Any DIYers familar with Melos Maestro/SHA/Gold tube amp? Need help with hum. - Page 2

Uhm... take a look at the photo of the amp, it's not wired that way.  Please don't cut and reattach any wires.

Quote:

Originally Posted by shawn_low 

Thanks everyone from chiming in.

 

I'm not a DIYer by any means so would prefer if someone would be keen to have a look at it for me. I have STOPPED using it until it is fixed.

 

I did some digging and found that the transformer has Dual Primaries and according to Minivan, can be rewired to 220V. It's a Parnell Electronic Components Model AT D4011. Sticker on it says:

 

 

Blu (.)            (.)Blk

Gry                   Red

2 x 120V          12V + 12V

Vio (.)            (.)Ora

Brn                Yel

 

 

Minivan said: "in this case it look like the secondary is 2x 12v output and the input is 2x120v wired in parallel for 110v operation.Iin some transfomer it allow you to wire the 2x120 in series mean 120+120=240. so it's a possibility it can wire for 240v. but you have to check the datasheet of the transformer to confirm."

Likely not.  I recall the schematic showing three or four different secondary voltages off the transformer.  12V might be one, but you'll need two or three other voltages.  It's tough to find one transformer with everything you need unless you have one custom wound.

Another option is to buy a separate transformer for each of the voltages and house them in a separate chassis.  That, of course, will be expensive, but it might cost less than having a custom one made, especially if you can find surplus transformers.

I'm not a solid state guru, but the explanation you were given sounds reasonable.

Absolutely not.

You need something like 2x 12V, 1x 150V, or somewhere around there.  Check the markings on the original transformer, the secondaries could be written on the side.

Get the amp checked out, worry about replacing transformer later.

Quote:

Originally Posted by FallenAngel 

Absolutely not.

 

You need something like 2x 12V, 1x 150V, or somewhere around there.  Check the markings on the original transformer, the secondaries could be written on the side.

X2.  That transformer would only cover one of the voltages required.

If it makes more sense, you have to consider that there are probably three different voltages going through the amp.

The chips probably run at 12V or close to it, so you need a winding for that.

The B+ for the tube might be 150V, but I think the 6DJ8 will run between 90V and 150V or something around there, so you need to have a winding in that range to provide the B+.

The tube filaments run at 6.3V, so you need a third winding around there.

The transformer you listed can put out the needed 12V, but not the 6.3V or 150V.  You might have a hard time finding a transformer with all of those windings.  You should be able to find one with the B+ and a 6.3V winding - that's fairly common.  But you might need a second transformer for the 12V needed.

Go have it checked out.  As long as the transformer isn't fried, a tech can take readings off the various secondaries and know what they are.  And it doesn't sound like your transformer died.  Fried transformer gives off a distinctive smell - you'll know it when you smell it.

yeah I vagued on the single trannie for multiple voltages and only looked at the label you typed in. forget the trannie for now I agree with the guys above. you wanna get it working first. once its working you can see about getting it better suited to aussie mains voltage so yo can avoid the stepdown.