Sansui 9090 (non DB) bias adjustment question
- Thread starter hcruz
- Start date
kvflyer
Super Member
What's installed is usually correct if it is original. Service manuals are notoriously full of errors and I am not beating up on Sansui. Howard W. Sams comes to mind. But one has to go with what one has.
I would go with the original. And for that matter, very low value resistors are often still good. It seems that the large value carbon resistors are the ones that drift very often.
Sansui made alot of mid-stream changes with these 9090's..Likely alot of other models as well.
petehall347
the brandy coffee man
any luck with it yet ?
Engels13
Member
I had a problem with the adjustment and realized that the board can be inserted in two ways. My board was inserted as on your picture with the trimpots facing to the front side. However the manual has the trimpots facing to the back side. So at first I was adjusting the wrong channel.... The manual is ok but the board is mounted this way to get some better cooling as I read somewhere...
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hcruz
Looking for that NLA mosfet that fell off th bench
Little progress
A plumbing problem took priority over this so not much work done:sigh:.
Nonetheless, I did some progress furnishing the list of parts to change.
I'm going to do the full recap. I targeted zeners and electrolytic/tantalum capacitors for replacement (Edit: and fuse resistors
).
There were many differences from what's on the manual, mostly on the tuner board.
I'm also going to change the trimmers with multi-turn ones.
I'll post the list once I finish updating with mouser part #s. Hopefully I can order tomorrow.
A plumbing problem took priority over this so not much work done:sigh:.
Nonetheless, I did some progress furnishing the list of parts to change.
I'm going to do the full recap. I targeted zeners and electrolytic/tantalum capacitors for replacement (Edit: and fuse resistors
).There were many differences from what's on the manual, mostly on the tuner board.
I'm also going to change the trimmers with multi-turn ones.
I'll post the list once I finish updating with mouser part #s. Hopefully I can order tomorrow.
flip850
New Member
When performing the bias measurement on my 8080 I am not reading any current. Is there something wrong with my procedure?
1. Multimeter set to DC amperes
2. Pull fuse F07 or F08 (depending on channel)
3. Put test leads across fuse connections
4. Turn on receiver
The unit is staying in Protection mode as well.
1. Multimeter set to DC amperes
2. Pull fuse F07 or F08 (depending on channel)
3. Put test leads across fuse connections
4. Turn on receiver
The unit is staying in Protection mode as well.
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hcruz
Looking for that NLA mosfet that fell off th bench
Digging the old thread
Finally came back to this project.
On the driver board replaced the electrolytics, fuse resistors and trim pots. Turns out that one of the trim pots was bad. It read 1k and will not adjust when turning. This was probably the cause of my 1st issue when trying to adjust bias.
Hopefully the rest doesn't take me a year
Finally came back to this project.
On the driver board replaced the electrolytics, fuse resistors and trim pots. Turns out that one of the trim pots was bad. It read 1k and will not adjust when turning. This was probably the cause of my 1st issue when trying to adjust bias.
Hopefully the rest doesn't take me a year
hcruz
Looking for that NLA mosfet that fell off th bench
More progress (pics)
More electrolytics and fuse resistors replaced.
One capacitor that has me wondering is this one in the back of the F-2541 board. Did not take a picture of the polarity before removing it and I'm not sure if I did it right.
Also could not source the recommended omron relay. The only replacement I found was this NTE recommended on another thread. I guess it will do.
More pictures of progress.
.
More electrolytics and fuse resistors replaced.
One capacitor that has me wondering is this one in the back of the F-2541 board. Did not take a picture of the polarity before removing it and I'm not sure if I did it right.
Also could not source the recommended omron relay. The only replacement I found was this NTE recommended on another thread. I guess it will do.
More pictures of progress.
.
Finally came back to this project.
On the driver board replaced the electrolytics, fuse resistors and trim pots. Turns out that one of the trim pots was bad. It read 1k and will not adjust when turning. This was probably the cause of my 1st issue when trying to adjust bias.
Hopefully the rest doesn't take me a year
Those two center trimmers are going to be real fun to adjust.
hcruz
Looking for that NLA mosfet that fell off th bench
I made a mistake ordering those and thought the same when I received the parts, but after installing it I tried one of those small screwdrivers that come with repair kits for glasses and they are not an issue at all.
