Londoner L100A

[psafloyd]

I picked one of these up recently, mainly for an Eminence speaker that had been fitted bit if operable after a few fixes, I could pass it on.

I'm no electrical expert, but I had a look inside and apart from the easy replacement of pots that have had shafts snapped off, it all looked pretty clean.

However, there are two things I am a bit stumped on. Firstly, someone has wired one of the speakers from the slave socket and I can't think why.

The other thing is that each of the pots has had a continous piece of copper strand soldered across all the pots. Is this a backup groubd because you coukdnt trust the FDR electrics or possibly to resolve a grounding issue?

Any help gratefully accepted.

The model is identical to a Sound City RC100 and a Vermona Regent (the model the others sprang from and were renamed for export).

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[Jazz P Bass]

Yeah, that's a 'ground' buss.

Not too sure about the slave.

[Enzo]

Much of the time, the metal pot cover grounds itself to the chassis via mounting hardware, but not always.  By running a hard wired ground strap across the pot covers, we can make SURE they are grounded.  If they are not grounded they are limited in their shielding ability.  By grounding them, we are shielding the pots from radiated noise or signal.

[psafloyd]

Yeah, that's a 'ground' buss.

Not too sure about the slave.

Thanks for the comment.

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[psafloyd]

Much of the time, the metal pot cover grounds itself to the chassis via mounting hardware, but not always.  By running a hard wired ground strap across the pot covers, we can make SURE they are grounded.  If they are not grounded they are limited in their shielding ability.  By grounding them, we are shielding the pots from radiated noise or signal.

Thanks for the response. I can get that, but doe you mean they will be grounded to each other and therefore the chassis?
And is that just to reduce interference or to prevent shorts? The chassis is mimimal, just a plate with another plate carrying the transformer and capacitors.
Though running across each pot, apart from contact with the face plate, there is only a small wire running from the circuit board to the first of the pots. Would that be sufficient to ground them

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[Enzo]

Yes. grounded is grounded, it isn't like huge currents are flowing to require heavy wire.

It prevents noise, mainly hum, and I see no way that it matters to anything shorting to anything else.

[psafloyd]

Yes. grounded is grounded, it isn't like huge currents are flowing to require heavy wire.

It prevents noise, mainly hum, and I see no way that it matters to anything shorting to anything else.

Thanks again, Enzo, most enlightening. Makes me think it would be worth firing it up and if works, replace the damaged pots and generally tidy it up.


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