Crate VC5212 Combo Service and Bias Mod

A bit sick and humming.. customer sure at least one valve dead.. actually all good!A bit sick and humming.. customer sure at least one valve dead.. actually all good!Need bottom to thec hassis with the tubes held in place firmly.. these will not fall out!Need bottom to thec hassis with the tubes held in place firmly.. these will not fall out!Interesting output transformer very close to power transformer.. one at an angle to minimise coupling...Interesting output transformer very close to power transformer.. one at an angle to minimise coupling…Fairly neat single PCB designFairly neat single PCB designDSC_2326Intially thought this cap was the probelm.. but actually ttested out good and seems to be a cosmetic issue with these caps then they get hot..Intially thought this cap was the probelm.. but actually ttested out good and seems to be a cosmetic issue with these caps then they get hot..Cap out for testingCap out for testingMiain issue was bias.. no adjustment and tubes running too hot.. in with a DIY voltage doubler and adjustable pot..Miain issue was bias.. no adjustment and tubes running too hot.. in with a DIY voltage doubler and adjustable pot..Some glue to stop the components rattling loose..Some glue to stop the components rattling loose.. Once bias actually set to correct 70% power dissipation she was singing sweetly again! Suprised how nice she should great EL84 action!Once bias actually set to correct 70% power dissipation she was singing sweetly again! Suprised how nice she should great EL84 action!

5 thoughts on “Crate VC5212 Combo Service and Bias Mod

    • I think as you look at the chassis from the front it is the far left one (closest to the first input) that is with the tubes pointing down.

  1. Hey man, what do I need for parts and how do I do the install for the bias adjust? I have one of these and have always wanted to do that.

    • I have a circuit for it and can do it for you if you want. There is a circuit available if you search for it but it is a basic voltage doubler circuit. I modified it a little. I did not draw it out. I will email you what I have.

      Stewart

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