Bias Mod for Mk1 5150?

[Glenn Fricker]

Hey gang,

I'm just curious if anyone has a link for a Bias trim pot Mod for a mark 1 5150. I've got a tech who can do it, but he needs instructions/schematics, so any help would be greatly appreciated.

Believe me, I'd love to send it to Eurotubes or somewhere like that, but shipping it to the states is not an option.... I'll get dinged for an import duty, even tho it's an American made amp.

Thanks again,

-0z-

 

[LiveWire]

Hello all...First post...

I followed this guide...Worked great...

http://www.golgothagames.com/k626/5150biasmod.htm

 

[Glenn Fricker]

AWESOME! Thank you so much! A step - by - step guide. Damn, I couldn't have asked for more.

I'm still taking it to my tech, tho.... I get paranoid around high voltages.

-0z-

 

[LiveWire]

I hear ya...

I was sweatin' bullets the whole time...lol....

 

[Tachy]

Originally posted by OzNimbus

I'm still taking it to my tech, tho.... I get paranoid around high voltages.

Ah ah ah..The high voltage is brutal!, yesterday I have risck electric shock....

 

[Glenn Fricker]

The other thing is, I'm partially colour blind.... I'd definitley put in the wrong resisitor!

 

[Brett - K A L I S I A]

Aaaaah, "sweating bullet", been often wondering what it meant besides being a Megadeth song

 

[Tachy]

What is partially colour blind??

 

[006]

It means he's not totally grayscaled in the vision department. Basically some colors appear to be other colors, not a great attribute to have when working with electronics, .

~006

 

[Glenn Fricker]

I have a hard time telling the difference between certain colours. Red in front of a green background, for instance, I can't see all too well. Browns & blacks also give me a hard time. So yeah, reading values on resistors is pretty much a no-go for me.


--Interesting note on the subject: SawStudio's track fader hi-lite bar was originally bright red... a shade I have a hard time seeing. Bob Lentini was nice enough to mod the program so the colour can be made user-adjustable.... on my request. Now mine's bright yellow. Talk about great tech support!

-0z-

 

[Sinister Mephisto]

What does this mod do?

 

[Tachy]

Ok...I understand wath is your problem...don't worry OzNimbus! and stay away from high voltage!

 

[Brett - K A L I S I A]

1 person out of 10 is color blind in the world, and most user interfaces take that into consideration

 

[Glenn Fricker]

What does this mod do?

The mk1 5150 is 'fixed bias' meaning unadjustable. The mark2 has a bias pot. Essentially, if I've been reading correctly, the 5150 is a little bit 'cold' out of the factory, meaning there is 'crossover distortion.' Adding an adjustable pot in the bias circuit lets you fine-tune how much juice the tubes get. Too little, the amp can sound fizzy, too much, you'll overload your tubes. I just want to make sure my amp can sound the best it possibly can for recording.

Ok, I'm a rank amateur with this stuff, so I'm sure someone's going to chime in & tell me I'm an idiot.

-0z-

 

[Tachy]

Brett have all my support!!....am...who is the girl that sing in your project? she is beautiful!

 

[Glenn Fricker]

1 person out of 10 is color blind in the world, and most user interfaces take that into consideration

Actually, the interface is user adjustable. The hi-lite bar was the one thing that wasn't.

 

[Glenn Fricker]

Brett have all my support!!....am...who is the girl that sing in your project? she is beautiful!

I always thought it was Brett trying to do a post Poison revival.

 

[Brett - K A L I S I A]

The girl in my avatar (Floor Jansen from After Forever) is not singing in my band unfortunately (she never called back, nor did her sister ). But our actual female singer is quite good looking anyway, so come to our shows when we'll do some !!!

PS : GO Bret Michaels !!!

 

[Tachy]

ah..ah..ah!!! goood...If my girlfriend Know wath I'm tell at this time I think she will kill me!!!aaaaaaaaaaaaaaaaa!!!!!!

 

[Mr. Brokenamp]

Just get a bias trim pot. Set it to the value of the bias resistor. Then replace the bias resistor with that. Common mod on old marshalls. goto acplink.com
or www.firebottle.com/ampage also maybe www.schematicheaven.com might have the 5150 schematic in the post 70's amp section.