[wianieq]

Hi everyone.

I completed my Cornet2 build last night and thing seemed allright for a while.  I made a wooden skirt for the sides and had the 12x8 Hammond top plate and a metal back plate.  At first I had some pretty overwhelming hum but after a bit it struck me that the top plate wasn't connected to the back and therefore the transformers weren't grounded.  I connected a test clip between the two and it was instanly silent. 

NOw though, I have a bad static type sound in one channel.  It increases with the volume and makes it unlistenable as its as loud as the music.  I swapped out tubes, I only have one 12au7 but I put a 12ax7 in that spot and the noise remained.  Different tubes in the other spots didn't change anything either.  I checked all the voltages and they all are just a little low.  Within 10% though.  My heater voltage is at 5.69v and I have read about adjusting the resistor for that and I will do that.

I really need some help trying to track down that static-y noise.  It sounds like a dirty pot when you turn it only it is constant and crackling and loud.  If I was working on one of my solid state pieces I would be thinking caps or transistors.  Would the transistors be a problem like that being where they are?

Any inputs or suggestions would be greatly appreciated.

[hagtech]

It would be a bad connection somewhere.  Broken solder joint or loose connector.  Could even be your interconnect.  Try swapping channels.

jh

[wianieq]

Well I don't know what I did, but I got it to work.  I basically unhooked everything so that I had access to the bare pcb.  I swapped out the final coupling capacitors with Auricaps and reflowed all the solder joints.  One of the crimp jointed terminals slipped out and I had to recrimp it.  Would that likely have been it?  I checked those multiple times and they seemed okay.  I even tugged on them to make sure and they felt secure.  But one of them did slip off.  That is the one area I did not feel comfortable with.  I first tried my combo stripper crimper tool and that turned out to be inadequate.  I ended up buying two more different tools, one was solely a crimper.  No matter what, that part never went gracefully.  Is there a specific recommended tool for this?

I did get to spend a couple hours listening to it finally.  I love it.  Down the road I'm going to rebuild a chassis since my top plate looks a little gnarly.  I was going to go with the Lansing chassis, but now this thing is dead silent so I may just go with a new top plate and wooden skirt.

And thank you for your prompt reply.

[wianieq]

Hi everyone.

Well, up until the last couple of weeks my Cornet has been working great. 

Then the same symptoms appeared with the crackling noise, except this time it came on fast and then the channel died completely.  No crackling or anything.  One thing from my previous problems that I had noticed was that one of the 47uf 450v capacitors was leaking something.  The caps I used had narrower leads than whats on the board and I think I may have damaged them by bending them too much, causing the cap at c207r to leak.  I put in some new Nichicon pw caps and the leads matched and thought I was good to go.  With all my screwing around soldering and desoldering I lifted the trace for the positive terminal hole on c207r.  I jumpered two components connected to it and it worked like a champ.  So from around March until now it has worked great. 

A couple of weeks ago the problem came back and the channel stopped working completely.  I replaced the cap at 207r again but that didn't work so I replaced the transistor and components around it and that did it.  I listened to it for a night then the next day I started it up and there was the crackling and then completely dead after a few minutes.  I reflowed all the solder joints and replaced c207 again and tightened up my jumpering job and the same thing happened, it worked for the rest of the evening and the next day it all started again right after I turned it on.

So it appears I have only been treating a symptom and the cause is elsewhere.  One area that is still a little janky is the crimp terminals.  I didn't think that a problem there would only affect one channel.  I have planned on soldering the wires to the terminals, but wanted to get everything else straightened out first. 

I guess I 'm just looking for any ideas on what it might be or what I should try next.  I have had to go back to using my Bugle, and while that isn't too bad, it is no match for the Cornet and I miss it.  

Thanks for any input.

[wianieq]

Thought I'd add that my next plan of attack unless I hear otherwise was to desolder everything on the right side and reinstall all new components and directlty solder the transformer wire to the terminals.  I'm hoping to avoid that because I really don't enjoy the desoldering part as I'm sure no one does.

[poty]

It is really tough question...
I've not completely understood what you have done in each case, but... It seems that the problem is in the 6.3V rectifier circuits. Check all the diodes (D101-D104), and the capacitors in the circuit (C106, C209-211). Maybe C205 also.
It may be the 12AU7 tube also. Try to swap it.