi Chiily, what ebay boards did you go for?

 

[Stal]

Bugger....these came through the post today...

View attachment 956842

Ahh! I'm guessing it was these.

 

[chiily]

Ahh! I'm guessing it was these.

Ah, no. These are the pinkmouse boards, which is passively cooled, flatpack output device KSA50s. The Gerber files were posted just recently in this thread.

The ones I bought from eBay are High Power Pure Class A amplifier PCB KSA50 mkii ! | eBay

I bought a pair. They sound fabulous.

I bought the heatsink tower from Jim's Audio too.

 

[Stal]

PCBs ordered.
I've got 2x 22V-0-22V transformers at about 500VA each so I won't have the full 50W rating.
What o/p transistors did you use?

 

[chiily]

I used mj15003/mj15004s.

 

[Stal]

Did the original KSA 50 have one fan or two? I.e. did it have one at the bottom of the heatsink as well or just on top?

 

[chiily]

Did the original KSA 50 have one fan or two? I.e. did it have one at the bottom of the heatsink as well or just on top?

It had just the one fan from pictures I've seen on line.

I put mine at the bottom, blowing upwards.