Carver MXR2000 Part2 - "The Magnetic Field Power Supply "

[johnlsenchak]

Carver MXR2000 Part2 - The Magnetic Field Power Supply
Published on Sep 23, 2018
In part 2, we look at the power supply. The first 30 minutes or so contains a lot of theory. Skip ahead if you want to see the measurements on the power supply.

[joseph nicholas]

Nice teardown and commentary.  Can't wait for more on this.

[johnlsenchak]

Agree  , I was  waiting to see the "flux  capacitor"  connected to the Triac  !

[glarsson]

Odd that Carver built their own diac using four transistors. Was this cheaper than a diac or do they trigger the triac in a way that is not possible with a standard diac?

[SeanB]

That way they could select the 4 transistors for breakdown voltage, and get matched sets, so the triggering is symmetric (not guaranteed for the run of the mill diac) and thus there is no long term DC component through that really small power transformer. That also had the side benefit of making the power dissipation a shared item across 4 large devices, removing a lot of the thermal drift as well.

They probably used the same transistor elsewhere in volume, so simply doing an incoming binning for those within a specific set of parameters, and taking components for sections out of the same bins for every version, made sense for them in ensuring all the units were consistent, and they had more control over process spreads. They also had the incident add on of only having Carver supplied parts working well in repairs, as the circuits were optimised for narrow gain spreads and other parameters.