humming overdrive

[ChrisM]

Not all chassis grounding points are created equal.

[bcook]

Can you sketch out your relay wiring? Maybe I'M missing something.

[llemtt]

deriving relay supply from filaments it's source of noise problems... you better should try to avoid it

anyway you have at least to ground (chassis) reference the resulting dc supply, you can try with two 100ohm resistors from dc- to ground and from dc+ to ground

teo

[phsyconoodler]

I'm going to get a filament transformer today and bypass all these issues.
this is the diagram I used to make my relay supply.It works but is noisy.

[ChrisM]

You shouldn't be using a bridge recto if your heater winding has a CT. You should use a full wave recto, just two diodes.

Also have you tried feeding the relays with a regulated supply voltage? A LM78xx would do.

[phsyconoodler]

The filaments don't have a center tap.I was told by one friend that a regulator will lower ripple by 500 %.
If that's true,maybe just a regulator will fix this??

[guitardude57]

If you built this according to the drawing....no wonder you have hum. Ground loop issues..............

As suggested above, just use 2 diode bridge, and regulator.
The regulator will ground, and the filters will ground. Nothing else.

I personally would use a 3-0-3 or 6-0-6 tranny/filter/reg for the supply. The trannies are 5 bucks at the shack. 2 bucks for the reg.

[phsyconoodler]

Ok,so if I just ditch the bridge,it should be fine?The filters ground leave alone?
I could easily do that.It's starting to make sense now.I should end up with 4.66v at the relays or thereabouts.That should do the job.
One question from a solid-state illiterate person;
Will the use of a regulator in this circuit keep the voltage from dipping too low as well as too high?

[ChrisM]

Ok,so if I just ditch the bridge,it should be fine?The filters ground leave alone?
I could easily do that.It's starting to make sense now.I should end up with 4.66v at the relays or thereabouts.That should do the job.
One question from a solid-state illiterate person;
Will the use of a regulator in this circuit keep the voltage from dipping too low as well as too high?

Ground the filter caps and regulator at the same point. Use a CT xformer and use two diodes to make a full wave recto.

The regulator will keep the voltage at a constant level. This thing is going to be quiet. Just make sure the voltage you put into the regulator is about 3V higher than the output voltage. So for a 5V regulator/relay you want to put in 8V DC, this means you want an AC voltage of 8/1.414 = 5.66V AC, so use a filament 6.3v AC transformer.

Also for the current your going to be drawing your filter caps are way oversized. I'd use 470mF before the regulator and maybe 100mF/47nF after.

[phsyconoodler]

Thanks!
So I have access to a 5 v center tapped transformer.That should give about 7.1 rectified DC volts.Will that be sufficient?
What about filtering?PI filter with 1000uf caps?
Why filter before and after the regulator?

[ChrisM]

Thanks!
So I have access to a 5 v center tapped transformer.That should give about 7.1 rectified DC volts.Will that be sufficient?
What about filtering?PI filter with 1000uf caps?
Why filter before and after the regulator?

That transformer should work fine. You'll probably get more than 7.1 with the high line voltage everyone seems to have these days.

Read my last post. 1000mF is way overkill. The general rule for filtering is 1000mF for every 1A, your going to be drawing 100mA max.

Every application schematic for regulator shows pre and post filtering.

[phsyconoodler]

Thanks a bunch ChrisM,
You are a lifesaver!

[BobW]

A voltage doubler derived from the filaments w/ a floating ground will also work and is a quiet circuit. The relay coils don't need a regulated voltage, just a sufficient amount over the data sheets minimum Vp (pickup voltage) parameter.

[phsyconoodler]

Ok,I'm all ears about a floating ground.

[phsyconoodler]

I just installed the 5-0-5v transformer and it works perfectly.No hum,no switching problems and the LED's work perfectly too.No pops,no nothing.
I used a 470uf cap,that's it.
Thanks guys for the suggestions!