Jim I really Need Your Help w/ My Cornet

Doc Jr 8156 · « **on:** 16 Nov 2003, 06:12 am »

Jim,

I read the explanation you provided with GRD's grounding question. I too did the same as well as accompany each signal wire with a ground wire connected to the board. I also tried isolating the RCA jacks. I relocated my RCA per your layout since at first I move them to the side of the transformer. In short I did lots of things to eliminate the hum. I followed your instruction on the assembly point by point. I tried co-ax wires. I tried moving the transformer away from the whole chassis in separate box. I don't know what else to do. I still have a humming Cornet. Is it inherent to this phono pre to have a hum? How come I followed each and every suggestion provided to me by GRD, Mike G, and all other tips and still my Cornet is humming? I'm wondering whether if the time will come that my Cornet be hum-free. I'm open to anything and anyones suggestion. I'm desparate. I like to enjoy my Cornet. Thanks and please forgive my rant.

Marbles · « **Reply #1 on:** 16 Nov 2003, 02:27 pm »

Quote from: Doc Jr 8156

Is it inherent to this phono pre to have a hum? ...

Mine is dead quiet....black like a moonless night. Good luck.

hagtech · « **Reply #2 on:** 17 Nov 2003, 05:44 am »

Doc,

Did you have a phono stage in your system previously that did not hum?

jh

theint · « **Reply #3 on:** 17 Nov 2003, 05:45 am »

Are you sure your power supply is working properly?

Doc Jr 8156 · « **Reply #4 on:** 17 Nov 2003, 04:39 pm »

Hello,

Jim, yes I had a phono pre (Monolithic Phono w/ power supply upgrade) that never hummed before. I still have it. To answer theint's query, I emailed Jim personally to discuss what I discovered regarding the power supply of my Cornet. I literally checked every parts, connections and layout and started all over again. Finally, I discovered that the caps on C2, C4, and C10, which were specified in the manual as 47uF/450v, have the wrong values. Mouser sent me 4.7uF/450v instead. Its my fault also because I should have check each packet (parts) before installing them. Maybe I misread the label on the caps as 47uF and missed the "." Anyway, I ordered the correct values and hopefully this will be it. Happy listening!

theint · « **Reply #5 on:** 18 Nov 2003, 12:57 am »

Ten times the capacitance is a good thing. Good luck.

GRD · « **Reply #6 on:** 19 Nov 2003, 04:22 am »

Sounds like the solution. Let us know how it turns out. We'll have a toast in my household once we hear.

All the best,

GRD

(My wife has first hand experience at this)