Troubleshooting an humming WOPL : need help!

[Coldsmoke]

Hi there,

I couldn’t come back sooner here, being on a professional trip for the rest of the week… So I moved my request from my presentation to here...
Summary of my problem : I recently bought a WOPL 400 that was sounding cristal clear at the salers place and I can now ear a 50hz noise through the speakers (from any source selected on the p-amp).....
Just a quick summary of your various propositions concerning my humming issue… :
"Flip the plug ? ": checked, no difference
"First does it hum with NOTHING plugged into the input RCA Jacks?" : yes it does
« If it is not external, I wonder what the power wire routing looks like inside. If its 50hz, it sounds like an AC mains wire is too close to an audio signal wire. If it was 100 hz, thats a sign of bad power supply capacitors. » : I put here down a couple of pictures… I didn’t see anything obvious…
« tighten the bolts that hold the transformer to the châssis » : checked, no différence
« power cable - the original wiring was two pronged and it is important to plug this in correctly. If you have a three pronged plug the earth ground should not be connected to the chassis. » : I think my cable is original, two pronged at least…
« is it a hum through the speakers ? » : Yes it is
I think I am stuck now with this issue… I seriously don’t understand what can have changed between the moment I listened to i tat salers place and my home….
Hope you have an idea,

Florian

 

[Northwinds]

If your preamp is also two prong, flip it. Carver amps do the same thing if a component it's linked with has polarity reversed on the plug

 

[Coldsmoke]

It is actually powered through a PL 2000, I tried all 4 combinations, but the hum remains... I also tried an adaptator plug (directly plugged to the main) both positions hum....

 

[Northwinds]

There is far more knowledgeable Bro's here then me who can get this figured out. Give them a bit and they will have you fixed up

Do you by chance have a power conditioner to try?

 

[Coldsmoke]

Unfortunatly not... And I am actually trying to figure what could be wrong with my amp before trying any external solution :/

 

[kevin]

Do you have any type of TV cable near this amp ?

 

[orange]

That would imply you have a TV or digital video etc. with noisy power supplies and spurious, but legally permitted, emissions.

 

[Coldsmoke]

Do you have any type of TV cable near this amp ?

Nope the TV set is in the other corner of the room

 

[orange]

Whatever is legally permitted in Belgium, which may be different in Hornu than Brussels...

Or as my lady friend the high school exchange student kept calling it, HORNY BELGIUM...it was 1982.

 

[orange]

Bet she was fun with the Flemish...she became a lawyer here after graduation.

 

[Coldsmoke]

I don t know about 82 I was only one year old, but I think you could still call it horny belgium

 

[FredR]

Try cutting the ground wire between the bottom most speaker post and the copper ground plate that the RCA jacks attach to. Confirm that the copper plate has the insulator under it to keep it from making contact with the chassis.

SAFETY ISSUE: The power supply capacitors stay charged for several minutes after unplugging the amp. Do not touch them when charged!

 

[Coldsmoke]

Try cutting the ground wire between the bottom most speaker post and the copper ground plate that the RCA jacks attach to. Confirm that the copper plate has the insulator under it to keep it from making contact with the chassis.

SAFETY ISSUE: The power supply capacitors stay charged for several minutes after unplugging the amp. Do not touch them when charged!

What you say is very interesting, I remember having read somewhere that this copper bus was supposed to be insulated from the chassis. I can confirm you that the negative of the speakers is at the same potential as the negative of the cinches and as the chassis. Do we have something here?

 

[FredR]

What you say is very interesting, I remember having read somewhere that this copper bus was supposed to be insulated from the chassis. I can confirm you that the negative of the speakers is at the same potential as the negative of the cinches and as the chassis. Do we have something here?

The floating ground should touch the chassis in only one place. If you search on the board you'll find a lot of stuff about star point ground that gives detail on this issue. Also, should avoid loops with a star point ground. The connection between the RCA ground and speaker post ground is such a loop. We always get rid of it when doing a WOPL conversion. Ground problems are often the source of hum.

 

[Coldsmoke]

So you think that I could try to cut this wire and put somme kind of insulation under the cinches? Is it safe? I think I will take advantage of doing this to replace the rca inputs

 

[FredR]

So you think that I could try to cut this wire and put somme kind of insulation under the cinches? Is it safe? I think I will take advantage of doing this to replace the rca inputs

Just cut the ground wire between the lowermost speaker post and the copper plate the RCA jacks are on. It's perfectly safe to do that. See if it fixes it. If not I'd wait till Gepetto gets on the board. He designed the WOPL and is on daily.

 

[laatsch55]

There should be no grounding between the negative speaker posts and the RCA input ground copper ground plane. If it is stock PL inputs there are insulators under the copper plate. The only reason you were measuring the same is because the ground plane was grounded through the negative speaker posts and then the star ground point. Cut that wire as Fred has suggested, the rca's are now grounded through the #5 solder pad on the WO board. Also make sure the shield of the input wires IS NOT TIED TO GROUND ON THE WO BOARD AT #2 solder pad, just the input wire gtound there...

 

[Coldsmoke]

I dis what you proposed and I just faced a very strong and weird noise through my speakers...! Hope I haven t blown anything :s

 

[laatsch55]

Is the pre amp on and interconnected to the RCA inputs??

 

[Coldsmoke]

It is