my mark III is barely legal

[JimAnsell]

it showed up yesterday on its 18th birthday!
:lol:

 

[adrenaline junkie]

Now you can violate it with no fear of legal problems!! ;-) Looks like new inside.

 

[jvk]

My god, that's cleeeeeen. Is it a head? I suppose it has a seal on the head cabinet?

 

[Boogiebabies]

Hey Jim,

Excuse me for prying, but on the other picture of this amp the DC rectifier bridge in front of the bottom 30uf/500V cap on the preamp board has two 4.7K resistors around the two 100 Ohm heater reference resistors. These should be only 39 ohms. I would call MB to see if this is ok to keep.


Ed

 

[JimAnsell]

are you talking about those 2 brown resistors?
yeah that looked a bit strange to me too.

i'll give him a ring.

 

[Boogiebabies]

Jim,

It's the ones that are on each side brown ones that are suspect and should be 39 ohms instead of 4.7K. The two 100 Ohm brown resistors are pure Boogie. They have used them for tons of amps. Those are to hold the reference to ground for the tube heater supply.

Ed

 

[Shep]

its clean because of the guy who wired it. K D

 

[JimAnsell]

Jim,

It's the ones that are on each side brown ones that are suspect and should be 39 ohms instead of 4.7K. The two 100 Ohm brown resistors are pure Boogie. They have used them for tons of amps. Those are to hold the reference to ground for the tube heater supply.

Ed

i looked at some of the guts shots i had from some mark III's, and you're right, this is the only one with out 39 ohm resistors there.

what is with that first one where the 3rd resistor from the left is going to a different diode than the other 2?

i've been playing the amp all day, and there is no problem with it or anything.
would this different value effect the tone at all?

 

[Boogiebabies]

The first one is a repair due to trace damage. I have seen this issue on more MK III's than I can remember. The rectifier bridge is used to convert the V1 heater voltage to DC. I don't understand why a 6.3V circuit would take such a beating.

 

[JimAnsell]

mike said it'd be fine to leave it as is.

 

[Boogiebabies]

That's good to know.