Meridian Unplugged - Powered by MrTechGuy.co.uk Forums Discussion Meridian - Systems G68 loud humm from right TRC output

Hello all,

Yesterday I connected a pair of active speakers to the main L/R analog outputs of an G68ADV, and I get a lot of humm (ground loop like) noise from the right speaker

Tested the speakers on another pre amp and they work fine, so the problem is coming from the right analog main out.

I tried to retype ( to type 2 ) and leaving the machine off the grid for the night - but still hum ( even as the machine is completely disconnected )

anyone an idea what could cause this ?


AND if the output socket is broken can I use the Rz out as an replacement ?

I played around with mconf yesterday but I can't figure out how to configure Rz as main...

Thanks

Hi,

Have you checked the other analogue outputs? If any of the rest of them buzz, then I suspect you may have a faulty card...

It is more likely a cabling or socket issue.

I would try different cables to see if that makes a difference.

Good luck,

Steve

thanks steve,
Yes I checked the other analogue outputs and the all work fine.

I also tried different cables but the same hum/noise with all of them

Have you tried it with everything disconnected except the connection between g68 and loudspeakers?

yes tried that


there's also noise when the G68 is not connected to the mains

what me makes think that the connector is broken a makes a fals contact

thats possible. You can also change left and right speaker. If the hum stays at the same channel then i would check the solderjoints of the cinch connector on the circuit board of the g68

I think i'll try to open the machine to have a look

are there any precausions to take or can i just scew off the back plate and tear the card out - of course with the mais disconnected

Hi Andy,

Be careful when opening the G68.

You'll need to go in through the top to allow removal of the cards.

Undo the four bolts on the top outer plate, then remove the inner plate with the glass top (another dozen screws!)

Remove all the screws on the last backplate (note the position of each screw/bolt - they are different!)

Some units have metal rods that keep the cards as a stack - these will need to be removed from the top.
Some units have clips that keep the FICL and DSP cards (hidden in the middle of the end stack) in place.

You will probably find, on removing the cards, that the edge connectors have oxidised - they will need cleaning, along with the connectors on the backplane - grab a can of deoxit...

Check for dry joints around the faulty phono socket - sounds like the ground is not making good contact - check with a multimeter (if you have one)

Good luck,

Steve

hi Steve, thanks for your detailed message !

Although i like to play around opening up machines i'm not really technical so please forgive me asking stupid questions

Do i need something like a grouding braclet while doing this ?

Ideally yes - although if you ground yourself and the unit before working on it, it should be fine.

Just regularity keep touching the case metalwork so you remain at the same potential.

Cheers,

Steve

I opened the G68 and striped out the Analog card and measured the RCA soldering - they seem to be ok, but probably the problem lies here

I took the card to a local electronics guy, he gonna replace the capacitors.

That's not looking good!

Hopefully, replacing the faulty capacitors should resolve your problem.

Make sure the tech checks the others around the failed ones - they can still look OK but test bad.

Good luck,

Steve