Hi Doc, thanks for the photos, very useful.
Can you read the values of the two resistors in your first photo ? The ones between the two trafos? I believe they're the ground connection to the chassis and safety earth.
I've just checked the remnants of the wiring loom, that is the earthing point and the resistors are still there, 100R, 5W. This is what mine looks like.
Can you read the values of the two resistors in your first photo ? The ones between the two trafos? I believe they're the ground connection to the chassis and safety earth.
I've just checked the remnants of the wiring loom, that is the earthing point and the resistors are still there, 100R, 5W. This is what mine looks like.
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Concerning my unit I see that those boards are different from those of MKII seen here and there. They look like KSA100 boards with their 4 separate blue sinks under the one piece blue drivers sinks.
Anyway I mailed Dan D'A. for help about Ve. Hope he wont bin my query.
I'll tell you.
![IMGDEAD]](/community/proxy.php?image=http%3A%2F%2F%5BIMGDEAD%5Dhttp%3A%2F%2Fimageshack.us%2Fa%2Fimg820%2F582%2Faqge.jpg%5B%2FIMGDEAD%5D&hash=46e76929088a1b12078ea49a85e29b5a)
Anyway I mailed Dan D'A. for help about Ve. Hope he wont bin my query.
I'll tell you.
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Yess! Ive had a message from Dan D'A.
300mV is the right setting for my amp.
300mV is the right setting for my amp.
An externally hosted image should be here but it was not working when we last tested it.
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Yes. Basically the voltage drop over one Re. So that means the total bias is then:
300mv/0.5R * 2 = 1.2A since there are 2 output pairs on the original KSA50.
Yes, I've sent Dan the Ve I measured on one device, otherwise it would not make sense, as you usually take the voltage across one single resistor.
Ive also questionned the tech that made the check up in june 2011, and he told me to set the bias at Ve = 360mV on turn on, as he said this will decrease as the unit gets warmer.
We're in the same numbers.
He told me also that with +/- 50V rails on this MkII, the output devices died if fully biased to 50W.
Ive also questionned the tech that made the check up in june 2011, and he told me to set the bias at Ve = 360mV on turn on, as he said this will decrease as the unit gets warmer.
We're in the same numbers.
He told me also that with +/- 50V rails on this MkII, the output devices died if fully biased to 50W.
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It should not decrease to 152mV though. However, the devices is not suppose to just die if you bias it to 50W, unless there is a problem with heat management. The correct way would be to bias and then to check the junction temperatures of the devices after an hour or so.
The Thread Lives on !!!
Hello All. I have been dipping my toe in the this hobby as of late and have my first attempt based on the "cheap" Ebay KSA50 assembled board. I'm not sure how close it even resembles a Krell KSA50.?.
Here is the short thread that I have been chatting on: http://www.diyaudio.com/forums/solid-state/190411-ebay-ksa50-needs-2-voltages.html
I have to say it seems to works quite well and is dead quite at idle (600ma bias).
Fun so far. Not sure If I want to build this one a house or experiment with different designs before I commit to all that aluminium.
I have never heard a real Krell so have nothing to compare to. Also, at the price of these boards (< $40 USD complete) many have questioned if the 1943/5200's are authentic. I have no idea how to truly know. Based on the threads and sites I have researched they look original. I also have 7 sets of them sitting on my desk that I pulled from a dead Arcam AVR250 and they look very similar.
Trying to find out input sensitivity for these boards. If anyone is up to translating the Chinese from the attached schematic I would appreciate it.
Thanks
Hello All. I have been dipping my toe in the this hobby as of late and have my first attempt based on the "cheap" Ebay KSA50 assembled board. I'm not sure how close it even resembles a Krell KSA50.?.
Here is the short thread that I have been chatting on: http://www.diyaudio.com/forums/solid-state/190411-ebay-ksa50-needs-2-voltages.html
I have to say it seems to works quite well and is dead quite at idle (600ma bias).
Fun so far. Not sure If I want to build this one a house or experiment with different designs before I commit to all that aluminium.
I have never heard a real Krell so have nothing to compare to. Also, at the price of these boards (< $40 USD complete) many have questioned if the 1943/5200's are authentic. I have no idea how to truly know. Based on the threads and sites I have researched they look original. I also have 7 sets of them sitting on my desk that I pulled from a dead Arcam AVR250 and they look very similar.
Trying to find out input sensitivity for these boards. If anyone is up to translating the Chinese from the attached schematic I would appreciate it.
Thanks
Attachments
Thanks troystg! I'll look into that one. I want to build a nice "D" and then compare directly with this class A biased "bomb" as my wife refers to it. I have to say that this amp is missing what I would call mid-bass to mid-mid crack or snap. I guess punch. My speakers aren't monsters (Spendor S5E's) so I'm not expecting theatre level lows but one of my amps is an RTEC (rotel) MPA150 that's a dual mono class AB with 150Wrms per and it makes the low sensitivity Spendor's sit up and put out a little more to my taste.
The Krell KSA-50 was well known for a good grip on speakers. Especially difficult loads.
I would expect an issue with the physical layout / power supply over the circuits inability to control the speaker before writing it off.
Now on the other hand the Rotel (which is a very good company) may have some "character" engineered into the sound of your amp that adds that extra snap.
I would expect an issue with the physical layout / power supply over the circuits inability to control the speaker before writing it off.
Now on the other hand the Rotel (which is a very good company) may have some "character" engineered into the sound of your amp that adds that extra snap.