sansui g8000

[maclvrbr]

scraped test points and still have the same bias readings? These appear to come from the outputs, could there be an output trans issue? thanks

 

[maclvrbr]

The signal I used was from an FM station

 

[maclvrbr]

I connected the cd player to main in connectors on the G and still get just the right channel only. I had the connected switch in the wrong place earlier thanks for redirecting me.

 

[dr*audio]

Check all 4 10A fuses, F01 and F02 with your ohm meter, don't rely on your eyes. Confirm they are all good. If so, measure the voltage to ground at R01 and R02 in both supplies. You can have zero bias if you have no supply. I have seen these with bad windings in the transformer.

 

[maclvrbr]

Both 10 amp fuses were open, put new fuses in DBT very bright, checked output transistors found 2 bad on left channel had a replacement available. Turned unit on relays engaged I have sound from both channels. I had previously checked them (fuses)in circuit) and at least believed they were all good, I was wrong. Thanks for the help

 

[kevzep]

Nice work!! Once we established the problem was in the power amp on that channel I knew it would be obvious.
Always good to use a meter on fuses, easy to get caught out with that...

What replacement transistor did you use?

 

[maclvrbr]

mJ 15024g and mj 15025g

 

[kevzep]

mJ 15024g and mj 15025g

Perfect!!
Now crank that sucker up!! I can't hear it here in New Zealand yet?

 

[maclvrbr]

You guys are great and thanks to everyone

 

[kevzep]

Thats what we are here for, you're most welcome....

 

[LBPete]

Glad it worked out. It's not loud enough, I can't hear it in Long Beach either.

- Pete

 

[maclvrbr]

I spoke too soon. First the DC offset on the left channel ( the one that had the shorted outputs) will not hold a DC offset. When I adjust trimmer near 0mv the meter shows the dc offset going negative, I readjust near zero and then it continues to slowly fall into negative DCmv. Also when attaching probes to test points on corners of receiver i am getting 0mv and the bias trimmer does not change that voltage. Ideas are appreviated. While using the receiver I was getting a distorted sound as well this was not very noticeable at lower volume. thanks

 

[dr*audio]

No bias on one channel or both? Check R23 and R24 on both channels.

 

[maclvrbr]

No bias on either channel both channels r23 and r 24 were 4.7 or 4.8 ohms

 

[dr*audio]

Check R29, R30, R31, R32, R17, R20.

 

[maclvrbr]

R 29 both channels 4.8 ohms, r 30 both 4.8 ohms, r 31 both 10 ohms, r 32 both 10 ohms, r 17 178 ohms and 222 ohms, r 20 175 ohms and .644 k ohms. thanks

 

[dr*audio]

R 29 both channels 4.8 ohms, r 30 both 4.8 ohms, r 31 both 10 ohms, r 32 both 10 ohms, r 17 178 ohms and 222 ohms, r 20 175 ohms and .644 k ohms. thanks

Ok, now lets put on our thinking cap. Look at your readings and look at the values in the schematic. There's something obvious here you should notice. I don't want to do your thinking for you.

 

[maclvrbr]

yes I discovered the values on r17 and r20 to be out of range will be ordering those and thanks

 

[maclvrbr]

replaced both r17 and r 20 on both channels with 150 ohm resistors. Left channel bias did adjust set at 15 mv. the right channel bias adjustment only allowed a range of 0 dc mv to -4.5 mv. Ideas? Again thanks for the help hopefully getting close.

 

[maclvrbr]

I tried to adjust dc offset from speaker post but the adj pots will not affect the dc voltage now.