Metropoulos Forum

Hello Metro forum!!
It has been a while since I have been on here. My question is I have a vintage Fender power transformer I am installing on a 5F6-A build. The tranny has a copper shield with a wire to ground it. I am using the "Larry" style grounding layout which I have used on my last couple builds with great success. My post was the one that Larry replied to and spelled it all out for us. Thanks again Larry!!

http://forum.metroamp.com/viewtopic.php?t=14020" onclick="window.open(this.href);return false;

Anyway, I was wondering where the best spot to ground this copper shield to when using Larry's grounding layout. If anyone has any thoughts on this, please let me know. As always, thanks for the help!!

Tonecat wrote:Hello Metro forum!!
It has been a while since I have been on here. My question is I have a vintage Fender power transformer I am installing on a 5F6-A build. The tranny has a copper shield with a wire to ground it. I am using the "Larry" style grounding layout which I have used on my last couple builds with great success. My post was the one that Larry replied to and spelled it all out for us. Thanks again Larry!!

http://forum.metroamp.com/viewtopic.php?t=14020" onclick="window.open(this.href);return false;

Anyway, I was wondering where the best spot to ground this copper shield to when using Larry's grounding layout. If anyone has any thoughts on this, please let me know. As always, thanks for the help!!

I'd ground it as close to the power transformer as possible.

It's an inter-winding screen, and it doesn't matter where you ground it, It's not part of a circuit, (there's no current being recycled through it) it just for shielding. stick it to the chassis wherever it is convenient.

I'd prefer to ground it together with the mains filtering and the output tube cathodes

Roe,
Thanks for the advice. That's what I wound up doing before I saw that you even replied. I hooked it up there and the amp is dead quiet!! Thanks Again!!

If I may respectfully interject here -

That doesn't mean that it wouldn't be dead quiet grounded elsewhere. I feel a lot of people overthink grounding and make it more trouble than it's worth. The only time I've ever had an issue with grounding was on the first run of Super Lead clones I built, I accidentally created a ground loop by grounding the bridge rectifier to the ground buss wire on the back of the pots...or so I THOUGHT it was a ground loop.

As it turns out, the ONLY place you would want to ground either the rectifier output (on a full wave bridge rec circuit) or the center tap (on a full wave grounded center tap arrangement) would be right at the first stage filter caps. This is due to the fact that you have "ripple" at the +/- rectifier output, and grounded anywhere near the audio signal chain will inject that 120Hz ripple right into the audio signal path. Grounding it right at the first filter cap references the first filter caps right at the source of the ripple, which allows them to do what they do best, which is to filter out the ripple.

I just moved the mains grounding on a komet 60 clone 1.5" and much of the noise dissapeared. just indicates that grounding on the PT bolts is rarely a good idea

Roe wrote:I just moved the mains grounding on a komet 60 clone 1.5" and much of the noise dissapeared. just indicates that grounding on the PT bolts is rarely a good idea

Not to sound pompous (as it's been a common thing to accuse me of around these here parts)...

...but it doesn't prove shit. Depending on how a Komet 60 is layed out, that may very well be the case...on a Komet 60 layout only!!! You may find that in another amp layout that grounding the mains to the PT bolts may very well be the ONLY way to ground it and keep it quiet.

Two things about electronics -

1) Everything is relative...just depends on what it's relative to

2) Regardless of how much you THINK you know, NEVER ASSUME SHIT