Marshall vintage modern 2266 manual woodworkers

Now if you increase the current through the tube to 52Ma you will end up with. If your bias reading is 31Ma and your plate voltage is 465 this would give you 14.4 watts idle dissipation: Normally as current rises in a circuit voltage drops but to show you how these two things affect each other i will keep the plate voltage the same.

When reading the bias just by using a milliamp reading only gives you half the picture, in order to know exactly how much the tubes idle dissipation is you need to know what the voltage is on the anode or plate.

With a KT66 your 70% of maximum idle dissipation would be 24 watts.

I have used a dual probe Bias King to double check tube bias idle currents as well then set final bias with the nicely built in bias test connector pin 1 & 3 method. Since then I don't like it but I actually use flat tip screwdriver on top of retainer screws and apply gentle lifting force under edge of base, alternating between sides with retainer depressed, to gently walk tube out of socket with no physical load at all on the glass bottle. Been using it for awhile and so far so good. I had a bottle separate from it's base and in desperation to continue playing I spun a bead of crazy glue around the seam and maintained light pressure while holding base side up until glue set. Suggestion when removing output tubes be careful & apply all pull force on base, and only use glass bottle for minimal circular steering motion to remove tube especially as original match sets age. A microphonic pre-amp tube usually sounds like background shattering glass noises while holding some notes. If it is going microphonic then replace pre-amp tube to eliminate mechanical interior rattles from being delivered out the speakers. I usually remove pre-amp tube and lightly pinch top top & bottom between two fingers then gently tap side of glass bottle with a fingernail. One suggestion is to check pre-amp tubes for microphonics. It doesn't do it all the time it seems intermittent. I have another issue at the moment where sometimes there is a crackle after the note decays when you hit the strings hard but turning guitar volume down just a tad or backing off your attack eliminates it. I can also see now why they rattled as the glass has detached from the base on one of them. Turn it down to 38mV and see what you think, alternatively crank them to 52mV and see how that sounds. I personally have my some of my amps set a bit colder because I like it that way, however I have my 2466 set at recommended setting now. Of course the hotter you set them the shorter life span the tubes will have. However many guys to this day run their bias setting a bit colder and others a bit hotter. Manalishi58 wrote:Hi new member here though I have been a frequent reader of this forum for some years. I will refit and check the bias of the original KT66 later today using the biasmaster.ДЎ) is it a fair assumption to take the biasmaster reading as read to be a direct correct reading ?Дў) should the trim pots be able to set the bias as high as it initially was ?ДЈ) what differences in tone or feel should I expect to find between the higher and standard bias settings I have done a quick sound check and all sounds good and blue glow is still present as it was before. I have adjusted them down to 46/7 mv each side as mine has TWO BIAS TRIM POTS one for each valve. I have just bought a TAD biasmaster and last night set out to check the bias again and got readings of 78 to 80 mv on both valves which are way off the recommended 43 to 48 mv but not showing signs of red plating just a steady blue glow in places. I tried checking the bias from the informative info on this site with a multimeter but just got very low and fluctuating readings and as I didnt want to keep sticking my hands in a live amp abanded this method(might just be my meter)

I put them in and all sounded reasonable to me. I have had the VM since Jan 2016 ( 2011 model) and decided to put in a new set of Marshall branded KT66 as the original ones rattled terribly. Hi new member here though I have been a frequent reader of this forum for some years.ДЄmongst other amps I have a 50 watt VM combo and a 1974x.

Marshall vintage modern 2266 manual woodworkers