Peavey 5150 (6505) Bias Mod
Aug27

Peavey 5150 (6505) Bias Mod

Years ago when I purchased my first Peavey 5150 I researched doing a bias mod on the amp and then on an old band web site I wrote up an instructional post.  In looking back I must say that I like the way the stock amp sounds better considering the amount of work that went into modding the amp and the possibility of DEATH associated with opening up an amp head without proper training. There was a difference but maybe not as big of a difference as I once thought. Of course each amp will react differently so this may be a good choice for you and your 5150/6505.  Here is what I wrote: ====================================== So I purchased a Peavey 5150 and heard about doing a bias mod since the stock one has a fixed bias.  Being able to bias the 5150 I have found there is more clarity as you are out of the “crossover distortion”.  In researching how to do a bias mod I came across fjamods.com with their 5150 bias mod (Here is the link: http://www.fjamods.com/5150BiasMod.html), but I needed more detailed instructions and I wanted an out-board bias so I wouldn’t have to open up the chassis every time I needed to bias. I then contacted Bob at www.eurotubes.com, which is where I buy my tubes, and he was a big help giving me pointers and making the mod procedure more clear. To be honest, I was scared to open up the 5150 head, or any head for that mater, because I don’t want 400+ volts running through my body and KILLING ME!  So I was very cautious. IF YOU ARE PLANNING ON DOING THIS MOD BE VERY CAREFUL.  AMPS HAVE HIGH VOLTAGE RUNNING TROUGH THEM AND CAN KILL YOU!  IF IN DOUBT TAKE IT TO A PROFESSIONAL. Also, I am NOT a professional tube amp repairman.  The mod done here was done by a half witted crazy guitar player, me.  PLEASE BE WARNED: You are responsible for either your own death and or blown head, NOT ME. If you want to do this mod you do so at your own risk!!! Now lets get on with it. What you need: Decent soldering skills (if you don’t have experience here, get some before doing this or have a pro do it) Philips head screw driver 10k pot Knob for your pot Between a 4.7k and 6k resistor Wire Solder Soldering iron rated between 15 and 30 watts Electric or cordless Drill and drill bits You can readily get these supplies at a Radio-Shack. Oh yeah, and Patience STEP ONE: Disassemble Chassis I did this mod to an original 5150 head, I...

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