Re: Running an amplifier without load

In message snipped-for-privacy@bancom.co.uk>, tony sayer snipped-for-privacy@bancom.co.uk> writes

In message snipped-for-privacy@mid.individual.net>, Rob snipped-for-privacy@invalid.net writes

Great idea, thanks. Amp reassembled now, and everything reconnected. Much, much better than before but not quite one hundred per cent perfect, so next is trying IPA down the spindle.

This sort of broad-brush advice is not at all helpful. Even a bit old-wive's tales-y.

Start high, go low. Maximum might be the transistor rail voltage, possibly 12-15V if things are really bad.

Any reading at all over a few millivolts may case serious noise when the control is turned. It really ought to be zero.

Ah, someone who has never seen (or rather, heard) this happening.

Do you know the circuit, do you know the design? You write as though you do. If so, my apologies; if not -

Blind speculation - however well-intended - is not helpful.

In message snipped-for-privacy@jrenewsid.jretrading.com>, Joe snipped-for-privacy@jretrading.com writes

Excellent, thanks.

A transistor amp of that period will typically be powered from one or two 9-15V rails. If you have more than millivolts of DC across the pot the scratch will be heinous...

Mostly it wont be leaking caps, just dirt in the pot.

Oh it happens, but in general its bleeding obvious not a 'tad scratchy'

If you'll notice, I did earlier mention that there may be neither input nor output capacitors at the volume control, depending on circuit design. But if one or both is there, and leaking, there *will* be severe noise when the control is turned. It's usually fairly easy to locate them, if present.

If there are noisy controls, it is one of the first things to look for, after a cleaning attempt has not worked well. The problem may also be a damaged track surface, which can be fixed only by replacement.

I have heard of, but never tried, of Caig DeOxIt...

Claims sound a bit true-believer snake-oil-ish, but one source I respect well enough. It's expensive!

Thomas Prufer

I believe from several people I know, that "it" is good stuff.

Unfortunately "it" has evolved into hundreds of products within dozens of specialised ranges, so I don't know which to buy, instead I just have a can of WD40 contact cleaner ...

Throwing solvents down a spindle greased with slicone is not a great idea. Every part of the average pot can be reached through the slit between the legs....

I am sure it works as do may other solvents.