Help please with a humming Cornet II

chriss · « **on:** 8 Jun 2006, 02:57 pm »

Hi All,
My friend and I recently completed a Cornet II. Thing is there is a hum that we can not seem to get rid of. I thought perhaps that folks here might be able to help.

Here are the details…At first, all it would take to make it hum was to attach a set of IC’s to the input. Regardless of what, if any thing , was attached to the other end. When my TT is attached nothing effects the hum. It does not matter if the ground from the table is connected or not.

Next we replaced the input wire from the RCA’s to the board with shielded cable. This seemed to help as it no longer hummed when there were a set of IC’s connected. But when the TT was connected to the pre it would hum. Again, it does not matter if the ground wire from the table is connected or not. You can attach and remove it with no change in the hum whatsoever.
I have tried three cables, shielded IC’s and two different amps. This table has been used with at least 6 different pres with no noise at all. And I am listening right now to it through my Creek integrated and it sounds fine. I really do like the sound of the Cornet but right now it is un-listenable and I admit to being a little discouraged.
Any help would be appreciated..
Thanks
chris

Yoda · « **Reply #1 on:** 9 Jun 2006, 06:43 pm »

What is the proximity of your tt to the pre, amp or to any transformers or motors? (or 120vac in the wall?)
Have you double checked all solder joints, PS connections to board?
Maybe the TT wiring is faulty (aged) or should be shielded.
Type / gain of cartridge?
Have you tried another TT with the cornet?
Faulty tube?

BobM · « **Reply #2 on:** 9 Jun 2006, 08:03 pm »

Which transformer is on your unit? Have you measured the incoming voltage from your AC plug?

I also have a humming Coronet with the smaller 270BX transformer. My mains voltage goes to about 122-124 volts regularly. Jim thinks that's what's causing my hum - yes, it is definitely the transformer. I used a stethescope and that's the culprit.

He recommended stepping down the voltage with a resistor change (I forgot where and which one though). Or upgrading to the 370BX transformer.

I haven't had a chance to do this yet, but I plan to this summer (if Jim responds and tells me which resistor and value again - sorry).

Enjoy,
Bob

hagtech · « **Reply #3 on:** 9 Jun 2006, 09:58 pm »

Chriss, I'm still thinking it might be the anodize on the chassis. Have you made sure that all pieces are connected well to the earth ground?

jh

chriss · « **Reply #4 on:** 10 Jun 2006, 01:26 am »

Hi jim and everyone,
I will try the chasis stuff next.I did get it to stop when just one channel was connected.Odd huh?
As far as others help heres my answers......

"Which transformer is on your unit? Have you measured the incoming voltage from your AC plug? "

I have the 370 and I don't know that is been measured

"Have you double checked all solder joints, PS connections to board?
Maybe the TT wiring is faulty (aged) or should be shielded.
Type / gain of cartridge? "
Yes , Yes and I have tried three diffrent cables and the arm, AQPT9 is not that old cart is Benz Glider HO 2.6mv outout

Thanks for all the suggestions
chris

G Georgopoulos · « **Reply #5 on:** 10 Jun 2006, 01:54 am »

First of all your amp needs a nice service
second hum is an easy thing to fix it is mainly due to an amp problem

cheers

chriss · « **Reply #6 on:** 10 Jun 2006, 02:23 am »

Thanks for the reply but...well..I don't quite get your point.
My amp is near new and may not be the best it is at least competent.
Perhaps you missed my statment that this occured with 2 diffrent amps. One the Bluenote Steroid one Signiture and the other a Creek5350 classic.

Perhaps you could me more specific when you say "the amp needs service" any diagnosis you could provide would be welcome.

G Georgopoulos · « **Reply #7 on:** 10 Jun 2006, 02:37 am »

Perhaps you missed my statment that this occured with 2 diffrent amps. One the Bluenote Steroid one Signiture and the other a Creek5350 classic.

-------------------------------------------
then whats the problem? check for bad interconnects, maybe youre
mistaking buzz for hum

cheers

Gooch · « **Reply #8 on:** 10 Jun 2006, 09:14 pm »

Quote from: G Georgopoulos

Perhaps you missed my statment that this occured with 2 diffrent amps. One the Bluenote Steroid one Signiture and the other a Creek5350 classic.

-------------------------------------------
then whats the problem? check for bad interconnects, maybe youre
mistaking buzz for hum

cheers

G Georgopoulos
I have heard the the pre it's a HUM not a buzz. I had it hooked to my system and it humedso the pre has been hooked up to three diffrent amp

Regards,
Dave

hagtech · « **Reply #9 on:** 10 Jun 2006, 10:46 pm »

As a last resort, you can always send it in to the shop.

jh