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Old 29th January 2007, 06:16 PM   #1
Lipaso is offline Lipaso  Poland
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Default How to set Power transistors on Kenwood ka-5500?

I instaled new power transistors in my ka-5500 and they are very hot after few seconds. How to set them?

please help
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Old 29th January 2007, 06:38 PM   #2
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Do you have a schematic or a pic of the board? Can you identify the bias adjust pot?

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Old 30th January 2007, 12:41 PM   #3
Lipaso is offline Lipaso  Poland
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Default How to set Power transistors on Kenwood ka-5500?

I instaled new power transistors in my ka-5500 and they are very hot after few seconds. How to set them?

please help
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Old 30th January 2007, 12:45 PM   #4
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Jan has already responded, asking the question again and ignoring his useful advice is not going to get you very far.
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Old 30th January 2007, 01:43 PM   #5
ilimzn is offline ilimzn  Croatia
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And are you sure that:
1) Power transistors were the only part that needs change?
2) That the BIAS was set to the lowest position prior to installing new transistors?
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Old 30th January 2007, 02:48 PM   #6
Lipaso is offline Lipaso  Poland
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Sorry I thout, that I wrote this post in wrong place and I write it again in other place. Probebly moderator changed this and paste it here. This schema is to big i added onely a piece of it. There are variable resistors (BIAS) but i don't know what voltage on which element should be. Power transistors are 23, 24, 25, 26.

BIAS are not on the lowest position.

sorry Jan

thanks for help
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Old 30th January 2007, 03:08 PM   #7
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You need to turn the bias pot so that the voltage across the output device emitter resistors is as low as you can get. This will mean setting the pot to lowest resistance.

Then increase the pot a bit at a time. You need to aim for about 25-33mV across the output device emitter resistors.
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Old 30th January 2007, 03:38 PM   #8
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Quote:
Originally posted by richie00boy
You need to turn the bias pot so that the voltage across the output device emitter resistors is as low as you can get. This will mean setting the pot to lowest resistance.

Then increase the pot a bit at a time. You need to aim for about 25-33mV across the output device emitter resistors.

Hi richie00boy

Everything you wrote is correct , except that for minimum current across the output devices , the pot must be set at is highest resistance value.
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Old 30th January 2007, 06:49 PM   #9
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Yes sorry, squinting at the schematic I got the transistor the wrong way round.
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Old 31st January 2007, 09:14 AM   #10
Lipaso is offline Lipaso  Poland
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Thank You very much.
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