Power transformers in parallel

[alerich]

Let's say I buy a cheap solid state Marshall amp (say a Master Reverb 30 Model 5203) and I want to gut it and build a JCM 800 inside the chassis..... *but*..... I would like to retain the original power transformer and supply to use for a low voltage DC supply to power a fan, relays or whatever else I think of. Could I safely just parallel the primaries of the original PT and my new PT assuming each is safely and separately fused?

[PRR]

On stage I have a bass-amp, a guitar amp, a PA system, and an iPod recharger.

How are all these transformer primaries connected? Just parallel.

Boxing them all up together, combo bass/guitar/PA/iPod, doesn't change anything electrically.

[alerich]

Thank you, PRR. I suspected it would work ok but I never really thought of it that way. Good call.

[eleventeen]

Lotsa guys I play with use either their phone or an ipad to display charts during sessions...versus bringing fake books.

[HotBluePlates]

Ummmm....... it was a hypothetical, to point out that everything you plug into the wall is in parallel due to the wiring to the service panel.

 

[HotBluePlates]

Gotcha.

Ground loops won't be a problem with respect to power transformer primaries. That's because the two ends of the primary each travel independently to the wall outlet, and from there to the service panel. The ground wire of the power cord connects 1 time to the shared chassis.

Ground loops between equipment have to do with separate pieces of gear, each with their own ground wire, which are also interconnected by signal cabling. Each item finds ground through its own wire but also through the common ground on the interconnect, which allows circulating ground currents.

Try for yourself & see. No different than adding a filament transformer to an amp when wanting to use bigger output tubes.

[HotBluePlates]

The outputs of the bridge rectifiers are connected? Then no, there is a 0% chance of phase problems.

If the secondaries of the transformers were connected prior to the rectifier, then yes, there is a 50/50 chance of phase problems if winding phasing isn't accounted for.

If the transformers are used as proposed in the original question (two independent circuits feeding 2 independent loads, with the only connection at the primaries), then no, there is a 0% chance of phase problems.

So a 50% chance of phase problems in one of three scenarios; sounds like ~17% chance of phase problems to me. Unless, of course, we stick to the original scenario.