Amplifier Question

oavelasco · 11th January 2012

My Fender Pro Jr was having some issues so I investigated the problem. Turns out any vibration or tapping of one of the power tubes caused it to momentarily buzz. It didn't do it all the time, but it started happening enough to where I figured reflowing the solder joints would be a good idea. Lo and behold, it worked and there's no more buzzing, except...

...now the amp is acting real funny, in that it puts overdriven sound when the amp is turned down to zero, and cleans up when I turn it up. Its not till I get to 4 or 5 that it starts driving again and that definitely wasn't the way it was before because its only a 15 watt amp! I'm not sure if, while taking the pcb that the tube sockets are mounted on out, I pinched a wire. One word. Help.

AndyFromDenver · 12th January 2012

I'm sooo not an expert, but in resoldering did you accidentally make an unintended connection? Aka is there a glob of solder over some contact points?

LeeYoo · 12th January 2012

Hi oavelasco.
Buzzing or crackling when you tap a faulty valve is quite common.
I even had a small, soft rubber hammer for that in my toolbox.
Sometimes you can see sparks flying around inside.
Replacing is the only solution.
But, the problem you have might be introduced by soldering the joints.
Try to step back in time with everything you did.
Or post some pics.
Leo..

oavelasco · 12th January 2012

Going to get new preamp tubes tomorrow. That ought to fix it.

oavelasco · 17th January 2012

New preamp tubes didn't do it. I did a test point check with the official Fender schematic and got all correct readings on the DC points but some bad ones on the AC. Most notably, the one on the input jack, and then all of the ones on the power tubes, among some others (all of V2 AC TPs and the ones of pins 1 and 2 on V1).

I re-soldered the joints on the input jack, but that didn't work. Then I thought re-tensioning all the tube sockets that were giving me problems would be a good idea, to no avail. I already ordered new tube sockets. I'm going to start with replacing the ones for the power tubes since thats where the root of the problem was from the start. It was V3 that gave me a problem to begin with and I'm thinking I may have caused an arc (or two) inside the sockets when I was cleaning them (I accidentally dripped some cleaner inside..ok ok it was purposeful, but how was I to know? I was much younger last week...)

So anyone have any idea what I can do in the meantime?

11th January 2012	#1
oavelasco Gear interested Joined: Oct 2009 Posts: 10 Thread Starter	Amplifier Question My Fender Pro Jr was having some issues so I investigated the problem. Turns out any vibration or tapping of one of the power tubes caused it to momentarily buzz. It didn't do it all the time, but it started happening enough to where I figured reflowing the solder joints would be a good idea. Lo and behold, it worked and there's no more buzzing, except... ...now the amp is acting real funny, in that it puts overdriven sound when the amp is turned down to zero, and cleans up when I turn it up. Its not till I get to 4 or 5 that it starts driving again and that definitely wasn't the way it was before because its only a 15 watt amp! I'm not sure if, while taking the pcb that the tube sockets are mounted on out, I pinched a wire. One word. Help.

12th January 2012	#2
AndyFromDenver Lives for gear Joined: May 2010 Location: Athens, GA Posts: 756 1 Review written	I'm sooo not an expert, but in resoldering did you accidentally make an unintended connection? Aka is there a glob of solder over some contact points? __________________ Good credit, bad credit, no credit, what is credit, can't read or write... www.myspace.com/marshmallowcoast http://en.wikipedia.org/wiki/M_Coast

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12th January 2012	#3
LeeYoo Lives for gear Joined: Feb 2010 Location: New Zealand Posts: 754	Hi oavelasco. Buzzing or crackling when you tap a faulty valve is quite common. I even had a small, soft rubber hammer for that in my toolbox. Sometimes you can see sparks flying around inside. Replacing is the only solution. But, the problem you have might be introduced by soldering the joints. Try to step back in time with everything you did. Or post some pics. Leo..

17th January 2012	#5
oavelasco Gear interested Joined: Oct 2009 Posts: 10 Thread Starter	New preamp tubes didn't do it. I did a test point check with the official Fender schematic and got all correct readings on the DC points but some bad ones on the AC. Most notably, the one on the input jack, and then all of the ones on the power tubes, among some others (all of V2 AC TPs and the ones of pins 1 and 2 on V1). I re-soldered the joints on the input jack, but that didn't work. Then I thought re-tensioning all the tube sockets that were giving me problems would be a good idea, to no avail. I already ordered new tube sockets. I'm going to start with replacing the ones for the power tubes since thats where the root of the problem was from the start. It was V3 that gave me a problem to begin with and I'm thinking I may have caused an arc (or two) inside the sockets when I was cleaning them (I accidentally dripped some cleaner inside..ok ok it was purposeful, but how was I to know? I was much younger last week...) So anyone have any idea what I can do in the meantime?