Opinions on Power Supply HT Ripple Current

[techbiker]

I've been diagnosing an annoying hum that I am hearing from my vacuum tube headphone amplifier. I'm working with Mr. Thompson-Bell on the problem, however I'm wondering if anyone would be willing to take a look at this oscilloscope video to see if there is anything wrong with this ripple current. It definitely

The power supply that I am using is Mr. Thompson-Bell's Poor Man's Tube Amplifier power supply. I checked and verified that all of the diodes and blocking resistors are within spec. This supply uses 4 470uf, 400v smoothing capacitors and a couple capacitors that I believe are designed to reduce the noise from the diodes.

Is it normal to see this kind of ripple current from a regulator-less power supply? Do you see anything that could be wrong?

By the way, in this video I am switching between 2 and 5 mV on the Ampl/DIV dial on my scope.

Vacuum Tube Amplifier HT 1x Probe - YouTube

Thanks!

P.S. Happy New Years!

[sawreyrw]

How can we give you any feedback without seeing a schematic?

[techbiker]

I'm sorry about the delay. I wanted to get permission to post the schematics.

After talking with the designer, he mentioned that it appears that I am getting 60hz hum on the HT line.

Here is the power pcb schematic (the tube gain make-up stage):



Amplifier PCB Schematic 1:



Amplifier Schematic PCB 2:

[Nikon1975]

Is that the ripple on the HT or on the output ? Ripple on the output could come from the heaters, as you are using AC for them.

D.

[techbiker]

Nikon,

I ran this test on the HT line, however I am getting some weird readings on the outputs even when the HT is disconnected. I wonder if the power from the heaters is leaking into the outputs somehow.

Thanks

[gorgon53]

I hope that by now your problem is solved. It looks to me that you see on HT with the scope looks like second and fourth harmonic plus some noise, at only a few mVpp it should be ok. This is only speculation because you have not given any values of amplitude or timescale settings.

The "weird" signal on the output, is it taken between the output and ground? If so, then it is garbage picked up and will go away if you ground one side of the OPT secundary.

Try to find out if the "hum" you are hearing is from the PS-transformer coupling into
your amps electronics or even directly into your OPT. Change the locations of the transformer(s) and listen if that makes any change.

[dtproff]

The hum could also be the heater supply.

Tony

[techbiker]

Gorgon and dtproff, thanks for the replies. I apologize but I actually figured out what the problem was already. It turns out that I hadn't taken enough care when running the heater lines. They were interfering with the HT supply. Once I carefully routed the heater lines along the outside of the chassis and away from the HT supply, the noise was nearly eliminated.

Dtproff, I live in Plano as well! It's a small world.

[dtproff]

Techbiker;

I have a CCS Heater supply I have been wanting to try out on someone. If you are interested, let me know.

Tony

[techbiker]

Tony,

I'd be very interested in testing out your CCS heater supply. The only thing is that while I built this amplifier for my brother as a Christmas gift back in Plano, I had to head back to Georgia for college. If you could wait until March when I return for break, I might be able to help you out then.

Dallas