Two for One

[MrBump]

Got a couple of techy questions, if I may.

Firstly, I've noticed that I get an amplified scratching sound if I rub my finger over my tele scratchplate through my amp, particularly if I'm playing through an more gainy setup.  Nothing from the pots or bridge, just the scratchplate, particularly the screws...

Secondly, is it necessary to drain the filter caps on my Orange if I'm going to remove the valves?  I'm sure it's recommended, and I understand the dangers of brushing against the caps while working on the beast...

Ta.

Mark.

[Philly Q]

Not the foggiest idea on question 2 (as you'd expect), but on the scratchplate I think it's static electricity and you can fix it like a shielding problem.

Stick some copper (or even aluminium) foil on the back of the scratchplate.  This then needs to make contact with a ground point.  I don't know if the pickup cavity is shielded, if it is the foil can make contact with the foil/conductive paint in the cavity.  If not you could use a separate ground wire, or even rig it so the foil touches the metal pickup cover. 

If you can't be bothered with all that, apparently this works:  rub the scratchplate with one of those "Bounce" anti-static sheets that go in tumble dryers with the washing!  :lol:

[MrBump]

Not the foggiest idea on question 2 (as you'd expect), but on the scratchplate I think it's static electricity and you can fix it like a shielding problem.

Stick some copper (or even aluminium) foil on the back of the scratchplate.  This then needs to make contact with a ground point.  I don't know if the pickup cavity is shielded, if it is the foil can make contact with the foil/conductive paint in the cavity.  If not you could use a separate ground wire, or even rig it so the foil touches the metal pickup cover. 

If you can't be bothered with all that, apparently this works:  rub the scratchplate with one of those "Bounce" anti-static sheets that go in tumble dryers with the washing!  :lol:

That makes sense - I didn't use any shielding when I built the thing.

Next restring I'll give it a go.

[Dmoney]

if you're changing the valves in your amp and you need to rebias, then you have to have the amp running anyway, so discharging the caps isn't needed for that.
I've swapped tubes about plenty without discharging the caps. In my amps though, I know the caps drain themselves when i flick off the power switch, and leave on the standby. I just give them time to do so.
I wouldnt trust that though...

id say switch off your amp, leave it a min a two, change the valves, switch on and re-bias.
if you're not confident then take it elsewhere. also, its not JUST the caps you need to be careful of, its what is inside the chassis that is connected to them, and if you leave the power cable in, the bare terminals on that beast.
dont go flailing around with your fingers in that fella.

[MrBump]

^ Yeah, it's just the filter caps that everyone mentions in their nightmares.

I remember getting a mighty whack from an OT in an old Marshall bass amp that I owned about 20 years ago.  I still remember how it felt!!!