FJA modded 5150ii tube question

[tk7261]

So a while back the other guitarist in my band bought a used FJA modded 5150ii. When he got it he didnt ask what the mods where, so i dont know what was done to it. So its come time to record and i was thinking we should change the tubes. The ones in there now say Fender Doctor 6 on them and i have never heard of those. Do you think it would safe to get some new JJs in there? Will that improve my sound at all. I have no idea when they were changed last. could have been years.

edit: i forgot to type the tube name TAD 6l6wgc-str. will my tone improve if i get some JJs cause i dont know too much about this tube.

 

[MatrixClaw]

TAD is just a brand (Tube Amp Doctor). They make good tubes, JJs work well, though.

Whether they'd be better is totally up to your preferences.

 

[tk7261]

Well i think the TADs are pretty old. so i mean how much improvement will a new set of tubes make.

 

[Sloan]

Buy a few different brands of preamp tubes and swap them around to find what sounds best to you.

 

[drew_drummer]

TAD do not manufacture tubes. They just brand them. All tubes on the planet come from one of three places - China, Czech Republic, and Russia. Don't fall for the hype of expensive tube brands. All you're paying for is a shiny logo.

Also generally speaking V1, and V2 are most often the ones to focus on. V3 and V4 are usually drivers for the tone-stack - they don't give you any gain characteristics, they give you EQ tonal characteristics, very subtle. V5 is usually a phase inverter, and again... it's not going to give you any gain characteristics. You need a low noise tube in this position, but basically any will do. All depends on the amp though. Not 100% sure on the 5150, should probably read up on the various tube stages.

YMMV, IMHO, etc.. etc...

 

[tk7261]

so should he get new preamp tubes as well as power tubes? or could we get the power tubes first and see if that helps first?

 

[tk7261]

So guys i have to bring this thread back. The big question is with the bias. i know that 5150iis are cold so you can just plug in any 6l6. but i have no idea what mods were done to his head, and if its still set like the factory. so can i just plug in the jj 6l6gcs without hurting anything? cause ive been asking everywhere in my area for someone that can adjust the bias for his head and no one has any clue. im just about to give up and start asking to borrow someone elses head for the recording.

 

[psycle_1]

Yes, you can plug in the JJ's without hurting anything.

 

[tk7261]

Yes, you can plug in the JJ's without hurting anything.

thanks for the quick response even if the previous owner set it hot? that would just mean the tube wont last as long right?

 

[Leevious]

If you run the serial number of the amp on FJA's site, I believe you will be able to see the mods performed (or at least ensure that Jerry did the work to it). If that doesn't work, email him and he will be able to tell you for sure. As far as the tubes are concerned, I would still get the bias checked when replacing them. Does the 5150II have external bias pot / test points? If so, you could do it yourself. My 6505+ does, not sure about the 5150II...

 

[sprack]

5150II == 6505+

 

[MatrixClaw]

The 5150 II / 6505+'s stock adjustable bias range isn't hot enough to do any damage to your amp, even if set all the way up. However, since it's been FJA modded, there's probably a good chance that the bias mod was done, which would mean getting it properly biased would be a good idea. Just buy some test probes online for like $15 and do it yourself, it's pretty easy, no point spending $50+ for some else to do it.

 

[tk7261]

@Leevious - unfortunately the sticker with the serial number on it has been damaged by the previous owner. i can only read the last 4 numbers. so ill have to email him. also i hear the bias test terminals are useless on the 5150ii/6505+.

@MatrixClaw - yea i hear how narrow the range is. if i knew for sure there was no bias mod i wouldn't have to worry. i was looking into bias probes but didnt know which was least likely zap me to death. any recommendations for probes?