Realy dodgy Jaycar DI box

jaycar.com.au  catalogue number  AA0402  Direct Injection Box.  $25.

A DI box (Direct Injection) is a box that is used to connect things other than microphones to the mixer in a PA system.  Mixers traditionally have a balanced input.  Many other things - DVD players, lap top computers, electric piano / keyboards even guitars have unbalanced connections.  A balanced input allows you to have a long run of cable and minimises the pick up of noise.  The old wire line phone, remember them? uses a balanced connection to the telephone exchange.

Later last year I bought four of these DI boxes from Jaycar.  (Two then one then one and no receipts kept of course) Blow me over if three seemed to have stop working.  The only one that is still working is connected to the electric piano at Church.  Divine intervention maybe.

In need of DO boxes tonight at the bush dance, I figured I had better take a look. 

On the outside these are pretty rugged and look good.  The cover not shown here extends past the connectors by about 10mm and so protects them from being kicked or bashing against other gear.  There is an attenuator switch to lower large signals and a switch to allow the ground line to be connected & disconnected from the box its self.



Inside it was pretty obvious what the problem was.  The transformer which is a pretty heavy is sitting high off the board and had caused the pads on the PCB to break away.  Presumably when dropped at some time.  Mind you it should have been glued or sat down hard on the PCB. 





The plan was to scrape away some of the green stuff and then bend the pins over.

In the process I discover that it seems that pretty much all the pads have a crack where the pad connects to the track and where the green stuff ends.

Sort of fixed.  I noticed that when I solder, there is a crackling sound.  I suspect that the copper is delaminating under heat.  I also had to track down and fix the same type of disconnected solder pad - track connection where the 6.5mm connector is soldered on.  I think these are just too dodgy to use unless every track is backed up with a piece of wire.  Too much effort.