My sca-35

[dcriner]

not sure WHICH are true NOS.

To be considered NOS, a tube should be in its original box, the tube must test GOOD, and the tube should show no signs of wear (e.g. on pins). If it's not in the original box, then it's only used or a pull, "like new," not NOS.

[Ty_Bower]

I haven't tried them myself, but I've heard good things said about the JJ EL84. Bob Pletka over at Eurotubes sells them, and I'm sure they're are plenty of other JJ vendors too.

I mostly use the old Russian 6pi14pi in my ST35 amp. eBay is probably your best bet for these.

[erichayes]

I have over 100 tubes that are NOS, but have been reboxed due to decomposition of the original boxes (the old boxes had high acid content in the cardboard) so this is not a relevant criterion. NIB (new in box), on the other hand, must meet the criteria Doug describes.

Mullard 6BQ5s used a halogen-based (iodine or bromine) getter that probably resulted in many tubes getting replaced that were perfectly good. I have a couple of quartets that look like hell but still meet/exceed original spec.

I use Sovtek 6BQ5s in the 1773 due to its superior damping factor over the JJs, but this is a hi fi amp. The prototype of the guitar amp based on the 1773 uses the JJs because they break up more linearly. If your musical tastes lean toward jazz/classical, use the Sovteks; if you're more rock/rap/whatever oriented, try the JJs. FWIW.

[dcgillespie]

I am in no way suggesting that a visual inspection replaces a proper testing of a tube. But neither is that to say that certain visual characteristics are not valid as they relate to a tube's condition, either.

The four tubes you offer, two of which have stain marks give no particular visual indication of being bad per say -- although they could be if they have been abused. In this case though, I absolutely agree with Terry that the staining you question is completely normal for certain tubes, Mullard included.

The visual indication I'm referring to has nothing to do with any internal stain marks, but everything to do with the evaporation of the internal flashing material that appears at the top of the tube. With the three tubes in the SCA-35, the evaporation has continued to the point that you can almost start to see through the flashing material.

The flashing of a tube is part of the manufacturing process, that along with the getter, works to absorb any residual gas left in the tube from the manufacturing process. However, over the working life of the tube, more gas is expelled from the elements within the tube, that normally the getter would absorb. When it is exhausted from this process, then the flashing starts to deteriorate as well, giving the visual appearance of the tubes in question.

Just as you can tell much about the condition of an engine simply by visual inspection of the exhaust smoke it (might) emit, so can you about the condition of a vacuum tube. In this case, there is little doubt of the extended use these particular tubes have had, and equally little doubt that they will test very poorly.

David G.

[erichayes]

David, I don't want to start a pissing contest regarding getters, but . . .

Flashing is a process, not a result. Getters are exposed to an intense RF field to literally explode the gas-absorbing material in the getter cup or halo. There is no "flash" that continues in conjunction with the life of the tube.' The getter is it. Period.

http://www.tubeseller.com/getterinfo.html

[dcgillespie]

Eric --

Completely agree! Your thoughts are what I was trying to say, and thought I had, but I appreciate you're making the point crystal clear.

The site information you provided was excellent. I hope it, along with this exchange, helps everyone realize that judging the visual appearance of the getter flashing is in part, a valid approach to use in helping to determine the remaining life of a given tube.

When I go to ham fests and the like where tubes are often sold without boxes in as is condition (no tester available), I use this analysis regularly and would immediately reject any tube with the appearance of those in question in the SCA-35 offered in this thread.

Thanks for the clarification.

David G.

[Ty_Bower]

I hope it, along with this exchange, helps everyone realize that judging the visual appearance of the getter flashing is in part, a valid approach to use in helping to determine the remaining life of a given tube.

It depends on which end of the article you read. At the top, it says:

Examination of the getter is a good way to tell if the tube is in good condition.

At the bottom, it says:

The ONLY way to accurately determine the health of a vacuum tube is to test it ELECTRICALLY. PERIOD.

Personally, I never throw out a tube just on appearances. I test for continuity across the filament using an ohmmeter. Then I use the ohmmeter again to check for any shorts on the other pins. Be aware that some tubes do have internal connections between certain pins (example, 7189A is internally connected between 1 and 2). After I'm satisfied with the ohmmeter, I stick the tube in an emissions tester and verify reasonable emissions. After all that, I still don't know if the tube is good - I really only know that it isn't obviously bad. I suspect the "right" way to test a tube would be on a curve tracer, and compare the results to the tube's datasheets. Unfortunately, most of us don't have curve tracers.

At a hamfest you won't have the opportunity to go through any kind of methodical testing. You spins the wheel, you takes your chances. If it makes you happy to judge them by the appearance of the barium deposits, more power to you.

What's your opinion on the state of this tube?

[dcriner]

I have over 100 tubes that are NOS, but have been reboxed due to decomposition of the original boxes (the old boxes had high acid content in the cardboard) so this is not a relevant criterion. NIB (new in box), on the other hand, must meet the criteria Doug describes.

There is no legal definition of NOS that I'm aware of. But as a buyer, my definition includes the requirement that the tube be in a matching, original box.

Eric, I'd believe you when you say your reboxed tubes are truly NOS. I assume that you know for a fact that they are NOS. But for eBay or other tube peddlers, my policy is if No Box, I'm not paying NOS price. I have a pair of NOS Sylvania 45s in their original 1930s boxes. The boxes aren't in all that great a shape, but they match the tubes. It seems surprising that out of a hundred NOS tubes, all their boxes would be ruined and have to be trashed. The value of those tubes might have been enhanced, in the eyes of some, if you would have stuffed the crumbling original boxes, along with the tubes, into the new boxes.

There are plenty of used tubes or pulls that look and test much like new. How many unscrupulous people clean them with Windex, rebox them, and sell them for NOS? A while back, I returned some reboxed tubes to AES that were sold as NOS, but by my inspection, were clearly used. They cheerfully refunded my money.

[CpuZapper]

Were tubes not sold in bulk all the time?
No individual boxes, I think they should still be NOS.

For me it's the tube but I do know some people like to have that pristine original box as well...

[dcriner]

For me it's the tube but I do know some people like to have that pristine original box as well...

As a rule of thumb, good used tubes and pulls sell for about half the price of NOS. I don't care about the box for the box's sake, nor do I care if the box is "pristine." But I do care about paying the NOS price for a tube that I'm unsure is really NOS. And without the original, matching box, what evidence is there that a tube is really NOS?

If a seller convinced me that he has a bulk of NOS tubes without boxes, I would pay NOS prices. Otherwise, not. I'd like to see a photo of his box with all the bulk tubes in it.

There is no one answer to this that everyone will agree with. I am expressing my opinion only.

[erichayes]

Doug, I agree with your stipulation with regard to buying tubes on eBay (which is why I don't buy tubes on eBay). In my case, the tubes were bought from an estate sale of a TV/radio repairman. I checked to make sure the tube brand matched the box (you'd be surprised how many don't; TV repairmen were very lazy creatures) and reboxed them in white boxes for protection. Since I'm not in the tube reselling business, I'm not concerned with what type of box the tube's in.

I have a NOS tube inventory of between 3 and 4 thousand tubes, so it's no big deal for me to verify whether a tube is really NOS. But I, too, have received tubes from AES that were brand A in a brand B box. When I called them about it, they said it's financially better for them to deal with the occasional mispack after the fact than it is to dedicate an employee to open each box before shipping--which makes sense, since they're dealing with millions of tubes.

[dcriner]

In my case, the tubes were bought from an estate sale of a TV/radio repairman. I checked to make sure the tube brand matched the box (you'd be surprised how many don't; of tubes.

The standard operating procedure was to plug in a new tube and slide the old tube into the new tube's box. Maybe the repairman was just willy-nilly replacing tubes, one at a time. Or, maybe he knew that a marginal tube might work OK in another set.

I have a large tube caddy from an old-time radio/TV repairman. I'd guess that about 75% are truly NOS, in original boxes. The rest are a hodge-podge of tubes in non-matching boxes and loose tubes rolling around in the caddy. Some of the non-matching boxes are marked in pencil, e.g.: OK or weak.

Eric, I'm like you - I'm not a tube salesman. But, from time to time, I am a tube buyer, which is where my "box" NOS philosophy comes into play.

I have an interest in 1920s-'30s antique radios. For those sets, I never buy NOS tubes - used only. (Some of the old tubes even have thoriated filaments that can be rejuvenated to restore emissions to like-new.) For later radios or audio amps, with more plentiful and less expensive tubes, I would tend to buy only NOS (or newly manufactured, perhaps).

I may have to lean on my pair of NOS 45s (in original boxes) to help fund my retirement!

[tech_fanatic]

Great discussion, thanks!

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Update:

Fixed the fuse holder, just needed some solder.

Worked on my little speaker terminal mod also. It's a combination of radioshack and philmore terminals - much more user friendly now.
-Kevin