Ground loop issues in D-lator

[martin manning]

I am very puzzled. It's odd to me that I get the hum when the D-lator is plugged in, but not turned on.

I assume that the signal cables are all plugged in for this? And then if you lift the earth ground on the D'lator the hum stops?

[Mark]

How loud is the hum?

I was expecting ground loop hum when I built a Dlator, but it was much quieter than I expected.

Have you experimented with the various inputs and outputs to see if the hum is specific to a certain part of the Dlator?

By this I mean input to the follower and output to the amp via the send jack.

[jlatrace]

Yes that is the case. Also, it stops if I unplug the return cable running from the D-lator to the pwr amp in. Both are true whether the D-lator is tpwered on or not. The D-lator only needs to be plugged into an outlet.

Also I have tried switch outlets, using an isolated pwer supply, etc without sucess. The only sucess I have had is lifting the earth ground on the D-lator.

I am going to try isolating the signal ground causing the issue tonight. Other than de-soldering each one by one, do you have any trouble shooting suggestions?

[jlatrace]

How loud is the hum?

I was expecting ground loop hum when I built a Dlator, but it was much quieter than I expected.

Have you experimented with the various inputs and outputs to see if the hum is specific to a certain part of the Dlator?

By this I mean input to the follower and output to the amp via the send jack.

Yes I have experimented and find the hum to be present in the return through the output section of the D-lator. Maybe I should relocate the cliff jack grounds for thi section of the signal path? Or maybe just the Output jack ground?

[jlatrace]

I also removed the bypass switch shown in the pictures to make sure it wasn't the problem.

[tubedogsmith]

check your continuity on all your grounds and shielded cables if you haven't already.

[wjdunham]

Did you make sure to grind off all the paint/power coat where all your pots, jacks, switches and ground lugs contact the chassis? From looking through your photos it's hard to tell, but I would have expected to see more evidence of the paint being ground away especially around the ground lugs. If so, then disregard, but I've seen a lot of ground issues caused by marginal contacts where the chassis finish was preventing good electrical contact.
Bill

[jlatrace]

Thanks Bill. Yes I did grind the star ground points to make sure there is agood contact.

[erwin_ve]

Did you ground the back of your pots to the buss bar?

[jlatrace]

I did not, but I will tonight. I hope this is the magic bullet.

[jlatrace]

Do you have a diagram of a "Yin-yang diode breaker"?

Here's the relevant picture from that site, though he may not call it "yin-yang". (The name comes from the anti-parallel wiring of the diodes.)

Mark,
I'm having trouble visualizing how to fit the "yin-tang diode breaker into the grounding scheme of the D-lator. For example, my gut is that I need to tie the power board grounds and not the signal grounds to the diode, is that correct? Or do I tie all grounds to one star connected to the DC side of the diode with the earth ground to teh AC side?

Do you have any pics of your install?
Les

[Structo]

It's probably something simple and you will kick yourself when you find it.

So you took the bypass switch off, right?
That was going to be my next suggestion, triple check the way that is wired.

Do you have a wire connecting the two star grounds?

Here is what mine looked like shortly after I built it.
Notice I did not twist the heater wires, I built it just like HAD.
It was pretty quiet.

Later I did twist the heaters.

I think most likely it is your jack wiring that is the problem.

[Structo]

Have you checked out how Nik wires his Cliff jacks?

And how Brandon wires his?

[glasman]

Here is a trick I have used when I have had a similar issue.

Try connecting the plate of the cathode follower through a .01uf disk ceramic to ground. Use short leads.

Also if you are using Cliff jacks, separate out the stages (CF and Recovery) ground wires on the jacks and return them to the same location in the chassis, return the CF and Recovery amps on separate ground wires. (if you have already done this cool).

Gary

[jlatrace]

It's probably something simple and you will kick yourself when you find it.

So you took the bypass switch off, right?
That was going to be my next suggestion, triple check the way that is wired.

Do you have a wire connecting the two star grounds?

Here is what mine looked like shortly after I built it.
Notice I did not twist the heater wires, I built it just like HAD.
It was pretty quiet.

Later I did twist the heaters.

I think most likely it is your jack wiring that is the problem.

Thanks,
Did you run a ground from the signal pwer filters to the signal star ground? I followed Nik's layout. He runs aground wire from the filters to the star ground in the signal section (not teh power section). Maybe this si the issue, but I think not.