[Clive]

The grey wire from the PTX connected to ground has not helped the hum I get with my Cornet2.  Due to where my Cornet2 is positioned it would be easy for me to have the input RCAs on the side of the chassis just behind the front panel.  I would cut the pcb tracks coming from the RCAs at the rear.  I can't help wondering whether some hum pickup occurs via these long pcb traces.

Anyone got any thoughts on this before I try it?

BTW my hum issue maybe different to some as my mains is 50Hz.  I've found in the past that the magnetic field at 50Hz can be significantly different to a 60Hz magnetic field.

[fandersen]

Are you sure it's the Cornet that is the source of the hum?

When I first built my Cornet I also had hum. Turned out to be a bad interconnect cable.

[poty]

Before doing some destructive things I agree with fandersen - try to determine if the problem lies in the input side. The most easy way to do this - short-circuit the R200s. More precise - unsolder R201 and short-circuit the grids of V200 (to the ground).

[Clive]

Good advice, I'll try it over the weekend.  I'm not hopeful though.  The Cornet has always had some hum no matter what kit I use with it.  I have 2 TTs with different cartridges, I have 5 phono stages to play with.  It's the only one that hums.  It's humming more now than it used to, this may be down to positioning.

[poty]

Is it the Cornet with the heavily upgraded capacitors (almost treasure sort to say)?

Good advice, I'll try it over the weekend.  I'm not hopeful though.  The Cornet has always had some hum no matter what kit I use with it.

Do you have proper ground in your outlets (the third wire)? You mentioned 50Hz - it means you are not in USA? The dedicated ground wire is essential for Cornet.

It's humming more now than it used to, this may be down to positioning.

How long have you had the Cornet? The problem may be in the electrolytic capacitors, but it can be leackage in the diodes in heating power supply or the rectifier tube problems too as well.

[Clive]

Is it the Cornet with the heavily upgraded capacitors (almost treasure sort to say)?Do you have proper ground in your outlets (the third wire)? You mentioned 50Hz - it means you are not in USA? The dedicated ground wire is essential for Cornet. How long have you had the Cornet? The problem may be in the electrolytic capacitors, but it can be leackage in the diodes in heating power supply or the rectifier tube problems too as well.

I wouldn't say the caps are heavily upgraded, just the 3 pairs in the signal path.  I'm in the UK.   The unit is grounded.  I had it pretty much since the early days of the Cornet2.  I'll try a different rectifier this weekend too.  I did try loads of things a couple of years ago but gave up.  The hum is worse now so I ought to track it down.

[Tone Deaf]

I have an original cornet rather than cornet 2, but yes - for me the quietest configuration is with the turntable input on the front edge of the chassis, as far away as possible from the power tranny.  The only hum I've had with the cornet it turned out to be magnetic interference, from it's own t/x or adjacent units.  It's fairly sensitive to placement, due I suspect to the exposed valves.  I built another one, fully enclosed in a steel box - that was much better but not very pretty!
 
I'm also on 50hz (& in UK!)

TD

[boss_e]

Clive,I assume the RCAs are not pcb mounted.

If the pcb is mounted in a metal box it kills the hum if you mount the RCAs on the outsside
of the this box, just like you wrote. You don´t need to cut any pcb tracks. The RCAs can be mounted on the side near the back panel. Drill a hole in the box for the wires so they meet the pcb at a 90 degree angle.
Mount an option extra metallplate on the inside to shield off the transformer wires, this is were
the hum comes from. No hum is picked up from the pcb tracks.
 
This is a great design, way better than EAR 934P that I had before and it is quiet.
Now you don´t need five phono stages.

[Clive]

I've still not got around to doing anything more with the Cornet2.  The RCAs are board mounted currently.  Good ideas, thanks.  I have an RCA mounting block somewhere that I can attach.