Preamp Tubes? - Who, What, When, Where, Why, and How?

[RiverRatt]

I've wanted a tester since I started tube rolling with my little handful of RCA and GE 12AX7's. I'm obsessed

 

[MM54]

I got my first tester along with my first little shoebox of tubes I still have it, a Jackson 598.

 

[Marshall Mann]

I got it from ebay a while ago, just under $200. It was the third or fourth one I bid on, so your search seems to be going similar to mine.

Yep, sounds like it Matt.

I am kicking my self now for letting that first one go for $155.00.

I did find another on rebuilt for $350.00, but damn that still seems like a lot of money.

 

[RiverRatt]

Is the Jackson an emissions tester? From what I've read they made some good stuff.

 

[Marshall Mann]

Yeah I dont have that many tubes

This is just what I have not had time to got through.

Most of these are oddballs. But I did find a Mullard 10MM Gold pin 12ax7 in one of these boxes.

 

[MM54]

Is the Jackson an emissions tester? From what I've read they made some good stuff.

The meter is labeled something like "Dynamic Conductance" and it's got a lot of fancy wording on the instruction sheet, but I'm pretty sure it's just emissions. It's a good tester, I'll give it that. Plus it can do old 4- 5- and 7-pin tubes as well as B7G, Noval, Octal, and Loctal (Ah, loctal tubes, such a novelty )

 

[RiverRatt]

I'll probably hang on to my little Sencore Mighty Mite. It's a nice emissions/shorts tester. I need to fix the 9-pin socket as is to be expected. For some reason, the emissions side of my B&K reads shorts on just about any tube tested in it.

 

[RiverRatt]

This is just what I have not had time to got through.

Most of these are oddballs. But I did find a Mullard 10MM Gold pin 12ax7 in one of these boxes.

I had a hefty bag like that. I found two Mullard GZ34's in it and a few 6BQ5's. I gave the rest away. I've got hundreds of useless tubes still lying around. They've been gone through time and again and unless you're fixing an old TV they are worthless.

 

[MM54]

Sure there's not a short in one of the sockets somewhere that the jiggling of the pins going in/out is kicking on and off?

Also a lot of tubes will show "shorts" that are normal, the tube manual will tell you what ones.

 

[MM54]

I had a hefty bag like that. I found two Mullard GZ34's in it and a few 6BQ5's. I gave the rest away. I've got hundreds of useless tubes still lying around. They've been gone through time and again and unless you're fixing an old TV they are worthless.

I have a bunch of tubes like that as well, but I like it I like having a large collection (which is usually growing) of tubes. Some day they have to be worth something (like $2 or more!!)

 

[Marshall Mann]

I had a hefty bag like that. I found two Mullard GZ34's in it and a few 6BQ5's. I gave the rest away. I've got hundreds of useless tubes still lying around. They've been gone through time and again and unless you're fixing an old TV they are worthless.

I paid $60 for three boxes of tubes. The Mullard (If I can test it, and it's strong) could sell for $150.00 by it's self. I also found 20 or so 12at7 and 12au7's that all test good in my amps. I just done have any use for them.

I think if I remember correctly, I found quite few 6bq5's in there. What are they good for Alan?

 

[MM54]

i paid $60 for three boxes of tubes. The mullard (if i can test it, and it's strong) could sell for $150.00 by it's self. I also found 20 or so 12at7 and 12au7's that all test good in my amps. I just done have any use for them.

I think if i remember correctly, i found quite few 6bq5's in there. What are they good for alan?

6bq5 = el84

 

[RiverRatt]

Sure there's not a short in one of the sockets somewhere that the jiggling of the pins going in/out is kicking on and off?

Also a lot of tubes will show "shorts" that are normal, the tube manual will tell you what ones.

It's something in the switch bank. The shorts don't have any meter deflection and go off when I press the grid leakage test button. They are on whether or not the Shorts button is depressed. I've calibrated the shorts test using the 1m resistor.

Is there a simple way to test tubes like 6L6 and 6V6 octals for shorts and emissions on the lower sockets? If you set up for a normal socket 29 test and switch to the lower sockets and use #38 it should be the same, right?

 

[MM54]

It's something in the switch bank. The shorts don't have any meter deflection and go off when I press the grid leakage test button. They are on whether or not the Shorts button is depressed. I've calibrated the shorts test using the 1m resistor.

Is there a simple way to test tubes like 6L6 and 6V6 octals for shorts and emissions on the lower sockets? If you set up for a normal socket 29 test and switch to the lower sockets and use #38 it should be the same, right?

Well I suppose if you knew the right switch settings for the 6L6 and friends you could set it up for testing them, but why?

 

[RiverRatt]

I think if I remember correctly, I found quite few 6bq5's in there. What are they good for Alan?

Like Matt said, they are EL84's. Also look for 7189's. They are the same. A 7189A might be an EL84 as well, but sometimes they have an internal connection to pin 1. They can still sub for an EL84 if the amp socket doesn't have anything on pin 1.

 

[RiverRatt]

Well I suppose if you knew the right switch settings for the 6L6 and friends you could set it up for testing them, but why?

For troubleshooting. I want to take a tube with no shorts and test it in socket #38 and see if I can figure out where the problem is.

 

[MM54]

I have a 7868 around here somewhere, I think they're good for something

 

[MM54]

For troubleshooting. I want to take a tube with no shorts and test it in socket #38 and see if I can figure out where the problem is.

Well if you can figure out the switch settings to match it up (I don't know what switch corresponds to what element) it makes sense that it would work.

 

[sccloser]

I have an Accurate Tube Tester Model 157. I think it was made around 1963. It was the one my dad used when he worked on electronics in the 60's and 70's. Works well for me.

 

[RiverRatt]

Well if you can figure out the switch settings to match it up (I don't know what switch corresponds to what element) it makes sense that it would work.

Controls A and B are the heaters. C is a lockout.