Fisher sockets

[jertub]

Where can I get replacement 12ax7 sockets for my fisher X100B? The ones with the flange for the sheild. And some have the center ground sleeve (not sure whats that called).

I went to desolder a pin on V4 and as soon as I put the tip on the terminal it snapped right off. It must have been intermittent for a long time.

Please advise.

Thanks
Jerry

 

[jertub]

I was reading another thread where someone said to just replace the pin in the existing socket.... I sure would like to do that!

Pin 9 of those tone control sockets is empty, can I simply push out that pin and reinsert into the broken slot?

I cant find the 9 pin replacement with the flange for the shield. Any ideas?

 

[knockbill]

You can replace the socket connector on some sockets... also the shield holder is available separate from the socket,,,
I get them at hamfest etc,,, not sure who has new ones... AES, possibly? Can you post a pic of the socket your working on...

 

[audmod01]

Look very closely at the contact in the donor tube socket underneath. If you see a small dimple or depressed area in the metal of the contact it may have to be flattened with needle nose pliers before you can extract it from the socket. Once you get it out it should be fairly easy to insert it in the original socket of your Fisher. Try to get a donor socket that looks exactly like the one in your fisher (shape of lugs for the contact underneath, length etc.). Once a contact has been inserted into the original socket you might use a bit of solder to keep it from pulling back out or may be able to renew the small dimple in the contact to keep it in place.

Joe

 

[vendo81]

Look very closely at the contact in the donor tube socket underneath. If you see a small dimple or depressed area in the metal of the contact it may have to be flattened with needle nose pliers before you can extract it from the socket. Once you get it out it should be fairly easy to insert it in the original socket of your Fisher. Try to get a donor socket that looks exactly like the one in your fisher (shape of lugs for the contact underneath, length etc.). Once a contact has been inserted into the original socket you might use a bit of solder to keep it from pulling back out or may be able to renew the small dimple in the contact to keep it in place.

Joe

Thanks Joe. I have a socket with 2 bad pins I was going to work on soon. I've only changed pins once and it's been quite a while.

 

[HiFiHarv]

I'm curious just how important that center grounding sleeve is. I understand why it is there, but I don't see it on many modern tube components. Anyone care to comment?

 

[audmod01]

In many cases the center grounding sleeve just provided a close and convenient way to ground capacitors and resistors and keep component leads as short as possible. (It also helps avoid having to add so many terminal strips near the tube socket and every penny saved represents more profit.) That is more of an issue in RF and IF circuits. At audio it is not so critical. It is best to keep the same or replacement parts grounded the same as they were originally in order to avoid ground loops. There are exceptions. Dave Gillespie had one thread on a preamp he was restoring which had issues with lead dress and hum from day one from the factory. He worked out changes to lead dress and ground points that cured the hum issues. Fortunately most Fisher gear does not have such problems.
Joe

 

[audmod01]

I forgot to mention on removal and installation of tube socket contacts, be careful not bend the contact any more than necessary to avoid developing metal fatigue and having the contact break apart. Use solder wick to get as much solder off of any components that may be attached to a donor socket contact to make removal of parts leads easier.
Joe

 

[jertub]

For the record, I don't think its possible to remove the connectors from these sockets. Maybe the base is molded around it. The connector does have that dimple but I couldn't flatten it properly to slide thru the slit in the bakelite base.

I was able to find a replacement socket though locally and I think its a better idea to drill the rivets, install new and remake all the connections instead of trying to extract a terminal.

My only fear is after desoldering, the leads will be long enough to reach the new terminals so I wont have to use new components.

 

[larryderouin]

As long as you DO NOT CUT OR BREAK any of the leads (meaning carefully unwrap them from the connection, and number them for which pin) they'll have plenty of length to reach the new pins. Make absolutely sure, if/when you replace a complete socket to orient it exactly the same way as the old one. You have 2 ways, correct and 180* out.

The terminals can be removed from the socket. Done it plenty of times. Take a very small pair of needle nose pliers and locate the dimple on the bottom of the solder end of the terminal. Flatten it, and push the remains out thru the top. Then insert the new terminal down thru the top, and dimple the end like the old one. Just go slow, be patient, and beat on the drywall with your hand instead of your noggin. The 1st time doing them is frustrating because it's one of those things the manufacturers don't want you to know about. They'd rather have you buy a new socket.

 

[gadget73]

It is possible, and I have occasionally done it but often when the terminals need replacing the insulation on the socket is about shot and its not worth bothering with.

 

[jertub]

A friend of mine has a coffee can full of sockets and we found one that was almost identical down to the flange even. I installed it no problem with all the same components. However, I needed use some downward force to get the shield on. So much so that I hope I don't have to take it off any time soon, its gonna be hard.

Should the shield sit loosely on the socket or is it common for them to take some effort to get on and off? Generally are they "universal".?

 

[gadget73]

might have to tweak the flange in a little bit so its less difficult to get on and off. Some do sit looser than others, but it shouldn't be so loose that it feels like its barely on there. It also shouldn't be so tight you have to strain to get it installed.

 

[larryderouin]

+1 what Gadget said!

 

[audmod01]

It is possible, and I have occasionally done it but often when the terminals need replacing the insulation on the socket is about shot and its not worth bothering with.

The tube sockets I have had to change over the years that had insulation damage were usually output tube sockets where the tubes tend to run much hotter than preamp and line amp stages. The only 12AX7 sockets I have changed were ones that had been damaged by plugging in tubes with crooked pins and caused contact damage beyond correction by tightening contacts. Some output tube sockets have had to be changed for the same reason.

In the case of output tube sockets, ceramic sockets often make good sense as replacements because the ceramic material will withstand extreme temperatures without degradation. Of course one needs to make sure that the tubes are operating with correct voltages and current per manufacturer's specification or with careful attention to grid bias or cathode bias. Implementation of Dave's EFB in Fisher output stages will lead to longer tube life and less heat dissipation as well as greater power output and less distortion - the best of all worlds.
Joe

 

[gadget73]

Usually output tubes, definitely. I did have to replace the 12AU7 socket in my Pilot amp though. The hole that the pin sits in had gotten damaged somehow and would no longer retain the contact. Someone had put a blob of hot glue on it before I owned it to hold it together. I found it when changing a cap, the soldering iron melted the glue. The rest of the contacts in that socket were fairly sloppy as well, so it was no great loss.