Bravo John!!!!!

I must admit a certain lack of temperance for other's learning curves myself, so I most certainly would be the pot calling the kettle black if I balked at Codefox's impatience.

But when I find myself under a similar thinking cap I try to conjure this paraphrase from Thomas Alva Edison:



What if Edison and Tesla had access to a venue such as these forums? Would they have given up after 10 posts? To me that is just as irrelevant a quantification as if they would quit after 5 cups of coffee, 10 flap-jacks, or two thunder showers.... In fact it eludes the objective entirely, which would be a lit bulb or half a million volts traveling through the air to the next town. Quiting for any reason only represents a low measure of passion and conversely a great measure of lost potential. At least I try to think of these things.... It makes success a little sweeter!

John Richter

I second that; here, here!

Posts such as that are smug and inexcusable acts showing a total lack of intellect which clearly demonstrates ignorance.
I apologize for such behavior because it troubles me to think that any member here would ever act that way.
You new fellows ( or anyone for that matter) should never have to encounter such an inexcusable lack of good manners.

Thank you, Peter.

I replaced the 50C5 with a new tube today. Still reading positive voltage on pin 2.

You checked voltage without the coupling cap, replaced 50C5 twice, grid resistor is within spec. Is there anything else connected to pin #2 or pin #5? If not all that's left is socket leakage. Positive 2 volts on grid #1 will lead to distortion and higher current being drawn.

'

The resistor and capacitor are all that are connected to pin 2. There is no connection to pin 5. The cap is connected to pin 2 of the 50C5 and to pin 7 of the 12AV6. What does one do about socket leakage, other than replace the socket?

Usually replacing the socket is all that is left. A socket is like a mini printed circuit board and can develop carbon tracking on interior layers. Mark Oppat http://www.oldradioparts.net/ or someone else can find you a virginal socket. Drill out the rivets real slow, blast the chassis with air, even canned air if you do not have a compressor, bang it a few times, more air and replace the socket connections with machine screws, and either a lock washer and a nut or a locknut. Clean the new socket pins and the tube. Re-solder and good to go. Label carefully before you detach anything.

You could shoot a gallon of cleaner in there, but the problem would probably come back.

OK; I'm in unfamiliar territory now, and I want to tread VERY lightly. How do I disconnect THESE?

I don't know what you've got there.
looks like some kind of sockek mount pins that are protruding from the other side?... and I assume they make contact with printed circuit traces on the other side?
.. and they are probably soldered on that side to the traces?

you'll have to show a few close ups of both side b4 I can tell you what to do.
But most likely you'll need to heat the other side where these studs meet the PC traces and using a good solder-sucker or some De-soldering braid... to suck away or "wick" away all the solder from each pad without destroying the PC traces,
http://www.electronix.com/heavy-duty-de ... obth5m3290

Then if you can get a replacement socket of the same style... reinsert it and solder it in.

If that all becomes a nightmare... providing you have some room.
You might be able to drill out the center of that old phenolic socket and examine and clean it.. or better yet.. remove it as best you can. Then try to mount a more-conventional 7-pin socket on a couple studs and wire the lugs with short jumpers over to the PC board pads as required.

Someone else here who knows those sockets may be able to better advise you.

Exprof, it's hard to see from the photo. My 447 has a circuit board that is attached to the metal chassis. There is about a 1/2 inch gap between the circuit board and chassis. The result is that when the tubes are inserted through the holes in the chassis they sink down about a half inch to reach the socket on the circuit board below. Is that how your chassis is set up?

If so, the gap between the circuit board and chassis is not accessible unless you remove the circuit board. Removing that circuit board will be extremely difficult. You will remove everything off the chassis that is connected to the circuit board below. And then there are several wires on the bottom side of the board that need to be desoldered, and a couple of components. Once all of this is taken apart you can remove the circuit board with four clips. And I'm only guessing you will find the standard 7 pin sockets on top of that board because i don't know.

Guys, can he use a pick with some sort of abrasive to clean out the socket? Even cleaning up the abrasive material would be much easier than removing the circuit board from these models....

John Richter

I agree it's hard to see enough from that photo.
Looks like the photo is only showing the bottom on the socket.... tube enters from other side?

But the socket looks like it is a sandwich of phenolic layers.
If there is or was a short or arc between the pins of the socket between the layers it is almost impossible to fix it because even if you remove the rivet eyelet holding the sandwich together and examine the burned phenolic... it is not easy to clean or repair even if you scrape it because usually the phenolic itself becomes conductive from the burned carbon ... so even scraping does not remove the carbon between points because it's too deeply burned into the phenolic itself.

Apparently there are pins in the tube socket that fit into these odd little conical things, which themselves appear to be the undersides of terminals into which leads of the various components fit.

So, Peter, bouncing your latest comment: would it be possible to remove the tips of these cones with a dremel tool, mount a seven-pin socket in the hole and run leads from the conical terminals to the terminals on the replacement socket?

Yes.. I guess that will do the job
Anything to get that old socket completely removed and mount a new one there some how,
Then simply completely re-route all the leads and components directly to the lugs on the new socket.
Sounds like a plan.

OK, now I see. it looks like you already have access to the other side of th e CB. Yeah, that one looks like it's pretty dark, like it may be burnt. Is it burnt or do you think it's supposed to be that color? Peter said the board itself could become conductive under burnt conditions? So if it's burnt, will you have to cut out the burnt part so it won't make contact with the pins? And then just mount a whole new socket to the bottom of the board? I used a flashlight to look down in the recesses of the tube slots on my chassis and none of them look black like that. This is over my head, I think...

You might start by cleaning that area good and then measuring for leakage...
If still leaking THEN drilling out the center rivet and look under there to see what it is that's conducting.

Step by step.
But I suspect a whole new socket is what will do the trick.

At this point, my inclination is to replace the socket and be done with it. It might seem like Civil War surgery, lopping off a limb to make a bullet wound easier to deal with, but replacing the socket seems like the simpler option, and the one most likely to yield a successful outcome--especially given my relatively limited experience and skill in this area.

Excellent reply, Pbpix. But if somehow it's still not clear, go to the back of the RCA tube manual (you need to have one!) and simply replicate the generic AA5 schematic there with discrete components. Works every time. I am NOT a fan of those multi-pinned wax coupler things!
Also, as others have said, it's very important to replace the cap from the 12AV6 plate to the 50C5 g1... any leak here is fatal.
Cheers,
Roger

Thank you, Roger.


To all:
It turns out that the socket wasn't actually a socket, merely a cover. The pin receptacles were attached in a radial pattern with clips to terminals mounted in the circuit board material, and the conical objects were the terminal ends. There was quite a bit of carbon on the receptacle ends of the terminals, so something happened there at one point. I clipped away the pin receptacle ends and cleaned the area underneath with denatured alcohol. I've ordered a tube socket, and once it arrives, I plan to solder jumpers from the ends of the conical terminals to the lead ends of the socket. I now have the uneasy feeling in the pit of the stomach that comes from being completely invested in one and only one outcome.

I'll let you all know how it turns out.