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Message |
    
Cm3885
Intermediate Member
Username: Cm3885
Post Number: 412
Registered: 12-2003
| | Posted on Sunday, May 16, 2004 - 8:28 pm: | 
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#1 is it necessary to have all tubes in a amp all be the very same brands?
#2 is it necessary to have all the tubes matching tubes? |
Bruce
Senior Member
Username: Bruce
Post Number: 1250
Registered: 9-2003
| | Posted on Monday, May 17, 2004 - 4:39 am: |
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#1 no, #2 no ( but it might work better ) |
Tech237
Moderator
Username: Tech237
Post Number: 25
Registered: 4-2004
| | Posted on Monday, May 17, 2004 - 8:48 am: |
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Matching tubes (particularly at the output)MAY help with neutralization - the process of ensuring your amp doesnt oscillate, but even thats not a given.
Bruce is right both answers are really No. |
Cm3885
Intermediate Member
Username: Cm3885
Post Number: 413
Registered: 12-2003
| | Posted on Monday, May 17, 2004 - 1:33 pm: |
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What i meant by matching tubes is tubes that are all in the same precentage of each other ie 95% 90% 100% ect ect. They dont all have to be perfect do they?
I have some tubes that are withing about 10% of each other but they are old and eventually im goung to replace them all with new ones.. |
Bruce
Senior Member
Username: Bruce
Post Number: 1251
Registered: 9-2003
| | Posted on Monday, May 17, 2004 - 3:02 pm: |
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matching is done by gain or current draw at a givin bias ..... i used to have a drake 6 meter transverter with 3 6jb6's and matching tubes didnt mean a thing. |
Tech833
Moderator
Username: Tech833
Post Number: 697
Registered: 8-2002
| | Posted on Monday, May 17, 2004 - 6:00 pm: |
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If you have tubes of varying strength in parallel, and you run them very hard, then the stronger tubes will simply work harder than the weaker tubes. Eventually, the stronger tubes will be weakened enough that they will all match pretty closely anyway.
Best bet, if you have a number of tubes running parallel, run them very conservatively then it makes no difference if they are closely matched or not. |
Cm3885
Intermediate Member
Username: Cm3885
Post Number: 414
Registered: 12-2003
| | Posted on Tuesday, May 18, 2004 - 1:11 am: |
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Well most of my 6LQ6 tubes all pretty much have percentages + or - 5 to 10% but they are old anyways. I do need to good used 6JT6 tubes to replace 2 that were shorted. Im going to run them for now until i get new ones then they will ALL be replaced.
Another question i have is are the 6JT6 and the 6JT6a the very same tubes? |
Bruce
Senior Member
Username: Bruce
Post Number: 1252
Registered: 9-2003
| | Posted on Tuesday, May 18, 2004 - 7:23 am: |
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3885
FORGET THE % GOOD you need to know the TRANSCONDUCTANCE of the tube.......if your going to get fancy ! But again i have never found a good reason to " MATCH" tubes. |
409
Member
Username: 409
Post Number: 57
Registered: 3-2002
| | Posted on Thursday, May 20, 2004 - 3:12 am: |
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As a rule, you can't really test power amp. tubes on a tester and get a true idea of what they will do. The tester can not load them like they will be in an amp. Many testers show tubes with good emission but when under heavy load in an amplifier they tend to have fall off. |
Cm3885
Intermediate Member
Username: Cm3885
Post Number: 419
Registered: 12-2003
| | Posted on Thursday, May 20, 2004 - 1:21 pm: |
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I dont know of one tester that can test them under load. I wonder about tubes that are sold as NOS. If they sit unused for years at a time wont they lose some emissions? I was wondering because i just bought 4 NOS 6MJ6 tubes off of Ebay and the guy says they all test well over 100% emissions. But if they are bad i can get my $$$ back he has a 7 day guarantee. |
Mdiver
Intermediate Member
Username: Mdiver
Post Number: 106
Registered: 11-2003
| | Posted on Thursday, May 20, 2004 - 9:45 pm: |
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Cm3885 Have you heard of the Graphite Tubes that you can get in replacement of the 6lf6's |
Bruce
Senior Member
Username: Bruce
Post Number: 1255
Registered: 9-2003
| | Posted on Thursday, May 20, 2004 - 11:31 pm: |
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gosh 813 and 811's were graphite if i remember right but no sweep tubes........Hummmmmm NOS ?????? BAD then they WERE NOT NOS.... NOS MEANS NEW ( NEVER USED ) OLD STOCK. |
Cm3885
Intermediate Member
Username: Cm3885
Post Number: 421
Registered: 12-2003
| | Posted on Friday, May 21, 2004 - 1:55 am: |
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No i have not.. Who sells them?
Another question i have is when a fella puts new tubes in his amp does he have to neutralise the tubes like you do in a Yaesu FT 101 or do you just intall the tubes and leave the amp on for a lenth of time to "burn in" the new tubes? Ive seen guys install new tubes in am amp and then turn on the amp and let it warm up for 15 minutes then use it like it was before it had new tubes. |
409
Member
Username: 409
Post Number: 58
Registered: 3-2002
| | Posted on Friday, May 21, 2004 - 3:50 am: |
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No..tubes do not lose anything as long as there not used or lose there seal. I have seen tubes 30+ years old operate just like new when put into service. They do not detoriate since there is no air inside to cause oxydation. The NEW OLD STOCK tubes should work as new. If yours are NOS, they should be good-to-go . Always take note of the black spots on the sides or around the top of the glass envolope. Black is GOOD !! This is where the getter's were fired to remove any excess gas after they were evacuated. If those spots are brown or milky then the tube is gassy or has an air leak. |
Tech833
Moderator
Username: Tech833
Post Number: 702
Registered: 8-2002
| | Posted on Saturday, May 22, 2004 - 1:41 pm: |
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As long as the tubes are not gassed, they will not deteriorate just sitting on the shelf. What ages a tube is when the thoria is used up. Thoriated tungsten grids inside the tube will not lose their thoria just sitting, the tube has to be burning for that to happen.
Now, if the tube develops a leak, and 'inhales', then it will go bad quickly. You can usually tell if a tube has gas in it by a milky color to the getter flash. The flash should be silver color (like mercury). If a tube gets all purple inside when the B+ is on and you are drawing current, then that will also tell you that your tubes may have gas in them.
Tubes do not need a 'burn in' per-se. However, for the first 200 hours or so, it is important to keep the filaments at their rated voltage to expell any lingering oxygen in the envelope.
Graphite tubes tend to release oxygen when they are run hard. I would not recommend graphite tubes in a linear amplifier unless you have good self restraint. |
Cm3885
Intermediate Member
Username: Cm3885
Post Number: 424
Registered: 12-2003
| | Posted on Saturday, May 22, 2004 - 3:41 pm: |
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I got the NOS tubes today in the mail and they look absolutely perfect in every way.. The getter spots are very dark like mercury. I guess im good to go then!!
Hey guys, i want to TY all for the good info that has been provided to help me out! Ive never had to retube an amp befor so this is all pretty new to me.. ive always had someone do it for me. |
Tech833
Moderator
Username: Tech833
Post Number: 703
Registered: 8-2002
| | Posted on Saturday, May 22, 2004 - 5:08 pm: |
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Congratulations! |
Cm3885
Intermediate Member
Username: Cm3885
Post Number: 427
Registered: 12-2003
| | Posted on Saturday, May 22, 2004 - 11:12 pm: |
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NP!!!!
Oh, anyone know the power output on the 6LQ6/6JE6 and the 6JT6A tubes??
Just asking. |
Tech833
Moderator
Username: Tech833
Post Number: 707
Registered: 8-2002
| | Posted on Sunday, May 23, 2004 - 11:52 am: |
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A 6LQ6 is a 30 watt plate dessipation tube. Safely, you can get 60 watts of RF out of it before you start ruining it. |
Cm3885
Intermediate Member
Username: Cm3885
Post Number: 429
Registered: 12-2003
| | Posted on Sunday, May 23, 2004 - 7:44 pm: |
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Anyone know of a place that had filter caps for the mav 250? I need new ones even though the ones in mine are probably ok im gonna replace them anyways.. They are 80uF 4560 volt devices.... |
409
Member
Username: 409
Post Number: 59
Registered: 3-2002
| | Posted on Monday, May 24, 2004 - 12:31 am: |
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I think you mean 80/450V electrolytic. You might try Mouser Electronics. 4560V caps. Hummm....that would be a whopper of a power supply !! |
Radiopat
Junior Member
Username: Radiopat
Post Number: 10
Registered: 9-2003
| | Posted on Monday, May 24, 2004 - 5:31 am: |
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Does your new tubes use a grey or black plate? I have much better results with ones using grey plates. More output and they run cooler.
Patrick |
Cm3885
Intermediate Member
Username: Cm3885
Post Number: 432
Registered: 12-2003
| | Posted on Wednesday, May 26, 2004 - 2:58 am: |
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They are a dark grey looking plate. |
