Krell KSA 50 PCB

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#701
wim:
On Jan's schematic one endpin from a pot is connected to the wiper of that pot, the other endpin goes to Q108.

On the PCB layout the two endpins from each pot are connected and the wiper goes to Q108.

I looked at the datasheet from the cermet bourns pot, and the middle pin is the wiper.
Click to expand...

Sadly I have to admit that you're right in your observation :bawling: I had two 10-turns pot in my lib. and have obvious chosen the one with "wrong" pin-configuration 😡
 
#703
This is an easy way to solve the layout problem
 

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#705
is it possible to use 2sc3421 instead of 2SC3955? Every thing looks good I have a few of these so I may as well try it. I dont have the schematic handy, whats the voltage across the 2SC3955? 2SC3421 is good for 120V at 1 amp and 10Watts.
 
#706
K-amps said:
The boards came in today... for lack of a better word,


they are PERFECT!!

Thanks to Troy and Jan for making this possible.

Cheers!!
Click to expand...


I wanted to wait until someone rx'ed their boards before I said anything.

Did you notice the boards are 50% thicker than "regular" PCB's(.093" instead of .062")? Also the copper traces are 1.5 oz instead of the usual 1 oz.

I did that for 2 reasons.

1. More solid main board that will be less likely to bend or pick up micro phonics.

2. Output boards should be able to withstand the heat and current better than a thin board ensuring many years of trouble free operation.

Hey Jan-

Thank you for the super fast updat on the fix!
 
#707
To Luke : Instead 2 SC 3955 you can use every NPN transistors in ML ( full insulated ) TO 126 case. Working voltage Uce of this transistor at this position is very low, so you have practicaly any limits of breakdown voltage. Jan designed this type of transistor for easy mounting ( any problems with insulation ), but concrete type isn't critical at this position 😎 .
 
#708
Thanks for the packaging...

The boards are great, the quality of the packing was stressed for mine, someone decided to try and test the bounce and tear characteristics of the package...

Under normal conditions there is a max of perhaps 15v across the 2sc3955, when you are trying to drive 50amps into a 1ohm load, most of the time it will be much less than that, I think it is only as the amp moves into class B that any big voltage swing can occur.

What's the preferred method for cleanly snapping the scores?

Once again thanks for a great job guys.

Stuart
 
#717
ACD said:
Hi all 😉
Thanks for your cooperation and understanding 😉
Click to expand...


Hey Jan-

You drew the schematics and designed the PCB's.

Then you POSTED for ALL to critique.

If anything is wrong, it is ALL of our fault for not catching it. And anyone can suggest fixes to problems found. It is NOT just your responsibility!

This was/is a GROUP design and purchase. We all have responsibilities.


But thanks anyway for the quick suggestion on the fix!
 
#718
emitter resistors...

Hi All,

I was thinking I can perhaps assist anyone still collecting parts...

I have hundreds of panasonic 10w, 0.68 resistors, they are about the size of a stamp, and maybe 3mm thick, about 1/4oz each. If you want a sane number, like 4/8/12 whatever, send me an email, I'll give you my address, then you send me a postage paid envelope, to wherever you want them delivered. You can do the math to get the weight, packaging, postage right etc, other than that they are free for the asking, assuming you bought boards for the ksa50...or contributed to the thread, before this posting of course...

Stuart
 

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