A question on socket pin tension

[glebert]

I'm working on a Univox 1221 tube head that is being quite tempermental. Problem I'm having is that volume will drop out, especially on a loud note, and comes back if you hit the top of the amp If I go and tap gently on tubes the 6AN8 that is used for preamp/PI seems to be the culprit, as taps cause big pops or cutout/in of volume. Rocking the tube or pushing down can also cause the same symptoms. I had tried cleaning and tensioning the socket pins of the socket (and have also tried all the 6AN8 tubes I have) with same result. I did reflow the solder on the socket pins as well. I don't know if the socket pins are compromised or I didn't get them tensioned properly. Any tricks for testing pin tension, or should I just replace the socket?

Thanks in advance,
Greg

[The Dude]

IMO, if you already resoldered the wires to the socket, cleaned and re-tensioned the socket pins, and tried different tubes, a bad socket is the most likely culprit. I'd just replace the socket. Cheap and easy in that amp. Also, good insurance.

[mikeydee77]

Could try gently twisting the glass envelope to see if it is moving within the base or if not this movement can often tease out pin problems.

I have some bits of old denim jeans to protect my hands.

[Chuck H]

An old and over used socket may no longer have enough spring tension to hold the adjustment. I'd repeat cleaning and retensioning and test again. Clean the tube pins also. Just because you tried other tubes doesn't mean they may not all have oxidized pins. Don't be too gentle on the socket pin contacts. You do want to see that they are physically moved toward the inside of the pin hole. Since you've already done this procedure once you might be able to see if the socket pin contacts are already pushed out toward the edge again without springing back. If this is clear to you then replacing the socket is probably the best solution.

[Mick Bailey]

If you really wanted to test pin tension, find a metal rod that's the same size and shape as a tube pin and fix it to the end of a piece of wood or plastic. This can be used to test the grip of each location by feel. You can reduce a piece of metal rod or length cut off a screw by rotating in the drill chuck while filing, then polish it with wet or dry or emery cloth and round the end. Maybe even cutting the pin off a donor tube and soldering it to a piece of rod would give enough useful length for this purpose.

[J M Fahey]

Sadly too thin and long to be turned from a fatter piece of metal, cutting tool pressure will bend it.
I wind my own transformers so have an assortment of different enameled wires, a small piece is perfect to test socket tension (o lack of it).



1mm diameter wire is perfect, but "just in case" socket should still grab 0.9mm wire with _some_ tension, at least when new.

You may recycle some wire from junked transformers.

Or maybe you have some 1mm copper or brass wire for bus bars.

Also hobby shops or Artisan suppliers have brass or aluminum wire in various diameters, for DIY jewelry.

But in this particular case I also suspect some broken or very poor connection nearby, lightly pull/twist/wiggle any and all wires and parts legs nearby.

Some components such as carbon composition resistors or paper/plastic capacitors or electrolytic positive leads can have a broken/intermittent connection inside.

Wasted lots of time many times chasing such goblins.

[g1]

Is the socket board mounted? If so, it's possible one of the legs is cracked.

[The Dude]

As far as I know, the sockets in this amp are not board mounted, but wired. A socket change should be a pretty easy repair.

[glebert]

Yes, chassis mounted, so easy to replace but I have to order some sockets.

[drewl]

I find that quite a bit on Univox amps, same with Silvertone amps.

If it's just one or two bad pins, you can sometimes just replace the bad pins.

[glebert]

I find that quite a bit on Univox amps, same with Silvertone amps.

If it's just one or two bad pins, you can sometimes just replace the bad pins.

I thought of trying to replace pins, but figured if one pin is bad there might be more that are on the edge, so might as well replace the whole socket. As The Dude said the sockets on this amp are super accessible, so no reason to try to take a shortcut.

[SoulFetish]

I thought of trying to replace pins, but figured if one pin is bad there might be more that are on the edge, so might as well replace the whole socket. As The Dude said the sockets on this amp are super accessible, so no reason to try to take a shortcut.

Depending on the kind of terminals/socket, I've actually transplanted individual socket terminals from a donor socket. I'll do this when it is the best and most efficient repair, vs replacing the socket altogether. For instance, in most Silvertone amps, the sockets are riveted to the chassis and the component leads are wrapped a couple of times through the terminal and soldered. It makes sense to find the source of the problematic pin/s, and replace them if all others test okay and can be cleaned. I think there's a thread where I demo how I do it. It's pretty quick and works great

[glebert]

Got a socket and installed it. Amp is rock solid now. Thanks for all the advice.