Sony HB-75P RGB out

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Door QBee Sam

Champion (281)

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19-05-2022, 15:24

I've been using RGB potenciometers to fix the blue image from my Sony HB-75P, now is better than the original but not much beter, there is some kind of trick, procedure or so to improve the image quality instead of try and error that I've did?

Original picture:

Current picure, a bit clear but not good, still blue:

Emulating with OpenMSX I get this, so far from real and not sure if is possible to improve even more:

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Van Jipe

Paragon (1559)

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19-05-2022, 16:22

turn RGB potenciometers for obtain a very good white color and normally the other colors are good
on chapter 6 of the service manual you have the RGB ADJUSTEMENT by required an Oscilloscope

Van Wierzbowsky

Guardian (3492)

afbeelding van Wierzbowsky

19-05-2022, 17:35

The procedure is described in the service manual (Chapter 6, page 6-1 and 6-2). You need to trim a few pots using the oscilloscope. And this is major pain in the back because RGB test points are hidden under the huge radiator. One wrong move and it touches something on the motherboard. Besides, trimming should be done after color15,15 command, so the keyboard also needs to be temporarily connected. This doesn't make things easier.

Van sdsnatcher73

Prophet (3534)

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19-05-2022, 18:01

Which explains why they were supplied with such bad calibration

Van Nprod

Expert (100)

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19-05-2022, 19:23

Sort of off topic, but here's a reminder to change the RIFA filter capacitors on the pcb at the left side if you haven't yet.

Van sdsnatcher73

Prophet (3534)

afbeelding van sdsnatcher73

20-05-2022, 14:04

Why is that? Are they known to cause trouble? If so what kind of trouble Wink?

Van QBee Sam

Champion (281)

afbeelding van QBee Sam

21-05-2022, 18:24

Nprod wrote:

Sort of off topic, but here's a reminder to change the RIFA filter capacitors on the pcb at the left side if you haven't yet.

Oh, thanks.

Van QBee Sam

Champion (281)

afbeelding van QBee Sam

21-05-2022, 18:25

Jipe wrote:

turn RGB potenciometers for obtain a very good white color and normally the other colors are good
on chapter 6 of the service manual you have the RGB ADJUSTEMENT by required an Oscilloscope

I'll take a look, thank you!

Van QBee Sam

Champion (281)

afbeelding van QBee Sam

21-05-2022, 18:27

Alexey wrote:

The procedure is described in the service manual (Chapter 6, page 6-1 and 6-2). You need to trim a few pots using the oscilloscope. And this is major pain in the back because RGB test points are hidden under the huge radiator. One wrong move and it touches something on the motherboard. Besides, trimming should be done after color15,15 command, so the keyboard also needs to be temporarily connected. This doesn't make things easier.

This doesn't sounds easy for my knowlege, I have no osciloscope btw, so I'll try my best, thank you!

Van Wierzbowsky

Guardian (3492)

afbeelding van Wierzbowsky

22-05-2022, 16:44

One more thing - even with the installed and secured radiator please make sure that your screwdriver doesn't touch the terminals of the voltage regulators that are conveniently located very near the holes that lead to RBG pots. If you touch the radiator and one of the powered terminals, there will be fireworks.

Van Wild_Penguin

Hero (644)

afbeelding van Wild_Penguin

30-05-2022, 18:47

I'm not sure but no matter how well the calibration is done, it seems there will always be a slight blue tint on the HB-75P - but it could also be some components (capacitors?) have not aged well on my unit, or I've done the calibration incorrectly (I'm a self-learned hobbyist, after all). But the blue tint should not be that severe, it will still look decent, and I'll take it over any composite output any day.

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