Ghost note problem...help!

wdelaney72 · Post by **wdelaney72** » Mon Nov 19, 2007 10:48 pm

SDM and Rochstah have both posted this grounding scheme. It works really well, but I think it has a lot to do with seperating the grounds for the mains filter caps and the screen filter caps.

I can't speak for why it works, but it works for me very well. I'd do this and increase the choke before increasing the value of the filter caps as that could really compromise the "feel' of the amp.

toner · Post by **toner** » Mon Nov 19, 2007 10:58 pm

wdelaney72 wrote:SDM and Rochstah have both posted this grounding scheme. It works really well, but I think it has a lot to do with seperating the grounds for the mains filter caps and the screen filter caps.

I can't speak for why it works, but it works for me very well. I'd do this and increase the choke before increasing the value of the filter caps as that could really compromise the "feel' of the amp.

Larry has also shared why certain stages of the amp should or should not be grounded together. I won't pretend to understand all of it, but apparently the typical plexi grounding is far from ideal, technically.

Every amp is different and anything is worth trying. I spent way too much time trying to fix ghosting. I learned a lot but it's not my idea of fun!

tonebottle · Post by **tonebottle** » Tue Nov 20, 2007 9:51 am

Thanks for the great diagram Toner. Here's how my presence pot is wired now. Do I just reconfigure it to the diagram you provided? Should I change the cap to a .1?

tonebottle · Post by **tonebottle** » Tue Nov 20, 2007 6:51 pm

I ran a jumper with alligator clips from the presence pot to the filter cap ground, but it didn't make any difference. Maybe it needs to actually be soldered? I'll work on the grounds some more and maybe even run a redundent ground from the amp chassis to the outside of the house and into the earth.

I'm not an electronics tech, and I certainly don't know a lot about what I'm trying to do, but I've been wondering about the choke since Billy Batz mentioned maybe getting a higher H and I value one. Could the choke possibly just be bad? I have to think that this amp was not born with this problem. I don't remember it ever doing this years ago when I gigged with it, but I mainly used it for rythum stuff, and played leads through my 45 watter.

I don't really want to go changing the character of this amp too much as everybody has cautioned, because it sounds great otherwise, but I may try filter cap stiffening if nothing else helps.

Or...maybe...I just need to gut this thing and start from scratch. I have one of George's board kits, and maybe I'll learn a thing or two that will help me to restore an older 100 watter I have that is dead.

BTW - this isn't my idea of having fun either Toner!

toner · Post by **toner** » Tue Nov 20, 2007 7:21 pm

There's no need to change the presence cap or the resistor. That's stock on early 70's 100w as far as I know.

I don't know for sure, but I think the key to changing the ground is to isolate the presence pot from the other pot's ground buss. You would have to clip that buss wire, which you may not want to do if you're concerned about keeping the amp as original as possible.

Steve's (SDM) diagram also shows that the presence cap is not grounded to the back of the presence pot. However, mine still has that connection so I don't know if that's critical to ghosting.

I would send a PM to SDM to get further ideas. He knows MUCH more than I ever will about this stuff. Good luck.

tonebottle · Post by **tonebottle** » Tue Nov 20, 2007 7:49 pm

Thanks Toner. I don't have a problem with clipping the buss wire. I replaced all the pots anyway, because they were worn out, so it probably doesn't matter much. This amp is one of the first with a printed board, so I've even been considering swapping one of George's boards into it. I don't know that it would hurt the value, I just hope the tone wouldn't change much, because this amp has real tone.

I'll study the diagram some more and mess with the grounding, and if I don't have any luck, I'll send SDM a PM and ask for some help.

Thanks for all your help Toner, and thanks to everyone else who contributed their knowlege and ideas. On my own, I'm not much, and there are no good techs around here that I know of. Necessity is the mother of my frustration.

planetjimi · Post by **planetjimi** » Tue Nov 20, 2007 7:58 pm

Tonebottle I see you live in Ohio. I live in cleveland and know a few techs, if you want a name PM me.

uiovbged332 · Post by **uiovbged332** » Wed Jul 06, 2022 1:05 pm

uiovbged332 · Post by **uiovbged332** » Wed Jul 06, 2022 8:52 pm

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Ghost note problem...help!

Re: Ghost note problem...help!

Re: Ghost note problem...help!