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Need help with understandin average mutal conductance

From my experience so far 60 to 65 percent are worthless for a single tube. But I may have 100 of that tube so it maybe worth something in large lots like I have of almost all the tubes for example so for I counted 185 5u4gb tubes so far.
 
I picked up 5000+ and figured 90% trash.

However, as I go along, I am finding more and more tubes that actually have a use.

SO, maybe 50% trash.

AND, I have not even looked into the old tube radio world. I floated through there a little, that is a whole other AK like community

But 100,000! really? 20 times the pile I have, JEEEEEEZuuuuuus!
 
chaztaylor said:
I recently bought out 3 radio store full of vacuum tubes. I have roughly 100000 vacuum tubes to test on a hicok tube tester that I just bought. I understand the roll chart up until it say average mutual conductance. Is that the min the tube should test to be good. Does that number for example 5000. If I test the tube and it tests at 5100 is that a really strong tube or just barely good. Thanks for any help.
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To answer your question, mutual conductance is I/V (current divided by voltage). It is the reciprocal of Ohms (V/I).

Average mutual conductance means that is an average reading of amplification or gain of that tube type. So if you measure more, great. If you measure less, you may still have a new tube or one that meets the specifications on the tube's data sheet.

I learned a long time ago that my Hickok 600A mutual conductance tube tester gave low mutual conductance results for certain power tubes, like the 7591. So you may measure 4000 micromhos but in reality the tube might really be 6000 micromhos.

So yes, average is if one took a huge lot of tubes and measured them, and if your tester said that 5000 was average, well then a 4000 might be within specification too. So don't throw them out unless you are sure they are bad.

Hope this helps. I wanted u to know that testing tubes is not as black and white as it seems and results will vary frpm tester to tester.

But it is fun to test tubes. Takes time though for the dual types, like triode/triode or triode/pentode since these are like two tubes in one package. They share the same filament though.

Have fun. If u have a question, post it here.
 
chaztaylor said:
From my experience so far 60 to 65 percent are worthless for a single tube. But I may have 100 of that tube so it maybe worth something in large lots like I have of almost all the tubes for example so for I counted 185 5u4gb tubes so far.
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Ha! In a lot of the lots I buy the 5U4Gs are keepers compared to the rest.
On a first go round, I'd keep most of the 6 and 12 volt tubes, the 5 volt rectifiers, the 4 digit tubes like 5751 and 7062, and the old 2 digit radio tubes as well as 3 digit radio tubes in globe envelopes.

I'd probably dump most of the small 7 pins and all the metal tubes; there's just not enough of them financially worth while to sort through, and certainly not test. I sold a bag of about 100+ 7 pins a while back for something like $12 shipped.

And even the 6 and 12s can be sketchy. I've got 150+ lot up in BT for $40 shipped with zero interest right now.

Just like buying a couple pallets of LPs; there's a LOT of Herb and Babs in there....

0696998611924.jpg
 
gadget73 said:
That is such an awkward photo. Neither one looks like they are happy about being there.
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How true. I wonder if they had any idea how many copies it would sell.
I see it it practically every box of records I thumb through and probably more than "Whipped Cream"
 
Im just going from box to box looking them up on ebay. Alot of them I know by heart what there worth at this point and I only whet through about 10000 so far. I am also not counting the tubes with out boxes if you count those tubes. It may be more like 150,000. I have 6 18x18x 24 boxes filled so ill be checking tubes for years to come. I have a ridiculous amount of aa5 tubes sets atlest a few thousand.
 
Also I would like to know if the tester says the average is 5000 lets say what would you recommend as a strong tube reading and a weak tube reading. Also thank you all for your help.
 
Does anyone know anything about a pj7 ge globe vacuum tube I cant find any test data and or any info about this tube at all which is weird becuse I have had no problems up to this point thanks
 
Blhagstrom u said you picked up 5000 tubes where did you get them from I watch the market very closely and the only recent auctions for that amount of tubes was in ohio and Pennsylvania with in the last week .
 
chaztaylor said:
Also I would like to know if the tester says the average is 5000 lets say what would you recommend as a strong tube reading and a weak tube reading. Also thank you all for your help.
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What's the Hickok model? If that is average of new, as on my 600A, 5000 would be strong.
If it's minimum, that's trickier. I'd expect strong to be probably 33% more at least, maybe more like 100% if 505 were weak.

Yes, those are double digits, but not great ones. they might get culled out on Round 2. Plus you have to open every box to make sure the right tube is inside.
Hit the globes first as they always bring more.
 
When looking them up on eBay look at SOLD listings. There are lots of tube types with a 100 listings at $10 to $30, but when you look at SOLD listings there are few or no sales. Then there are the tube types where there are 500 listings for that tube type, so the chances that yours will sales are slim to none. Here is a good list of desirable tubes you can download and print here https://vacuumtubesinc.com/tubeswearebuying. Ignore his pricing. If he is willing to pay more than $5, you probably have a real keeper. The short list of easy to sell tubes are -

#1 5AR4 made by Mullard. Can be branded by others. Extremely rare and highly prized by guitar players.
#2 European made 12AX7 tubes with Telefunken being king of the hill. 7025 is the version frequently used in guitar amps.
#3 Large bottle tubes like 211 and 845.
#4 Power tubes used in guitar and audio like 6L6, EL84, 7355, 6V6, 7591, 7868, 5881, EL34, 6550, KT88, etc. Matched pairs and quads increase the value significantly.
#5 Western Electric tubes. Look up sold listings on eBay for the ones highly coveted by the Asian market.
#6 A bunch of others you will figure out with some experience under your belt. This is a hard way to make money when you figure out the time involved to sort, test, list and ship.

Good luck!
 
Hiya,

So many of you audiophiles overlook sweep tubes which many times bring 20 to 40 each if they are used in CB/Ham amplifiers.

And that 532 is not going to test many of this type. If you are seriously going to get into the tube reselling business (Like it seems) you will get tired of that 532 and its limitations pretty soon.

Frannie
 
Lol sweep tubes thats what those tubes Are called why does my tester not have a pin set up for this tube and I have 4 more testers that cant test it either whats up with that.
 
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