C+ help please (what's that sound?)

[Mr. Blues]

My C+ is making distorted noise during the first 3-5 minutes after warm up period. The sound is only when I play a note, not when at idle.
After a few more minutes of playing the noise is gone and everything is beautiful for the rest of the gig. Then the next night the same behavior repeats itself. What's going on? What to check, look for etc.??? All connections appear clean and tight, everything works flawlessly, except for this start up glitch that has me concerned. Thanks for all replies.

 

[lesterpaul]

oooh..sounds bad...I will buy it from you :lol:c..mmmmon...pleeeeaaaasse??

 

[Mr. Blues]

NOT!!!
It's bad to duh bone with my Hamer Special.
It LOVES P-90s.
Absolutely KILLS other amps. I've gone against BF Super Reverbs,
Marshalls, Vox, and all agree this one boogies!
Don't know what I'd do if it crapped out. ACKK!

Meanwhile... what do think is going on? Caps starting to freak?
everything is original except for JJ tubes.

 

[Mr. Blues]

THANKS! What's the Triode thingy? I notice a slight reduction in power when the noise/distortion behavior occurs - then after 10 minutes all is well.
Hmmmm???

 

[Boogiebabies]

There are two triodes in each 12AX7, so basically it's two tubes in 1.
If any of the 10 triodes goes bad, or half of any one preamp tube it could amplify the signal to the rest of the tubes or of one dies, the signal can get cut off. Try the V1 near the ouput transformer. It's dressed in armor.
In certain tubes you can get sputtering, ghost notes, fuzz, crackling and when it heats up it goes away. Also, tubes seem to have an ability to behave when you filp you standby switch off and on for a few seconds.

 

[Mr. Blues]

BB

So you're suggesting replacing V-1?
Flipping stand by switch off & on while POWER is on?
Doesn't that stress things a bit?
Thanks for your reply.

 

[Boogiebabies]

No, you can pull a preamp tube out with the power on full and not damage it.

The tube may exhibit the behavior on start up and stop after you flip the standby. It still does not mean it's a good tube and needs to be replaced because it will fail at the most critical time. Let's try swapping the tube and firing the amp up after 1 minute of warm up.

 

[Mr. Blues]

THANKS!!!

I'll try it tonight.

 

[Boogiebabies]

If the tubes do not work, disconnect the reverb cables. You may have a bad reverb ground or intermittent loss of the ground.

 

[Restless Rocks]

You probably already know this but I have experienced a phenomenon like that when I turn on the power and standby at the same time. The amp will just make farting sputtering sounds untill I put it in standby for several seconds . When I let the filaments warm for a couple minutes after turning on the power then flip the standby on there's no problemo.

 

[Mr. Blues]

Right. I always let the tubes cook for awhile (like when setting up for a gig) before I switch to power on. This is a different behavior. Thanks for your reply.

 

[Mr. Blues]

Boogiebabies -

You ARE duh man!

Swapped out the V1 tube with an old one and fired it up.

No distortion while playing. Behaves perfectly.

Many thanks!