[jackman]

Hi Guys,

I found an old pair of NOS Tung Sol 5688's in my office junk drawer. They look shiny and new but the getter flash has a brown spot and most of the silver is gone from the top of the tube. I plugged them into my Modwright CDP and they sound perfect. No microphonics or noise. Listening to Miles and everything sounds great.  How long can tubes last with clear tops or dark spots? 

Forgot I had these and I have a couple pairs of backup tubes either way. Also, if a tube fails could it hurt my CDP or speakers?  They sound perfect, highs are detailed and extended and mids are like my other set of NOS Tung Sol's.  He bottom end of these is powerful but maybe not as punchy as the Raytheon tubes I tried. Both sound very good.

I'll keep them in until they fail or one fails. Don't recall when I got them but it was at least 6 or 7 years ago.

Cheers

Jack

[Pez]

General rule of thumb. When the getter silver starts to have issues the tube is not long for this world. Maybe a few months?

[jackman]

General rule of thumb. When the getter silver starts to have I issues the tube is not long for this world. Maybe a few months?

Thanks Pez.

Oh man!   :cry:I was afraid that was the case.  I'm going to keep them in and see how long it takes.  The getters are glowing very brightly but it could just be more noticeable because most of the silver is gone.  My other pair of Tung Sol 5687's are also pretty clear at the top.  I've got backups but these might be my favorite.  Will have to keep my eyes open for another pair.

Cheers,

J

[JakeJ]

J,

Do you have the ability to get them tested?  Also, browning of the flashing is generally a bad sign but bluing is more just due to aging and not necessarily a bad thing.  However testing is your best bet. 

Your ear may not detect a sonic flaw due to electrical failure in a vacuum tube fast enough to save the circuit it is failing in.  Although small signal tubes do not typically cause catastrophic failures like power tubes can.

[jackman]

Okay, thanks guys. I don't have any testing equipment. It I just did a listening test comparing these to a set of 1956 NOS tubes I bought from Rob on our very own AC classifieds.  The Raytheon tubes were extended and music came to life.

After his brief evaluation, it's obvious the Tung Sol tubes are tired and almost cashed out.  These fresh Raytheon tubes are sounding great. Cymbals sound like metal again, with nice sharp pitch. The old tubes sounded like a fizzy splash.

These Raytheon tubes might be my favorite but I can't recall what the Tung Sol's sounded like when they were new.  They are better than my other backup set of NOS Sylvania tubes.  I guess old tubes don't have to be totally dead to sound lifeless

Up until today's tesT of the Tung sol tubes, I was using some fresh nos Raytheon tubes but this pair is better sounding.

Jack