Blackstar HT5 MOSFET PI repair kit.
£12.00
Description
Some early Blackstar HT5 units have issues with the MOSFET PI. The unit arcs between the pins of the TO-220 MOSFET. Blackstar fixed this issue on later units by putting gaps between the pins in the PCB design.
Depending on the existing damage, sometimes these issues can be fixed by drilling away the space between the MOSFET pads, but it’s sometimes useful to mount the MOSFETS off the board.
This circuit uses IRF830 MOSFETs in place of a phase splitter to provide the signal for the 12BH7 push pull output stage. The circuit runs between -15V and positive HT. R38 and R39 22K resistors are in the MOSFET drain (equivalent to anode in a traditional valve circuit) TR4 provides a regulated voltage for the source (cathode equivalent).
Kit contents:
2 MOSFETs and 2 MOSFET mounting boards (drill a hole and mount these off the PCB)
22K power resistors for the Drain resistors (raise these off the PCB)
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