Why Do I Do This?-Classic 30 problem

[Teleman55]

A regular customer brings me a Classic 30 combo-"One of the output tubes is glowing red,must be a bias thing" he says.So I swap tubes around and it is always the same socket.Remove the boards and start measuring cap and resistor values,check the schematic and find it hard to believe a component would affect a single socket.More head scratching.I stop,breathe and think-Start at the source of the problem.I look at the tube socket solder joints,nothing obvious so on go the magnifying glasses now I see maybe a problem and when I wiggle the socket 2 solder tabs move.Problem solved.I just sometimes over complicate things when the reality is that working amps get banged around and it is usually a physical problem.It never fails that when I stop and or walk away,and take a deep breath I can get back to logical problem solving and when unsure or completely lost come here for help.My thanks to all the knowledgeable folks here and your willingness.You have helped me learn a lot.-Kevin

[Enzo]

SO it is working. Glad we could help.


Here is one for you, the typical tube socket pin is a circular female part that grips the tube pin, and a tail off that that pokes out the underside as a solder tab. You have a problem like the one you just solved. You look at the female part to make sure it has not spread open to lose its grip - looks fine. You go underneath and look at the solder - looks fine. YOu take voltage readings or resistance readings. WHatever is supposed to get to that tube socket is indeed getting there. But it doesn't work.

I have only seen this a few times in my many many years, but i have seen it in amps and even in the socket for picture tubes in video monitors. The socket pin is broken in two, The female part is fine, and the tab part is fine, but inside the socket, the tab has broken away from the female. I now check for it, but believe me, I had major hair loss the first time.

[micri5446]

lol tube sockets...the weakest link?? i love troubleshooting

[Teleman55]

Lets not forget dirt.I am always amazed when someone raves about how I improved their amp when all i've done is make a simple repair and give it a thorough cleaning,otherwise the amp is stock.In fact I was amazed the first time I did this to my own amp.Yet I still can forget to start with the basics.Then again I don't do this for a living and can go quite a while between repairs.

[Enzo]

I know it is not what you meant, but whenever the board comes out of an amp, the empty panel is simple to wipe clean with a cloth and some windex. Even with the controls and knobs in the way, I at least take a paint brush to it to clear away the dust. The customer gets back an amp that looks nicer than when it came in. Even if they don;t know that is what I did, just the little improvement in appearance makes them feel better towards their amp.

It is like a mint on their pillow.

[Ronsonic]

Cleaning is the one thing the customer can actually see that we did. Or didn't do. The dirt it came in with looks a hell of a lot worse going out.

I got an early lesson when I was a punk kid before I started doing anything serious with my own gear. My Traynor was sounding and playing bad. Threw tubes at it, still rotten. Took it in, got it back looking and playing better than it ever had before, downright brilliant. Read the ticket "general cleaning, cleaned tube sockets, conx & controls. Set bias. $35." Realized I could learn to do that and save that exorbitant fee.