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Kenwood KR-7400 Bias setting

EastPoint

EastPoint

Recycler
Subscriber
Hi folks. The service manual for the KR-7400 gives instructions for setting the bias with both a voltmeter and an ammeter. It's kind of confusing. Looking at the board schematic, I think the correct method to adjust bias should be:

Attach your red lead to pin #10 and your black lead to pin #11. Adjust trimmer VR1 for 40mv DC. Then switch your red lead to pin #15 and your black lead to pin #14 and adjust trimmer VR2 for 40mv DC.

Is this correct? Also, when I googled "KR-7400 bias" I ran into someone who had restored one of these and set the bias to 20mv instead of 40mv. That seems more reasonable--40 seems pretty high. Does anyone know for sure?
 
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I would connect my mini grabbers on test points (pins) 7/8 and dial VRe1 in 40mV

17/18 and VRe2

The emitters are .47 R

V=IR

V = 40mA x (.47+.47)
V = 40mA x .94
V = 37.6mV

I think you can use either. They are close to the same.

40mV or 40mA

I think measuring across the emitters is easier.
 
rickl said:
I would connect my mini grabbers on test points (pins) 7/8 and dial VRe1 in 40mV

17/18 and VRe2

The emitters are .47 R

V=IR

V = 40mA x (.47+.47)
V = 40mA x .94
V = 37.6mV

I think you can use either. They are close to the same.

40mV or 40mA

I think measuring across the emitters is easier.
Click to expand...
yeah, you beat me to it. i was drawing.

Annotation 2024-09-11 154008.png
 
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