Tube power supplies

[4krow]

When considering a tube power supply, I thought everything was great as long as you have adequate voltage and amperage. With this idea in mind,  I replaced a power supply for a Musical Fidelity X10 V3 unit. Next thing I know the unit is pissed at me and blows the output transistors(it is a hybred unit). Then, no voltage on the rails. But the strange thing was, after I replaced the abused transistors, voltage was back. Of course, I don't have a schematic so shootin in the dark is the norm here. And when I measure the power supply disconnected from the circuit, it reads 14V (it is center tapped, and both sides read good). As a parting note, I will admit that there could easily be something amiss else where, since I replace almost every component in this unit, thinking it would be golden afterward.

 

[Grainger49]

Greg,

With most power supplies, if you don't draw much current the voltage floats high.  Did you measure the voltage you ended up with? 

 

[4krow]

Didn't get a chance yet. The first time around, it was over before I knew what. I did try the original power supply, and things seemed ok. So that is why I wondered about this.

 

[mrarroyo]

Is your new PSU 12-0-12Volts AC 30VA (24VCT)?

 

[Grainger49]

I'm with MrArroyo,

Knowing what the end point is, is important.  Do you know what open circuit voltage the power supply puts out? 

 

[4krow]

As I mentioned in post #1, the open circuit voltage is 14-0-14V. The circuit requires only 500ma, and off hand I don't recall the specs of the torrid that I used. But I will say that it was much heavier than the original transformer.

 

[Grainger49]

You can use a pair of three pin regulators to hold the output to 14-0-14V.  As long as the circuit doesn't draw more than specified current, and the regulators can handle a half an amp, you should be in high cotton.

 

[4krow]

So, could an MJE350 do that, cuz' I think that is what is in the circuit presently. I will check this stuff out before posting further. This poor unit actually worked when I got it, but I don't know how! It had burn marks on the circuit board where the output transistors were, and the RCA jacks were hit and miss for contact. oh boy..

 

[Grainger49]

The MJE 350 is not what I had in mind.  A variable regulator is like the LMJ 085 used in the Eros as a variable positive voltage regulator. 

As Desert Pete said, "Have faith my friend,"  I'm not going to say that there is water down below.