Stubborn 9-pin socket

[mcrushing]

VERY stoked to finally be working on my kit - it's been a pleasure so far. Last night I installed all the hardware to the chassis and labeled the terminals. Before calling it a night, I decided to pop the tubes in - the idea being to confirm the sockets were adequately fastened to the chassis NOW, rather than after they've got a buncha stuff soldered to them.

The octal is a fairly tight fit, but the big guy wiggled its way in. Pins seem in good mechanical contact all-around.

The 9-pin is a different story. It took what seemed like WAY too much effort to get the 12AU7 in there. I did manage it - VERY carefully - stopping short of getting the tube totally flush with the socket. It feels like 2 or 3 holes are way too small, and the holes opposite them don't seem like they're in good contact with the pins at all. For all the effort inserting it, the tube still wobbles around in the socket!

At first I suspected the tube vs the socket, BUT: The 12AU7 from the kit fits happily into a 9-pin socket on my Manley, but a spare 12AT7 that I know fits in the Manley won't go into the socket on the Crack, either. SO... did I crank the bolts too tight? Do these sockets need to "break in"? Or I have a bad one?

See attached - note that at one point I had the tube farther into the socket, but I opted not to go that far when I put it back in for the photo - I was actually worried I might break the glass!!

THANKS for any help!

[Paul Birkeland]

Some of the newer tube sockets I've worked with are indeed a bit tight.  I think you'll find that the kit will work OK with the tube pressed in that far, and that the socket will loosen up a little over time.

In order to open the socket up, you would need a tool with a shaft diameter that's just slightly less or exactly the same as the socket pins, and that can be tough to find!

[mcrushing]

Thanks, Paul.

I was hoping you might say that it's no big deal. But man, it's tight, though.

Definitely planning to roll some tubes through this amp, so good chance the "tool" I ultimately use to open the holes up will be the stock AU7.

If I eventually decide that socket is too much of a PITA to deal with, or is a risk to spendy tubes, should I obtain a replacement from you guys, or will any chassis-mount unit with 4-40x screw holes - say, this AN model with its big, honkin' pin receptacles - likely work for me?

https://www.partsconnexion.com/audio-note-9-pin-chassis-mount-tube-socket.html

[Mucker]

Is it possible to get solder inside the pin sockets with these particular sockets?

Like PB said, my recently built S3X had scarey tight pin sockets but they loosened up nicely after less than 10 insertions.

[mcrushing]

You’re talking about solder flowing into the pinholes while I’m wiring up the terminals, correct? I haven’t actually used any solder on that socket yet, so that’s not the problem... But I hadn’t thought of that possibility, so thanks - I’ll be cautious of it when the time comes.

Glad to know you had the same issue with your kit, and it resolved itself with some use. (Scary tight is a good description.) The Manley is the only other tube amp I’ve owned and I bought it used, so I wasn’t really aware sockets needed to ‘break in’

[Mucker]

Yes, the pin holes and that's good to know solder isn't there. The tube should seat next to the cereamic after some breaking in.

Usually, I haven't had to deal with tight sockets on a dozen tube amps I've owned. The S3X was the first one I came across where I thought the tubes weren't going to go in, it was that hard. After about 5 insertions, things got better and now it's alot better and working the way I am used to. Honestly, I'd rather have tight pins than loose one's.

[Deluk]

I'd certainly make the pins shiny with some 1000 grit (or finer) paper to help them a bit. I don't know what the official pin size is but the shank of a drill could be used. A drill slightly smaller could also be wriggled in the socket too but don't overdo it. Sockets are inexpensive but if you go to Bottlehead for a replacement perhaps they could check it with a tube before sending it out.

[Doc B.]

They loosen up with use. Tubes from different countries of manufacture have slightly different pin diameters which further complicates the issue. Russian tubes tend to have slightly fatter pins. If that 12AT7 is Russian it would likely be more difficult to insert than an old stock US made tube. At any rate, it's usually not a big deal if the tube wont fit all the way into the socket initially. I have a TV-10 tube tester that I have been using every week for about 30 years now. It's gone through many socket savers, which purposely have slightly tight pin holes to begin with. So I just insert the tube maybe 2/3 of the way or so for testing until the pin holes loosen up enough for the tube to be inserted all the way easily. And they do loosen up.

[AB2KH]

I have come across this problem many times as well,I have saved back DUD tubes of each base configuration (all others go to the range to EEK-OUT that last ounce of enjoyment) and straighten the pins, also make shure they are not bowed vertically,I wrap a turn or two of masking tape around them (for grip). Insert the tube into the socket as far as it will go with minimal pressure, at this point I hold the tube tightly and rock it to and fro left and right applying moderate downward pressure until it seats to the socket,converslly remove the tube in the same manner, do this several times, you will get a nice tight fit.
A good tight mechanical connection will give a good low impedance electrical connection which is what we want.
As Doc said "And they do loosen up."

Chris / AB2KH

[mcrushing]

Thanks to everyone for the feedback. This forum is almost reason enough to buy/build these kits on its own.

A few tries inserting/removing has opened the socket up enough to encourage me to continue trying. Also, the pins on that tube weren't the straightest, so I (carefully) took a needle nose to them and rectified that a bit. This is interesting, Doc:

If that 12AT7 is Russian it would likely be more difficult to insert than an old stock US made tube.

Begs the question - is SOCKET rolling a thing ?)  Anyway, the 12AT7 I tried to fit was a GE, nos JAN. (Occurred to me to try one of the gold-pin Mullards currently running in the Stingray and... uh, no.)

But while I have your attention, I'm curious about the 12AU7 that came with the kit. Any markings are now likely on the sticky side of the bubble wrap it came in, if it had any. Photo attached, note the flash is concentrated on one side of the top. Can you ID it so I've got a reference? 

[Doc B.]

There might be faint etched lettering saying 12AU7 or a mil number like 5814 or 5963 on the glass, most likely near the top. If I could see that I could guess. I'm not enough of a geek to be able to identify it by plate structure alone. There sure might be someone around here that could, though.

[Drew1d]

Full disclosure, I’ve ordered the Crack but haven’t gotten it yet. I’ve built and rebuilt a few guitar amps that use tubes. What I do generally is spray either deoxit or wd-40 on a rag and wipe the pins and try inserting it a few times and that generally does the trick. I’ve noticed that some vintage tubes, the pins seem thicker.

*****Disclaimer - Don’t kill yourself ****
••••••I’m just some idiot on the internet ****
Unplug amp, Discharge the filter caps 220 before going further. I alligator clip the ground first, then use one hand to alligator clip the + side of a 220uf of a filter cap. *sparks may fly* Then measure the volts with a multimeter. Make sure it’s only a couple of milivolts. I mean this amp should discharge automatically if built right.  But to check with a multimeter only takes like 30 seconds, and a multimeter is way cheap.

I’m more concerned when pins are loose. In that case if you push on the terminal side you can get the collar  to pop out on the other side, and ever so slightly, squeeze with some needle nose pliers.  Or if you file a small screwdriver, like ones that repair glasses, you can wiggle it between the wall and pin and tighten it up that way.

If the socket is new, you probably don’t have to do any of this.

I probably wouldn’t sand the pins. I mean, do whatever you want, but I wouldn’t.  I find generally reseating them a few times is fine, and sanding will probably promote more tarnish. Although that can depend on where you are. Like a shack in the Mississippi delta would tarnish, but a ac condo in Phoenix AZ probably not.

Good luck.

[Doc B.]

Don't hard short power supply caps with wire. Use a 10K resistor rated or 1/2W or more to drain them.

[mcrushing]

To Drew1d, I'm in LA, and close enough to the beach that my guitar strings are rusty nearly every time I pick it up, so I'm a BIG fan of Deoxit for the hifi... I rub a dab of it onto every exposed metal contact in my system every six months or so.

To everybody, I saw this video on Blueglow's youtube channel with detailed instructions for making a tidy little filter cap discharge probe. I plan on putting one of these together:

Doc and Paul, I worked the tubes in and out a few more times when I did the glow test and it's pretty clear all will be well, so I think we can call this one resolved. One or two more nights of soldering and I should have a working amp!

[Drew1d]

Cool little discharge tool. I guess I’m hard on things.  The first amp I built I soldered a lug of a 120k 1 watt resistor to the grounding tab, and used that.  I discharged quite frequently because I was experimenting with tone controls at the time. Perhaps I’m getting too lax nowadays. Glad to hear your problem is solved.