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Sansui Seven

robz2000

robz2000

New Member
Hey everyone. I have a sansui Seven that i suspect isn't getting the proper voltage to the tuner board. Do any of you have advise on how i can test the power coming to the board. i have swapped out all 4 of the underneath soldered fuses, to no success. i am not great with schematics, although i do see i am looking for 12mv, i am just not sure where, and also what supplies that 12mv to the tuner board(s).

all other functions work on the amp. so it's not the selector switch, controls, etc. it's def the tuner section. there is no sound and if i turn it up to about 4 or 5 o'clock i get a minimal amount of static, i suspect is just cross noise. that is why i beleive it to be a voltage problem.
any advice is appreciated.
ty
 
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Looks like some good quality schematic scans are at AKDatabase. The hifiengine.com copy not that great.
http://akdatabase.org/AKview/thumbnails.php?album=28&page=10

Looks like the tuner board gets 12V from the power supply. Power supply and amp circuits schematics are in "Sansui Seven Schematic". Tuner schematics are in the Seven Tuner pdf.

Looks like power supply is on board that should labeled F-1441. Looks like the 12V supply is fed by TR002 which is listed as 2SD330 transistor with D011 a R13A diode which appears to be a 13V 250 mW Zener that turns TR002 on and off to maintain 12V. If not 12V at the emitter leg of TR002 there is an issue in that part of the power supply especially if the other voltages are good. Voltages will normally measure a bit higher than schematic numbers - our modern AC voltage may be a little higher than 50 years ago.

If you get 12V at the emitter leg of TR002 but not at FM tuner board when function selector is on FM Auto you probably would need to look at the function selector. One of the disks will control power tuner board gets when FM Auto is selected, otherwise no power. AM tuner board gets power from same 12V source at same disk next position. If AM tuner gets 12V when selected but FM does not would look at function selector - may need cleaning or a break in the wiring.
 
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