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Sansui 9090db

Pete, they the rectifier diodes all turn on at .4 volts, also for Hyperion here on the thread did turn bias all the way down (no diff) DBT still bright? About to give up
 
What do you mean by they "turn on" at 0.4v? Are you checking them out of the circuit with the diode test function on your multimeter? You should see continuity in one direction and no continuity with you reverse the leads.

- Pete
 
LBPete said:
What do you mean by they "turn on" at 0.4v? Are you checking them out of the circuit with the diode test function on your multimeter? You should see continuity in one direction and no continuity with you reverse the leads.

- Pete
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Yes Pete, we did check continuity and they are ok----after some more careful checking we found the 2 caps at top left and top right C05 and CO6 on the F2624 board are in backwards (when we replaced them we didn't look at how they came out because we was replacing other componets and schematics aren't good about showing polarity on all, so we will be installing the board again in day or so and hopefully it will come up on DBT! Praying
 
bbpdoubleb said:
Yes Pete, we did check continuity and they are ok----after some more careful checking we found the 2 caps at top left and top right C05 and CO6 on the F2624 board are in backwards (when we replaced them we didn't look at how they came out because we was replacing other componets and schematics aren't good about showing polarity on all, so we will be installing the board again in day or so and hopefully it will come up on DBT! Praying
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Okay guys we are back at it! Got the f-2624 done! Comes up on DBT, red light flashes a few times , clicks and relay kicks in , but no green light(probably resistor going to light), anyhow we did put new bias current pots in (VR-03 and VR-04), with DBT still hooked up got DC offset at 0 at speaker terminals but we cant get more than 1 mA at the fuse clips f04 and f05 with fuses out, any ideas? are we doing something wrong?
 
exactly zero DC offset? You should be seeing it drifting slowly around zero, going pos and neg by a couple of millivolts. If you're seeing dead nuts zero there's something wrong with the measurement or the unit. Assuming it really is out of protection that is..What's the wattage of the lamp in your DBT?
 
Also volume is at min with no load, speaker switch on A, the new pots we put in are 5 turn 1K from digikey in lieu of the old 1/2 turn which one of them was bad (which we think was part of problem way back)
 
bbpdoubleb said:
there was some dc offset but pretty close to 0, DBT is 60 watt
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close to zero is fine but is it alive? Is it moving around or do you just have a zero error on your meter? Are you on the mV range?
When you're satisfied you have a genuine low reading for offset you may want to look at the bias again using a 100W lamp in the DBT...
 
When measuring DC offset are you sure the speaker switch is on A? If it's in any other position it will show 0v if no speakers are connected. It's better to test DC offset at the Blue and the Gray wires coming of the bottom of the power supply board.

As far as bias current, you won't get a good reading if the DBT has a 60w bulb. If you are still nervous about the amp, use a 100w bulb. That will bring the internal voltages in the amp closer to where they should be.

- Pete
 
Yes its moving around not at 0 exactly, okay I will put a 100 watt bulb in and will check at the blue and gray to chassis frame and yes we are on speaker A, and yes on mv range-----thx guys will report back later tonight when we can test again! Also I have read anywhere from 30 to 47 mA for bias current---correct??
 
Also I am going to put all new MJ21193 and 94 outputs in when I know all is good, right now have 2Sd424 and 2Sb554 that don't read real good compared to each other but are working for what im doing now (know they would not last if you was doing some cranking for periods of time)---will I have to reset the bias when I get to that point? thx bill
 
okay guys we are UP and running! we got the dc offset bouncing at close to 0 mV and bias set at 30mA and fixed the green light on protection it was just a bad connection------and we have music with a pristine looking 9090db! will get the new outputs and but them in. Do we need to reset the bias current when new outputs are in? Thx for all you guys help!
 
and it goes without saying but I'll say it anyway; the final set of the offset and bias is when the unit is directly on the mains and off the DBT...
 
Yes and we did have it off the DBT, the new outputs are on the way, will dial down the bias when we put the new MJ's in and go from there! Thx Bill
 
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