Hello Community,
This is my first post, so please let me know if this is in the incorrect area of the forum, etc. I'm excited to become part of the community!
I'm working on restoring an old Kenwood KA 3500 integrated amplifier - so far so good...all of the pots have been cleaned and all of the circuits appear to be working as prescribed except for two resistors on what appears to be the power supply (visually) but seem to be on the output (connected to speaker terminals - per schematic)
http://www.hifiengine.com/manual_library/kenwood/ka-3500.shtml - schematic I posted online.
For some reason, resistors R55 and R57 are running hot...like, crazy hot (R55 running around 500F, and R57 around 160F!)...I'm certain they are fried at this point. What I'm wondering is if due to being old, there was possibly drift that increased the resistance for these and eventually caused them to overheat and fry, which further increased how hot they are running, or if something else may be going on? The amp sounds really good and does not appear to be distorting, etc.
I'm not very familiar with this topology - as I said above, the resistors are physically located in the power section (not power amp section) of the amp, but are evidently linked to the output ....which is odd to me. I have never worked on am amp where the power supply was so directly linked to the output...
I have access to a 30meg scope and dvm, but no signal generator...wondering what my next steps should be in troubleshooting. Any help would be most appreciated. Thank you all in advance!
This is my first post, so please let me know if this is in the incorrect area of the forum, etc. I'm excited to become part of the community!
I'm working on restoring an old Kenwood KA 3500 integrated amplifier - so far so good...all of the pots have been cleaned and all of the circuits appear to be working as prescribed except for two resistors on what appears to be the power supply (visually) but seem to be on the output (connected to speaker terminals - per schematic)
http://www.hifiengine.com/manual_library/kenwood/ka-3500.shtml - schematic I posted online.
For some reason, resistors R55 and R57 are running hot...like, crazy hot (R55 running around 500F, and R57 around 160F!)...I'm certain they are fried at this point. What I'm wondering is if due to being old, there was possibly drift that increased the resistance for these and eventually caused them to overheat and fry, which further increased how hot they are running, or if something else may be going on? The amp sounds really good and does not appear to be distorting, etc.
I'm not very familiar with this topology - as I said above, the resistors are physically located in the power section (not power amp section) of the amp, but are evidently linked to the output ....which is odd to me. I have never worked on am amp where the power supply was so directly linked to the output...
I have access to a 30meg scope and dvm, but no signal generator...wondering what my next steps should be in troubleshooting. Any help would be most appreciated. Thank you all in advance!