Hi Bremen,
you may not need to remove the secondary windings.
The secondary is usually wound as 1 layer, if your's is similar then you can intercept the secondary winding at about it's midpoint opposite the tails. Try taking off the outer insulation and scraping off a little varnish at the physical midpoint of the secondary winding. Now safely connect the transformer to your mains supply and using your DMM measure the voltage you have at the tails and at your exposed point. From there you should be able to work out which side of middle you have exposed and measured. Since you will have 0V and 35V you have a large margin for error and just remove enough windings to get you down to 28V + regulation (about 30V). Then connect on new tails and re-tape the secondary.
The reduction in windings will reduce your VA rating slightly but not as bad as the pro rata reduction in output voltage. Your rating on each 28V winding will probably be about 220VA giving about 7.8A instead of 7.14A.
Alternatively you could remove fewer windings and try for a 30V output giving Vrail=42Vdc
you may not need to remove the secondary windings.
The secondary is usually wound as 1 layer, if your's is similar then you can intercept the secondary winding at about it's midpoint opposite the tails. Try taking off the outer insulation and scraping off a little varnish at the physical midpoint of the secondary winding. Now safely connect the transformer to your mains supply and using your DMM measure the voltage you have at the tails and at your exposed point. From there you should be able to work out which side of middle you have exposed and measured. Since you will have 0V and 35V you have a large margin for error and just remove enough windings to get you down to 28V + regulation (about 30V). Then connect on new tails and re-tape the secondary.
The reduction in windings will reduce your VA rating slightly but not as bad as the pro rata reduction in output voltage. Your rating on each 28V winding will probably be about 220VA giving about 7.8A instead of 7.14A.
Alternatively you could remove fewer windings and try for a 30V output giving Vrail=42Vdc
Cheers Andrew.
Anyone know the difference in components/circuit between KSA 50 and KSA 50S? this reviewer http://stereophile.com/solidpoweramps/404/index1.html reckons they're significantly different.
Anyone know the difference in components/circuit between KSA 50 and KSA 50S? this reviewer http://stereophile.com/solidpoweramps/404/index1.html reckons they're significantly different.
Mark A. Gulbrandsen ~ I wrote you an email concerning KrellClone PCBs - I would like to have 4 of them 
If you will have some time just write me an info how to pay for them ? You can write me to tomasz.j.chumiecki@delphi.com or chumi@tlen.pl I will wait for the info like my collected Krell parts are waiting for PCBs
If you will have some time just write me an info how to pay for them ? You can write me to tomasz.j.chumiecki@delphi.com or chumi@tlen.pl I will wait for the info like my collected Krell parts are waiting for PCBs
ksa50 vs ksa50s
To answer my own question regarding KSA50S:
The "Sustained Plateau Biasing" concept is a patent-pending way for Krell to have its class-A output-stage cake and eat it too, without paying the penalty of wasting large amounts of wall power as heat. A fast "anticipator" circuit, one for each channel, looks at the incoming signal and increases the output stage's bias current if the level would be likely to turn off one half of the transistor array on half-cycle peaks. In this manner, when there's little or no signal, the amplifier is not being asked to pass a large standing bias current with the concomitant radiation of heat. If the signal level allows it, the amplifier's output bias progressively drops back to the lower levels after 20 seconds or so. If continuous high powers are required that would lead to overheating, the amplifier reverts to classic class-AB operation.
this from the previous page of the stereophile review I quoted.
To answer my own question regarding KSA50S:
The "Sustained Plateau Biasing" concept is a patent-pending way for Krell to have its class-A output-stage cake and eat it too, without paying the penalty of wasting large amounts of wall power as heat. A fast "anticipator" circuit, one for each channel, looks at the incoming signal and increases the output stage's bias current if the level would be likely to turn off one half of the transistor array on half-cycle peaks. In this manner, when there's little or no signal, the amplifier is not being asked to pass a large standing bias current with the concomitant radiation of heat. If the signal level allows it, the amplifier's output bias progressively drops back to the lower levels after 20 seconds or so. If continuous high powers are required that would lead to overheating, the amplifier reverts to classic class-AB operation.
this from the previous page of the stereophile review I quoted.
Yeh, two 33KV lines!
But still a very impressive beast. Years ago I was doing a gig at Alexandra Palace and whilst wandering around, found part of one of the tech rooms from the 30's. I have no idea what all the kit did, but it sure looked impressive. even though it was covered with about 6" of dust and rubbish. I love old technology.
But still a very impressive beast. Years ago I was doing a gig at Alexandra Palace and whilst wandering around, found part of one of the tech rooms from the 30's. I have no idea what all the kit did, but it sure looked impressive. even though it was covered with about 6" of dust and rubbish. I love old technology.
Chumi,
You have E-Mail at chumi@.pl. I did reply twice to your other address but never received any response for you. Apparently I can get your e-mail but you can't get mine, sorry for the inconvenience.
For those that may not be aware there are some boards left. They are 14.00 each plus 3.95 shipping in the US and 3% PayPal. My PayPal address is cinerama84106@yahoo.com.... If you buy them through PayPal I will be notified by them of the purchase!!
Farley,
Here is the link tro the KSA-50 builders WIKI page. I believe there is a link to Pinkmouses Bill Of MAterial there. Don't use Jan's BOM for this board or you may let the smoke out..... there are differences in the semi's used.
KSA-50 Builders WIKI
Mark
You have E-Mail at chumi@.pl. I did reply twice to your other address but never received any response for you. Apparently I can get your e-mail but you can't get mine, sorry for the inconvenience.
For those that may not be aware there are some boards left. They are 14.00 each plus 3.95 shipping in the US and 3% PayPal. My PayPal address is cinerama84106@yahoo.com.... If you buy them through PayPal I will be notified by them of the purchase!!
Farley,
Here is the link tro the KSA-50 builders WIKI page. I believe there is a link to Pinkmouses Bill Of MAterial there. Don't use Jan's BOM for this board or you may let the smoke out..... there are differences in the semi's used.
KSA-50 Builders WIKI
Mark