UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - 120W PP EL34 amplifier re-born.

Diabolical Artificer · 15th Jan 2019, 7:22 am

Bang on and some good thoughts there mate. Yep, I think the problem is the EL34 htr wiring, I'm using a 16 way chassis connector to connect PSU to amp, the PSU sits on said 2mm ali plate, so is serarated from amp, as you say, electrostatically. Htr wiring are twisted and run on the RHS of amp chassis, tucked in a corner, but as they're series connected - 18.9v @1.5v, part of the htr cable run is single strand, IE not twisted. However it is away from the sig in cable. Htr's wiring is grounded on one leg to the ground bus bar, wonder if it'd be better grounded to chassis instead?

Though the twisted pair has reduced hum dramatically I'll still have about a cm of unshielded wire at the chassis connector, unless I wrap copper tape round the pins, which I'll do. Will also look at using humbuckers too, thanks Joe.

Andy.

15th Jan 2019, 7:22 am	#59
Diabolical Artificer Dekatron Join Date: Jul 2009 Location: Sleaford, Lincs. UK. Posts: 7,662	Re: 120W PP EL34 amplifier re-born. Bang on and some good thoughts there mate. Yep, I think the problem is the EL34 htr wiring, I'm using a 16 way chassis connector to connect PSU to amp, the PSU sits on said 2mm ali plate, so is serarated from amp, as you say, electrostatically. Htr wiring are twisted and run on the RHS of amp chassis, tucked in a corner, but as they're series connected - 18.9v @1.5v, part of the htr cable run is single strand, IE not twisted. However it is away from the sig in cable. Htr's wiring is grounded on one leg to the ground bus bar, wonder if it'd be better grounded to chassis instead? Though the twisted pair has reduced hum dramatically I'll still have about a cm of unshielded wire at the chassis connector, unless I wrap copper tape round the pins, which I'll do. Will also look at using humbuckers too, thanks Joe. Andy. __________________ Curiosity hasn't killed this cat...so far.