Baldwin Organ Amp Conversion to Carmen Ghia Clone

[HotBluePlates]

For pic 3, I'm thinking the power supply will be fairly clean d.c. at that point, so probably no shielding necessary.

For pic 6, the cathode wire is a fairly low-impedance point in the circuit and is less susceptible to hum than a high impedance point in the circuit. I'm still more concerned by the OT primary wires running in parallel to other stuff in the chassis, which gives the opportunity to couple hum into a high impedance part of the circuit. See the pic below.

But relocate that AC cord first, then see if you still have any hum issue. You may find it essentially gone.

[Platefire]

Just completed relocating the power cord as per attached pixs. Cut the unused wires on the PT off shorter and re-installed a wire nut cap on each one. Also rearranged the OT wires to be perpendicular to the heater and screen wires. It's hard to tell in pixs but I have 1/8" to 1/4" clearance between the wires.

The disappointment is I plugged the amp to the speaker without any tubes in it and turned it on---it's still has that hum as before. Moving the power cord had no effect. I have the PT grounded on the OT bolt---could that be it? I've got the filter caps, PT, can cap, power tubes all grounded on the OT bolt---but the way I read it that in accordance with the Phoenix schematic!

Got to be an answer for correcting that hum where it would be dead silent without any tubes or with the tubes in and on standby. Platefire 

[woolly]

hey Bob. maybe it's transformer orietation.  all the laminates are horizontal. If you could lift the OT
and try turning the laminates vertical and also rotating and listen while doing so may tell
 you something. If no change it's probably just the PT internal hum coming through.

[Platefire]

I could understand if it had an internal hum coming within the PT but this is transferred to the speaker and when you unplug the speaker it's gone. The AC operation is somehow reaching/effecting the output of the OT. The OT is about 1 3/4" from the PT on this amp. We would never build anything on a new build that close---it just goes against normal layout practice.

Previouly with the power cord in the old position I did a test with some tin foil folded up with serveral layers and wrapped it around the power cord at the location where it enters the inside of the chassis to attemt some kind of sheilding between it and OT. It did reduce the hum eveytime it got in one paticular position. That made me believe along with HotBluePlates suggestion that maybe relocating the power cord would help. So now we know!

If I was to discover that re-arranging/rotating the OT in another position would help it, it would be a major headache moding the chassis holes, bolt holes and lead wires to work. Because of space, that's all you could do is rotate it horizonally. Platefire    

[Platefire]

On a more positive note, I did some jamming on the amp last night using my tele (noisiest guitar) with no effects straight into the amp. The cranked distortion on the amp is something to rave about. Very focused and not flabby. I kept thinking Marshall tone. At 3:00 Oclock on the amp volume and guitar full volume brings you to a level where you get some great sustain for burning lead work ala ZZ Top
and turning your guitar down gives you a level of crunch rhythem that good support for vocals. Turning the amp volume up from 3:00 to full gives you even more sustained/harmonic lead levels--litterally screaming. It's just a little harder for land or find a good rythem level at that amp volume when you turn your guitar volume down, the slightest movement makes a big difference--kinda hard to control.
 
Considering the guitar I was using, the amp noise level wasn't bad at all. The very slight PT noise is still there and is only noticable when you first turn you amp on. Once you turn your B+ on the slight PT hum mostly buried in normal amp sound and it don't get louder as you turn the amp up. So it would be nice to solve this slight PT hum but I think I am nearing completing about all that can be done for this amp considering it is a old style P to P conversion is a limited chassis space. The amp's performace is very good. So I'm still open to suggestions on the PT hum. If not I'll probably sow it up and ship is very soon. I did tell the customer before I even started I was putting an un-proven reverse engineered schematic in a old cramped organ chassis and what he got he got. He agreed. Platefire
  
BTW-With my humbucker guitars LP & 335 the amp is very quiet. That is why I used my un-sheilded tele as a worse case scenario for testing.

Edit: Shipped it to customer 31 May 12