[sam6550a]

Good to know, Sam. I've never been able to find any Hickok-published manual or document that specifies what an 'acceptable' or maximum amount of leakage is, and perhaps for just the reason you detail where it depends on the type and application of the tube. Most of the 6080's, 6AS7's, 5998's, etc I've tested register some leakage, but it's usually in the 5+ megohm range so I've just considered that to be the norm (at my own peril perhaps). I haven't given up on the GE's...I have almost $50 invested in the two of them. Haven't had a chance to do the pins yet, but I'll certainly give it a shot and report back with the results.

OK, here is what I found, using the 1500 page bible of vacuum tubes, The Radiotron Designer's Handbook, F. Langford Smith, editor, 1953. You can download it for free from www.tubebooks.org. This is, in my opinion, the best tube tome around, and one entire chapter is devoted to the testing of tubes. On page 123, he states "The maximum leakage resistance from heater to cathode in new valves [tubes, to you colonials] varies from 1 or 2 megohms for power valves to 5 megohms for ordinary 6.3 Volt 0.3 Ampere voltage amplifier valves and even higher for rectifier types having separate heaters and cathodes". Methods of performing the tests are included, plus a lot more. Every time I look up something in this work I am amazed by how much I have forgotten!

I tested the 2 6AS7 and 2 5998A tubes that I own, using a B & K 707, properly calibrated with the shorts light illuminating at 2 megohms, all 4 -passed. Although the 707 wants to test the 6as7 and 5998A in the emission section, I test them in the Dynamic Mutual Conductance section in socket 25, with sensitivity at 75 for 6AS7s and at 60 for 5998As. Using the % scale on the 707, RCA 6AS7 was 65 & 70, Svetlana was 75 & 78, GE 5998A #1 was 90 & 90, and #2 was 85 & 92.

I hope this helps, Bill. PM me if you need more info---in the meantime, download old Langford Smith!

 

[therremans]

Quite the combination going on. Really enjoying the RCA VT-231 with the HD6XX.

 

[Slade01]

Quite the combination going on. Really enjoying the RCA VT-231 with the HD6XX.

They RCA Gray Glass reputation still living up to the hype! I can't believe the prices they are going for these days though....

 

[therremans]

They RCA Gray Glass reputation still living up to the hype! I can't believe the prices they are going for these days though....

Yeah, it plays really well with some setups. I understand why people like it so much. Pronounced mids without muddy highs. Lucky me, I found this one for $18.99 on eBay, tests new.

 

[Slade01]

Yeah, it plays really well with some setups. I understand why people like it so much. Pronounced mids without muddy highs. Lucky me, I found this one for $18.99 on eBay, tests new.

This was my go-to budget tube and top recommendation for new-comers. A tube that offers a lot that doesn't break the bank. I guess that's not really the case anymore. Yeah, I remember finding mine for 13.99 as well. Easily had super bang for the buck value. Yeah for you to find one that tests new at that price - awesome.

I have to say that the military designations on tubes does make it a little bit more cool looking.

 

[therremans]

This was my go-to budget tube and top recommendation for new-comers. A tube that offers a lot that doesn't break the bank. I guess that's not really the case anymore. Yeah, I remember finding mine for 13.99 as well. Easily had super bang for the buck value. Yeah for you to find one that tests new at that price - awesome.

I have to say that the military designations on tubes does make it a little bit more cool looking.

Especially English or European military markings and in some cases the military tube is built slightly different or to higher standards and strict tolerances. Maybe that’s why they typically produce better music. Going rate for the RCA is around $75 now.

 

[bcowen]

OK, here is what I found, using the 1500 page bible of vacuum tubes, The Radiotron Designer's Handbook, F. Langford Smith, editor, 1953. You can download it for free from www.tubebooks.org. This is, in my opinion, the best tube tome around, and one entire chapter is devoted to the testing of tubes. On page 123, he states "The maximum leakage resistance from heater to cathode in new valves [tubes, to you colonials] varies from 1 or 2 megohms for power valves to 5 megohms for ordinary 6.3 Volt 0.3 Ampere voltage amplifier valves and even higher for rectifier types having separate heaters and cathodes". Methods of performing the tests are included, plus a lot more. Every time I look up something in this work I am amazed by how much I have forgotten!

I tested the 2 6AS7 and 2 5998A tubes that I own, using a B & K 707, properly calibrated with the shorts light illuminating at 2 megohms, all 4 -passed. Although the 707 wants to test the 6as7 and 5998A in the emission section, I test them in the Dynamic Mutual Conductance section in socket 25, with sensitivity at 75 for 6AS7s and at 60 for 5998As. Using the % scale on the 707, RCA 6AS7 was 65 & 70, Svetlana was 75 & 78, GE 5998A #1 was 90 & 90, and #2 was 85 & 92.

I hope this helps, Bill. PM me if you need more info---in the meantime, download old Langford Smith!

Wow. Thanks Sam! That site is a treasure trove of info, and I'd never run across it before. Very helpful!

Just don't tell @Paladin79 that I set the shorts sensitivity on his 707 at 1 megohm. That's per the manual I have on hand, but those manuals changed frequently and yours may be different.

I'll give both GE's a spin in the Weston 981 before and after I solder them to see what it shows. Haven't tried that yet 'cause it's in the closet and I'm far too lazy to drag it out.

 

[Deceneu808]

Ok so I've managed to squeeze the DV back on the desk and I'm happy I did.

 

[Paladin79]

Wow. Thanks Sam! That site is a treasure trove of info, and I'd never run across it before. Very helpful!

Just don't tell @Paladin79 that I set the shorts sensitivity on his 707 at 1 megohm. That's per the manual I have on hand, but those manuals changed frequently and yours may be different.



I'll give both GE's a spin in the Weston 981 before and after I solder them to see what it shows. Haven't tried that yet 'cause it's in the closet and I'm far too lazy to drag it out.

I do have the 707 tester but generally I just hand Finnegan new tubes I receive and those he does not break I figure I should give them a chance to be plugged into an amp. My form of natural selection.

 

[sam6550a]

Wow. Thanks Sam! That site is a treasure trove of info, and I'd never run across it before. Very helpful!

Just don't tell @Paladin79 that I set the shorts sensitivity on his 707 at 1 megohm. That's per the manual I have on hand, but those manuals changed frequently and yours may be different.



I'll give both GE's a spin in the Weston 981 before and after I solder them to see what it shows. Haven't tried that yet 'cause it's in the closet and I'm far too lazy to drag it out.

I will be glad to clean out that closet for you!

 

[maketus]

can i just replace default pot new alps 50k 6legs in default circuit

 

[therremans]

can i just replace default pot new alps 50k 6legs in default circuit

Yes and no. It’s not a drop in fit and will require some modifications. Importantly, the alps pot legs will not align to the stock pcb that the stock pot is soldered to.

 

[maketus]

what modifications ?

 

[Deceneu808]

what modifications ?

Need to take the old pot out with the PCB that's sticked to. Then solder the wires directly on the Alps. Most if not all, drilled the front hole to accommodate the bigger Alps pot but I've just used hot glue to stick it inside and on the front. Took me two minutes and it's quite sturdy. It takes a bit of force to unglue the pot from the frame on the inside. Had 0 problems so far

 

[maketus]

are orginal spot and alps legs differentt order . thats whay just needto solder wires dirictly on the alps