SANSUII BA-3000 PROBLEMS

Some of the posts take a LONG time to refresh here.... like 6 min !

I just thought you fell asleep in front of the computer like I always do. I can go to sleep sitting, standing, any old way.

No, I'm not sure what it is that you want me to do next. I missed it somehow.
 
2511 Protect board:
Protect relay
Yellow ( out of the BRICK ) is left ( 2509 is the part # OF the bricks PCB) PIN N goes ( on a large Yellow wire with a female spade lug ) to protect board relay IN pin 19 Pin 20 is the OUT to speaker switch
Red is right 2509 O goes to protect relay IN pin 18 pin 21 is the OUT to speaker switch

1) Check the red wires going in & out of the protect board
2) Hook the speaker up to the right channel
3) turn the right volume down 1/2 way
4) turn amp on ( hold ears )
5) IF NO AUDIO on speaker back probe pin 18 on protect board
IF audio is there
6)Back probe pin 21 on protect board.. IF YES clip lead speaker to 21 and chassis GROUND and see if you have audio
 
2511 Protect board:
Protect relay
Yellow ( out of the BRICK ) is left ( 2509 is the part # OF the bricks PCB) PIN N goes ( on a large Yellow wire with a female spade lug ) to protect board relay IN pin 19 Pin 20 is the OUT to speaker switch
Red is right 2509 O goes to protect relay IN pin 18 pin 21 is the OUT to speaker switch

1) Check the red wires going in & out of the protect board
2) Hook the speaker up to the right channel
3) turn the right volume down 1/2 way
4) turn amp on ( hold ears )
5) IF NO AUDIO on speaker back probe pin 18 on protect board
IF audio is there
6)Back probe pin 21 on protect board.. IF YES clip lead speaker to 21 and chassis GROUND and see if you have audio

I understand everything except what do you mean when you say BACK PROBE?
 
When you have a connector in place , in this case a male on the PCB and a female connectiing to it.. there is a shell on the female connector to prevent from shorting.
Using a paperclip ( or similar ) with a cut tip ( at a 45 deg ) you slide the paperclip in the backside of the connector so you can make contact with the actual metal bit of the connector
 
When you have a connector in place , in this case a male on the PCB and a female connectiing to it.. there is a shell on the female connector to prevent from shorting.
Using a paperclip ( or similar ) with a cut tip ( at a 45 deg ) you slide the paperclip in the backside of the connector so you can make contact with the actual metal bit of the connector

I'll go give it a try Mike. I may know what you mean so I will give it a try.
 

I got it Mike. I checked for signal with Leader cable on and I had signals both channels. I then just connected the speaker up to the right channel and connected the inputs from the cassette deck, punched the start on deck and I was listening to John Denver. I had the right pot open about 1/3 but I noticed the light in the DBT getting brighter and brighter until the amp kicked out. Then the bulb would go dim and the amp would come back on until the bulb got too bright again. Then I adjusted the bias while playing music down to where the bias would peak at about 30 MV with lows at about 15 MV. I stopped and went back and set DC offset which was way up there to about .320 VDC so I backed it down to +- 3 MvDC. I then played more music and so long as I kept the right pot down so that the bulb in the DBT didn't get too bright it would keep playing music nicely. I checked signal and it was there but now a stereo signal. I need to call it a night but tomorrow I could use you to explain why the surge of bias and the amp shutting down when it got say over about 50 when the music got louder (not me turning up pot as I kept it at 1/3 or less.

We now can play music but I want to be sure the amp is worlking right with this bias going up so high and the amp shutting itself down.
 
#1 NEVER ADJUST BIAS WITH PROGRAM
#2 The amp is shutting down due to lack of stable voltage, we need to go up to 75 watt DBT or 100...
The amp needs MORE power, because you are putting a load on it
 
Good night Mike. I have to go home now. I will yell at you in the morning. I sure is nice to hear music out of the amp again. I just want to be sure it doesn't do as it has in the past which was to play music for 10 minutes and then go up in smoke. And I mean just that. It would go up in smoke after about 10 minutes of play time. I hate to eat and run but I must.
 
#1 NEVER ADJUST BIAS WITH PROGRAM
#2 The amp is shutting down due to lack of stable voltage, we need to go up to 75 watt DBT or 100...
The amp needs MORE power, because you are putting a load on it

Now that really makes sense. When I had nothing playing thru the amp I had no bias. It was when I started the cassette that the bias went up.
 
So Audio in UNDER 35 !

I haven't counted them yet but I think you are right. I will have you explain more tomorrow about the bias rising so high with program. Like I said, I just want to be sure it doesn't go up in smoke like the last 3 times I got it playing music. I will yell at you when I get over here and drag my body out of bed in the morning.
 
The SAFE play ( for now ) is to run with the bias cranked off or as low as possible,
Without bias the audio might distort at low level program ( soft passages ).
The bias just sets a "just START to turn on " all the transistors to the start of conduction.
The HIGHER the bias the more the transistors turn on. BUT audio on top of the bias is what DRIVES the transistors.
If you clip the amp you are at full power
If the Bias runs away you are at full power and a runaway is not momentary like program so things go POOF !


Remember we are looking not at actual bias current but voltage, at IDLE , using the magic of ohm's law we can calculate the bias current.
AND
You are only measuring voltage on 2 of the 6 emitter current limiter resistors to do this calculation to set bias.
this assumes all 3 pairs of transistors / resistors MATCH !

But that's bias measurement a moot point once you start throwing the coal's to it, Louder music,using more power
That measurement is USELESS at that point. once you set bias leave it,
Your next best gauge is the temp of the pre driver heatsinks ( and yes they get HOT 125 deg when banging on the roof ) AND the bricks them selves.

That is one reason the external bias transistor was moved to be on the pre driver VS the bricks.

Remember 170 REAL RMS X2 watts into 8 ohms which means a MAX DRAW of 1100 watts AC.
If your just putting around 25 or so watts output = ~330 watts

Your 60 watt DBT will make the power supply SAG BAD as you try to make any audio over IDLE with only 1 brick.
BUT that is the cost of protection of keeping things from going POOF....AT IDLE.


Oh and when the supplies loose regulation ( Sagging ) bias & DC offset are no longer fixed

So as confidence builds thru testing you can work with less of a net, eg bigger bulbs ( less voltage drop ) or NO DBT
 
Extra wires & De molexing.... these are all stop gap repairs typically for worn or broken connectors.
OR to get around this....
The black or green death
Sansui made a BIG DEAL of GOLD PLATED connectors BUT they cheaped out.
The Gold was usually only on 1 of the 2 connection points and it was plate on tin.
So when you have dissimilar metals, over time these corrode.
You develop many heat cycles, and connections get funky, resistance builds up and POOF.

So it became practice to neuter all the connections for a more POSITIVE contact,

This point can be argued till the cows come home, but cleaning on initial rebuild or replacement
will let these units live on for another LONG period of time, unless you live near the ocean or other body of water..
Then all bets are off unless you used Dielectric grease
 
Extra wires & De molexing.... these are all stop gap repairs typically for worn or broken connectors.
OR to get around this....
The black or green death
Sansui made a BIG DEAL of GOLD PLATED connectors BUT they cheaped out.
The Gold was usually only on 1 of the 2 connection points and it was plate on tin.
So when you have dissimilar metals, over time these corrode.
You develop many heat cycles, and connections get funky, resistance builds up and POOF.

So it became practice to neuter all the connections for a more POSITIVE contact,

This point can be argued till the cows come home, but cleaning on initial rebuild or replacement
will let these units live on for another LONG period of time, unless you live near the ocean or other body of water..
Then all bets are off unless you used Dielectric grease

I'm awake and almost bright eyed and bushy tailed. I was WASTED last night. Night after night of midnights had worn me out.

Ok, what I am trying to understand is where should the bias be set at idle? Also, when setting bias, where should the pots on the front of the 2513 board be set? The same goes for where should the pots be set when setting the DC Offset? Like I said last night, it was wearing me out when I was working on my amps without help when I would get an amp fixed (I thought) when trying to set the bias it was a MOVING TARGET. The bias would say be at 2 MV when I thought the amp was fixed so I would do what the service manual said and turn it up to just under 20 MV. Once I did that the bias was climbing constantly for hours and hours with the amp not connected to anything. I could set the bias at say 18 MV and go to dinner. When I came back i was at 35 MV and still climbing. Then when it would stop climbing it would start falling. I could never get the bias set to 20 MV no matter what I did. Then I would finally say to myself, SELF, its time to put music to this amp. I would connect the preamp and turn on my tuner and the amp would sound just fine and then 10 minutes later, go POOF like you say. And I do mean POOF to the highest level. It would look like my Lionel Train on Christmas Day with smoke coming out of the smoke stack. THAT'S WHAT I DON'T WANT TO HAPPEN AGAIN!!

In regards to the female connectors that were cut off of the cables going to the 2513 board, what about getting some good quality 2 and 3 pin male to female connectors and soldering them directly to the PCB of the 2513 board where the current male connectors are soldered to the PCB of the 2513 board? Then I wouldn't have to keep trying to find something to connect to the existing worn out ugly male connectors on the 2513 board.
 
Morning Mike
Setting bias...
AMP HAS TO BE UP TO TEMP .. The small signal transistor as it heats or cools will affect this setting, so if you set it with the amp cool.. it will drift.
These amps drift a fair amount anyway.... ~ 10 mv or so... so worry about 40 mv drift, not a 10.
How clean the connectors can affect this is a BIG WAY
ALSO DID YOU SWAP THE DIODE (VD -1212) near TR-05 ?
 
Bias set
turn bias as low as possible, run the unit ( play music ) ~ 5-10 min
( BTW you probabaly want to up the wattage in the DBT )
Turn source music off You want NO SIGNAL coming in
Close both input pots
Set for 100 volts AC IN ( keep meter on power source )
Set bias 20mv..... give it ~ 2 min.. set it for lowest avg
Play a tune
Kill inputs again
Check bias

If it still wanders you have something moving
Starting at the top ( TR-03 ) and go straight down to TR-05 check ALL resistors ( or replace with 1% )
Remember on the schemo F G H are the 3 lines that go to the teeny transistor on the brick and all that needs to be 100%
 
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