7JP4 Tube Grading
 

So I have seen "A" grade before and I just figured that it was a good tube in nice working condition. Someone is selling a "C" grade tube that he says is a good working tube. So this has me thinking- what the heck criteria is the grading based on? And how does one determine the grade? it sounds like it may be a bit subjective.

Don't really know what I am talking about...BUT I would guess that maybe an "A" grade would be NIB--tested perfect or nearly so. "C" grade would likely be a pull--in unknown condition, or maybe marginally good, but NOT perfect, not holding life test or cutoff, etc

I see grade 'A' on RCA Hi-lite tube all the time, the sticker usually states the envelope was checked and a new gun installed. So an 'A' grade rebuild would be a used envelope with new gun, anyone's guess what the other grades mean- probably some sort of defect causing a small blemish in the image.

I've seen type grade AA, meaning new glass.
The RCA HI-lites were originally all new, where the Colorama's were the re-guns. I suppose, that changed later.
The local rebuilder used to state on their labels, "Electronically, this is a brand new picture tube." :scratch2:

Here are the official New York City CRT grades. I have seen a Florids document that has the same details.

(1) Black and white picture tubes.
Grade AA—Description—All new components and materials, including new glass envelope.
Grade A—Description—Used glass envelope, all other components and materials are new.
Grade B—Description—Used glass envelope, used phosphorescent viewing screen, used alumination, used internal conductive coating, all other components and materials are new.
Grade C—Description—Used picture tube for resale, all significant components and materials are used.
(2) Color picture tubes.
Grade AA—All new components and materials, including new glass envelope.
Grade A— Used glass envelope, new or used shadow mask, all other components and materials are new.
Grade B—New electron gun, all other components and materials are used.
Grade C—Used picture tube for resale, all significant components and materials are used.

So by New York City's official grading, RCA2000 would be correct in his mention of a "pull in unknown condition." This leads me to a couple of questions. First, who is New York City in relation to CRTs? Second, why would someone market these "Grade C" tubes for resale based on that description?

Perhaps there are other criteria involved in this such as a "Grade C" being a pull from a decently working set with some other problem that made it more lucrative to part than to sell as a set. But if CRTs were your business, one would think that you would have the capability to test one. Then you could have at least a smidge of security to offer the buyer that the tube might work.....

Could be that grade C came from 'trade in' sets that were no longer worth more than the parts inside.

Did any rebuilder actually produce "Grade A" color CRTs? This description:

would indicate that the tube was rephosphored. Depositing a new tricolor phosphor screen would seem to be FAR beyond the capability of CRT rebuilders. The shadow mask was actually used as a stencil in a multistep photoresist process to locate and deposit the dot triads in exactly the right locations. This would involve separating the faceplate and mask from the funnel, rescreening the phosphors, and then resealing the tube together using a frit seal process as the OEM did. Sounds like WAY too much work to be economically viable.

RCA both made new CRTs, and rebuilt them. If both those operations were under the same roof, then it would not be out of the question to take an old cleaned faceplate walk it over to the NEW tube line phosphoring station and get it done.

Perhaps not out of the question, but *highly*unlikely. If the faceplate/funnel/shadowmask/phosphor were not usable, the best option would have been to simply scrap the tube!
It is a VERY labor intensive/time consuming process to cleanly separate the faceplate from the funnel, remove the remaining frit and prepare (lap and acid fortify?) the faceplate for re-deposition of the phosphor... MUCH cheaper to use a new part.

jr

I've seen that grading chart, on the back of a Sears parts invoice.
I thought when I read the "Grade C", I wonder if they scrapped the sets, that were damaged in transit or it might have been sets that no one was able to repair properly. This was at least 40 years ago. :sigh:

Many large cities probably have or had similar laws, intended to protect consumers from shady businesses, back in the days when CRT replacement was relatively common and also relatively expensive. New York just happens to be the one that I found in a Web search.

Here is the reference to the comparable Florida law, apparently from when it was repealed. So, in Florida now, you may be able to call a CRT a "class-A used" one, without getting arrested. :)

http://www.myfloridahouse.gov/Sectio...6&Session=2011

This one as well, is simply what came up in an online search.

I picture some rebuilders testing duds and finding some were okay, or maybe just needed cataract surgery or short removal, sockets, etc. There use to be lots of places that dealt in used receiving tubes. I suspect in cities (NYC in particular) there was quite a market for such things.

This may have been possible if the faceplate was never fritted to a funnel, but I have strong doubts the two could be separated successfully once joined.

Edit: I see the same comment above. A secondary thought is that after the phosphor deposition was complete, and before joining the funnel, if there were significant flaws, the face assembly could be reprocessed, possibly discarding the shadow mask if that caused the problem (like missing holes). But it would take some kind of intrusive investigation of a factory to determine if this was done and the resulting tube was "Grade A" instead of "AA." This seems like a typical kind of legislative language mistake due to misunderstanding of technical issues.

Guess that it depends on what is meant by "new" :scratch2:

I would argue that the faceplate panel has never left the factory, never been turned on is *still* new. I would think that any phosphor deposition process would have "rework loops".... first pass yields should have been high, but I'm guessing *not* 100%... seems like tubes assembled with these panels would rightly be marked "AA", IMHO.

jr