C-lator hum

[martin manning]

Perhaps the PT is leaking a lot of magnetic flux, and the enclosure is creating a path for induced current to flow when the cover is on? Did you try powering the C-lator with only the PT primary connected, in the same configuration that we have been discussing (only C-lator output cable plugged into the amp)? I'm starting to think the problem is the transformer itself.

[ynor]

Perhaps the PT is leaking a lot of magnetic flux, and the enclosure is creating a path for induced current to flow? Did you try powering the C-lator with only the PT primary connected, in the same configuration that we have been discussing (only C-lator output cable plugged into the amp)? I'm starting to think the problem is the transformer itself.

No I haven't come to that yet. But will try tomorrow.

Maybe there's dual problems: PT leaking magnetic flux, and something weird about grounding? But yes, I still suspect the PT. Their previously layout had the PT outside the chassis, and have not heard of problems with those.

[martin manning]

There is no reason that the PT can't be inside the chassis, recall mine and others have been built that way with no issues.

How much height do you have inside the chassis? Let's see if there is a replacement PT that would fit.

[ynor]

There is no reason that the PT can't be inside the chassis, recall mine and others have been built that way with no issues.

How much height do you have inside the chassis? Let's see if there is a replacement PT that would fit.

40 mm height inside the chassis. The PT has 41 mm height though, so it should actually bend the lid.

If this PT design has excessive magnetic flux that is converted to current inside a closed chassis, maybe that was not a problem before when this PT design was mounted outside?

I could disconnect the secondaries. Then extend the leads, put the PT outside the chassis, lift the ground and see what happens in each step.

[bepone]

Will try your suggestions.

I see that the 2x 100 Ohm resistors are indeed grounded to the first filter cap, as you stated! Should I try grounding to signal ground instead?

ofcourse

[bepone]

And another mystery:

While not connected to anything, the PT of the C-lator vibrates and hums when the lid is on. I can feel the vibrations when touching the chassis. But when I remove the top lid, the PT is completely quiet, as in no vibrations. Why is that?? Putting the lid on makes everything worse: the vibrations appear, and the hum is increased in the amp.

aha mechanical vibratios also are causing humm.. i forget that before but also can be in your case! mechanical vibrations are shaking sensitive grids of input tube and making small voltage, like microphone, and you have permanent hum inserted via signal with vibrating!

ok remove power transformer out from the chassis with long wires to cure that and probably if is gone, you cannot use this PT anymore.. there is a solution but after we will see.

[bepone]

I have measured VAC on all caps while powered on: 0.0 V. If there is mV > 0.00 (by that I mean more than one decimal), my meters probably can't read it.

will be good to have mVAC reading to see the ripple...

[ynor]

I have measured VAC on all caps while powered on: 0.0 V. If there is mV > 0.00 (by that I mean more than one decimal), my meters probably can't read it.

will be good to have mVAC reading to see the ripple...

Yes, I'm waiting for my new meter (with oscilloscope) to arrive

[bepone]

5.6 VAC for the heater is too low this is starving filament, and is not good for the tube.. this PT has several primary taps? need to change tap...

[bepone]

Yes, I'm waiting for my new meter (with oscilloscope) to arrive

ok no problem we have a lot of time

[ynor]

5.6 VAC for the heater is too low this is starving filament, and is not good for the tube.. this PT has several primary taps? need to change tap...

No it doesn't not have several primaries, unfortunately.

[ynor]

aha mechanical vibratios also are causing humm.. i forget that before but also can be in your case! mechanical vibrations are shaking sensitive grids of input tube and making small voltage, like microphone, and you have permanent hum inserted via signal with vibrating!

Weird thing is, when lid is off it does not vibrate at all. Put the lid on, and the whole chassis starts to vibrate and also sounds like an electrical buzz, from the chassis and PT without connection to the amp.

[GAStan]

What are the chassis and lid made of? Are they both the same material?

[Richard1001]

The chassis and lid are made of steel. This could explain vibrations. Especially when it lays lose on top of the chassis.

The transformer in the enclosure was probably not the best idea Nik had. I dont understand it either because it looks like the exact same PT, except the bell cover.

[timrobertson100]

Another discovery!!!

When the C-lator is on, there is hum while on both standby or off standby.

When the C-lator is off, the hum is much less.

But when I then remove the C-lators AC mains connected to the wall outlet, there is NO HUM!

Can I just check: Are you saying here that having the device main power switch set to off (I.e. primary PT loop is broken) you *still* get a hum, albeit lesser, that only stops when the IEC cord is removed?

Can you please retest that, ensuring that the caps are discharged?