Loud hum on Piezo settings

[LewA]

Hi,
I have a Fly original serial no 0640103BMH - unmodified except for a repair to a ribbon cable connected to the output jack. This checks out ok on the multi-meter.

It has suddenly developed a very loud hum when the piezo is switched in. The piezo still outputs on all strings. The strange thing is that if the strings are all depressed, say by a capo, the hum disappears and all works well. I've just noticed that this also seems to be the case if I bar the 1st and 2nd strings. Generally if the strings are touched in any way they initially make crackling and loud noises rather like if they are not grounded, but if gently I put my hand on all strings the hum reduces. I've tried grounding the strings to the output plug with a jump wire but it makes no difference.

There is no hum on magnetic.

I think it may be a problem with the 1st and 2nd string piezo as output particularly on the 1st string seems to be low.

I would welcome any ideas on the problem and failing that someone who is competent on Parker electronic repairs in the UK.
Lew Aldridge

[vjmanzo]

Hi @LewA,

Welcome! Ground hum issues can be particularly troublesome—best approach is to isolate the variables. The piezo preamp can be a pain when it comes to the electrical wiring in some houses/buildings. Have you tried the usual checks (grounded outlets, power conditioner, etc.) Sometimes this happens. Are you using a good 1/4" cable? A good 9 volt battery? Either of those can be the culprit.

Have you explored the FAQs about Electronics? Any of those issues sound familiar?