MSX Toshiba Pasopia IQ HX-20 HX-21 HX-22 Improved PSU

Par kinchan

Supporter (4)

Portrait de kinchan

16-03-2022, 07:59

Hello Friends,
I have been working to redesign and make it real.
It is 1:1 form-factor power supply unit board for the Pasopia IQ HX-2x series (MSX) made by Toshiba.
Fully protected against over-voltage, over-load, short circuit, reverse current, over-temperature, RF noise.
It comes with status LEDs and very low output ripple noise on each rail.
Original heat-sinks and harness can be reused from the existing hardware.

https://www.pcbway.com/project/shareproject/MSX_Toshiba_Paso...

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Par gdx

Enlighted (5684)

Portrait de gdx

16-03-2022, 10:17

Is the original problematic?

Par kinchan

Supporter (4)

Portrait de kinchan

16-03-2022, 14:20

well, yes it is. After recapping the whole machine and replacing BJTs, Zener diodes and OAMP on the power board, the 5V and 12V rails were affected by a wavy noise (audible). The noise was reflected in the stereo audio. In addition, the original board had not any kind of protection and this does expose the transformer and the motherboard to the risk of failure. I have redesigned the power board using low-noise LDOs and better ground routing. Everything is fully protected (poly fuses, no polarity inversion, no latch-up between +12V and -12V, lower risk of overload & short circuit, monitoring of over-temperature, over-voltage, and finally RF noise filters on both inputs and outputs).

Par Wlcracks

Champion (471)

Portrait de Wlcracks

16-03-2022, 18:18

wow nice deisign and series inductors! I like to use blm murata ferrite beads.

Par kinchan

Supporter (4)

Portrait de kinchan

17-03-2022, 06:40

Wlcracks wrote:

wow nice deisign and series inductors! I like to use blm murata ferrite beads.

ferrite beads are good to cut high frequency noise indeed