400 Series II (standard) repair

FredR

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#1
I have 5 or 6 unconverted amps in the closet so thought I'd play around with one to see if I could get it going non-WOPL mode. First thing I noticed was repair work replaced all the outputs on the left side of the amp and all the emitter resistors as well. With ceramic. Then I noticed that each channel is supposed to have a 10 ohm resistor that you set bias across. This one only has a single 10 ohm on the repaired side. Another 1 ohm resistor coming off the attached point for emitter resistors on the repaired side. On the un-repaired side both resistors are 1 ohm coming off the emitter resistor connect point. I've attached photos of both sides and the service manual. Are divergences between the manual and the amp like that common?
 

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mlucitt

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#5
Brown (1) - Black (0) - Black (x1) is 10 Ohms. The fourth band is Silver and gives a 10% tolerance. The reference I have (IEC 60062) shows the fifth band may indicate a temperature coefficient (ppm/K) and will be Brown (100 ppm), Red (50 ppm), Orange 15 ppm), or Yellow (25 ppm). I believe you have 100 Ohm, 10% Tolerance, 25 ppm Temperature Coefficient resistors in you unit. They often measure less than that due to age and heat cycling.

If you have another standard that shows a fifth band with a different meaning, I am all ears. Not saying you are wrong, at all. Mine were just like yours and measured low as well.
 
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FredR

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#15
Another question. The interconnect diagram 2-7 shows only two 10 ohm resistors, but this amp contains four. Maybe Ed can help.
 
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