Rail voltages on biasing settings?

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redrooster

redrooster

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I bought a not working Sansui AU-5500 amplifier, I recapped it and replaced a fried 2SA808 output transistor with a 2SA808A because I couldn't find an 808? The only difference is the voltage, the 2SA808 is 80v the ''A'' is 100v. I also replaced the VR trimmers with 25 turn sealed types for the DC-Offset and Bias but when I measured across the fuse holders as per the Service Manual with a 72W DBT connected I found it was reading 33.5v across each fuse? (I'm trying to get 25mv) I tried to adjust it down but no such luck. The DBT doesn't show a short anywhere? Any ideas where I should look for this Gremlin? :wave2:
 

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redrooster

redrooster

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JonSnell Electronic said:
Find out why the output transistor failed, repair the fault and try again to set the correct measurements.
By the way, you measure the current flow in place of F01 and F03, not voltage.
See page 4 of the service manual.
Click to expand...
The 2SA808 blew because of a flaky VR when I was adjusting the bias. Well, that's what I presumed it was because I can't find anything else wrong other than it burnt out R37 100 ohm fusible resistor on the rail voltage? I replaced the resistor and all the VR trimmers. The mv should have been ma of course (typo) That's where I got mixed up! So I'm right from here on I hope? Thankyou JonSnell.
 
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