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Philips VG8020/20 PAL encoder

Door aplonogax

Supporter (3)

afbeelding van aplonogax

01-03-2022, 09:28

Hi all,

I recently got hold of a philips vg8020/20 (at least, from what it says on the label). My knowledge of this computer is nil, so first I opened the case to check if there were any major problems on the board. Everything's looks good but comparing to other pics found on the web the PAL Encoder doughterboard is missing. Is that normal? What should I expect to come out of the monitor connector? non-PAL signals or absolutely nothing?

I have a board that convert YPbPr to VGA for another project, so following the schematics (of the VG8020/00) I tried to connect the YPbPr signlas from the VG board to my converter and somethings shows up, but from the monitor connector or the RF modulator nothing...

So, here are my questions:

  1. the pal encoder board is mandatory in order to use the monitor connector?
  2. there are project of this board replacement?
  3. there are other solutions to make the monitor connector works again?

Thanks a lot!
have a good day
Tommaso

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Van Jipe

Paragon (1614)

afbeelding van Jipe

01-03-2022, 10:15

the board 37 542 B12 (Page 6) and the schematic PAL ENCODER U100 (page 18) is on service manual
https://archive.org/details/philipsvg8020sm

Van aplonogax

Supporter (3)

afbeelding van aplonogax

01-03-2022, 11:14

Hi Jipe,

I've seen the service manual, I was wondering what can be the difference between the /00 and /20 version. Looking the board I see some differences. That's why I was asking if the PAL encoder is mandatory for che monitor connector to work properly.

Also the pal encoder board use some discontinued ICs, that's why I was asking if there are project to replace this board with modern component.

Thanks a lot
Tommaso

Van Jipe

Paragon (1614)

afbeelding van Jipe

01-03-2022, 14:03

what is the vdp model on this 8020 ?
the 9918 puts out composite whereas the 9929 puts out component video.

Van sdsnatcher73

Prophet (3962)

afbeelding van sdsnatcher73

01-03-2022, 14:18

The VG8020 is a PAL machine so it’s VDP relies on an external encoder to generate composite and RF signals. The PAL encoder (often a LVA510) does the work but these do break down occasionally (a rough guesstimate is about 10-15% of machines with these chips develop issues). The reason it is missing is that the previous owner most likely had found it to be broken, removed it but did not replace it.

So you need this chip to get a composite signal on the DIN connector as well as an RF signal. The chips can be bought online but as with all old chips you may get a broken one or even a rebranded one. There are some reliable sources, e.g. RepairBas, who have tested the chips (and they come from otherwise broken MSX machines used as parts donors).

Van Repair-Bas

Paragon (1175)

afbeelding van Repair-Bas

02-03-2022, 11:33

I have pal encoders and complete boards in stock