Dumbleator build, help with strange voltages

[norburybrook]

Tom,

Yes they're connected to the ground of the first Axial cap as per the layout, and then grounded at the ground point between the board and the pots.


Marcus

[norburybrook]

Martin there's 2x 100r resistors by the heater connections on the power board.

The earth points are scraped clean of paint and the pots are connected to the bus bar, all the shields are connected to the bus bar as well at the pot ends.



Marcus

[martin manning]

Are the pot cases electrically connected to the bus? They can be grounded through their bushings, but they need one or the other.

[norburybrook]

Pin 3 is connected to the bus bar, do I need to connect the back of the pot too?



Marcus

[martin manning]

Or make sure that they are grounded by their bushings.

[Charlie Wilson]

Marcus, if your chassis is painted and I suspect it is and the panels screw together and I suspect they do, then your front panel is isolated from your bottom which is were your grounds are. You need to solder a wire on the back of each of your pots and run that to your buss.
CW

[norburybrook]

update;

Wired another ground from the back of each pot to the bus bar and everything seems to be now OK, funnily enough letting the valve warm up for a while seems to have lowered the noise as well. I was testing with the amp constantly being switched on and off and I think the valve needed some time to stabilise.

Anyway, it's all finished now, thanks for everyone's help on this, getting those caps the wrong way round certainly led to a whole heap if issues as I'd used the legs to connect the 2 caps together originally and then didn't when replacing them, hence the low voltage.

I'll post some pics of the finished rig in a day or so as I'm busy in the studio at the moment.



Marcus

[martin manning]

Glad it has been solved. I personally don't like soldering to pot cases as the element can be damaged by the heat and it makes it hard to replace the pot later. Removing the paint from the panel and placing star washers on the bushings will work, provided there is a good electrical connection from the front panel to the bottom of the enclosure. That can be made through the joining screws or if need be a wire to the star ground.

[norburybrook]

good points Martin, I couldn't be arsed to take the pots out at the time so did the quick and easy method


Marcus