Is this jumper on a 9090 driver board stock?

[Robisme]

I don't remember seeing this before, and the last 9090 I did had the fuses on the driver board like this one.

Any ideas?

Thanks.



Rob

 

[Hipocrates]

Any ideas?

Not present on mine.
That's weird.

 

[Robisme]

Thanks for checking. It is weird.

Rob

 

[Hipocrates]

I'm trying to see what it does, but I'm too dumb for that.

 

[I LIKE MUSIC]

If my copy of the schematic is correct, the jumper is connecting terminals 7/8 and 11/12 of the edge connector together.

This is the location of the jumper in red. See the edge connector terminals circled in blue.






And on the schematic. Red circles, edge connections 7/8 and 11/12. Blue circles show that they grounds.



In general (not necessarily specific to this board) this is done to reduce differential ground currents (ground loops) or if there is an issue with the edge connector or its wiring.

I have not been inside one of these in a long time.

 

[Hyperion]

I am inclined to think that the jumper may be have been added to cover up for a poor ground connection, maybe at the board edge connector. If ground connections have been separated like this it is for a reason, usually in favour of a 'star ground' somewhere else.

 

[tnsilver]

It's ground and the jumper is stock. Here's a pic of one of my spare driver amps. Haven't checked in years, but I'm pretty sure the one in my unit is the same.

 

[ManyMoonsAudio]

Yes, it is present on most of the 9090's I have worked on.

 

[The Fuxtor]

It's on mine too

 

[Robisme]

Good news. Thank you all.

Rob

 

[LBPete]

One more variation to the 9090/8080 driver board.

- Pete