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matching tubes
- Thread starter 517 Leroy
- Start date
It would be ideal if they were all matched with a tube tester but it will work fine with different brands in it as long as they all are good tubes. Sweep tubes are too scarce and expensive to be picky.
Some of the local guys went out and bought tube testers. I repaired one sweep tube amp and found that if you hold an am carrier for several seconds the good tubes start to turn red faster than the weak ones and the duds do nothing. Don't over do it though. Sweep tubes have paper thin anodes.
Some of the local guys went out and bought tube testers. I repaired one sweep tube amp and found that if you hold an am carrier for several seconds the good tubes start to turn red faster than the weak ones and the duds do nothing. Don't over do it though. Sweep tubes have paper thin anodes.
If anyone wants to trade tubes that turn red for ones that won't, I'm happy to make that deal 
The truth is if you get rid of the ones that don't turn red, the ones that do won't have to work so hard and you'll see more power out. I am a fan of the "red plate" test that 543 mentions above because it's an indication of how the tube is responding to both DC and RF under load. Lots of factory matching is only done with DC. As 543 says, don't over due it with sweep tubes. You only have to key the amp long enough to spot the first signs of color change on the plates. Don't wait for the weaker ones to change color because you already have your results once the first one does.
The truth is if you get rid of the ones that don't turn red, the ones that do won't have to work so hard and you'll see more power out. I am a fan of the "red plate" test that 543 mentions above because it's an indication of how the tube is responding to both DC and RF under load. Lots of factory matching is only done with DC. As 543 says, don't over due it with sweep tubes. You only have to key the amp long enough to spot the first signs of color change on the plates. Don't wait for the weaker ones to change color because you already have your results once the first one does.
If it isn't already it will be soon.
The gray "plate" structure inside the glass isn't supposed to light up.
Unless it's a big tube the size of a fruit jar. They're different.
Your Scout 20 is either set up wrong, or some parts have gone bad from 3 or 4 decades of age. There is more than one kind of problem that can cause the tubes to overheat and "cherry", showing color on the plate structure inside.
73
The gray "plate" structure inside the glass isn't supposed to light up.
Unless it's a big tube the size of a fruit jar. They're different.
Your Scout 20 is either set up wrong, or some parts have gone bad from 3 or 4 decades of age. There is more than one kind of problem that can cause the tubes to overheat and "cherry", showing color on the plate structure inside.
73
Economy Electronics Inc
225 Frontage Road
Lonoke, AR 72086
Phone:(501) 676-3234
Last I checked, this guy has a warehouse of obsolete stuff like that.
225 Frontage Road
Lonoke, AR 72086
Phone:(501) 676-3234
Last I checked, this guy has a warehouse of obsolete stuff like that.
Shadetree Mechanic
Delaware Base Station 808
Shadetree Mechanic
Delaware Base Station 808
There are also a handful of other tubes that cross reference to this one. I don't know if they are drop in replacements but I think they are close enough to work from what I have read.
Shadetree Mechanic
Delaware Base Station 808
Here is my thread on my Context amp. It uses the 6LQ6 in a 1 driving 4 configuration. One of my posts contains info from Ken's electronics about tube swapping to the 6KG6. There are other tubes that are a direct swap. Looking through my notes now.
https://www.worldwidedx.com/threads/contex-500-tube-amp.226894/page-4
https://www.worldwidedx.com/threads/contex-500-tube-amp.226894/page-4
I have a bran new set of 4 matching RCA 6JE6A-6LQ6 that I bought from Tube Depot a few years ago for spares to my Kicker 500 Amp (1x3)...Last set of matching RCA's I seen were going for $350+...
Hard to find 4 matching NOS tubes...most are sold as singles or pairs.
Hard to find 4 matching NOS tubes...most are sold as singles or pairs.
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The problem with the 6LQ6 tube is it wasn't only popular in CB linears. It was also used in some of the most expensive audio amplifiers ever built in matched sets of 8! If you own one of those 8 tube AF amps, it doesn't matter if the tubes cost $250 each. Those owners will pay anything to keep them alive.
If they were tested in an amplifier, maybe.
A tube tester is good at identifying bad tubes.
A tube that checks good in a tester may still produce a blue flash and break down under load in an amplifier.
Given the odds, I would recommend getting five or six good tubes to run a 4-tube amplifier. We recently fixed up a Maco 750 that used a terribly-rare tube called the M2057. It arrived with eight tubes in it, and three of them flunked my tube tester. Found five more to use that tested okay. One of those went "SNAP" after the amplifier was keyed a dozen times or so. The tester confirmed that this tube now tested bad.Tested okay before that.
Same thing happened to another tube after running it a while.
So now, after starting with a total of 13 tubes, it has eight that work in it.
Only a question of how long before another one goes "SNAP!".
Your mileage may vary. The Maco amplifier is famous for being hard on the tubes.
73
A tube tester is good at identifying bad tubes.
A tube that checks good in a tester may still produce a blue flash and break down under load in an amplifier.
Given the odds, I would recommend getting five or six good tubes to run a 4-tube amplifier. We recently fixed up a Maco 750 that used a terribly-rare tube called the M2057. It arrived with eight tubes in it, and three of them flunked my tube tester. Found five more to use that tested okay. One of those went "SNAP" after the amplifier was keyed a dozen times or so. The tester confirmed that this tube now tested bad.Tested okay before that.
Same thing happened to another tube after running it a while.
So now, after starting with a total of 13 tubes, it has eight that work in it.
Only a question of how long before another one goes "SNAP!".
Your mileage may vary. The Maco amplifier is famous for being hard on the tubes.
73