Who has rebiased their EVH 5150 100s?

[Rick Lee]

As long as it has the external bias points and wheel, I think I'm gonna DIY this when the time comes. I can't find anything on Youtube about this. Anyone here done it? Do I need anything other than a multimeter?

 

[fusedbrain]

Do I need anything other than a multimeter?

A small phillips screwdriver to remove the bias pot cover and a small flat to adjust the pot

Got my 100s brand new in a box and the bias read approx 90 mv ( which = 90ma ). The plate voltage was 480 something, I can't remember exactly, so I uppped the bias to 130. That's about 32-33ma per tube, which is not that hot for the plate voltage, but the amp sounded much better so I didn't go any higher. The original 22ma/tube was stone cold and didn't sound that great.

 

[Rick Lee]

I probably have a little less than half the tube life left in these. It was repaired in Sept. and got new Winged Cs. I've run it pretty hard since then.

So what settings do you use on the multimeter?

 

[Distored]

Keep it coming..

 

[crwnedblasphemy]

Haven't checked mine yet...need a new probe wires.

 

[romanianreaper]

I had a 5150-III years ago. I can't remember but isn't the bias adjustment near several capacitors? I didn't remember the points being external but mine was probably a 2008 version.

 

[Rick Lee]

The 100s (S= Stealth) has external bias points and wheel. The non-S versions do not.

 

[fusedbrain]

Set your multi-meter to milli-volts. Your measuring the voltage drop across a 1ohm resistor, so according to ohm's law 1 milli-volt = 1 milli-amp in this case.
To get the plate voltage to do a bias calculation you'll need bias probes or measure the voltage on pin 3. If your not comfortable checking the plate voltage on pin 3 ( it could kill you if you don't know what your doing ) you could use an educated guess of around 470 - 480 volts for the plate voltage in the bias calculation.
Or screw the calculation and just get the bias up to around 30 -34 ma / tube and rock out

 

[Lord Toneking]

On the 100s head the bias should be around 90-93 from the test points per Howard Kaplan. You might want to double check cranking that up to 130 on the trim pot

 

[fusedbrain]

90 / 4 = 22.5 ma /tube
Howard must like the sound of his tubes set cold.
Or Fender / EVH just wants to make sure the 6l6's make it out of the warranty period. Whatever

The bias for a quad of 6l6GC's that run at a plate voltage of 480v. is: 30watts / 480v = 62.5 ma x 60% = 37.5 ma x 4 = 150 ma.
The factory setting is 90-92
MY amp is way less thin and fizzy @ 130 than it was @ 90, and as you can see, I'm no where near even 60% dissipation.
YMMV

 

[Bill935]

My 100s pot only goes to 52 or 53 is that right?

 

[napalmdeath]

My 100s pot only goes to 52 or 53 is that right?

WAY too hot. I assume there's one adjustment in the 100, like the 50?

I did several of the 50 watt, and and kept them around 32-34mA.

50-53 would be over 80%, and likely sound like shit, (not to mention kill your tubes, and possibly SGR's.

 

[Kagami]

The measurement should be for all four tubes, I put some JJs in mine since I like them more than the stock in the III amps and set it to 120 or so.

I did try some of those 7581s that looked like I slapped them into an oven when I cut it on to bias so there's that, they worked fine in my Satan so the tubes were fine at least lol. Amp still works fine with the JJs.

90 / 4 = 22.5 ma /tube
Howard must like the sound of his tubes set cold.
Or Fender / EVH just wants to make sure the 6l6's make it out of the warranty period. Whatever

The bias for a quad of 6l6GC's that run at a plate voltage of 480v. is: 30watts / 480v = 62.5 ma x 60% = 37.5 ma x 4 = 150 ma.
The factory setting is 90-92
MY amp is way less thin and fizzy @ 130 than it was @ 90, and as you can see, I'm no where near even 60% dissipation.
YMMV

I think Eddie just likes that sound since the Peaveys are really cold too.

 

[Bill935]

My 100s pot only goes to 52 or 53 is that right?

WAY too hot. I assume there's one adjustment in the 100, like the 50?

I did several of the 50 watt, and and kept them around 32-34mA.

50-53 would be over 80%, and likely sound like shit, (not to mention kill your tubes, and possibly SGR's.

I settled for 25 hopefully that works out.

 

[PBGas]

I have the new 50s so I’ll have to take a peek with the multimeter and see what the bias ports are giving me for numbers as stock. It sounds great now so I’ll probably just leave it as is.

 

[riffermadness]

I have the new 50s so I’ll have to take a peek with the multimeter and see what the bias ports are giving me for numbers as stock. It sounds great now so I’ll probably just leave it as is.

I just got on the waiting list for the 50s..already jonesing..