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In Reply to: Can tube sockets be too tight? posted by desert dweller on August 16, 2006 at 09:35:10:
desert dweller, hi. I think you don't have to replace the sockets. Just remember the laws of physics when you remove/insert tubes. As the cj sockets are soldered to the circuit board you will want to hold and support the socket with one hand while you torque the tube with the other. Ideally the socket pins in a chassis socket are designed to float somewhat. With a circuit board socket the pins can't move around at all. Just be careful with force applied to removing/inserting tubes. Ideally the sockets should be attached to the board so the bottoms of the pins are not what is holding the socket to the board.
Follow Ups:
Elektron,I talked to my tech and he said it is the bottoms of the pins that are holding the sockets to the board. He's going to go through the whole board and check all the connections and re-solder anything that looks suspect (in addition to the loose cap that's making the noise).
He had to take the preamp completely apart to get to the board. 2 hours. Is there a rational reason why CJ would design the thing without an easily removeable bottom (aside from the extra repair revenue it generates)? I'm seriously thinking of selling it and getting something that's easier to repair.
Thanks again for your help,.
desert dweller, hi. As long as your tech is going to do the rework on some tube pin to board connection have him do them all. It won't take much bench time ($) - maybe a second or two per joint - but is a wise thing to do. Intermittent solder joints are the bane of otherwise nice designs where circuit board type tube sockets are used. I understand your frustration. These things happen. I don't think it was part of the design plan. You can blame the lead based solder all you want. I haven't used any lead bearing solder for 15 years or so. Pb/Sn solder can crystalize over time and cause big trouble. Circuit board tube socket joints are particularly vulnerable as they are subject to both mechanical and thermal shock. I hope the surgery goes well and solves the problem.
Elektron, thanks for the info and the encouragement. Is Pb/Sn solder the usual tin/lead stuff? I didn't know it can crystallize. What do you use? My tech is using 2% silver.My comment about CJ's design motivations was (mostly) tongue in cheek. Is there a different kind of design that provides easy repair access? Next time I consider buying a tube component that will be a deciding factor, especially if it's used.
Desert Dweller, hi. You are most welcome. Glad to help/share. Usual solder alloy used to be around 60/40 - 60% tin and 40% lead. You can get others with small % silver. I got away from lead bearing solders a long time ago and never looked back. The solder your tech is using is probably a tin/lead combo with 2% silver. You can get solder without any lead at all with activated rosin core. I have been sourcing from Capp Alloys in Pennsylvania. They make with only virgin metals. This stuff is the nuts! There should be other companies that make similar as the whole of the electronics industry is moving away from lead. I use a 96.5% tin 3.5% silver solder. It must have a rosin core for flux. It works great. And, yes, Pb/Sn solders can crystalize at junctions. It can (over time) do other obnoxious funky stunts anathema to audio. Get the Lead Out should be everyone's motto for electronics. Besides, you won't have to worry about inhaling lead vapors.Bill T is a prince of a guy. Besides cj themselves he is the go to guy for cj in my book. I happen to like cj preamps. I build/built amps but not preamps (yet). I still have 3 cj preamps. The main one is a cj Prem 14 - which is just super & it is remote controlled. The Prem 14 uses 6GK5 not RU tubes. I have a Prem 10 too in another all horn system. Although not quite as refined as the Prem 14 it is no slouch either.
A pre design like some of Dennis' work at CARY would probably be easier to access. All point to point wiring. Virtually no circuit boards. Some are remote controlled but am not sure how he does it.
The cj Prem 14 uses little sealed switches that bring in or out various Vishay resistors to control gain. This is greatly better than a pot of any kind. The Prem 10 uses fixed resistors on a multi rotary switch. Probably the Best way would be a Transformer Volume Control using different tappings on the secondary to yield different voltages out (volume).
Elektron, Thanks for the info, especially about supporting the socket. This is my first tube piece and is actually a PV8 that was upgraded to PV12 status by Bill Thalman. I was told that it shouldn't need service again for 10 or 20 years.I didn't know about the lack of strain relief and was told that it's ok to gently rock the tubes a little if needed. I thought I was always pretty gentle but I'll have to be even more careful in the future. I'll also check with the tech to make sure that the bottoms of the pins are not what is holding the socket to the board.
PS shortly after I got it, it went back to Bill for another $200 in service to fix a nasty hum and blowing fuses. Now this. Hopefully it won't need service again for at least the next 10 years.
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