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Sansui 500A, Roo8

T

Tom A.

Member
Hello, I am working on this Sansui 500A. I have it fixed and it's working fine. I'm just a little confused as to the location number of a resistor that someone previously replaced. It's a 3.5K about 10 watt resistor. Ican't find it on the schematic. It has 260V on one end and 195V on the other. I believe it's one of the 3 resistors that Sansui calls R008. The parts list shows R008 then it lists 3.3K, 3.3K, 2.2K all at 3 watts. I don't see these on the schematic unless I'm looking in the wrong place or the schematic version is incorrect for the model I have. Any help is appreciated.
 
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I spent some time looking for R008, but I couldn’t spot it either. Could not even figure out how to find the “coordinates (7C for R008) in the schematic diagram”. Did you look for R008 on 5E on the chassis diagram?

The schematic I have says R008 has a value of 8.8 kOhm comprised of 3.3+3.3.2.2k 3 watt resistors.

Good luck!
 
I see 3 resistors forming a 'U" shape near 5E. One of them has been replaced with a higher wattage 3.5K resistor. The other 2 are 2.7K . The one that has been replaced starts on the C005/C007 can then to the first 2.7K resistor then the next 2.7K resistor, then that goes to the can with C006, C008, C009 and C0015. The connections on the cans have letters but the schematic doesn't. Oh well, my unit is working, but I would love to see these resistors on a schematic.
 
I found it! R008 goes from C007 to C015. See attached. I don't know where BM is. I'm assuming it's the junction of R003 and C007. On the schematic attached look to the right of TP7.
 

Attachments

Good find! Well hidden! Thanks for sharing the answer to the mystery.

I guess the BM indicates a reduced B+ at point M, where-ever that is. Main thing is to have a 8.8 k Ohm resistor string for R008 capable of dissipating 9 watts or more.

Enjoy the music!
 
I believe these switch plate voltage to the tuner with the mode selector, so have a look around that area to see if thats where BM is.
 
yep, and those switches will cause you problems from arcing and just general crustiness. If the tuner is dead or dies, check for plate voltage in the IF strip. If nothing, look at the mode selector to see if its not passing current anymore.

not the worst idea to bridge that with a resistor that will give maybe 20v on the plates of the tuner even when its not selected. Tubes that are lit and get no plate voltage will eventually die from cathode poisoning. Giving the electrons somewhere to go, even if its not in a big hurry will help with that.
 
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