Moreplay transformer

[taubear]

Moreplay kit-all resistances and voltages checked out fine and it ran beautifully for about an hour and then blew its fuse. It instantly blows its fuse with or without tubes installed. Brought the Moreplay up on a variac and it drew a lot of current even at low voltage. Unsoldered both low voltage filliment output and high voltage for DC output from the transformer to isolate it. Even with no load it still drew lots of current with low voltage variac input. My friends who trouble shoot audio stuff a lot suggest the transformer is toast.

As well one of my troubleshooting friends noticed one of the two 160v x470mf caps in the DC power supply has a bulging top and suggested that it be replaced as well. Attached pic shows petals of aluminum beginning to separate.

I loved the signature sound the Moreplay gave to each of my two sound systems and can't wait to hear it back in operation. Please advise, I think I need a new transformer and a new cap.

 

[Paul Birkeland]

Can you provide more pictures of your build, especially around the area where the caps are?

It's most likely that the issue that has initiated the failure of that capacitor is what took out the power transformer. This could be something like a poorly soldered or missing 270K resistor on that terminal strip, a backwards diode, or very loose solder joint in there.

You can also burn up a power transformer if the wiring for the heater supply (the shielded twisted pair wires) gets shorted out between the power transformer and one of the tube sockets.

It's super important to remedy whatever issue you have in the underlying build before fitting a new power transformer, as it's likely that whatever fault is present will burn up as many power transformers as you can fit into the preamp.

-PB

 

[taubear]

Can you provide more pictures of your build, especially around the area where the caps are?

It's most likely that the issue that has initiated the failure of that capacitor is what took out the power transformer. This could be something like a poorly soldered or missing 270K resistor on that terminal strip, a backwards diode, or very loose solder joint in there.

You can also burn up a power transformer if the wiring for the heater supply (the shielded twisted pair wires) gets shorted out between the power transformer and one of the tube sockets.

It's super important to remedy whatever issue you have in the underlying build before fitting a new power transformer, as it's likely that whatever fault is present will burn up as many power transformers as you can fit into the preamp.

-PB

thanks much Paul for the wise guidance, I will look carefully at the shielded twisted pair feeding the tube sockets and the other things you mentioned and also shoot and post pics so we can look for mistakes. Appreciate the guidance as I am a beginner learning about audio tube circuits

 

[taubear]

Looks like the bulging cap had a cold joint so I removed it from the circuit and shot pics, let me know if I missed anything critical that you need or want to see, (note that in addition to one cap removed that outputs from the transformer are also unsoldered) thanks

 

[Paul Birkeland]

Your power transformer primary winding is an invalid configuration and would probably be enough to roast the power transformer.

Is the jumper present between 29 and 30?

 

[taubear]

yes the jumper runs between 29 & 30 strung across the back of the terminals and soldered in front. I will also go back step by step and check the primary wiring of the transformer and see where it went off a cliff. A friend tossed me a new pair of filter caps to sub in for the suspect cold joint ones.