Krell KSA 50 PCB

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#9,401
john65b said:
I have three pairs of Toshiba 1943/5200 for output device...still my favorite amp....I only really use it in the wintertime...

The advice for the Variac is spot on for all these first power-ups. Mine was $50 (500VA) and I use it all the time.

The other day my Wife was trying to make yorgurt and needed exactly 109 degees, and crock pot in lowest setting was too hot...so out comes the Variac! It worked perfectly!!
Click to expand...
Now watch for Kitchen Aid to come out with a kitchen styled variac....😆😆😆
 
#9,406
You don't need a speaker attached for the first power up test. At the very first powerup with a dim bulb tester you should look at basic things like the bias current, bias current control and the output offset voltage.

See if the voltages in the circuit make sense.

Do you have a speaker protection board?
 
#9,410
Mark Allen said:
As far as what bias point? There is actually a calculator chart posted within these almost 600 pages somewhere.
Click to expand...
Found it. Post 1426.
Around 400mV for 22W.
Did I fill get it right?
Two pairs, 25v rails, 8ohm speakers.
 

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#9,411
kmj said:
Found it. Post 1426.
Around 400mV for 22W.
Did I fill get it right?
Two pairs, 25v rails, 8ohm speakers.
Click to expand...
I spent a while looking for that and never could find it. Thanks for sharing the page number.
BTW: I had +/- 42 volt rails derived from a single primary dual seconday 1200 va transformer. It also had three pair of outputs per channel, was forced air cooled and could easily drive my ribbon speakers which dropped to 2 ohms across the response. The amp never so much as flinched, but neither have my Aleph 2's.
 
#9,412
Mark Allen said:
I spent a while looking for that and never could find it. Thanks for sharing the page number.
BTW: I had +/- 42 volt rails derived from a single primary dual seconday 1200 va transformer. It also had three pair of outputs per channel, was forced air cooled and could easily drive my ribbon speakers which dropped to 2 ohms across the response. The amp never so much as flinched, but neither have my Aleph 2's.
Click to expand...
I have an acquaintance who has a bunch of 300VA 2x24v Transformers but he is not easy to track down or get to reply. I plan on upgrading the Transformers to a pair of these if he ever replies and if I get the Amp to work.

By the way, I take the response as I got it right 🙂
 
#9,416
#9,419
kmj said:
Found it. Post 1426.
Around 400mV for 22W.
Did I fill get it right?
Two pairs, 25v rails, 8ohm speakers.
Click to expand...
Glad to see the file I created is benefitting folks 18 years later... I did it in this build (Pinkmouse boards) as I did not understand how to bias Class -A amplifiers. Interestingly enough, it was papa Pass who walked me through the calculations, and I built the spreadsheet. I was forever in his debt that day forward 🙂
 
#9,420
K-amps said:
Glad to see the file I created is benefitting folks 18 years later... I did it in this build (Pinkmouse boards) as I did not understand how to bias Class -A amplifiers. Interestingly enough, it was papa Pass who walked me through the calculations, and I built the spreadsheet. I was forever in his debt that day forward 🙂
Click to expand...
You and a lot more people 🙂
 
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