Where in the World..... is Paul Cornford?

syscokid said:
Ok, that makes sense now. I know AJ and that amp. AJ used to work at the EBMM guitar factory in SLO and bought this amp about 5 to 8 years ago from the amp room that EBMM uses to test their products. I actually opened it up and took about 3 pics of it, mainly to capture the builder's signature and use it to contact and confirm that it was indeed built by Mr Martin Kidd (Yes it was!), who at the time had just moved on to the newly formed Victory Amplification.

What I do remember from seeing and playing through that amp after AJ bought it, was that one of the input jacks was all wonky. I can't remember if it was damaged or just missing a part. But told him it was an easy fix and how to go about it.

The Cornford Mk50 H is a fantastic amp and I so wish i could have bought this if I would have been allowed to do so. AJ got an insane deal on this used amp while working for EBMM. The matching Cornford 4x12 cab came with it too.
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Funny you mention the wonky jack, Sysco. Not exactly on track of this thread but I have one SG jack that has particularly sensitive and crackling pops from the jack if the cable moves just a touch. It is very annoying. I need to see the best fix for this as I pore over this Cornford.

It's not the cable either. It does it with different ones too.
 
syscokid said:
These following schems are for the Cornford Mk50 HII
Click to expand...

I think the hum is solved now.
What I did was: moved 2 of the ground connections.

1. Foot switch jack ground:
This ground wire also supplies ground to effects send / return jacks and 2 shielded audio wires.
Normally this jack ground wire is connected to the chassis, located at the power tube socket chassis ground terminal.
But I relocated this above wire grounding point to the volume control ground buss wire.
This cut the hum in half.
Noise measured at speaker output jack (master volume full clockwise):
Before mod: 13mv AC
After mod: 6.4 mv AC

2. Bias power supply ground:
Normally this ground wire (for the bias supply filter cap) connects to the volume control ground buss wire.
Similar to most HW Marshall amps...
But I relocated this grounding wire point to the chassis. (there is plenty of available chassis ground terminals already in the amp)
This eliminated the remaining audible hum.

It seems like the 120 Hz noise is entirely gone now...
I sent this info to Victory. Hope this helps with other amps.

So I wound up solving this myself, after all....
But I was hoping somebody else already knew the answer.
I took me about 3 hours of staring at that thang before I figured it out :pound-hand:
 
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chilipeppermaniac said:
Funny you mention the wonky jack, Sysco. Not exactly on track of this thread but I have one SG jack that has particularly sensitive and crackling pops from the jack if the cable moves just a touch. It is very annoying. I need to see the best fix for this as I pore over this Cornford.

It's not the cable either. It does it with different ones too.
Click to expand...

@chilipeppermaniac - I was wearing out input jacks every couple of months. Then I started using True Tone Jacks that feature dual sets of contacts. Very good quality and not at all expensive...
 
AMS, Good to " read" that you no longer " hear" any hum. AND from your solution, no failed parts seem to be the culprit.

I still remember chasing an intermittent hum issue in my amps/guitars. I never could 100% attribute it to one of several guitars, or one of several amps because of all the usual culprits with the equipment.

Details to address: Single Coil guitars vs Humbucker, Tube vs. SS amps, Combo vs Head and Cab setups, Foil Tape added vs Stock Shielding painted control cavities, Strat or Tele style vs LP/SG style guitars or bad cords etc..

Since the problem was intermittent, it took AWHILE to arrive at the cause.
My memory takes me back to how I figured it out. It is a bit hazy, but the low down was a process of elimination. I think when I realized I could make the issue occur in all the amps, all the guitars, with different cords etc, I decided to relocate and try amps in a different room. This resulted in the hum going away, then reoccurring once I took the same setup back to the bedroom. So, I basically eliminated a hardware issue. The problem turned out to be whether the ceiling light in the living room below the bedroom where I practice was on or not. The dreaded dimmer switch turned out to be the cause. What a relief that it wasn't any failure in my gear.

Now AMS, tell us some stories about that Cornford. NOT necessarily secrets, but what can it do that say a 5150, or Bassman, Twin, 50 watt JMP or Laney AOR, Boogie Triple Rec, etc can't?
 
Robert Herndon said:
@chilipeppermaniac - I was wearing out input jacks every couple of months. Then I started using True Tone Jacks that feature dual sets of contacts. Very good quality and not at all expensive...
Click to expand...

Thank you, Robert. I saw you say you ordered something to plug your unused Speaker jack that you don't want to plug into by error and get a mismatch Ohm scenario.

Funny thing is I have one of those plastic Body and Fender barbed cap trim panel retainers that I suggested to you sitting on my tray table in front of me. Is this what you ordered?
 
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