Panasonic FS-A1 Mk II - no video signal

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By l_oliveira

Hero (531)

l_oliveira's picture

21-06-2015, 02:55

It's possible to obtain black and white composite signal from adding up R, G, B and CSYNC from the VDP pins using four 75 ohm resistors. That could be a test to prove if the VDP is faulty (I don't believe it is faulty at all).

By sd_snatcher

Prophet (3454)

sd_snatcher's picture

22-06-2015, 04:09

The Sony HB-F1XD features a very similar video/audio daughterboard. Since the circuit is pretty much standard, you can probably use this service manual as a reference.

From the following picture, I can see that the pin-10 and 11 of the CXA1145 were badly affected by the corrosion, and those are the CYNC-IN and CSYNC-OUT respectively. You should check these connections carefully. Also check if the Vcc1 (pin-12) of the CXA1145 is properly connected.

By Jipe

Paragon (1499)

Jipe's picture

22-06-2015, 10:59

Quote:

check solder of IC's on mini-board before replace capacitors

Wink

By saez05

Expert (121)

saez05's picture

18-07-2015, 15:00

Hello friends,
Yes is ok that wiring. Is the same for Panasonic FS A1MKII, Sony F9s and Sanyo wavy23.
Regards

By sabre470

Resident (35)

sabre470's picture

24-01-2016, 00:26

Hey Folks,

Finally got some time to look at the FS-A1 again, got a big magnifier and a good flashlight and surely enough I found some eaten traces, few hours of soldering and I finally got an image Smile

The video output comes from composite (easy to test) but it's not complete yet, it's missing one or two layers of sprite.

Massive thanks to everyone for bringing me to that stage, was really busy with other things but finally it's working Smile

Here is a video, let me know your thoughts:

MSX2 FS-A1 almost working :)

By Grauw

Ascended (10011)

Grauw's picture

24-01-2016, 00:36

Congratulations on getting this far! Close now to get it working again Smile.

Check the VRAM lines next… There’s a problem with the connection of the VDP to the VRAM or the VRAM itself, causing the missing sprites and weird characters in Basic. Data lines to VRAM chips 0-3 by the looks of it. Check line 3 first, that one’s definitely not working.

By sabre470

Resident (35)

sabre470's picture

24-01-2016, 00:49

Grauw wrote:

Congratulations on getting this far! Close now to get it working again Smile.

Check the VRAM lines next… There’s a problem with the connection of the VDP to the VRAM or the VRAM itself, causing the missing sprites and weird characters in Basic. Data lines to VRAM chips 0-3 by the looks of it. Check line 3 first, that one’s definitely not working.

Thank you very much, I'm checking the RAM lines, I've noticed that the RAM chips get really hot is that normal? 2 out of the 4 are really hot the others not so much. I'm not leaving the computer very long as a result just in case Smile

By l_oliveira

Hero (531)

l_oliveira's picture

24-01-2016, 01:06

The ones that are hot are bad. That's why it's only detecting half the RAM. That model has 128KB.

The flashing pixels are noise caught by the VDP inputs when the bad chips are selected (the bad chips are not replying properly so you get the blinking dots).

Probably attempting to power it up many times with broken traces could be what broke the chips. Or the chips are just old.

I suggest you replace all four for four of the exact same kind/brand. Any kind of 4464 RAM that is 120ns or faster will do fine.

By Grauw

Ascended (10011)

Grauw's picture

24-01-2016, 01:06

Quickly identified Smile.

By sabre470

Resident (35)

sabre470's picture

24-01-2016, 01:42

l_oliveira wrote:

The ones that are hot are bad. That's why it's only detecting half the RAM. That model has 128KB.

The flashing pixels are noise caught by the VDP inputs when the bad chips are selected (the bad chips are not replying properly so you get the blinking dots).

Probably attempting to power it up many times with broken traces could be what broke the chips. Or the chips are just old.

I suggest you replace all four for four of the exact same kind/brand. Any kind of 4464 RAM that is 120ns or faster will do fine.

Nice thank you! My chips are MB81464-12 (8743 T31 BB).

Will these do the trick? Ebay

If yes I'll order them straight away.

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