Replacing tubes in rm100

[davidian]

Hi all,

I have ordered a couple of new replacement tubes and before i put them in i need to ask a few questions.

I have self biased the quad jj e34ls to 39mva between all. I am planning to put in jj 6l6gcs in the middle. From what i read abt the 6l6s is that the bias rate is 20-35mva.

Will i blow my tubes if i stick it to the slots which are 39mva or should i adjust my bias setting for the 2 middle e34ls first down to 30mva first before unplugging and replacing it with the 6l6s?

Also is there a guide on how to open the v1, loop preamp tubes for replacement? Got a couple of nos jan philips 5751s im planning to install in it.

Thanks so much :lol:

 

[nomad100]

just turn the bias all the way to 0 and go up from there. replacing the loop tube you just take out the old one and put in the new one.

 

[Julia]

I think 39 mV for the E34Ls is too hot. They're rated at 25W each.

 

[Shinozoku]

I've gotten my best sounds out of EL34s at 31mv actually. 6L6's I've gotten my best tones at 33mv.

 

[eedude]

I think 39 mV for the E34Ls is too hot. They're rated at 25W each.

i think you're mixing apples and oranges...there is static dissipation, dynamic dissipation and an output power.... the bias point (and B+)will set the static dissipation. Static dissipation in this case is P= ~450V*0.039A = ~18W. Not saying this is good or bad, just saying the 25W does not mean anything here...unless i missed something?

 

[davidian]

Hi all,

Thanks for the responses.

I biased the JJ E34Ls at 39mV as it is in the within Randall specifications (35-45mV). I don't want to run my tubes too hot (hard for me to get a replacement out here) . Same went for my JJ 6L6GCs @ 32mV

So far, the low end is starting to pick up. My JF ultra sounds much more clearer and is putting out more low end clarity than the usual middy crunch/punch (drop C tuning). My XTC is performing much better (yet to do the cap mod, hunting down the shop which sells it near my country) in terms of a more amount of bass response in the middy module than the usual mud.

Im using 4CM with my GT10 and using the Tubescreamer OD mod to sculpt the gain and I absolutely love it now.

 

[Julia]

I think 39 mV for the E34Ls is too hot. They're rated at 25W each.

i think you're mixing apples and oranges...there is static dissipation, dynamic dissipation and an output power.... the bias point (and B+)will set the static dissipation. Static dissipation in this case is P= ~450V*0.039A = ~18W. Not saying this is good or bad, just saying the 25W does not mean anything here...unless i missed something?

25W = maximum plate dissipation.

Randall tech support gave me 530V for the transformer for bias calcs. So if we use that number 530V*.039A = ~20W or 80% of max for the tube. Pretty hot.

40 mV is where I have my 6550s biased.

 

[speedemon]

Hey Shinozuku,


thanks for that,

I just threw a pair of EL34s in my RM100, and am not sure about the result just yet, left them at ~34 and the 6l6s at ~32,


Anyone else got a suggestion? my aim is to get a more "vintage" tone out of the Plexi and Tweed (as you all know, they have "old" USA 12ax7 and 5751s already).

Thanks!

 

[Julia]

Vintage tone? For the Plexi -- Celestion Heritage series G12M 20W rating; or the G12H

For the tweed, something Eminence "American toned" that has been around forever.

 

[speedemon]

Hi Julia,


thanks, I got it covered! I was testing in a 4x12 with g12h30s, and g12ts, and I will be using with the Scumback version of g12h30 and celestion blue, I got a Weber Fane clone on the way and a Jensen C12N (traded away a p12q, prob shoulda kept it!)

Perhaps the bias doesn't make much difference on that? (shrug)

Is it worthwhile to find old Fender and Marshall bias specs?

Thanks!

 

[Julia]

Absolutely worthless for this amp to look at the bias settings and stuff on another. Speakers and speaker cabs will have the biggest impact on the sound, after one's playing ability. Yes I'm saying tone is in the fingers.

 

[warlok]

Yes I'm saying tone is in the fingers.

Anyone got any fingers for sale??

 

[HughJasol]

Anyone got any fingers for sale??

:lol: There's an obvious joke in there somewhere, but I'm not smart enough to figure it out . . .

 

[Julia]

Anyone got any fingers for sale??

:lol: There's an obvious joke in there somewhere, but I'm not smart enough to figure it out . . .

Joke = since tone is in the fingers, and he wants to buy fingers, he's saying he has no tone.

Me: want to buy a new and improved set that is stronger, faster, better. Maybe throw in both arms while you're at it. Make that a new body while you're at it.... How about a cylon?

 

[HughJasol]

Joke = since tone is in the fingers, and he wants to buy fingers, he's saying he has no tone.

Yes OK - I was actually smart enough to figure out that much :lol:. I originally meant there was probably a joke to be had that involved one finger in particular . . . :wink:

 

[warlok]

I'll give you each one finger... Guess which one.. :lol: (**** it, no "F-you" smilie..)

 

[speedemon]

doh,

I think I play ok....lol But it is not as easy to change from metal to blues and classic rock as it seems...

I was looking for that "loose, vintage" vibe. EL34s sound good I think, and I got some good sounds with tinkering, but like a dufus I put the good 12ax7 in the effects loop and the New Sensor in V1...(yes, you were about to say it doesn't matter, and I have recorded enough to know it, but this is about tricking MY ears :lol: )


Here come the men in the white coats...Ahhhh serenity...

Take it easy!