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Re: 250-4 [message #28632 is a reply to message #28618]

Fri, 24 June 2022 12:47

chicagobill
Messages: 2005
Registered: April 2003

Senior Member

Definitely check the differential pair transistors. They have a great effect on output offset voltage.

Bias is set by the three diodes that connect the bases of the driver transistors. The higher the voltage difference between the bases the higher the idle bias. The 1N4007 will work as replacements, but so will 1N4148s. There should be approx. 2 vdc different between the bases.

What transistors did you use as replacements for the outputs and for the drivers?

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[Message index]

		250-4 By: kb0rex on Wed, 22 June 2022 16:29
		Re: 250-4 By: chicagobill on Thu, 23 June 2022 15:49
		Re: 250-4 By: kb0rex on Thu, 23 June 2022 17:20
		Re: 250-4 By: kb0rex on Thu, 23 June 2022 17:17
		Re: 250-4 By: kb0rex on Thu, 23 June 2022 17:17
		Re: 250-4 By: kb0rex on Thu, 23 June 2022 18:09
		Re: 250-4 By: kb0rex on Thu, 23 June 2022 19:45
		Re: 250-4 By: stevem on Fri, 24 June 2022 06:20
		Re: 250-4 By: kb0rex on Fri, 24 June 2022 10:50
		Re: 250-4 By: kb0rex on Fri, 24 June 2022 11:00
		Re: 250-4 By: kb0rex on Fri, 24 June 2022 11:23
		Re: 250-4 By: stevem on Fri, 24 June 2022 11:23
		Re: 250-4 By: kb0rex on Fri, 24 June 2022 12:19
		Re: 250-4 By: kb0rex on Fri, 24 June 2022 12:34
		Re: 250-4 By: chicagobill on Fri, 24 June 2022 12:47
		Re: 250-4 By: kb0rex on Fri, 24 June 2022 13:56
		Re: 250-4 By: kb0rex on Fri, 24 June 2022 14:42
		Re: 250-4 By: stevem on Fri, 24 June 2022 15:09
		Re: 250-4 By: kb0rex on Fri, 24 June 2022 15:47
		Re: 250-4 By: kb0rex on Fri, 24 June 2022 16:07
		Re: 250-4 By: stevem on Fri, 24 June 2022 16:49
		Re: 250-4 By: kb0rex on Fri, 24 June 2022 17:22
		Re: 250-4 By: stevem on Fri, 24 June 2022 19:15
		Re: 250-4 By: kb0rex on Fri, 24 June 2022 22:16
		Re: 250-4 By: kb0rex on Tue, 28 June 2022 14:43
		Re: 250-4 By: kb0rex on Wed, 29 June 2022 12:12
		Re: 250-4 By: stevem on Thu, 30 June 2022 06:12
		Re: 250-4 By: kb0rex on Mon, 04 July 2022 13:19
		Re: 250-4 By: stevem on Mon, 04 July 2022 17:02
		Re: 250-4 By: kb0rex on Mon, 04 July 2022 22:03
		Re: 250-4 By: kb0rex on Fri, 08 July 2022 23:37
		Re: 250-4 By: stevem on Sat, 09 July 2022 17:15
		Re: 250-4 By: kb0rex on Wed, 13 July 2022 12:58
		Re: 250-4 By: kb0rex on Wed, 13 July 2022 14:59
		Re: 250-4 By: kb0rex on Wed, 13 July 2022 15:13
		Re: 250-4 By: stevem on Wed, 13 July 2022 17:17
		Re: 250-4 By: kb0rex on Wed, 13 July 2022 22:18
		Re: 250-4 By: stevem on Thu, 14 July 2022 05:51
		Re: 250-4 By: stevem on Thu, 14 July 2022 07:17
		Re: 250-4 By: kb0rex on Thu, 14 July 2022 12:25
		Re: 250-4 By: kb0rex on Thu, 14 July 2022 11:27
		Re: 250-4 By: kb0rex on Thu, 14 July 2022 11:56
		Re: 250-4 By: kb0rex on Thu, 14 July 2022 12:08
		Re: 250-4 By: kb0rex on Thu, 14 July 2022 12:09
		Re: 250-4 By: kb0rex on Thu, 14 July 2022 13:19
		Re: 250-4 By: kb0rex on Fri, 09 September 2022 16:46
		Re: 250-4 By: stevem on Fri, 09 September 2022 20:06

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