A multitude of tube questions

[apehead]

Hello all, long time no post for me, I've accumulated a few problems with some gear, and was just looking for some opinions.

#1 I have a Mesa-Boogie Bass 400+ with a broken power tube socket. Is there an easy way to remove it off of the one-piece rails used in this amp for all of the parallel connections, and install the replacement?

#2 I have a Peavey Classic 400 in which only one of the power tubes is cherry plating. Most likely culprit?

#3 I have a Fender Quad Reverb (100W version). When standby is engaged, hums loudly with no signal coming through, then blows fuse. Most likely culprit?

#4 I have a Hickok model 799 Tube Tester. Needle is pegged to the left, even when testing line AC. Fuse bulb is off. Suggestions?

Whew! I guess that's it for now, any/all help would be greatly appreciated.

[acorkos]

#1 I have a Mesa-Boogie Bass 400+ with a broken power tube socket. Is there an easy way to remove it off of the one-piece rails used in this amp for all of the parallel connections, and install the replacement?

i would remove solder from the rails at the socket in question with a copper braid and see how the socket pins are connected. once you are able to see how the socket pins are connected, you will probably be able to figure out the best way to remove the socket

#2 I have a Peavey Classic 400 in which only one of the power tubes is cherry plating. Most likely culprit?

i dunno...swap the tube that's redplating with one next to it and see if the good tube redplates in the original redplater's socket....or if the original redplating tube redplates in the new socket position

#3 I have a Fender Quad Reverb (100W version). When standby is engaged, hums loudly with no signal coming through, then blows fuse. Most likely culprit?

i dunno...put in a new fuse and pull the power tubes....does the fuse blow with no power tubes installed?

#4 I have a Hickok model 799 Tube Tester. Needle is pegged to the left, even when testing line AC. Fuse bulb is off. Suggestions?

i don't know anything about that unit

[apehead]

i would remove solder from the rails at the socket in question with a copper braid and see how the socket pins are connected

I found a picture online of the internals:


They are the type of sockets with little tabs at the end of each pin, with one or two component/wire mounting hole(s) punched into them. Through the hole, a single, long piece of uninsulated wire has been threaded through every socket (6 per side) to complete the parallel connections between the power tubes. De-soldering, then clipping the tabs of the broken socket to remove it from the wires would be easy enough, but it would be impossible to install a new socket of the same type without modifying the tabs' holes into slots that can be be slipped onto the wires, rather than threading the wire through the hole. I don't have much experience with Mesa's, didn't know if they were all built this way or not. Just curious if anyone here has developed a good method they regularly use on these amps when this problem arises.

Good, commonsense troubleshooting starting points with the other amps, thanks for the help.

[Mark Black]

On the new socket: Rather than make a slot take a single snip to open up the terminal hole & twist the ends away from each other enough to get the wire in. Then twist the ends back to re-complete the hole.

That plus solder should do the trick.

[apehead]

Great idea, that should do the trick. Thanks.

[apehead]

Total thread resurrection, but I've finally gotten a sufficient work space to try to get these amps up and running again, so...

#1 Replaced the tube socket in the Mesa using the tab snipping method recommended here, and it worked great. The amp is my go to for gigging.

#2 Peavey had a bad tube, no cherry plating now.

#4 Ordered new fuse bulb for Hickock, tested all of my tubes.

That just leaves me with #3. The amp does not blow fuses with the tubes pulled. Maybe I could start replacing them one at a time and see if any sockets seem to make them blow. Where will we go to get fuses when Radioshack closes? LOL.

[Jazz P Bass]

Fender QuadReverb Schematic

On the #3 problem child, remove the output tubes.
It should then, most likely, hold the fuse.

I would start by checking that the bias voltage is good & is reaching each 6L6 pin #5.
There should not be any Vac ripple on the pins.

Next, make sure the screen resistors are ok.

If this checks out, you may have a bad 6L6.
You can try one tube at a time to see if anything is amiss.

Sometimes a really bad tube can be found by monitoring the B+ voltage on pin 3.
With the voltage high & the amp off, insert one of the tubes.
If the B+ drops really fast, that tube is a fuse blower.

Ideally, you should monitor the mains current going into the amp.

[apehead]

Thanks for the post. I pulled all of the tubes yesterday, fuse held. De-energized and populated the tubes one at a time and re-energized, starting with the preamp tubes in channel 1, then preamp tubes in channel 2, then in pairs in the power section. First V7 & V10, then V8 & V9. It's all good. Played for 20 minutes or so with no issues. The fuse blowing had started after I had traveled with the amp, so maybe the jarring had messed up the internals of one of the power tubes and caused the filament to short or something. Seems to be working now, just wish I had figured out such an easy fix four years ago lol!