Bad tube

audiocr381ve

I bought a quad set of tubes from one of our members and they arrived safely today except one of them seems to be bad. They are the GE JG5814A's (12AU7 equivalent I'm told). I plugged all 4 tubes into my Rogue Audio Perseus and heard a very loud hum coming from my left speaker. I immediately powered down. What I did next was pull one GE tube out and replaced it with a working JJ tube and fired the system up each time until I found the culprit.

I see these on eBay right now and knowing nothing about tubes I just want to make sure finding a replacement is as easy as it looks.

Here's the replacement I found: http://www.ebay.com/itm/Strong-GE-3-Mica-Gray-Plate-O-Getter-JG-5814A-Tube-/111374437186?pt=Vintage_Electronics_R2&hash=item19ee6f0b42

Here's where the CP member I bought them from bought them: http://www.polkaudio.com/forums/showthread.php?158486-5814A-6201-5687-5751-Tubes-NOS

Is this a good match? Also, can I leave the working JJ tube in with the three other GE tubes? Thanks gents

heiney9

Always cleans the PINs with DeOxit. You'd be amazed what that can do. I always clean the pins of tubes I sell, just so that's not an issue. Sometimes just taking the tube out and reinserting it does the trick as well. Many times people think they have a bad tube, but it's a bad connection.

What year JG's are they? Black plate? 3 mica? The early ones are sweet so make a rash judgment until you eliminate dirty or poor connections.

Don't mix and match tubes if in the same position on each side.

If you need a replacement it should be the same construction and about the same year of manufacture. If your's have horseshoe getters then the round getters aren't a replacement.

heiney9

Desireme is a good tube seller but the date codes on those are either 1962 or 1963, they are later than the ones I believe Snow sold you. Probably not a perfect match, some might not hear the difference. Sometimes there is a huge difference sometimes not.

audiocr381ve

Thanks for the input Brock.

I uninstalled all of the tubes and applied Deoxit to the pins, along with the "bad" tube. I reinstalled them into my preamp and there it is again, a very loud buzzing happening. I removed the bad tube and placed a good JJ in there to see what would happened and the buzz was STILL there. This makes me think this entire batch I received has issues. I tried different combinations with good and bad tubes and every time the GE's were in, the buzz was there.

Swapping all of my original JJ tubes in solved the problem, but of course it did. Trying to figure out what to do now.

heiney9

That is weird, not sure I've heard of that before. The 5814 is ruggedized version of the 12AU7 and electrically the same.

I guess my next question how do you know which is the bad tube if the buzz continues when you replace a tube with a single JJ?

It would be very rare for a tube of that caliber (the early JG's are bullet proof) to have issues with entire batch.

You need to replace each JG with a JJ one at a time and see if the issue gets better. Usually buzzing is not a sign of a bad tube. Usually hissing, popping, ringing, etc is the sign of a bad tube. Might be something else going on here.

H9

mhardy6647

Bad tube! No biscuit!

dudeinaroom

I'd take all of those tubes give them a good squirt with deoxit and take a metal brush to the pins. Scrub along side the pins as well as from the top down while the holding the rube upside down so you can get in between the pins. DO NOT use a heavy hand, you just want to remove any corrosion there. Be careful as to not bend the pins. They can be bent back, but use care. It is rare for a tube to cause a hum if it is bad, but it does sometimes happen. It also does not hurt to spray some deoxit into the tube sockets and work the tube with a circular rocking motion in the socket to help clean both at the same time. like H9 said, your best to stick with all the same tubes. You can run different brands, but sonics may suffer. I don't know what amp you are running these in, but being 12au7 variants, I'd imagine these are in the preamp and phono sections. You could always gun the two of the GE tubes in your pre section and the JJs in the phono section, of vice versa. Godd luck.

dragon1952

I'm the one that sold that quad to Shane. I got them from snow a couple months ago and they worked fine in my amp as a 12AU7 replacement. I've read where a small number of amps may have an issue with the higher filament current in the 5814 (175ma per section vs 150ma). I assume it depends on the amps design.

marvda1

check your interconnect connections.

audiocr381ve

Thanks for all the responses guys. So the plot thickens... I bought another set of tubes from eBay and they did not work either and the SAME loud buzz is happening. The only tubes that have worked are the ones that the seller gave me which made me think, "12AU7 must be the wrong tube" but I pulled out the manual and the preamp does indeed take 12AU7 tubes. I'm stumped. I'm going to call Rogue on Monday but would love to hear any other advice for troubleshooting.

audiocr381ve

Manual: http://www.rogueaudio.com/manuals/Perseus_manual.pdf

audiocr381ve

I should have mentioned that the very loud buzz is happening with the volume all the way down.

aboroth00

I have heard that Rogue preamps are a tad pickier on tubes than other preamps and I can testify to that with my 66. Give Rogue a call on the issue. Mark is usually very responsive and helpful over there.

audiocr381ve

aboroth00 wrote: »

I have heard that Rogue preamps are a tad pickier on tubes than other preamps and I can testify to that with my 66. Give Rogue a call on the issue. Mark is usually very responsive and helpful over there.

I called Rogue today and spoke with Nick who was incredibly helpful. He believes the JJ tubes have beefier pins than the vintage tubes and believes one of the sockets is causing a problem because of that. He recommends that I try and "tin" the pins of the tube that goes into the socket that is giving me problems. Seems like a better solution would be to replace that socket, but he'd know better than me.

Any advice on trying this? I've tinned the tip of a soldering iron but never several pins on a tube lol. And to have to do this with each quad set sounds daunting.

heiney9

Did you inspect the tubes? Do the JJ pins look beefier? Never heard that before. I'd say if you can't visually see a difference in PIN size and the other tubes fit snuggly, that's not the issue.

H9

Mike Reeter

Could be at some time a tube with a couple of bent pins was installed (if the JJ pins don't look beefier) and has spread a couple of the contacts in the tube sockets. I would inspect all the sockets with a magnifier of some sort, you should be able to see any irregular or enlarged contacts in the sockets.

I have "tightened up" the contacts before using a very small screw driver or awl and ever so slightly wedging the tool between the contact and the ceramic base, it doesn't take much pressure to squeeze the contacts back into original position, of course the unit needs to be unplugged first.

A good practice is to inspect all tube pins and straighten any that might be slightly bent and then clean before ever inserting them into the socket. I have seen where some new production tubes have had a larger diameter in the pin location, not the pins themselves, but the pin layout is a tad wider than the old originals, this would explain why the JJ's are still making good contact with the sockets and your nos tubes are not.

heiney9

Good points Mike. I too have had to tighten tube socket contacts. In my case it was a rectifier base which is much larger than a signal tube. Use caution it doesn't take much.

H9

Mike Reeter

heiney9 wrote: »

Good points Mike. I too have had to tighten tube socket contacts. In my case it was a rectifier base which is much larger than a signal tube. Use caution it doesn't take much.

H9

Repeat, Use caution it doesn't take much!!!

marvda1

I have heard at one time jj had a problem with it's pins being too small.

audiocr381ve

Mike Reeter wrote: »

Could be at some time a tube with a couple of bent pins was installed (if the JJ pins don't look beefier) and has spread a couple of the contacts in the tube sockets. I would inspect all the sockets with a magnifier of some sort, you should be able to see any irregular or enlarged contacts in the sockets.

I have "tightened up" the contacts before using a very small screw driver or awl and ever so slightly wedging the tool between the contact and the ceramic base, it doesn't take much pressure to squeeze the contacts back into original position, of course the unit needs to be unplugged first.

A good practice is to inspect all tube pins and straighten any that might be slightly bent and then clean before ever inserting them into the socket. I have seen where some new production tubes have had a larger diameter in the pin location, not the pins themselves, but the pin layout is a tad wider than the old originals, this would explain why the JJ's are still making good contact with the sockets and your nos tubes are not.

Thanks for the input guys. I popped open the top of the preamp to do a visual inspection of the sockets and didn't notice anything. I don't have a magnifying glass handy so it's hard to tell. Gotta get back to work but I'll check this out again later.

mhardy6647

The bigger pins issue is well established on the current production Russian 7868 power tubes... but I haven't heard of it on anybody's modern nine-pin miniature tubes. If the preamp is point-to-point wired, it's pretty straightforward to "re-tension" the socket's individual "pin receptacles" with a pair of hemostats.

dragon1952

You could also maybe just spread the pins on the tube outward slightly for a snugger fit.

audiocr381ve

I'm having a hard time figuring out how to re-tension the "loose" sockets. I have a small flathead screwdriver that fits in the socket, but what exactly do I do next?

"I have "tightened up" the contacts before using a very small screw driver or awl and ever so slightly wedging the tool between the contact and the ceramic base, it doesn't take much pressure to squeeze the contacts back into original position, of course the unit needs to be unplugged first."

This isn't making very much sense to me, need laymen terms hah.

Mike Reeter

audiocr381ve wrote: »

I'm having a hard time figuring out how to re-tension the "loose" sockets. I have a small flathead screwdriver that fits in the socket, but what exactly do I do next?

"I have "tightened up" the contacts before using a very small screw driver or awl and ever so slightly wedging the tool between the contact and the ceramic base, it doesn't take much pressure to squeeze the contacts back into original position, of course the unit needs to be unplugged first."

This isn't making very much sense to me, need laymen terms hah.

Shane, I'm sorry if my comments came off a little vague. There are many different tube sockets, the sockets in my Rogue Ares are a very tight and precise alignment for the small 9 pin tubes. The signal tube sockets in my Rogue Cronus are a tad bit different in the fact that the plated contacts are not as tight and allow for a little "wiggle room" for the tubes to seat.

I have "tightened up" the contacts in the sockets of the Cronus before using a Jewelers screwdriver and wedging the tip of the screwdriver between the outside edge of the plated contact and the ceramic socket and very slightly pushed the contact together where it had spread a little too far to make a snug fit around the pin.

If it would help I will try to take a couple of pictures that might help to show what I'm trying to describe, I'm not the best with a keyboard at getting a point across sometimes.

Also, spreading the pins on the tubes a little as mentioned might be a better fix. The Hemostats would probably be the best tool for tightening up the contacts.