I recently rebuilt an 1150 with a blown-up left amplifier module. Outputs were replaced with mj21193/4gs, bias transistor was replaced with an mje243, and the larger driver transistors were replaced with mje15032/33s. Everything seems to be working, except the bias will not go below 14 mV when it should be 10 mV. Is there a resistor value I can change or should I try the ksa940/c2073 pair with a lower gain? Any help would be appreciated. Thanks!
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Thud3
Active Member
marantz 1150 bias issues revisited
I want to start out with a quote from ecluser in regards to bias adjustment. Then I will describe my issues with this 1150. I understand his qoute is based on a 2270 but the circuit concept is the same. I am hopeful someone can lead me in the right direction. quote;ecluser Thanks for the...
audiokarma.org
I am not a tech, so I don’t know what you guys are talking about, except that it involves an 1150
I tried replacing H10 with two 1n4148 diodes in parallel. The Vbe (Vf?) was higher than 600 (which worked in that post) and was around 640-650 Vf (?) on my peak atlas (in parallel). I checked the original diode, and it was actually slightly lower than this “solution”. Sure enough, I couldn’t get a bias below 16 mV now. Is there another 1N4xx diode with a lower Vbe I can use?
Good to see you on AK!
I’ve had this happen a few times. That pair is really slow but you gotta do what you gotta do.