If I wasn't seeing it with my own eyes, I wouldn't believe it.

[eleventeen]

Have a Deluxe Reverb II on the bench. Nice amp, actually. Rivera-era Fender, 1-channel Deluxe Reverb with ch switch and boost. Complaint: blows fuses. This is a school amp, so I doubt it is ever played stressed, though it *may* be left on for gig-length periods of time.

So, I do the usual. The e-caps (stock: 3-in-a-can) have been replaced w/individual externals. OK. All else seems just fine and stock. 6V6 output tubes = newish JJ's. Replace fuse with teeny wire short, power up amp into a dummy load and let cook @ 0. All seems fine. Dial up to 5, let cook. no problem. Dial up to 10, no problem. The thing puts out plenty of volts, my dummy load is heating up mildly, output trace somewhat distorted, more than I would like to see, even at low volumes. At higher volumes, 6V6 outputs are HOTTT, but not redplating. 

I decide to put a 1 ohm resistor under the cathode of one tube to see how much current the thing draws in use. Easy enough, tack it in there.

So I also pull out the 6V6 tubes, they look very good. Put them back in. I am putting them in upside down, with the amp chassis in a cradle. Not exactly thrilled with how much the terminals wiggle and waggle when I rotate the 6V6s to align the key. Very loosy-goosey. Power back on. Hmmm. Zero cathode current thru my resistor. Huh? One 6V6 does not light up (the one whose cathode I lifted) and I start to hear a sizzling sound and smell electro-stink. Quick, shut down.

The particular octal sockets used in this amp allow these 6V6 JJ tubes [only] to be inserted into the sockets without regard to the tube-base key!! I have the sucker in one pin off on one of the output tubes! RCA, Sylvania, and GE tubes of many diff vintages (some as old as WW2) will all orient at least two ways in these particular octal sockets; correctly, and 180 degrees off.  Five different manufacturers of octal sockets sitting in my junkbox and other gear lying around. The JJ's orient properly, only one way, in any of them. The center hole in these Fender-amp sockets are too big. In terms of the size of the key in either the base or the socket, but especially the center-hole in the socket, we are talking teensy amounts, but enough to allow an octal tube to be put in wrong. Never seen that before.

This of course has nothing to do with the original complaint. This is maintenance-induced failure. Even though it reads per spec (-33 vdc) I think I am going to cool out the (fixed) bias by at least 5 volts, though. Now I have a conundrum as to whether to replace the output tube sockets. Probably should.

Just thought it was an unusual experience.




   

[stratele52]

I have some new ceramic type socket for 6V6, 6L6 ...and center is too big .You can plug the tube in any direction.

[sluckey]

I'd like to see those sockets. Can you post a pic?

[eleventeen]

Shall do. Coming right up.

I wonder if I could fix this by putting a small bead of super glue around the circumference of the hole in the hopes that a teensy amount of buildup around that hole would reduce its effective size.

I feel obligated to change out the sockets. Oversize hole or not, I am really unhappy about how loosy-goosey the pins are. And I know it will 99.999% never matter as this is a school amp.

[eleventeen]

Here you go, sorry for the last pix, but you can still see what's going on. The socket is indifferent as to how the tube is inserted.

[stratele52]

I'd like to see those sockets. Can you post a pic?

Sure . Tomorrow if you don't mind

[plexi50]

I found this same problem  in a 5E3 a customer brought in. I was surprised to see that the key would go in the socket in any direction. I think i posted that 5E3 issue here on the forum a few years ago

[stratele52]

These are ceramic socket which you can easely put tube's guide pin in wrong place. I bough some news few years ago .

[HotBluePlates]

... Complaint: blows fuses. ... The center hole in these Fender-amp sockets are too big.
...
This of course has nothing to do with the original complaint.

I think it has everything to do with the original complaint. It's very possible to blow fuses if you get the tube inserted incorrectly (as folks will tell you about tubes with broken guide pins).

I've also encountered sockets like these, especially the ceamic sockets stratele52 posted (which have a way-too-big keyway, but yet the knife socket contacts often grip too tightly and take much force to insert a tube).

Just manufacturing slop. In the Fender sockets, I might suspect they use a molding process to make the socket before inserting the pin contacts, and they kept a master mold of the socket too long (molds are good for only so many uses before their tolerancing gets skewed). Fo the (probably Chinese) ceramic sockets, the dimensioning was probably never right, IMO...

[eleventeen]

"I think it has everything to do with the original complaint. It's very possible to blow fuses if you get the tube inserted incorrectly (as folks will tell you about tubes with broken guide pins)."

Oh absolutely, in fact, I'm a tad concerned that I might have cooked the output tranny.

However in this case, my suspicion (of course no way to know with perfect certainty) is that nobody particularly monkeyed with the amp. Still...newish JJ 6V6 in there and all the other tubes are original Fender-branded.

And then again.....when I got the amp, there was a load of wax that had dripped out of the output tranny. Which is a tad odd, since the tranny (looks like a regular Deluxe OT, metal-encased) is mounted upside down and thus the holes where the wires enter the end bells is UP. Means more heat than one would expect cooked that thing. There was more that cooked out of it after my little "one pin off" episode.

[birt]

so there's a big chance that the person who installed those new JJ's put them in the wrong way and concluded the amp was broken because there's new tubes and it doesn't work.

[darkbluemurder]

Just thought it was an unusual experience.

Not so unusual. In fact I had the same thing with a Concert of the same era. Inserted the 6L6 incorrectly - why this was possible escaped me until I read your post - and had some nice fireworks, a burnt socket and an unforeseen pleasure to replace the socket. Lucky enough I still had some spare sockets.

Cheers Stephan

[eleventeen]

"so there's a big chance that the person who installed those new JJ's put them in the wrong way and concluded the amp was broken because there's new tubes and it doesn't work."

Allow me to restate (from the Sherlock Holmes standpoint) ....the amp WORKED when I got it, but the complaint was that it blew fuses.

Yes...I think the 6V6 (or at least one of them) were inserted incorrectly....the fuse blew, then someone looked at the amp, saw that one 6V6 wasn't lighting up, or, the relative positioning of innards of the two tubes did not match. They took the tube(s) out to look at it/them, and then got it right upon re-installation.

Of course this all supposition, but the above scenario makes the most sense to me.