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Old 20th January 2013, 08:26 PM   #81
kevinkr is offline kevinkr  United States
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Maybe we should call this the yellow light district...

Not sure if all of the bias leds for the 2A3 are red or yellow. There are incidentally jumbo red leds with vf of 1.9V with what I understand is typically slightly lower dynamic resistance than is the case with yellow leds, based on your results I would guess the yellow should be fine imo..

Glad to hear it is working well...
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Old 20th January 2013, 08:40 PM   #82
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One yellow for Tesla E180F, 126 red ones - for one 6C4C. There was something wrong with CMPSA92 transistors, so replaced the with BF241.
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Old 2nd February 2013, 09:43 AM   #83
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Default Output @ 100Hz, 1 kHz, 10 kHz

Here are voltage traces of the output loaded with 8.2 ohm resistor
Upper traces are input 1V/div
Lower traces are output 5V/div
100Hz .........................1 kHz.............................10 kHz
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Old 2nd February 2013, 07:56 PM   #84
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Default Same condition except output xfrmrs are replaced

I used vintage push-pull output transformers in SE configuration as there is no DC current flowing through primary winding
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Old 8th February 2013, 05:17 PM   #85
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Default New transfomer arrived

New output transformer arrived - tested it @10kHz. Results below. Sounds great.
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Old 10th February 2013, 07:42 PM   #86
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Smile Almost finished - top plate to be made

Playing the amp for couple of days now. Some metal works need(top plate, cans for chokes and caps) to be done and is finished.
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Old 8th November 2013, 05:28 PM   #87
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Artosalo and RajkoM made me come back to this project and do some tweaky-tweaky.
I am going to optimise driver stage operation point either
1. using BJT CCS, changing resistor values which set Ia current and adding heatsink to BF421 (TO-92)
2. use DN2540 cascode CCS if (1) will not work well.

You may find the discussion in here E180F V EF184

Thanks RajkoM and Artosalo

PS. This exercise will help me design GM70 parafeed driver, I hope.
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