resistor burning on main amp

sssboa

Super Member
Hi

So the gear is Yamaha CR-800.
On switch-on the resistor R733 on the main amp left channel goes in flames. Initially I found the transistor TR715 next to it shorted. But after replacing TR715 the same happened, this time TR715 did not short. I replaced all transistors and diodes on the left side and still the same happens, the resistor R733 burns on start-up. I also roughly checked the board for continuity of traces but seemed ok, reflowed all solder points on the left side. All capacitors and relay are new.
Any suggestions?

Thx in advance,
Andy

cr800trtrred.jpg
 
Greetings;
Just a shot SM at hifiengine & your snippet is hard to read but I do see FR701 100 ohm 1/2w? . this fuse resistor may be going open. I can't read the basic voltage on the schema and some of the details.. so just a guess.
 
Longshot, maybe dc offset trimmer (VR701) open?

Thinking high R733 current due to high TR715 Vbe, so look at the base voltage, maybe out of spec R731(470)
or TR707 working hard...
 
Please please please find instructions on AK on how to build and use a DBT to prevent future flames....
 
Longshot, maybe dc offset trimmer (VR701) open?

Thinking high R733 current due to high TR715 Vbe, so look at the base voltage, maybe out of spec R731(470)
or TR707 working hard...
Yeah. I was thinking about the trimmer. Thx
 
Greetings;
Just a shot SM at hifiengine & your snippet is hard to read but I do see FR701 100 ohm 1/2w? . this fuse resistor may be going open. I can't read the basic voltage on the schema and some of the details.. so just a guess.
I think I checked all FRs, thx anyway
 
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